Tetraform 8 Anglais

TETRA Theoretical training

version 8.0

P. MINOT

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INTRODUCTION This training is mainly provided to engineers and technicians with some knowledge of radio technologies. It is based upon TETRA norm from ETSI with a lot of official documents which overcome this one in case of difference. Basic documents : • ETS 300 – 392 - 2 TETRA V + D air interface • ETS 300 – 392 – 1 TETRA general network design • th This document is periodically updated and this version is the 7 which takes into account comments and technology progress.

Your comments will be wellcomed for the next version

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1. GLOSSAIRE

AACH aloha access channel AL advanced link BER bit error rate BL basic link BNCH broadcast network channel BS base station BSC base station controler BSCH broadcast signaling channel C_Plane common plane CLCH common linearisation channel CMCE circuit mode control entity DPSK differential phase shift keying DMA frequency domain access ISI Inter System Interface LA location area LLC logical link chanel LS line station MAC medium access control MCC mobile country code MCCH main signaling channel MER message error rate MLE mobility link management MNC mobile network code MS mobile station PEI peripheral equipment interface SAP service access point SCH signaling channel SCCH secondary signaling channel SSI short subscriber identité STCH stealing channel SW switch TCH trafic channel TCH/7.2,TCH/4.8,TCH/2.4 TDMA time domain access TEI TETRA equipement identity U_Plane user plane

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2. RADIO FEATURES

2.1. COMPARISON WITH ANALOG RADIO - COVERAGE In a general point of view, any digital radio caracteristic is more ‘squarred’ as for analog radio ; this is due to threhold effects involved in a lot of digital process. In that way, link quality with digital radio (GSM,TETRA,DECT,..) is quiet the same whatever be the signal to noise ratio if this ratio is larger than a threhold – under this threhold, link quality drops down drastically. It is possible to perform audio quality measurement in laboratory, through a digital and an analog radio link, according to S/N. One notes: • With good S/N.value, the subjective quality of a digital radio transmission is a little lower than the quality for an analog one – that is because digital technologies involve speech compression which slightly decreases quality • As soon as the S/N decreases, the quality of an analog radio trensmission decreases while the digital remains constant • Near from a threhold, digital quality falls downs while analog stay audible, even with a lot of noise. • Below the threhold digital link is broken

Subjective quality 5/5

Digital radio SQUELCH

4/5 3/5 2/5

Analog radio

1/5 0 Noise/Signal Such measurement is made in laboratory with S/N simulation. Situation is not exactly the same with real conditions : a radio transmitter is installed in a fixed location and a mobile radio receiver go away from this transmitter. The S/N decreases with increasing the distance between the radio equipments – but another

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effect influences the quality : multipath propagation. When measuring the RF field received by the mobile, one may find fluctuations and separates. • A mean value of the RF field which is the same as the only effect of the S/N • A ‘fine’ value which fluctuates rapidly with dropouts These dropouts are not regular, as for their positions, as for their depth. This may be expressed only with statistics with the probability for a dropout and a probability for the depth of such dropouts ; these probabilities are related while the probability of large depth dropout ( more than 30 dB) is low and probability of small dropout ( less than 3 dB) is very high. Dropouts are moving according to time and location – that is, even in a fixed place, their are RF field variations. RSSI Digital radio 5/5 UNSTABLE

SQUELCH

4/5 3/5 2/5 1/5

Analog radio

0 Distance from transmitter This fluctuation have different effect over analog or digital radio : with analog radio, the effect is the same as a S/N fluctuation ; with digital radio, the S/N fluctuation could be with no effect as soon as the RF field do not reach the threhold level. These effects may be different according to the different time constants involved in the digital equipments; near from the threhold, the system may switch between two states ( on state ‘link on’ and one state ‘link off’ according to the time constants. Rafly, the threhold with fading is 8 to 12 dB upon the S/N threhold – this difference is the difference between the ‘static sensitivity’ and the ‘dynamic sensitivity’. As result, the radio coverage around a fixed base station is expressed according to statistics – the probability to get a radio link with two ratio: • Coverage percentage during time • Coverage percentage around an area. In that way a 90/90 coverage is the area in which the radipo link is achieved at 90% of the point around a location and during 90% of the time. Obviously a 99/99 coverage is more difficult to achieve than a 90/90 and involves more base stations. As result of the threhold effect for digital radio, coverage map are with two colors: black and white (link is OK or not) while, with analog radio, coverage is full colored, each color for an link quality (mainly subjective audio quality). Practically, it is often better to provide analog coverage measurments as digital ones, while, with digital, nothing is known about margins and it’s impossible to predict the effect of any change (antena gain,..) – the main problem is to evaluate the digital scale fro the analog one, that is to correlate an analog radio field with the digital threhold. This is achieved with link budget..

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2.2. LINK BUDGET, TRANSMITTED POWER 2.2.1. transmitter TETRA uses TDMA technology, that is a communication uses only a part of the time on the radio channel : exactly ¼ of this time ( 4 communications may be simultaneously provided through a TETRA channel) Terminal equipments transmits with burst only during ¼ of the time. As consequence, the crest power of a TETRA terminal is different from the mean power : exactly 6 dB difference. For a base station providing simultaneaously 4 communications, it is always transmitting and the crest power is the same as the mean power. TETRA normalizes classes according to the maximum mean power

classe 1 2 3 4 5 6 7 8 9 10

BS Power watts 40 25 15 10 6,3 4 2,5 1,6 1 0,6

Power dBm 46 44 42 40 38 36 34 32 30 28

classe 1 2 3 4

MS power watts power dBm 30 45 10 40 3 35 1 30

During normal operation, the transmitted power from a mobile station could be reduced below the maximum for there is a regulation method which allows to automatically reduce power when a mobile is close to the base station.

2.2.2. receiver TETRA uses 25 KHz bandwich channel. For such BW, with ambiant temperature, the thermal noise is -133 dBm Static sensitivity for receivers are, according to TETRA norm:
-112 dBm for MS
-115 dBm for BS Dynamic sensitivity for receivers are, according to TETRA norm:
-103dBm for MS
-106 dBm for BS According to TETRA modulation caracteristics, signal upon noise ratio must be higher than about 12 dB to achieve low error rates – ie a perfect base station can’t have a static sensitivity down to – 121 dBm. In practice, - 188 dBm is reached, that is a global noise factor of 3 dB for the base station (what is excellent) while the TETRA norm admit up to 6 dB of signal to noise ratio. In most cases, good sensitivity is not used while the noise received from an antena is much higher than the therotical white gaussian noise. In urban area, the noise level with 25 KHz bandwith is higher than – 120 dBm, du to industrial noises and radio noises from surrounding transmitters.

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2.2.3. Link budget The link budget indicates the max propagation attenuation, taken into account all system parameters. Following table is a typical example:

Tx power Tx coupling duplexor Cable + connectors Tx Antenna gain Body effect Radiated power Body effect Rx antena gain Cable + connectors duplexor Dynamic sensitivity Max propagation attenuation

downlink Infra to mobile Infra to handy 40 dBm 40 dBm - 4 dB - 4 dB - 1 dB - 1 dB - 2 dB - 2 dB + 5 dB + 5 dB 38 dBm 38 dBm - 10 dB 3 dB 0 dB - 103 dBm - 103 dBm 144 dB 131 dB

uplink Mobile to infra Handy to infra 34 dBm 30 dBm + 3 dB 0 dB - 10 dB 37 dBm 20 dBm 5 dB 5 dB - 2 dB - 2 dB - 1 dB - 1 dB - 106 dBm - 106 dBm 145 dB 128 dB

With digital radio procedure, a radio terminal can’t receive a transmitted signal from infrastructure if it is not registered to this infrastructure – as important consequence, the radio link is achieve only if and only if the uplink and the downlink are right. It does not matter to increase infrastructure radiated power above the level which balance uplink and downlink budgets. (the only effect of such increase is to increase interference probability). The only parameters which influence the balance are: • The difference between mobile and infrastructure Tx power • The 3 dB difference of sensitivity between mobiles and infrastructure • The Tx coupling loss in the infrastructure (in cas where several TETRA carriers are used on the same antena) Typically, the coverage is mainly limited by uplink with handportables. As information element, the following diagram indicates typical propagation attenuation

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dB

FREE SPACE ATTENUATION 450 MHz

120

110

100

90

80 0

5

10

15

dB

20

25

30 m

Km

50 m

100 m

30 m

Static budbet

150

30

50 m

Dynamic budget

100 m

140

130

120

110

100

Rural area

ATTENUATION / 400 MHz According to antena high

90

Suburban area

(mobile antena : 1,5 m)

80 0

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Km

2.2.4. OPTICAL COVERAGE With flat terrain, coverage may be limited by optical coverage, due to earth radius ; it is usefull to remember the following formula : d = 2, 5 ( √ h1 + √ h2 ) d max coverage radius, kilometers h1 et h2 hight of infra and mobile antena, meters example : 30 meters pylon for BS and 1 meter for handportable : max distance : 16 Km

2.3. MULTIPROPAGATION, TERRAIN PROFILE As indicated, propagation caracteristics are mainly influenced by multipath propagation with reflexions and diffractions. This is of the most importance if one may consider the percentage of time when an handy is with direct view from the infrastructure antena during normal operation : only a few percentage. So, these effects could be benefit if one know how to manage it. Theoretical models may be set up by considering there are an infinity of path possibilities from one antena to another : each path is caracterized by a delay ( the time for transmission ) and an attenuation.

Delay T1, attenuation A1

Direct path

Tx

Rx Delay T2, attenuation A2

Relative levels 0 dB

Discrete model

Direct path Continuous model

0

T1

T2

delay

Direct path

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Two model types are used : - discrete model : paths are with limited number, each of them is caracterized by a delay and an attenuation - continuous model: there are an infinity of path and caracterisation is made by the enveloppe of the density of paths. First model use dis the RAYLEIGH one which involve an infinity of particules in th espace. Each particule may reflect the signal at any moment with a fixed probability and the density particules is constant over the space.

Tx

Rx

Spatial model

Surface model

Other models are used which are better suited to usual radio transmission : for these models, reflecting particules are mainly on the ground surrounding antenas In order to qualify equipments and process, TETRA norm defines 6 different typical situations with discrete models:

MODEL

path

static rural Typical urban

1 1 1 2 1 2 1 2 1 2 3 4

Difficult urban Hilly terrain experimental

Relative delay (microseconds) 0 0 0 5 0 5 0 15 0 11,6 73,2 99,3

Relative level (dB) 0 0 0 -22,3 0 -3,6 0 -8,6 0 0 -10,2 -16

speed static ( v= 0) RICE CLASS CLASS CLASS CLASS CLASS CLASS CLASS CLASS CLASS CLASS

Delays must be appreciated by comparison to the baud rate : one effect of relative delays is to receive different symbols transmitted from different times. As result, symbols may overlap. TETRA symbols are transmitted wit 19 Kbaud – that is about 50 microseconds time intervals; that means with experimental model, up to 3 symbols may overlap. TETRA norm classes equiment quality according to their ability to support different multipath model : • class B : equipments which support static and rural conditions

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• class A : equipment supporting hilly terrain and urban difficult conditions • class E : equipment supporting extreme condition (experimental model) – these equipment include, in general, a special multipath propagation filter)

2.4. MULTIPATH PROPAGATION AND ANTENAS 2.4.1. antena gain (for remember) A theoretical antena radiates uniformly radio power in the space. A real antena only radiates power in a part of the space ; antena gain is the ratio between the RF field received in some place and the Rf field receved iwhen the antena is replace by an ideal antena. In that case, an antena radiating only in half of the space is with 3 dB gain. The reference antena is the vertical dipole one which radiates power uniformaly all around but which do not radiates on the axis. This antena is with 2.5 dB gain. An antena gain may be expressed : - Either by comparison to ideal antena: it is the gain written “dB” - Or by comparisaon with dipole antena : it is written « dBi » .. there are 2.5 dB difference between these two gains antena gains are identical for Tx and Rx.

2.4.2. multipath and contrast the question is : is it possible to use directional antenas to improve signal quality with multipath propagation. Thet is: is it possible to improve the ratio level between direct path and reflected path with such antenas ? With spatial model ( Rayleigh), it is clear that a directional antena improve this ration by eliminating a lot of refelected signals.

Contrast between direct signal and refelected signal is improved by eliminating paths outside the antena cone

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With surface model, such improvement is not possible by using antena gain ont the infrastructure but improvement may be achieved with antena gain on the mobile – unfortunatly such gain is not supported by handy which are not held vertically.

Contrast direct path/reflected paths is not improved while the antena directivity is not sufficient to separate the mobile from the surrounding area

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Contrast direct path/reflected paths is improved by using antena with gain on the mobile ( no possibility for handy)

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2.5. DOPPLER Mobile speed is included in multipath propagation models while effects are mixed. With free space, the received frequency by a mobile is affected by speed :

Fd = F0 v cos ϕ /c with

• v cos ϕ = radius speed of the mobile • c light speed • F0 central frequency

Typical value is 100Hz shift for 92 Km/h speed With multipath propagation, effect could be worst while the direct path may shift the Rx frequency in one way and the reflected path may shift it in the other way.

mobile

speed Tx As result, the received spectrum spreads around the central frequency (both sides). The shape of such spread is according to multipath model; with Rayleigh model the spectrum is given by: 2 -1/4 1/ (1 - x ) with x = ( f - Fd) / F0

frequency F0 - Fd

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2.6. SAME CHANNEL INTERFERENCE – FREQUENCY REUSE When a mobile receives signals from several different base stations transmitting on the same frequency, the effect is different according to the modulation used. - With analog AM modulation, the disturbance is directly related to the relative levels of the different signals. - With analog FM or PM modulation, there is a capture effect and one signal is completly rubbout by the second if it is received with a level higher than the other added to a fixed level. Unfortunatly, as levels fluctuates with multipath propagation, the gap between signal level must be increased. - With digital radio as TETRA, there is also a capture effect and the level difference is 19 dB: One must not that diagnostics of interferences for TETRA sytems are more complex than with analog while the only effect is a link failure ( with analog, one may ear disturbance ).

2.7. WIDE BAND TETRA NOISE Wide band noise can’t be filtered with passive components for mobiles. TETRA norm restricts the wide band noise according to following table : : Distance from the carrier 100 to 250 KHz 250 to 500 KHz 500 KHz to band limit Outside band

1 Watt mobiles

3 Watts mobiles

-75 dBc -80 dBc -80 dBc -100 dBc

-78 dBc -83 dBc -85 dBc -100 dBc

10 Watts mobiles and base stations - 80 dBc - 85 dBc - 90 dBc - 100 dBc

2.7.1. wide band noise transmitted by base stations Wide band noise is transmitted from any transmitter as as a noise decreasing far from the nominal frequency. The wide band noise transmitted by base station may disturb surrounding radio equipments and also its own base station receiver. In general, the duplex spacing between Tx and Rx of a base staion is 10 MHz. In order not to disturb Rx base station sensitivity, the wide band noise measured with Bw 25 KHz at 10MHz of the Tx frequency must be less than – 125dBm. In case of standard output power of 40 dBm, that means the wide band noise at 10 MHz must be below – 165 dBm the nominal level; what is impossible to reach with active components. The only way to reduce such noise is to use passive filtering at the output of the power amplifier with duplexor and/or cavities.

2.7.2. Wide band noise transmitted by mobiles For mobiles, the Rx sensitivity can’t be reduced by the wide band noise from it’s own Tx for mobiles are never transmitting and receiving at the same time ( pseudo duplex mode – see dedicated chapter). A problem could be with other mobiles: when a mobile is very close from a base station, it’s wide band noise may be received on the Rx frequency of this base station with a level higher than the received signal transmitted by another mobile located far from the base station.

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BS

Wide band noise transmitted by mobile M1 close to the base station could be higher than the normal signal received from mobile M2 far from the base station

M1

M2 There are two ways to avoid such problem : - Transmitted power regulation By decreasing transmitted power from near mobiles, one decreases also the wide band noise transmitted from these mobiles. Power regulation could be effective down to 15 dB for mobiles near from a base station;

-

Transmission time sharing from mobiles

But for ALOHA, mobiles never transmit simultaneously (neither usefull signal nor wide band noise) – that means theoretically their is no wide band interference ; unfortunatly, mobiles c’ant stop immediatly transmitting power from a time slot to adjacent ones. TETRA norm limits transmitted power : • in adjacent time slots to – 40 dBc down to nominal power • in no active time slots : down to – 70dBc from nominal power.

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2.8. INTERMODULATION By comparing to analog radio systems, intermodulation problem are identicals, but with two differences : • The threhold effect typical from digital radio : a ‘small’ intermodulation (down to the threhold) has exactly no effect, while a higher one breaks the link. • TETRA linearity requirements are very strong and intermodulation probability is lower than with analog. At the starting point, intermodulation is generated par any non linear component receiving several different high level signals; typically, a non linear component receiving frequencies f1 and f2 produces any frequency of the form: p*f1 + q f2 …p and q real positive or negative number. Remember there are 3 different intermodulation types with different effects: • Receiver intermodualtion : by receiving different high level signals, a non linear receiver produces intermodulation frequencies. Such receiver could be a mobile one near from a radio site with several analog or digital base stations (in that case the disturbance is limited in an area close to the radio site) or a receiver of any radio site equipment with generalized effect. To avoid such problem, for radio site equipment, a passive filter connected at the input of the disturbed radio site equipment is powerfull.

Tx Rx

Tx

• Intermodulation made by ‘external’ component : any non linear component near from several transmitters may produces intermodulation ; as example an old can is a perfect diode with metal/oxide junction. It produces intermodulations frequency which may be received close to this can Such intermodulation is detected in a very small area ( max 50 meters from the can); it could be bad when base station receiver antenas are close to such metal/oxyde junction. In that case, introducing a passive filter connected to the disturbed receiver has no effect.

Tx Rx

Tx

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• Transmitters intermodualtion : a Tx antena receives the signal transmitted by others antenas connected to other transmitters : in that case, this signal comes down to the power amplifier. This last is perfectly non linear for such backward signal ; it produces intermodulation frequencies which are fed forward to the antena ; this last is made to send away such signal. Finally, it is like the preceding can but with a very large area of disturbance. the way to prevent such effect is to use a circulator connected at the output of the power amplifier.

Tx Rx

Tx

With TETRA equipment, a circulator is often directly integrated inside the equipment (what was not with analog) and the problem is naturally solved in most cases.

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2.9. CELLULAR ORGANISATION Coverage management of a whole area is different according to frequency reuse : • Without frequency reuse, one search minimum of radio sites, only according to radio link budgets and coverage. The number of base stations on each radio site is according to the expected traffic for these sites • With frequency reuse, the optimum is not the same for one must take into account interferences between radio sites using the same frequencies; cellular model is used. A cellular model is based upon pattern : a pattern is equal to the number of cells using different frequencies. Traditionnally, cells are drawn as hexagons.

G B D

G E

F

E

A F C B

C B

E

B D

G E

A G

D A

F

F C

7 cells pattern C

B D

Topology rules indicates there are only specific pattern possibilities: only ones are: 3, 4, 7, 9,12, 13,16 ,19 21 ,25 ... cellules

Cellular organisation is made with following requirements : • A mobile must receive a base station in a cell with a minimum of level • A mobile must not receive another base station in another cell using the same frequency with a level higher than the preceeding minus 19 dB • A base station must receive a mobile in it’s cell with a minimum level • A base station must not receive a mobile in another cell using the same frequency with a level higher than the preceding one minus 19 dB ...these four requirements are taken into acount with following results :

Terrain type 90% 11,5 / 7 5,5 / 7 5 / 7

rural suburban urban

Coverage percentage 95% 9,5 / 7 5 / 9 4 / 9

99% 6 / 13 3 / 16 2,5 / 16

Optimum cell radius (Km) / pattern

( source : TWENTE University )

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By comparison, typical coverage without frequency reuse :

Terrain type rural suburban

Fixed mobile 22 13

Moving mobile 16 10

Fixed handy 8 5

Moving handy 6 4

Typical coverage radius (Km) / 400 MHz, base station antena 30m

2.10. HERTZIAN EFFICIENCY TETRA uses 2 frequencies with 25 KHz band (each of them) to provide 4 duplex communications. Following table compares spectrum efficiency of different radio systems :

SYSTEM TETRA PMR simplex TETRAPOL PMR GSM 2+ GSM

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2.11. RADIO LINK BETWEEN MOBILE AND BASE STATION Any mobile, at any moment is managed by one radio site. Mobile must register to this base station and then the established link is monitored as long as the mobile do not register to another base station. The monitoring is made according to several parameters :

2.11.1. MOBILE Tx POWER REGULATION

2.11.1.1.max Tx power allowed in a cell Any radio site broadcasts an indication ( MAX_POWER_CELL) of the max power to be use in it’s cell. This information is recorded in the mobile which must never exceed.

2.11.1.2.forward Tx power regulation Any radio site broadcasts an indication (ACCESS_LEVEL) of it’s own Tx power and a regulation parameter : access level

=

Base station Tx power - coupling, duplexor and coax loss + Tx antena gain - Rx antena gain + wanted Rx level by the base station

Radiated power Regulation parameter

From this parameter and from the measured received level by the mobile, this mobile is able to adjust it’s own Tx power (which must never exceed MAX_POWER_CELL° In a practical way, when one increase the ACCESS_LEVEL parameter of a base station, all the registered mobile increase their power.

2.11.1.3.Loop Tx power regulation When a mobile is received by a base station, this one measures the received level and may send to this mobile an order to increase or decrease the mobile Tx power. Such regulation may be used only during communication. This method is not so efficient than the forward Tx power regulation while it is unable to adjust the mobile Tx power at the begining of any exchange.

2.11.2. COLOR CODE Each radio cell have a specific ‘color code’. This code is broadcasted by the base station (in clear mode) and all ‘payload’ data transmitted by this base station are encoded with this color code. Any mobile records the color code when registering to the base station and use it to decode usefull data. In case when the code is false, it is detected by the mobile which breaks the radio link. This protection ensures a mobile will not change base station link with radio interferences. Such protection is powerfull not only against far carriers transmission but also against intermodulations. As consequence, it is recommended to program different color codes for any radio site, even if they don(t use the same frequencies.

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La qualité de la liaison est mesurée en permanence avec un paramètre appelé C qui prend en compte le niveau de champ recu par le mobile et le niveau minimal de réception déclaré dans la cellule ( voir paragraphe ‘mobilité – mesure de la qualité de liaison‘).

2.11.3. PROPAGATION TIME MONITORING Mobile transmissions are timed from signal received from the base station. As soon as the mobile go far away from the base station, it receives signal with a delay and transmits with this delay. The transmitted signal from mobile is also delayed of the same amount when coming back to the base station. Total delay is measured by the base station and distance between base station and mobile is evaluated; when exceeding a certain amount, the base station breaks the link.

Tx infra

Rx mobile 2T T Tx mobile T

Rx infra

The maximum delay is a parameter which is set up in order to avoid transmission overlaps for different mobiles ; it is around 250 microseconds, what means about 30 Km. As consequence, one must take care when using equipments which may introduce some delay – as repeaters. One have to remember the delay of a bandwith limited equipment is not directly related to this bandwith but to the shape between the bandpass and the bandstop frequencies (slope of the filter). Following table indicates theoretical limits:

Band pass to bandstop frequency 30 KHz 80 KHz 200 KHz 2 MHz

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2.12. SYNCHRONOUS TRANSMISSION In general, synchronous transmission is not used with TETRA ; however, the norm indicates this possibility. In any case, it is interesting to have a look over this technology while synchronous features are involved when using peripheral TETRA equipments like repeaters. At the first, synchronous transmission is looked as for analog.

2.12.1. CARRIERS EFFECT A mobile viewing two transmitters receives two sets of signals – for a first approach, one don’t care about multipath propagation and only direct signals are taken into account and the two transmitters are with exactly the same frequency. If one of these signal is received with a high level compared to the other, there is a capture effect and the lowest signal is completly ignored – for TETRA, it’s the same. Areas where could be interference are located when distances to the two transmitters are in the same range. In these area, there are maxima and minima of signals – maxima are quiet stable while minima are tight and fluctuating. Result is a map with interference hyperbole as Fresnel optical interferences. If now, we add a litle shift between the frequency of the two transmitters, the preceeding hyperboles moves from one transmitter to the other with a constant speed related to the frequency shift. If now, we use same center frequencies for the two transmitters and if we add a phase noise, hyperboles are moving ramdomly, with a speed related to the spectrum of the phase noise.

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2.12.2. MODULATION EFFECT One suppose there is no carrier effect – as example, mobile is located in an area where there is a maxima of signals with two perfectly synchronized transmitters. If modulating signals for the two transmitters are completly independant, no signal could be demodulated by the mobile receiver. If the two modulating signals are from the same source, demodulated signal from the mobile is only affected by the relative delay between the two paths. Delay is the sum of the ‘radio delay’ from transmitters to mobile and of the delay for the modulating signal to reach the transmitters (transmitters are supposed exactly the same) • With analog modulation ( phase or frequency modulation) the audio response curve is the same as a comb filter : minima are equally spaced according to the delay difference. • With digital modulation, symbols overlap and the eye close when the delay difference increase

2.12.3. TETRA MODULATION TETRA modulation is a diffferential phase one and, according to preceeding remarks, effects may be easily understood : • Capture effect will be amplified with the threhold effect • A frequency shift have simlilar effect as a Doppler with mobile moving • The transmitters phase noise is equivalent as a S/N decreasing • Modulation effect will be identical as the multipath one. As result, synchronous transmission have the same effect, for TETRA, as a difficult terrain profile with an increase of the mobile speed.

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2.13. DIVERSITY Diversity is to use several different receivers and to select, at any moment, the best demodulated signal.

ANALOG

DIGITAL

receiver 1

receiver 1

Burst decoder

receiver 2

receiver 2

Burst decoder

receiver 3

receiver 3

Burs decoder Min error number in the decoded bursts

best S/N

With analog, the diversity system selects at any moment the best S/N ratio – selection is not synchronized). With digital, the diversity is a ‘bloc’ diversity – that is each receiver decodes a burst and, thanks to error detection code embedded to TETRA norm, they evaluate the decoded burst quality. Selection is made synchroneously, for each burst. If the receivers are fed with the same signal, the only difference could be with the thermal noise of the receivers (these noises are uncorrelated ). But in that case, there is exactly no improvement because the selection of the best demodulated signal is made over long period ( a burst) and, statistically, over such time, there is no difference between receivers ( they are supposed to be of the same quality). Radio signals connected to receivers must be different and there are several ways to get such signals. •

• •

Space diversity : different antenas are connected to receivers. With such arrangement, no improvement could be expected from the thermal noise for the same reasons as previously mentionned. Improvement may be achieved with multipath propagation: during a burst, propagation conditions could be different from one antena to others an it may change from one burst to another. This asumption could be true if and only if antena are not close. Space diversity may give improvement only if antenas are separated minimum ten time the wavelength. Improvement may reach up to 6 dB with 3 ways diversity and 4 dB with 2 ways – such improvements are measured with standard receivers; improvement are lower if decoders are equipped with efficient multipath propagation filters. Polarisation diversity: antena use different polarisation. The improvement is because with reflexions, the radio signal polarisation may be rotated. This method is efficient in area with a lot of multipath propagation ( indoor, dense urban, industrial,..) but not fitted for rural or suburban areas. Sector diversity: each of the antenas takes a part of the space to be covered. That is in place of omnirectional antenas, one use directional one, each of them with different azimuth. The improvement is made because, directive antenas have more gain than omnidirectional ( with the same horizontal pattern). The improvement is equal to the antena gain difference.

Diversity may improve base station sensitivity, what is important with handportables while link budget difference is important for such radio terminals

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2.14. BASE STATIONS COUPLING Tx coulping must be achieved when several base stations must share the same antena(s). By comparison to analog systems, TETRA coupling is simplified while 1 TETRA carrier multiplexes 4 channels.

2.14.1. Rx coupling Rx coupling is made with low noise preamplifier with several outputs. In case when one use a low noise amplifier with only one output, a splitter must be added. The low noise amplifier must have more gain than the loss of the spiltter (in ordre not to decrease the S/N) The low noise amplifier is often with selective band in order to minimize interferences and intermodulation. When using diversity, one must use one low noise amplifier with multiple outputs per antena.

filter

filter

filter

Low noise Multiple outputs

Low noise Multiple outputs

Low noise Multiple outputs

BASE STATION

BASE STATION

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2.14.2. Tx COUPLING Tx coupling before using a common power amplifier must be avoided for no power amplifier is linear enough to meet the spectral specifications. Tx coupling is achieved either with hybrid or by cavities. Both solutions have advantages and disavantages according to following table:

Loss 2 Tx

2 Tx 4 Tx 8 Tx Channel spacing tuning Wide band noise & spurious cost volume

HYBRID COUPLING

HYBRIDS 3 dB 6 dB 9 dB No requirements no Not rejected low low

Tx 1

CAVITIES 2.8 dB 3.3 dB 4 dB > 300 KHz Yes ( but for autotune) rejected high high

Hybrid Hybrid

Tx 2 Tx 3 Hybrid

Tx 4

CAVITIES COUPLING

Tx 1

cavity

Tx 2

cavity

Tx 3

cavity

Tx 4

cavity

With cavities coupling, circulators are used in order to prevent a signal comes back to a power amplifier. The selectivity of a cavity is according to its size; with big cavities, selectivity is better and frequencies spacing may be reduced.

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CAVITIES COUPLING

A (dB)

∆F F1

F2

F3

If frequencies spacing ∆F is too low, the attenuation A introduces a coupling loss while the signal transmitted from power amplifier F2 comes back to power amplifier F1 and is dissipated in the circulator.

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2.15. TETRA and CONFINED AREAS Radio propagation in confined areas are complexe and several radiating equipments must be used ( antena(s) and/or leaky coax) Technologies for indoor TETRA are similar as for indoor analog but for followings : • Equipment linearity • Transit time • Gain control In another hand, diversity was in general not used extensivly with analog; for TETRA, diversity offers a large help to solve main problems.

2.15.1. leaky feeders There exist two types of leaky coax : • Constant loss cables: they are mostly used. Loss is linear with length. The ‘holes’ density is constant and the cable may be cut at any length. With such cable, transmitted signal is high leveled near from the begining of the coax and low at the opposite side. Reciproqually, a radio terminal is received with high level near from one end of the coax and with low level at the opposite. With such cable, the practical length is in the range 600 / 1200 meters for one section; by connecting base station at the middle of a section to two leaky cable, the total length is in the range 1200/2400 meters. • Progressive loss cable: the ‘holes’ density is not constant and the coax is optimized for a fixed length. As result, the transmitted signal is constant all along the total length of the cable. Practical maximum length are longer than with constant loss cable; in the range 900/1800 meters. These cables are more expansive and c’ant be cut at any length; for these reasons, there are not intensivly used. However for TETRA, the main advantage is that a radio terminal is received by a base station with the same level all along the cable – that is important for linearity and saturation problem.

Leaky cables may be used for Tx and Rx separatly or for both Tx/Rx by using standard duplexors.

Tx

Tx Rx

Duplexor or hybrid

Rx

SEPARATE CABLES

UNIQUE CABLE

Several methods exist to provide a whole leaky system from leaky cables sections..

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2.15.2. Methods using repeaters A base station is connected at the end of the whole system ; it is connected to different leaky cable sections according to a linear organisation with links parralel to the leaky cable. Links could be directly RF links or with optical fibers by using optical / RF converters. :  For downlink, splitters are used to fed each leaky coax cable with similar RF level.  For uplink, hybrids are used to fed the base station with the summ of the received RF signals Such organisations may used amplifiers to compensate link loss

Tx

DOWNLINK

BASE STATION

1.

Rx

UPLINK

1. This architecture may be used to share the leaky coax cable with several different radio systems (GSM, TETRA, analog,..) in that case, repeaters/amplifiers must be broadband ( with noise and saturation problems) or made from different narrowband equipments connected in parralel form through filters. One of the main disavantage of this method is with uplink. The summ of all signals from different sections increase drastically the noise and the S/N is reduced. The second disavantage for TETRA is that equipments connected in a serial form leads to add non linearities and as result, to increase intermodulation probabilities. Another problem could be with the transit time through a lot of equipments wich could be not compatible with TETRA requirements.

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2.15.3. Methods with diversity

Several receivers are used, each of them being connected to a cable section. This is exactly as for outdoor diversity and the uplink is drastically improved : • No S/N degradation by adding different Rx signals • No transit time problem • No linearity problem with added equipments

Tx Rx1 Rx2 RF or optical links

Rx3

BASE STATION

2.15.4. MIXTE COVERAGE INDOOR / OUTDOOR A common requirement is to get an outdoor coverage with indoor coverage in the building where the base station is installed. Indoor area may be covered with antenna r leaky feeders, it may also be covered with optical repeaters connected to antenna or leaky feeders. The most common way is to get indoor and outdoor circuits in parallel way according to: Outdoor antenar

BS

duplexor

spiltter indoor

Sometimes, one uses splitters/combiners to separate the balance power between indoor and outdoor to the balance of the sensitivity between indoor and outdoor.

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Antenne outdoor

spiltter

duplexeur

hybride

duplexeur

BS Système indoor

These simple arrangements are with low performances:* • loss of outdoor sensitivity: the loss is minimum 3 dB du to the Rx coupling • Industrial noises disturtance: the indoor antenna system is often very close from industrial equipments and may pick up a lot of disturbances, mainly non constant. The sensitivity is decreased, especially for outdoor • Sensitivity loss by overload: indorr radiating system may be very close from handportables (sometime less than one meter); in that case, the received level uplink is very high; as result, adjacent time slots of the time slot where the handportable is transmitting are interfering with outdoor allocated time slot. As result, the outdoor sensitivity is decreased. • Overlap coverage area: there are always transition areas where there are both indoor and outdoor coverage (typical example is door to enter into metro). In these areas, a transmitted signal from a terminal is received by two ways; by using a combiner, these two signals are added and there may be some nul – as result there are specific points in the overlapping coverage area where there is no coverage. By using diversity, all preceding problems are solved:

Antenne outdoor

spiltter

duplexeur

BS Rx1 Rx2

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• • • •

As there is no hybrid coupling device, there are no sensitivity loss of 3 dB Industial noises received from indoor radiating system have no effect on outdoor received signals Overload by close transmitting handportable from the indoor radiating system has only effect on oindoor coverage, not on outdoor In overlap indoor outdoor coverage areas, there are no signal cancellation for adding signals with different phases.

2.16. HERTZIAN REPEATER (using the same carrier) The first rule to apply for repater installation is to avoid a loop between antenas. A minimum margin of 10 dB must be provided in order to prevent reflexions with moving obstacles. Repeater gain < antenna coupling – 10 dB .. for each of the transmission ways reflector

Metallic wall

To base(s) stations

To area repeater

There are two types of repeaters : • Wide band repeaters/ these repeaters are more sensitive to noise and non linearity problem; especially in case when several different carriers are used • Channelised repeaters which are selective for a specific TETRA carrier: thes repeaters are not sensitive to noise and non linearity but they have a long transit time and several of them must be used in case of several carriers

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2.16.1. NOISE FROM A REPEATER In some case, using a repeater may decrease the base station sensitivity. The noise level at the input of a repeater is in the same range as the input of the base station. This noise, is amplified by the repeater gain and by the antena gain, then reduced by the propagation. At the total if this noise is higher than the input noise of the base station, these last is with decreased sensitivity.

Base station

repeater mobile

GR Repeater gain

GA antena gain

A propagation loss

GR + GA < A

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2.16.2. VARIABLE GAIN REPEATER, CAG Such equipments are commonly used for analog systems ; they must be absolutly rejected for TETRA. For a repeater may receive quasi simultaneously different signals transmitted from different mobiles (TDMA) In case when one of these mobile is closed from the repeater and another far away, the automatic gain control will regulate according to the high level and the low level signal from the second mobile will be completly in the noise. Typically a repeater with CAG will provide good result for one communication in its cell and can’t transmit the other communications. Far mobile Rx – 120 dBm

CAG regulation level

temps

Near mobile Rx – 30 dBm

One may imagine to adapt the CAG with a fast time constant in order to be able to change quickly from one time slot to another ; unfortunatly, fast time constant affects drastically the TETRA modulation at the begining of a burst and the receiver can’t recover the right modulation.

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2.16.3. REPEATER GAIN EFFECTS When installing a repeater, one have to tune two gains : the uplink one and the downlink one. These gains are limited to avoid RF loops and base station sensitivity decrease ; down to these maximum levels, one have to select right value to achieve good performance level. The uplink gain is the most critical: the main problem is with linearity : when an handportable is close to the antena repeater, the Rx signal amplified by the repeater uplink gain exceeds the maximum output power delivered by the repeater. As example, suppose a handportable transmitting 1 Watt with a distance of 5 meters from the antena; it will be received at – 20 dBm ; if the repeater is tune with 70 dB gain, that means, it must deliver + 50 dBm ( 100 watts) at the opposite output. Low gain restrict this close area but restrict also the area covered by the repeater.

Operational area

No coverage

repeater

Low gain

No operation

Operational area

No coverage

repeater

Medium gain

RF LOOP répéteur

High gain

2.16.4. SELECTIVITY

.If repeaters are wide band, they are sensitive to linearity problem as soon as there are several TETRA carriers – in the other hand, if they are selectiv, they have a transit time wich could be incompatible with propagation time requirement for TETRA

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2.16.5. UPLINK OVERLAP FOR AREAS WITH REPEATERS Whatever be the antena positions, thre always exists an area where a mobile may reach the base station either directly or through the repeater ; in that case, the base station receives two signals, one directly, the other transmitted by the reapter with another level and with some delay. This is exactly the same as for multipropagation model and the base station may decode if it is with a good multipropagation filter. The same for downlink : there are always areas where mobiles may receive both signals from the base station and from the repeater. Overlap areas are not exactly the same for uplink and downlink: they change according to the repeater gains (uplink and downlink).

2.16.1. DOWNLINK OVERLAP FOR AREAS WITH REPEATERS The overlap area between indoor and outdoor coverage is not exactly the same for uplink and down link; that is RF powers and repeater gains are different.More the signal transmitted by a repeater is strong and more the overlap area downlink goes far away from this repeater. In this area, it is like a multipropagation process while the two ways ends to the MS receiver with different phase and amplitude. The difference from the uplink is that MS are often with a lower multipropagation class. As result, the overlap is more difficult with downlink than with uplink.

2.17. REPEATERS WITH DIFFERENT FREQUENCIES Such repeater are commonly used with analog radio systems. The main advantage of it are beczause the RF loop is completly ignored.

F1

F2

F3 F4

Repeaters with frequency change

UNFORTUNATLY, THESE REPEATERS CAN’T BE USED WITH TETRA for, carriers are numbered from a basic frequency and the infrastructure indicates a frequency to mobiles with such numbers. With a hardware frequency change, a mobile is unable to recover the good channel.

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2.18. TETRA2 : RADIO FEATURES First of all, TETRA2 is with several version according to the channel bandwith; TETRA2 offers higher baud rate but the sensitivity of mobiles and base station decreases according to the increase of speed: as example, the dynamic sensitivity is according to following table:

Bit rate Kb/s Dynamic MS sensitivity dBm BS

TETRA1 π/4 DPSK 36 -103

TETRA2 π/8 DPSK 54 - 97

- 106

- 103

25 KHz BW TETRA2 4-QAM 38,4 - 111 - 108

TETRA2 16 QAM 76,2 - 103

TETRA2 64 QAM 115,2 - 98

TETRA2 4 QAM 153,6 - 102

- 106

- 101

- 105

100 KHz BW TETRA2 TETRA2 16 QAM 64 QAM 307,2 460,8 - 97 - 92 - 100

- 95

In another hand, the transmitted power are equivalent for TETRA1 and TETRA2; as consequence, the number of radio sites must be multiplied by 2 or 3 to reach higher bit rate with the same coverage. In that way, moving from TETRA1 to TETRA2 can’t be considered as a simple software upgrade while the whole network architecture is altered. Rafly, TETRA2 means ‘minimum twice the radio site number’

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3. MODULATION AND SPECTRUM FEATURES

3.1. MODULATION and THREHOLD EFFECT La modulation de phase correspond à l’élaboration du signal : s(t) = A sin ( ωt + ϕ(t)) ω représente la porteuse ϕ(t) représente le signal de modulation .. par la suite, seul le signal de modulation ϕ(t) sera pris en compte. TETRA modulation is a differential phase shift one with +/-45° and +/-135 degres jumps. Each modulation symbol represents two bit. The symbol rate (baud) is half the bit rate (bit/sec.) 36 Kbit / seconde 18 K baud (Ksymboles/sec.) each symbol may have 4 values (00, 01, 10 and 11), each of them being associated with a phase jump value.

01

00 +135°

ϕ(t)

+45° Preceeding symbol

-45° -135°

11

10

Phasis evaluated with absolute values may be 0, 45°, 90°, 135°, 180° , 225° ,315° degres When separating symbols in an alternate way (odd and even), one find each odd symbol is with 0, 90, 180 & 270 degres while even symbols are with 45, 135,225 & 315 degres.

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Odd symbols

Even symbols

Special modulation : some binary sequence are with specific modulations : : • sequence 0000... phasis increases 45° each symbol ; that means a fter 8 symbols – correspondaing to 8/18 milliseconds – it turns one round. At the final it is a frequency shift of exactly 1/8 of the frequency symbol that is + 2,25 KHz • sequence 101010.. the frequency shift is reversed from preceeding case, that is – 2,25 KHz • sequence 010101.. the shift is 135° for each symbol, after 8 symbo ls, the phase turned 3 rounds. The spectrum is made with two lines: the one at + 2,25 KHz, the second at – 6,75 KHz • sequence 11111 : two lines : the first at – 2,25KHz and the second at + 6,75 KHz differential shift keying modulation have a very good theoretical BER versus S/N ratio – drawn on the following shematic.

*

BER 10-1 -2

10

10-3 10-4 -5

10

10-6 S/B 2

4

6

8

10

12

dB

An overlook to modulation diagram gives indication about thehold effects : a receiver recover the phasis of the input signal ; if the clock is well regenerated, it must take decision of the transmitted symbol according to the phasis sampled according to this clock. The received phasis is equal to the transmit phasis added to an error function of the perturbations. If this error is less than 45° the receiver always make the good choice. Threhold effects are related to perturbations wich may affect the phasis by more than 45 degres. Consequently, one may consider that a disturbance will have no effect as soon as its amplitude is less than the circle of radius r on the following schematic :

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disturbance B

Phasis of the transmitted symbol

Usefull signal circle

r

R

A

Phasis of the preceeding symbol

… that is a threhold value r equal 0,76 R. The threhold effect is abrupt with sinus disturber, when the disturber is 3 dB below the signal. With a white noise, the threhold effet is not so abrupt. A similar overlook may evaluate the frequency effects : in case when the carrier is continuously shifted from the nominal value, the phasis is increased by δϕ for each symbol ; that means as soon as threhold Une approche similaire donne l’ordre de grandeur du seuil pour un décalage δϕ is less than 45 degre, there is no effect for the receiver. At the final, the system may accept frequency shift up to 2,25 KHz ; above this value it is not possible to decode the signal. .

Phasis of the transmitted symbol Usefull signal circle

δϕ Preceeding symbol phasis R

The maximum frequency shift is 45 degres per symbol, that is +/- 2,25 KHz

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3.2. PHASE PATH, SPECTRUM At significant modulation times , the phasis must be with predefined values according to symbols to be transmitted. Between these samples, phasis values are not taken into account for demodulation but they directly influence the spectrum of the signal. Three path possibilities for phase path between symbols are looked: • A phase jump exactly at the middle time between symbols (red line) • A linear path of the phasis between symbols (blue line) • A « smoothed » path of the phasis between symbols (green line)

3Π/4 Π/2 Π/4

-Π/4 -Π/2 -3Π/4 Π

The spectrum for these different three cases are shown below :

KHz

- 12,5

-19

12,5 F0

19

Obviously, spectrum are evaluated and/or measured with ramdomized symbol source – any periodic symbol source must be avoided.

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According to the phase path, the spectrum is very different and more the path is « smoothed », more the spectrum is limited. Smoothing is realized by evaluating the path not only from the nearest known phase points but also from adjacent phase points and adjacent from adjacen and so on – that is according to the number of symbols taken into account; it’s named the ‘horizon’ Sprectrum requirement for TETRA leads to an horizon of about 14. In order to smooth the phase path, one need not to use constant amplitude modulation, what is shown below :

A max

A min

In order to get a smoothed phase path, one need not to use constant amplitude : modulation is said to be with non constant enveloppe ( analog FM or PM modulation are with constant enveloppe).

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3.3. FILTERING, FILTERS HORIZON Filtering allows signal smoothing in order to achieve spectrum purity. For TETRA, the allowed bandwith is 25 KHz. The usefull spectrum is about 18KHz, that is the spectrum vanish in less than 3,5 KHz around the edges. There is a theoretical relation between the slope of the spectrum and the transit time of the signal through th filter. Aprroximativly, the transit time is the invers of the bandwith of the ‘corner’ of the filter.

FILTER FREQUENCY RESPONSE

FILTER IMPULSE RESPONSE

fréquency ∆F

T = 1 / ∆F

The transit time may be expressed with symbol period as unit – that is the number of symbols. Result is named the ‘horizon’ of the filter ; it is the total number of symbols one may take into account to calculate the exact modulation shape around the symbol placed in the middle. .

FILTER HORIZON

Symbol clock Symbols

Partial impulse responses

Shift register

A1(t) A2(t) A3(t)

multipliers

An(t)

Σ

output

In another hand, when the slope of a filter is high, the phase delay variation in the band increases and the transmission is altered for digital transmission. For TETRA the horizon must be above 9 for spectrum purity and below 17 for in band propagation delay variations.

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Transmit filter is used to adjust the signal bandwith ; for receiver, one must also reduce the band to the usefull part. According to the adapted filter theory, the best receiver filter has a frequency response identical to the signal spectrum to be decoded. As, for transmission, one may consider the modulation source with an infinite spectrum bandwith (compared to allowed signal bandwith of 25 KHz) the usefull spectrum is identical to the response of the transmitter filter (same impulse response). Finally, transmiter filter and receiver filter are identical. The complete transmission through these two filters must be very close from the rectangular form.

SYMBOLS

Transmiter filter

E

Receiver filter

R

Demodulator / decoder

Phase path evaluation

Transmitted signal

Tx FILTER = Rx FILTER = fréquence

As consequence, the phase path evaluation can’t be directly from the transmitted signal ‘E’. A measuring instrument must integrate a receiver filter to recover signal ‘R’. TETRA filter requirements are very difficult to obtain with analog filters; only digital filtering technologies may be used. Nevertheless, analog filtering must also be used to select the frequency band (pre filtering’ for digital filters can’t reject frequencies far from the useful band. .

Analog prefilter

f

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f

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Demodulator / decoder

f

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3.4. MODULATION ACCURACY It’s possible to display the signal phase on an ascilloscope as example X is fed by the signal and Y by the same signal with 90° phase shift ( phase shift of 9 0° over the whole frequency band). Phase paths are crossing at the significant points 0°,45°, 90°, 135 °, 180°, 225°, 270° and 315° on the circle. More, t hese points must be reached at instant exactly spaced with symbol period. These meeting points may be easily displayed by turning on the whenelt of the oscillosce at these moments. This is a measuring method for digital transmission: it shows the global quality of the signal : any default degrading transmission degades the constellation display: • Thermal noise • Phase noise • Group delay • Frequency response • ... For diagnostic, this display could also be of some help for some potential default have typical view: as ewample, a phase noise on an oscillator implies points around the cros points but always located on the circle. The quality is evaluated with the distance between points and reference points (related to the circle radius) with three quantities: • The mean value of the measured distances, related to the frequency shift • The rms value of the measured distances • The peak value of the measured distance

DISPLAY BY SUPERPOSITION OVER ONE POINT

MODULATION ACURACY

Peak limit

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3.5. INTERFERENCE WITH ADJACENT CHANNELS (Analog and Tetra channels) For analog channels, interferences between adjacent channels are evaluated with the spectrum, by measuring relative levels at the limit between the channels. For TETRA channels, interferences are evaluated with the message error rate (MER) induced in the ajacent channel. It is not possible to establish a direct relation between the relative levels measured with the sprectrum and the message error rate, for the message error rate is according to the shape of the transmitted spectrum in the adjacent channel (and not only according to the relative level at the edges of the channels). Consequently, it is not possible to qualify interferences when a Tetra channel is adjacent from an analog one. That is the reason why National regulation rules do not mix TETRA channels and analog channels in the same band : TETRA channels are allocated in a sub band and this sub band is spaced from others by a guard. The guard is, in general 12,5 KHz or 6,25 KHz – that is the reason why TETRA channels in a band may be declared shifted of +/- 6,25 KHz or +/- 12,5 KHz from nominal frequencies.

GARDE

TETRA CHANNEL

ANALOG CHANNEL

TETRA CHANNEL

60 dB 70 dB

25 KHz

25 KHz

12,5 KHz 6,25 KHz

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3.6. TETRA MODULATOR There are several ways to make a TETRA modulation – only few of them ay reach the severe requirements of the norm. From one end, symbols are digitally generated while the output must be an analog modulated signal. Digital to analog conversion may be achieved at different point of the modulator. Many of the process use IQ modulator which may be implemented either digitally or with analog technologies. They implement the trigonometric formula : Sin ( ωt + ϕ ) = Sin ωt Cos ϕ + Cos ωt Sin ϕ

I,Q modulator I FILTER

Σ

SYMBOLS 90° phase shifter

FILTER

Q

Sin ωt

Cos ωt

As previously mentionned, analog filters are difficult to implement. Consequently, filters are implemented with digital technologies and the digital to analog conversion may be implemented before or after the IQ modulator. Advantages and disavantages are summarized in the following table:

CNA numbers CNA sampling frequency IQ modulator Spectrum purity

CNA before modulator

CNA after modulator

2 low analog Sensitivity to the modulator (balance between ways)

1 high digital No balance problem for the modulator

There are also another way with only one CNA conversion after modulator and only one of the two digital filters. In any case, it is not possible to get after modulator (analog or digital) a signal with high frequency carrier: - with analog modulator because of the low spectrum purity at the output of the modulator - with digital modulator because of the CNA technology limits. ..as result, the signal is synthesized with an intermediate frequency carrier and one must use up converter to get RF signal.

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3.7. TETRA DEMODULATOR As for modulation, there are several ways to implement a TETRA demodulator. As for modulator, TETRA RF requirements are severe and it is difficult to use a direct demodulation ( Zero Intermediary Frequency) and a down converter can be used used to demodulate a lower frequency carrier signal. Demodulator itself is complex and can be achieved only by digital technologies. Analog to digital conversion must be used and, as for modulation, there are two ways to implement it: either after an IQ demodulator or directly on an IF frequency. When conversion is after IQ modulator, two CAN must be used and the sampling is performed at the same time for both CAN When conversion is direct from IF, only one CAN is used with sampling ticks shifted as drawn on the following shematic :

I,Q

I,Q

I,Q

T

Demodulation with IQ modulator and two CAN

I Q

T/4

I,Q

I

-Q

3T/4

I Q

I

-Q

Direct demodulation from IF with one CAN

Before evaluating the phase of the signal for symbol recovery, the signal must be processed to achieve multipath propagation filtering. Following steps are used : • Record all the samples of a paquet • Find out synchronisation sequence by autocorrelation between the signal and the signa representative this synchronisation sequence. This allows to exactly recover the middle of the paquet • Analyse the spectrum of the signal with a window aroud the synchro sequence. • Compare this spectrum to the ideal spectrum of the synchronisation sequence; the difference is repreentative of the channel impuse response from the transmitter to the receiver at time the paquet is transmitted • Calculate the filter which have an impulse response reversed from the preceeding one • Apply this filter to all the samples of the paquet (with a correlation function). • Evaluate the mean period symbol rate • Measure the signal phase at any symbol period. This process is more complex for there are several different synchronisation sequences for TETRA and there are two types of paquet: full time slot paquets and half time slot paquet.

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3.8. UP and DOWN CONVERTER If used, up and down converter are classical ; nevertheless, special care must be provided about local oscillators phase noise ( such requirements do not exist with analog PMR) and intermodulation (especially with mixers). Note that, for TETRA all signals must be synchronised – that involves all local oscillators must be synchronised to a common clock.

3.9. LINEARITY Non constant envelop modulation as TETRA needs very good amplitude linearity characteristics ; Any non linearity involves spectral spurious response One of the main effect of non linearity is looked with the spectrum around the useful spectrum : there are typical increase level symetrical from the center frequency, in the adjacent channels.

ADJACENT CHANNELS

TETRA CHANNEL

ADJACENT CHANNELS

SHOULDERS ORDER 3

SHOULDERS ORDER 5

frequency 25 KHz 50 KHz 75 KHz

There are several shoulders type : • Shoulders of order 3: the level of these shoulders in quiet constant over 12,5 KHz adjacent above and below 12,5 KHz from the center frequency • Shoulders of order 5: the level of these shoulders is quiet constant over 12,5 KHz adjacent above and below 50KHz from the center frequency ( shoulders order 5 are often below the ground noise level)

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Shoulders are made by a non linear element. By changing the level at the input of such element: • Main signal changes 1 dB for any 1 dB input level change • Shoulders order 3 change 3 dB for any 1 dB input level change ( that is the relative level to the main changes of 2 dB for 1 dB input change) • Shoulders order 5 change 5 dB for any 1 dB input level change ( that is the relative level to the main changes of 4 dB for 1 dB input change) Care must be provided for such measurement while the measuring instrument is often not linear enough – displayed shoulders may be sometime the fact of the measuring instrument. It is very simple to know if shoulders are from equipment or from measuring instrument: by inserting a standart 3 dB attenuator at the input of the measuring instrument: • If shoulders order 3 decrease 3 dB, shoulders are from equipment • If shoulders order 3 descrease 9 dB, shoulders are from measuring instrument. Obviously, linearity problems mainly affect power amplifiers; no standart amplifiers as they are used for analog PMR are suitable for TETRA linearity requirements. Different methods and arrangements of these method are used to reach these requirements: • Amplifier with very high compression point ( IP1 & IP3) • Clas ‘A’ amplifier : unfortunatly these amplifier are with very low efficiency ( theoretically maximum 27% and tupically 15 %) and a lot of power is dissipated • ‘Feed forward’ technology : a compensation signal is added to the usefull signal at the output of the amplifier. • Cartesian loop : a compensation signal is added to th usefull signal at the input of the amplifier ; this signal is evaluated according to the input signal and some compensation rules which are evaluated during learning time slots : during this time slots, a typical and known signal is used and the output signal from the amplifier is measured. Learning time slots are also used by some terminals – they are named CLCH ( Common Linearisation channel).

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4. PAQUET FEATURES

4.1. TDMA and PAQUET TDMA technology (time domain access) divides time into time slots : TETRA divides by 4 ( GSM divides by 8) Each time slot may have a paquet which represents a message. For downlink ( infrastructure to mobiles) these paquets are transmitted on the one RF carrier by the same base station ( but for the case of carrier shared by several base stations) – there is a continuous transmission from the base station and the paquets are linked. For uplink (mobiles to infrastructure), paquets are transmitted by different mobiles. Time slots are numbered from 1 to 4 and uplink time slots numbering is shifted by 2 from the downlink.

downlink

1

2

3

4

1

2

3 time

uplink

3

4

1

2

3

4

1

As example, a paquet may carry a part of an audio message and, if all time slots are allocated to different communications, there are 4 simultaneous communications transmitted by the same base station over one RF carrier. Uplink carrier is different from downlink one and these carriers are spaced by a constant frequency value : the duplex spacing ( 10 MHz for European TETRA bands) In most case mobile transmits and receives in one of the 4 time slots; nevertheless, some mobiles may use simultaneously several adjacent time slots on the same carrier: it’s the multislot feature which is mainly used for high data transfert requirements. Paquets are structured into frames, subframes and hyperframes according to following diagram.

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1 hyperframe = 60 multiframes = 61,2 seconds time

1 multiframe = 18 frames = 1,02 second

1

2

18 Control frame

1 frame = 4 Timeslots = 57 ms

1 timeslot = 510 bit = 14,16ms 1

2

3

4

509 510

255 256

1 subslot = 7,1 msec. 1

2

3

255

4

1 symbol = 2 bit = 56 microsec.

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4.2. PAQUETS TYPES and STRUCTURE There are 6 paquets types : 1 timeslot = 255 symbols (510 bit) = 14,176 millisec.

continuous synchronisation downlink paquet 12 2

80

ϕ

120

38

block 1

Frequency correction

216t block 2 or PA linéarisation

30

2 ϕ

Broadcast bloc

synchro

10

Continuous donlink standart paquet 12 2

216 bit

14

ϕ

22

16

216

2

bit

10

ϕ

synchro

Discontinuous downlink synchronisation paquet 10 2

80

ϕ

38

120 block 1

Correction fréquence

216 block 2 ou linéarisation du PA

30

8

ϕ

Broadcast bloc

synchro

2 2

Standart discontinuous downlink paquet 10 2 2

216 bit

14

ϕ

22

16

216 bit

2 2

8

ϕ

synchro

Standart uplink paquet 34

4

216 bit

22

216 bit

4

14

4

15

synchro

Half uplink paquet Subslot 1 = 255 bit

34

4

84

30

84

Subslot 2 = 255 bit

4

15

34

synchro Ramping and linéarisation PA

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4

84

30

84

synchro trainée

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Garde

There are characteristic field : • Synchronisation sequences ( grey colored) • ‘Scrambled’ bit fields ( light grey colored) • ramping and guard fields ( very light grey) • ...etc.

4.2.1. Paquet synchronisation With analog radio, the synchronisation sequence is at the head of the paquet and decoders where with two operation modes : one searching mode (for synchronisation recovery) and one tracking mode (for demodulation). As previously mentionned, TETRA signal process is more complex and it is not possible to use such ‘real time’ searching mode and tracking mode ; the whole paquet is stored and, after complete receive, the signal process may start. In that way, the synchonisation sequence may be implemented anywhere in the paquet. As, from the received synchronisation signal, some parameters of the transmission are evaluated ( the implulse response of the channel), it is better to get the synchronisation sequence exactly in the middle of the paquet for minimizing fluctuation effect of these parameters during the paquet transmission. Several different synchronisation sequences are used : • A 38 bit sequences ( 19 symbols) for downlink synchronisation paquets • Three 22 bit (11 symbols) different sequences for standart paquets • A 30 bit sequences (15 symboles) for half paquets.

4.2.2. Ramping and linearisation fields These fields are used at the beginning and at the end of discontinuous paquets ; RF transmitted power is set up and down during the transmission of these data. Power up must be shorter than the ramping time and power down shorter than the guard time. More, power up and down transcient must be according to a specified form in order to prevent spectrum disturbances.

ramping

guard

time

paquet

4.2.3. Phase adjust field According to modulation method, the RF signal phase change from one time to another is sensitive to the transmitted symbols during this time. That means the phase after a paquet is sensitive to the paquet content, what increase the level of the spectrum near from the center frequency (instead of the optimum flat characteristic). In order to prevent this effect, symbols are added to the data paquet which are evaluated in order to get a phase at the end of the paquet always the same as at the begining of it plus 45°.

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Consequently, the global RF phase increase of 45° e ach 14 milliseconds (time slots duration) that is 360° every 112 milliseconds – which correspond to a frequency shift of 8,9 Hertz from the nominal carrier. This shifted value must be taken into account if accurate frequency measurements are provided for calibration. Each phase adjust field is one symbol (2 bits) and there are two of such field : one at the begining of the paquet, one at the end.

4.2.4. Scrambled and non scrambled fields Most of the data fields in a paquet are scambled with the color code affected to the radio site which transmits the paquet. Nevertheless some fields are not scrambled – especially the data fields concerning broadcasted informations while they indicate the color code itself.

4.2.5. Frequency correction field This field is made from 64 bit set to zero – it involves a pur sinus signal shifted + 2,25 KHz from the nominal RF frequency ( see preceeding chapter ‘modulation’ ). It allows a receiver to exactly tune its master clock. This signal is placed between two short sequences corresponding to pur RF sinus signals shifted – 6.25 KHz from the nominal carrier.

4.2.6. Tail bit These symbols take place at the begining and at the end of an uplink paquet ; they are with fixed 4 bits and are used to prevent transcient effect and transit time effect in the filters.

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4.3. CODING 4.3.1. Coding theory summary Encoding consists in adding redudancy bit to a message in order to protect it and to get the possibility to detect and/or to correct transmission errors as soon as there are not too much of such errors. There are two types of codes : • Bloc codes : for a message of fixed n bit, k bit are added – the places where are inserted these redudant bit is not of importance while it’s always possible to reorder the bit. • Convolutional codes : redudant bit are periodically inserted into a continuous data stream. TETRA only use bloc codes. Let a bloc code with n usefull bit and k redundant bit – this code is named a n,k one. n n+k There are 2 possibilities of usefull messages and 2 possibilities of received messages (in case of very high transmission disturbance) . n+k n From these 2 possibilities, only 2 correspond to non altered messages. One may look all possible messages as a cloud in a space an non altered messages as some points in this cloud. The ‘distance’ between two messages is equal to the number of bit which are different between this two messages. When they are only few transmission errors, the distance between the received message and the original one is small; when the eroor number increase, the distance increase. When receiving an altered message, one selects the real message nearest from this message in the cloud – that is the ammowed message with minimum distance from the received one. The code distance is the minimum distance between two authorized messages. A code is a perfect one if the distance between any of the authorized messages ic constant. There are only few perfect codes; nevertheless, there are codes which are close from the optimum; they are named ‘quasi perfect’. Code distance is directly related to the capability of detection and correction of the code according to following table :

Code distance 2 3 4 5 6 7 ....

Perfect codes, if they exist are with : k N+k+1=2 k 3 (N + k )+ 1 = 2 k 6 (N + k )+ 1 = 2 ….. k+1 e (e + 1) (N + k + 1) = 2

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Detection capacity

Correction capacity

(error number)

(error number)

1 2 3 4 5 6 ...

0 1 1 2 2 3 ..

for 1 error correction capability for 2 errors correction capability for 3 errors correction capability for e errors correction capability

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K

N 1 error correction

1 2 3 4 5 6 7 8 9 10 11 12

2 errors correction

1 4* 11 26 57 120 247 502 1013 2036 4083

3 errors correction

1 5 15 35 57 128, 331 671 1353

4 errors correction

4 14 34 76 160 330 670

5 errors correction

5 17 42 92 193 397

9 25 58 125 261

* Hamming code Code efficiency is the ratio between usefull data and transmitted data – that is : η = N / ( N + K)

4.3.2. Residual error rate Let BER as the bit error rate of a transmission channel. As soon as this rate is low, the mean error number on a message is ( Poisson rule) : (N+K) BER The n,k code allows to correct maximum e error – if the error number is larger than this value, there is a residual error rate after decoding. As consequence, a code may be looked as an ‘error rate divider’ but never as an ‘error rate canceller’. By using a code, one decreases the transmission error rate by a factor which is linear with the distance code and inverse linear with message length ( the bit number n).

MER MER WITHOUT CODING Code distance / number of bit to be encoded d/n

MER WITH CODING S/N

When the number of corrected errors increases, the confidence level in the resulting message decreases ; in a practical way, in order to keep a sufficient confidence level, one rejects messages with an error number approaching the code limit.

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4.3.3. TETRA CODES The choice of a code is dependant of the desired confidence level for transmitted informations. In order to optimise a transmission system, different codes are used according to the data field to protect. In that way, TETRA uses a large number of differrent code according to the information type to be transmitted. Following table gives indications about these codes with : • The number of bit to encode (n) • The number of transmitted bit (n+k) • Factor d/n • The code type

: AACH

BSCH

TCH2.4

TCH 4.8

TCH 7.2

2,4Kb/s data

4,8 Kb/s data

7,2 Kb/s data

60 120 1 √

144 432 2

288 432 0,5

432 432 0

√

√

√

√ √

Iformation Network for a mobile broadcaste access a d channel information

n n+k d/n K1->k1 +16 Reed Muller RPC +puncturing entrelacement scrambling FCS

14 30 1,14 √ √

√

SCH/HD BNCH STCH

SCH/HU

Signaling informations

124 216 0,75 √

92 168 0,82 √

268 432 0,61 √

√

√

√

√

√ √

√ √ (√ )

√ √

√ √ (√ )

√

(option en mode de base, intégré en mode avancé)

Four code types are used : • The Reed Muller code : it is a linear one (it uses only XOR operaions) ; it is used only for the AACH channel which carry autorisation for a mobile to transmit over the air interface. • The code K1 -> K1 + 16 : it is also a linear code which add 16 bit whatever the message length. • The « puncturing » code : it is also a linear code which add redudancy and scrambles the messages. • Interleaving : it does not add any redudancy but scrambles bit over several messages which allows to spread the effect of burst of error ( a code is efficient if errors are spreaded over the whole message). • The scrambling : it’s the color code used to distinguish Le scrambling est un brassage fonction du « coloriage » de chaque station de base

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4.4. SPEECH CODING A very special coding way is used for the audio. The audio source is according to standart telephone quality – that is sampled at 8 KHz with 8 bit per sample ( with A or µ law compression) ; the global source rate is 64 Kbit/sec. The vocoder transform it into blocs of 137 bit every 30 millisec., that corresponds to a rate of 4,567 bit/sec.

4.4.1. Vocoder General architecture of the vocoder (generator part) is as followed :

Long term prediction

Filter parameters

weighting

Preceding excitation Exciting pulse period (pitch)

Adaptative table

+ index

High speech pass filter and scaling

Short term prediction filter

Algebraic table

Grey colored areas correspond to parameters transmitted over the TETRA channel. 4.4.1.1.SHORT TERM FILTER This filter is defined with 10 points, it is evaluated every 30 milliseconds – that is, for a 30 millisec. Window, it samples a 300-3300 Hz signal with 333 Hz spacing ( equivalent to a 100 Hz sampling )

0

frequency

333 Hz

Curves are received every 30 millisec. are smoothed from one to another and the real response of the filter is modified every half frame ( 15 millisec.) .

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finally, the ten parameters for any 30 milliseconds period are within 26 bit.

30 milliseconds

30 milliseconds

4.4.1.2.LONG TERM PREDICTION This process evaluates the frequency of the exciting pulses which are fed to the short term filter ; it is made with two steps : • selection (upon 30 millisec – that is 240 samples) of the best exciting frequency from the following possibilities : • 56 to 100 Hz with 11 Hz accuracy 11 Hz ( 66 possibilities) • 101 à 200 Hz with 11 Hz accuracy (132 possibilities) • 205 à 400 Hz, with 33 Hz accuracy (48 possibilities) there are 256 possibilities encoded into 8 bit • fine evaluation over 7,5 milliseconfs of the frequency around the frequency as evaluated in the first step. The result is express as a distance between the corse and the fine frequencies – it’s encoded into 5 bit.

4.4.1.3.ALGEBRAIC TABLE Algebraic table synthesis method uses predefined pulse configurations as exciter. Each of these configurations corresponds to a typical sound familar to the ear – they are named « patrons » and are typical from a language and/or an accentuation. TETRA vocoder uses 8 pulses configurations. The exact time position of these pulses are selected in the following table.

Table parameter Pulse with amplitude + 1,414

Pulse with amplitude - 1 Pulse with amplitude + 1 Pulse with amplitude - 1 global sign Global shift TOTAL

Pulse position (note) 0,2,4,6,8,10,12,14,16,18,20,22,24,26,28,30 ,32,34,36,38,40,42,44,46,48,50,52,54,56,5 8, 2,10,18,26,34,42,50,58 4,12,20,28,36,44,52, (60) 6,14,22,30,38,42,54, (62) ( reverse the 4 pulses) (shift 1 all positions)

Bit number 5

3 3 3 1 1 16

Note : les parenthèses signifient que l’impulsion peut être décalée dans la sous trame suivante. Evaluation is made every 7,5 milliseconds, that is every 60 samples.

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Before encoding, the input signal must be free of dc component and must be scaled in order to avoid any overflow ; it is made with a high pass filter and a limitor/compressor.

4.4.2. transmitted informations Following table gives informations to be transmitted :

PARAMETERS

30 milliseconds frame (240 samples)

Short term filter Excitation Algebraic code gain Total

TOTAL per frame

subframe 1

subframe 2

subframe 3

subframe 4

8 16 6

5 16 6

5 16 6

5 16 6

26 23 64 24 137

When translated to standart telephone PCM form, one have to translate clocks while TETRA and PCM clocks are differents – they must be tied together (same synchronisation) to avoid drift problems according to:

1 multiframe = 18 time slot = 17 x 480 PCM samples ≈ 17 x 2 x 30 millisec. (for 2,048 Mb/s based PCM) As frame 18 is preserved for signalisation, a time compression of 17/18 must be introduced for encoding and a time expansion of 18/17 must be introduced for decoding ; as consequence, there must be a minimum of 18/2 frame delay each time an audio signal pass through the TETRA world. All informations to be transmitted do not present the same importance. This is measured by subjective evaluation of the audio quality level when introducing artificial errors affecting one of theses informations. Such experimental research can separate three classes of informations : • classe 0 : it concerns 51 of the 137 bit which are the less sensitive • classe 1 : it concerns 56 of the 137 bit • classe 2 : it concerns 30 of the 137 bit which are the most sensitive each of these classes is encoded by different codes with different error protection capacity. In another hand, during normal trafic (no signaling during audio), encoding is performed directly over two adjacent frames, that is over 2* 137 bit corresponding to 60 milliseconds. • The 2 x 30 bit in the class 2 are scrambled with RPC coding and a 7 bit CRC is added with an overall parity bit. 4 tail bit are added and the 72 bit are encoded with a convolutional code with 18/8 rate. • The 2 x 56 bit in the class 1 are encoded with a convolutional code of 2/2 rate • The 2x 51 bit in the class 0 are transmitted without code Finally, there are : class 0 2 x 51

+

class 1 ( 2 x 56 ) 3 / 2

+

class 2 ( 2 x 30 + 8 + 4 ) 18 / 8

= 432 bit

... soit de quoi remplir un time slot - c’est à dire qu’en une trame de 14,16 millisecondes, on transmet 60 eme millisecondes de parole, l’ajustage de débit étant réalisé par la 18 trame.

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4.4.3. PROCESS AND TRANSMISSION TIME Audio transmission is not uniform while it is made over 17 frames for 18 frames period. There must be a buffer with a minimum delay of 18/2 frames. Other delays are added : • Analyse time over an audio frame of 2 x 30 = 60 millisecondes • Time for windowing – about 5 milliseconds • Process time for compression and encoding • Time to decode a TETRA time slot – about 10 milliseconds • Process time for audio synthesis .. finally, the end to end transit time is minimum 100 milliseconds; it may reach 200 milliseconds.

4.4.4. COMPARISON with GSM VOVODER Following table gives indications about both vocoders :

Analyse horizon Parameters number Ratio PCM bit / vocoder bit Number of transmitted bit Number of transmitted bit / number of vocoder bit Transmission rate

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GSM full rate 20 millisec. 260 4,92 456 1,75

GSM half rate 20 millisec.

TETRA 30 millisec. 137 14,01 432 3,15

22,8 Kb/s

11,4 Kb/s

14,4 Kb/s

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5. AIR INTERFACE EXCHANGES There are two types of links used for TETRA : basic link and advance link.

5.1. BASIC LINK There are two types of basic exchanges : • Non acknowledged data transmission • acknowledged data transmission normal exchanges for these types of transmission are drawn below :

LLC A

Air interface

LLC B

LLC A

BL_UDATA

Air interface

LLC B

BL_DATA

BL_ACK

Non acknowleged data transmission

acknowledged data transmission

For acknowleged data transmission, the procedure is classical with a time out for retry in case when no acknowlege is received:

LLC A

Air interface

LLC B

BL_DATA

Time out

BL_DATA BL_ACK

Time out

BL_DATA BL_ACK

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This procedure do not protect transmission against multiple transmission in case of loss of acknowledge messages. For downlink, the base station sequentially sends messages to different mobiles in the time slots according to rules indicated in the next chapter (association of physical logical channels to physical channels). For uplink, there are two types of exchanges, as for any radio system: • Uplink messages sollicitated by the infrastructure: typically it’s an acknowledge or a response from the mobile • Uplink messages non sollicitated by the infrastructure. Sollicitated messages are transmitted during a time slot which is preserved for the designated mobile – that is, the infrastructure allows only one designated mobile to use the time slot. Non sollicitated messages are sent by mobiles during window opportunities indicated by the infrastructure. Several mobiles may transmit in the same opportunity and there are collisions; collisions are managed with ALOHA.

5.1.1. ASSOCIATION TETRA basic link integrates a specific powerfull feature: the association: by this mean, a mobile with a pending message (waiting for an opportunity for sending the message to the infrastructure) and receiving another message from infrastructure with a preserved time slot for acknowledge may associate the acknowledge and the pending message in the same preserved time slot. Si la donnée devant être transmise par l’expéditeur arrive trop tard, elle est traitée comme une donnée à acquitter normalement (partie inférieure du diagramme ci-après) :

BS

Air

interface

MS Unsollicitated message

Message to send to the mobile BL_ADATA

Waiting for an opportunity

BL_ACK + DATA Preserved time slot

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5.1.2. Granting delay Preserved time slots are managed by infrastructure. In a normal way, a preserved time slot for a mobile is declared by infrastructure in the next frame after the transmission of the message to the mobile. With granting delay, this preserved time slot is shifted with a delay corresponding to a number of frames which may be programmed.

BS

Air

interface

MS

Message to send to the mobile BL_ADATA

Normal preserved time slot

Granting delay

ACK preserved time slot with granting delay

The interest of such possibility is with polling: the message sent from infrastructure to a mobile is a request to an application process in the mobile. Sometime the application process could be long and, the response time may be more than one frame ( the transmission times between transmission level and application level must be included); in that case, the preserved time slot is lost to carry the response and this last must be transmitted in the next ALOHA opportunity – that is with delay and possibility of collision with another mobile message. With granting delay, the application process have more time and the preserved time slot is not lost.

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Air

BS

interface

MS Without granting delay, the response is missed for the preserved time slot

Message to send to the mobile BL_ADATA

request

Granting delay

Application

response

ACK + RESPONSE

5.2. ADVANCED LINK Advanced is mainly used for long messages exchanges which must be fragmented into several blocs to exactly fill up the time slots. It’s a full duplex procedure – much more efficient than any half duplex procedure : blocs are transmitted in the same time than acknowledges what mean any bloc may be transmitted before receiving acknowledge of preceeding ones. This procedure have three steps: • Opening the advanced mode • Data exchanges with trafic regulation if necessary • Closing the advanced link When an advanced link is open between a mobile and the infrastructure, messages may be exchanged in both directions.

5.2.1. opening advanced link opening advanced link is a negociation between the mobile and the infrastructure. Some parameters define the quality of service and the process complexity ; during negociation, both party agree these parameters according to their possibilities. Requesting advanced link is from one party which indicates the desired service quality (AL_SETUP message); if the other party can’t accept it, it makes a proposal with a reduced quality of service; this new proposal is used as a request acknowledge but if it refuse – in that case it refuses with an AL-DISC message.

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LLC A Request with Qos service quality

Air interface

LLC B

AL_SETUP Qos is accepted or a lower Qos is proposed

Advanced link is open with specified Qos

5.2.2. advanced link exchanges once the advanced link is opened, both party may transmit their messages in an asynchronous way. Only one tyransmission way is taken into account in the following in order to simplify schematics. Data to be transmitted are divided into segments and any segment is transmitted with two indications : • end of segment ( noted F) • request of acknowledge(s) ( noted A) the sender may ask for acknowledge(s) at any moment ; the acknowledge message includes a list of the received blocs ( with bitmap format) and, if necessary, a list of received segments.

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LLC A Segment 2

Air interface

LLC B

Segment 1

AL_DATA 1.1 2.3 2.2 2.1 1.4 1.3 1.2 1.1

AL_DATA 1.2

A request acknowledge

AL_DATA 1.3 _ AR AL_ACK

A starts segment 2 transmission Before receiving the whole Segment 1 acknowledge

AL_DATA 1.4_FINAL

Segment 1

1.4 1.3 1.2 1.1

AL_DATA 2.1 AL_DATA 2.2

AL_DATA 2.3_FINAL_AR

Segment 2

AL_ACK 2.3 2.2 2.1

An overall check is used with FCS code (as optionaly used in basic link) – this encoding is made for each segment. Retry process in cas of missing bloc(s) is managed according to the maximum blocs number allowed to be transmitted in advance, that is without acknowledge receipt. (it is one of the parameters indicated with service quality).

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Interface air

LLC A Segment 3

Segment 2

LLC B

Segment 1

AL_DATA 1.1 3.4 3.3 3.2 3.1 2.4 2.3 2.2 2.1 1.6 1.5 1.4 1.3 1.2 1.1

AL_DATA 1.2 AL_DATA 1.3

bloc 1.3 is not received AL_DATA 1.4 AL_DATA 1.5_AR

A request an intermediate acknowledge ACK 1.3

B answer 1.3 not received A retry bloc 1.3 transmission and go on with indication this bloc is the end of segment 1

AL_DATA 1.3 AL_DATA 1.6 F AL_DATA 2.1

A go on with segment 2

AL_DATA 2.2 AL_DATA 2.3

A indicates 2.4 is the end of the segment And ask for an acknowledge

AL_DATA 2.4_F_A

ACK 1.3,1.6, 2F

Segment 2

2.4 2.3 2.2 2.1

B answers 1.3 et 1.6 are missing and segment 2 transmission is complete AL_DATA 1.3

A transmits again 1.3 et 1.6 and ask for acknowledge AL_DATA 1.6_F_A

A can’t go on with segment 3 while With negociation, anticipate Have limited to 2 the segment number.

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ACK 1.3 AL_DATA 1.3 Segment 1

ACK 1F

A acknowledge the whole segment 1 Transmission and transmit segment 3

1.6 1.5 1.4 1.3 1.2 1.1

AL_DATA 3.1

any bloc in segment 3 is correct but the final FCS control is false

AL_DATA 3.1

A transmits an end of segment 3 indication And request an acknowledge

AL_DATA 3.4_F_A

ACK 3 AL_DATA 3.1

B answer segment 3 FCS is false

AL_DATA 3.1

A transmits again the whole segment 3 AL_DATA 3.1 AL_DATA 3.4_F_A Segment 3

2.4 2.3 2.2 2.1

ACK 3 F

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5.2.3. Trafic regulation At any moment during an advanced link cession, any party may ask for a temporary stop of transmission ; it’s made with a AL_RNR message similar to an acknowledge. As an acknowledge, this message may indicate missing blocs. Transmission is resumed when the party requesting the temporary stop transmit a normal acknowledge message.

Interface air

LLC A

LLC B

AL_DATA AL_DATA _AR

AL_RNR AL_ACK AL_FINAL _ AR

AL_ACK

5.2.4. Closing advanced link At any moment, any party may break the advanced link cession by transmitting a AL_DISC message. This break is immediate, even if transmitted data may bel lost. Disconnect message is automatically sent in case when a party detects any connection disturbance with no received messages..

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6. CHANNELS With FDMA, channels are intuitive ; they are associated with the radio frequencies and, at any moment, any equipment is attached to one and only one channel while they can’t work on different frequencies at the same time. With TDMA, it’s more complex while an equipment on a RF channel may transmit different types of information at the macroscopic level.

6.1. TETRA CHANNELS Two types of channels are separated : • Physical channels : they are associated to time slots – a physical channel is a link between points access points whatever be the informations transmitted over it. • Logical channels : they are associated to different information types – a logical channel corresponds to a trafic type, whatever be the transmission link Logical channels are carried by physical channels. There are 4 physical channels per TETRA carrier, while there are 4 time slots per carrier.

Channel x carrier 1 Channel y carrier 2

Channel z

LOGICAL CHANNELS

PHYSICAL CHANNELS

Air interface

Physical channel bit rate is constant while logical channel bit rate is variable, according to : • The requested bit rate from application(s) • The share of the carrying physical channel by other(s) logical channels • The transmit mode of base station ... the last point is due to the possibility to use base stations not only with continuous transmission but also with pulsed transmission.

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Some logical channels are only one way (infrastructure to mobiles or mobile to infrastructure) – others are both way.

6.2. TETRA PHYSICAL CHANNELS There are three types of physical channels : Les canaux physiques TETRA sont classés en trois groupes : • Trafic channels • Control channels • Non allocated channels

6.2.1. Trafic channels These channels carry either speech or data exchanged with circuit mode or data exchanged with IP packet mode. Trafic channels are : • TCH/S : trafic channel carrying speech • TCH/7.2 : trafic channel used for a circuit mode data communication at 7,2 Kb/s • TCH/4.8: trafic channel used for a circuit mode data communication at 4.8Kb/s • TCH/2.4: trafic channel used for a circuit mode data communication at 2.4 Kb/s In most cases, trafic channels are used point to point that is with selective mode For speech communications, trafic channels use time slots according to following table :

Communication type Mobile / mobile Duplex monosite half duplex monosite Duplex multisite halfduplex multisite Mobile / téléphone duplex Group (half duplex) Monosite multisite

Number of used time slots 2 1 2 2 1 1 1 par site

6.2.2. Control channels Control channels carry signalisations which are CCC (common control channels) which are with several forms : • MCCH (main control channel) there is one and only one MCCH per radio site – this channel is associated to only one and only one of the frequencies used on any radio site (the main channel). Generally, this channel is supported by time slots 1 of frames 1 up to 18. When a mobile comes to a radio site, first, it search the MCCH of this radio site • SCCH ( secondary control channel) it is a signaling channel used mobiles designated by the infrastructure. If an SCCH is used, a mobile arriving on a radio site request a registration on the MCCH and the infrastructure may sent it to the SCCH.

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SCCH are used when the trafic on the MCCH exceeds its capacity. Management of SCCH is performed by infrastructure – it is not normalized. There are mainly three different methods. • Fixed mode : the mobile fleets are allocated to MCCH and SCCH(s) according to a fixed table • Load regulation: the number of SCCH is fixed and the infrastructure manages allocations in order to get equal trafic on these channels • Dynamic regulation: if the trafic increases above a fixed level for MCCH and SCCH, infrastructure automatically open a new SCCH and closes it if the trafic decreases. • ASCCH (associated control channel) – it is a temporary signaling channel used to extend a MCCH or a SCCH. A SCCH must be on the same frequency as the channe lit extends. It is used in case of expected long transmission with a specific mobile : the exchange starts on the MCCH or SCCH and go on the ASCCH allocated by the infrastructure.

6.2.3. Non allocated channels Non allocated channels may be used to broadcast some informations.

6.2.4. physical channels allocation on time slots physical channels are mapped to time slots according to rules: only one MCCH per radio site, on the main channel • MCCH is always on time slot 1 • SCCH are always on the main channels • ASCCH must be on the same frequency as the channel they extend.

TIME SLOT 1

2

MCCH

carrier 1

3 SCCH

carrier 2

4

ASCCH

TCH

SITE A

TCH

carrier 3

TCH

carrier 4

MCCH

carrier 5

TCH

TCH

SSCCH

TCH

TCH

ASCCH

SITE B TCH

TCH

Allocation example at one moment.

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A radio site may have several main carriers with several MCCH – in that case, it is considered as multiple radio sites physically implemented at the same place.

carrier 1

MCCH

carrier 2

MCCH

SCCH

SCCH

TCH

SCCH

TCH

SITE C At the same place SITE D

6.3. LOGICAL CHANNELS Each logical channel carry specific information types and is transmitted over physical channels. Mapping of logical channels to physical channels is specified.

6.3.1. Different logical channels Following lists the logical channels • BCCH (broadcast common channel) – these channels carry general information to all surrounding mobiles ; they are only used in one way (infrastructure to mobiles) and there are two such channels : • BNCH (broadcast network channel) : broadcasted informations over this channel are : • Main channel frequency of the radio site ( supporting MCCH) • The number of SCCH in use • The maximum allowed transmit power from mobile in the cell (MAX_PW_CELL) • The minimum RF received level by mobile to request registration (Rx_LEVEL_MIN) • The encrytion identification • The descrition of time slots used in case of base station time sharing • the parameters used for ALOHA • the network identity (MCC, MNC) • the description of neighbour cells • the late entry function • BSCH (broadcast synchronisation channel) : infrastructure broadcasts informations needed to synchronise mobiles with : • The color code • The time slot, frame and multiframe number • The detailes about offered services by the radio site • Sharing mode parameters (in case of base stations time sharing) • Registration requested or not • Deregistration requested or not • Indication if the cell is a preferred one • Possibility of minimum mode • Roaming possibility • Handover possibility • Speech service available or not • Circuit mode data service available or not • CONP mode data available or not

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• SCLNP mode data available or not • Encryption • advanced link Floowing information are also broadcasted when requested by a mobile : • changement de cellule • level threholds for cell change (fast and slow) • hysteresis for cell change (fast and slow) • cell trafic load • TETRA calendar • Neighbour cells informations • • • • • •

Main frequencies and extension Rx level min Max power cell User class allowed Service details Information about time sharing

• LCH (linearisation channel) – these are not exactly signaling channels while they do not carry informations ; they correspond to time slots allocated by the infrastructure for mobile linearisation. During these time slots, mobiles may transmit for in order to get correction parameters for future linearisation. • SCH (signaling channel) : they are signaling channels from differnt types : • SCH/F bidirectional signaling channel using full time slots • SCH/HD downlink signaling packet using half time slots • SCH/HU uplink signaling packet using half time slots • AACH (access assigned channel) this channe lis only use downlink ; it describes allocation for the next time slots – if a time slot is allocated to ALOHA, it indicates ALOHA parameters to be used. This channel is separated into 2 sub channels: • FAACH (fast AACH) carried by frames 1 to 17 • SAACH (slow AACH) carried by frame 18 • STCH (stealing channel) this specific channe lis used to transmit signalisations during a communication – it is only used on allocated time slots and signaling data are mixed to speech data.

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6.3.2. Mapping logical channels into physical channels The mapping is given with the three following tables which indicate, for each of the three physical channels (trafic, control and non allocated), the logical channels which may be mapped. .

PHYSICAL TRAFIC CHANNEL frame

downlink

uplink

Bloc 1 1 to 17

18

frame 1 to18

trame 1 to 17

bloc 2

bloc 1

TCH STCH + TCH STCH + STCH SCH/F SCH/HD SCH/HD BSCH SCH/HD SCH/HD BNCH

bloc 2

TCH STCH + TCH STCH + STCH SCH/F SCH/HU SCH/HU CLCH SCH/HU

NON ALLOCATED PHYSICAL CHANNEL downlink uplink Bloc 1 bloc 2 bloc 1 SCH/HD SCH/HD CLCH BSCH BNCH

bloc 2

PHYSICAL CONTROL CHANNEL downlink uplink Bloc 1 bloc 2 bloc 1 bloc 2 SCH/F SCH/F SCH/HD SCH/HD SCH/HU SCH/HU CLCH SCH/HU

18

multiframe

timeslot frame 18

1

2

downlink bloc 1

(MT)mod4=1

downlink bloc 1

BNCH CLCH BSCH

downlink bloc 2 uplink t

4

BSCH

downlink bloc 2 uplink

(MT)mod4=2

3

BNCH CLCH

BSCH

downlink bloc 1

(MT)mod4=3

downlink bloc 2

BNCH

CLCH

uplink downlink bloc 1

(MT)mod4=4

downlink bloc 2

BSCH BNCH

uplink

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CLCH

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RAMDOM ACCESS PROTOCOL As for any radio system, there are two types of uplink trafic : • trafic invited by infrastructure • speech or circuit mode data trafic • acknowledges • response to an infrastructure request • trafic non invited by the infrastructure, that unsollicitated trafic which is decided by mobiles, Unsollicitated trafic needs more ressources than the same usefull trafic in case when it is sollicitated (rafly three time more) and one always attempts to reduce it ; as example : the case when a mobile decided to transmit a long data file to the infrastructure : instead of transmitting these data during an ‘opportunity’, the mobile transmits only the begining of the datas with a request for transmitting the remainder; the infrastructure take into account the request and polls the mobile to extract the missing data; the effect is that the unsollicitated trafic is reduced and the majority of the uplink trafic is carried with sollicitated mode. Obviously, there are internal threholds in the system and when trafic optimisation is critical, one must know these threholds. Unsollicitated trafic may interfer while several mobiles may transmit in the same time; unsollicitated trafic is strictly restricted during ‘opportunities’ which are time slot(s) preseved for this purpose. During such opportunity, several mobiles may transmit simultaneously and, in that case, one or several of these messages are lost. Such failures implie that the mobile will retry during other opportunities; if retry rules are defined according to a deterministic method, the same mobiles may interfer again and again. Only a ramdomized method may avoid such cumulative situation: it is the ALOHA process.

6.3.3. Access classes Four mobiles types may be defined for aloha process ; they are noted A,B,C & D Each of these classes have different rules and parameters for parameters and the infrastructure may define opportunity for one or several or all of these classes. That allows to give highest access priorities according to the fleets.

6.3.4. class indication by infrastructure ramdom acces are only with half time slots and the infrastructure declares opportunities from one of these possibilies : • access preserved for one mobile ( used for sollicitated trafic) – noted ‘X’ on the following diagram. • Or access reserved for type A mobiles • Or access reserved for type B mobiles • Or access reserved for type C mobiles • Or access reserved for type D mobiles

1 slot A B

A

C

D

X

A

A

X

X

B

D

C

Example of opportunities declared by infrastructure

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A

6.3.5. RANDOM ACCES PROCESS Any unsollicitated requests from mobiles are transmitted in half time slots reserved for the class corresponding to the mobiles. A mobile with a pending request see several of such opportunities during time and selects one of them to transmit. In order to minimize cumulative interferences, retries from a mobile are made after a delay measured in time slots ; this delay is ramdomized by selection (by the mobile) of a number in the range 1 up to n, n is a parameter indicated by the infrastructure ; this parameter is of the most importance : • If n is large, the interference probability decrease but the mean time to transmit the message from a mobile to the infrastructure is long. • If n is small, the mean time to transmit is shorter but the interference probability increases. This parameter is broadcasted by the infrastructure for the different mobile classes. Infrastructure may optimise global performance by evaluation of the unsollicitated trafic: • In case when this trafic is low, n is decreased • In case of high unsollicitated trafic, infrastructure broadcast a larger valur for n This process is used for retries; for the first attempt, there are two methods : • Direct acces for the first try and ramdom process for retries • Ramdom process for the first try and for retries Infrastructure decides the mode to be used for each of the 4 classes and broadcasts these informations with n. Following diagram shows the process for a class A mobile which received an information with allowed direct access for the first try and a ramdom parameter of 4 corresponding to selection of a number between 1 and 4. (opportunities for the class A mobiles are noted with grey color)

Req

Req

Time out

Request from user or API

Selection of one of these 4 opportunities First retry

First attempt

6.4. MULTISLOTS CHANNELS With preceeding modes, a mobile always uses one time slot per frame. With multislots a mobile may use several of the 4 time slots in a frame – that means multislots uses always the same carrier. The multislots may be used only if the mobile and the infrastructure offer such feature: • The mobile must be with fast switching (see ‘mobile operating mode) and with the capability to manage multislot trafic • The infrastructure must be able to allocate multislots for a mobile in the same frame and must be able to manage the corresponding trafic. It must be noted that the full multislot capacity (the four times slots of a carrier allocated to the same mobile) does offer an unbalanced downlink and uplink trafic capacity; duplex protocoles can’t be used and the global capacity may be drastically reduced.

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7. BASE STATIONS OPERATING MODES Base stations (BS) may be used according to different modes in order to fit to different conditions from the large coverage-low trafic density up to the urban low coverage-high trafic density.

7.1. NORMAL MODE This mode is the most used an is the reference one. Each radio site have a ‘main carrier’ witch supports the Main Control Channel on time slot 1; transmission of this signal is continuous. Times slots 2 up to 4 are dynamically allocated as trafic channels according to trafic requests (audio and data). In case when the MCCH may be overloaded with large expected uplink trafic for data transmission (mobile requesting long data uplink transmission), the BS may temporary allocate a trafic channel for this transmission; it is an ASCCH channel. At the end of the transmission, the ASCCH is automatically closed. When there is a circuit mode data transmissions request, the mobile and the infrastructure negociate the transfert rate and the quality of service for both party may have different capabilities. Time slot(s) for trafic channel are allocated by the infrastructure according to the agreed parameters. As example, if the mobile request multislot transmission, infrastructure may allocate several time slots if it is able to manage it and if other trafics allow such capacity reduction at this moment.

Base station in iddle state

MCCH

MCCH TCH1

TCH2

MCCH ASCCH TCH

MCCH

MCCH

TCH1

TCH 2x ....

TCH 3x ...

Base station with two trafic channels (audio or data circuit mode) Base station with temporary signaling extension

Base station with one trafic channe land a two slots data transmission channel Base station with one 3 time slots data transmission channel

MCCH carries registration trafic, signaling trafic, roaming and hand over trafic, broadcast trafic and SDS. In case when the MCCH trafic is too high, it is possible to use SCCH (secondary control channel(s)) to unload the MCCH. SCCH are with times slots 2 up to 4 and the SCCH allocation is dynamically managed by the BS. A time slot allocated to SCCH is not available for trafic channels.

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7.2. EXTENDED MODE Extended mode is used when there are several radio carriers on the same radio site. One of these carrier is declared as the main one and other are working in extended mode on different carriers. The main carrier supports the MCCH – any mobile coming into the radio site area try to register on this MCCH channel. During signalisation exchange between a mobile and the infrastructure, a trafic channel may be allocated as trafic channel on other carriers. Time slots of the non main carriers are as extension of the time slots of the main carrier.

Carrier 1

MCCH

SCCH

TCH

TCH 4x...

Carrier 2 Carrier 3

Radio site with 3 carriers and supporting - a 4 slots data communication - three audio communications

TCH

In the preceeding example, one notes that a full carrier with the 4 time slots may be allocated for a data transmission.

7.3. MINIMUM MODE Minimum mode may be used for single carrier radio site : In case when the 3 trafic channels are allocated and there is a request for another communication, the base station may temporary allocate the MCCH as a trafic channel. When the minimum mode is in use, the signaling capacity of the radio site is drastically reduced but null while some signaling capacity remain with the 18 frame (what was not with MPT system minimum mode). Le mode minimum permet d’affecter les 4 time slot d’une station de base devant normalement supporter le

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TCH

TCH

TCH

TCH

TCH

TCH

TCH

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Base station with 3 allocated trafic channe and entering the minimum mode for a 4th communication

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7.4. FREQUENCY SHARING MODE This mode is identical as this used with some FDMA systems. One (or several) carriers may be used on any radio site. At one moment, the shared frequency is used by one and only by one of the radio sites : allocation of this frequency is made by according to the trafic request over radio sites. Every radio site must be equipped with a minimum of one carrier (one main channel supporting the MCCH per radio site) and is equipped with a carrier equipment which may be used or in iddle state.

SITE A BS carrier 1 BS Carrier 4 SITE B

Sharing carrier 4 SITE C

BS Carrier 2 BS Carrier 4

BS Carrier 3 BS Carrier 4

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7.5. TIME SHARING MODE This mode may be implemented only with TDMA system as TETRA. Several radio sites use simultaneously the same carrier : • The MCCH is shared by all the radio sites : each of them use some prealocated time slots of the MCCH and no other base station may use it at the same time. • Trafic channels are dynamically allocated over radio sites according to the trafic requests. Rotating MCCH over radio site is not completly periodic and one of the radio site is with a privilege. Time sharing may be achieved over 2,4,6,8,12,18,24 or 36 base stations. Frame 18 is always preserved for the privileged base station. This mose is espacially suitable for large coverage and low trafic density networks. It allows to use only one carrier for the whole network and it may allocate imidiatly a part or all of the radio ressources to one base station. The capacity of the whole network is limitated to 3 time slots over the whole network.

= MCCH

BS1

BS2

BS3

BS1

TCH BS7

BS4

TCH BS7

BS5

TCH BS7

Trafic allocated over BS 7

Example of time sharing over 24 base stations with one audio communication. Time sharing mode may be extended by considering non interfering base station. As the frequency may be reused by far base station, it is possible to set groups of non interefering base stations and to rotate the allocation of the frequency over these groups. At one time, the freqency is used by all the base stations in the same group. By this mean, it is possible to get a nationwide coverage with only one carrier.

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7.6. OPERATION MODES SELECTION Choosing modes of operation of the base stations is part of the architectural choice of networks; a large number of factors determine these choices and any solution is often case. Nevertheless, two General settings are more decisive: traffic density to support the number of available channels.. of course, these parameters are linked and cannot make networks high-density traffic with a low number of channels; Conversely, it would be expensive (and yet easy) perform a network low-density traffic with many channels. After the diagram below shows different areas of application of the various possible solutions::

Channels number

Extended mode Frequency sharing Minimum mode

Time sharing Trafic density

Compatibility modes between them must be considered on a case by case; typically, minimum mode hardly co-exists with other modes of operation synchronous mode is mélangeable in the following cases: • time share: Yes for part time slot frequency-sharing: very little interest • mode extended: interest if only part of the BS extension are mounted in synchronous mode minimum: very little interest

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8. MOBILES OPERATION MODE

8.1. IDLE MODE The mobile is registered but don't transaction with infrastructure. In this mode, the mobile listening the MCCH or another signaling channel that it has been designated the mobile must also be able to monitor the neighboring cells.

8.2. SIGNALING and PACKET MODE 8.2.1. SIGNALING AND PACKET MODE ON A COMMON CHANNEL The mobile is in this mode when it is on channel MCCH (main common Control CHannel) and not involved in an audio or data communication

8.2.2. SIGNALING AND PACKET MODE ON A SECONDARY COMMON CHANNEL The mobile is in this mode when it has been redirected to a secondary signalling channel which is dedicated to him or reserved for a part of the MS Park which he is a member for some types of transmission by the BS (example: transmissions of data packet mode).

8.2.3. SIGNALING AND PACKET MODE ON AN ASSOCIATED CHANNEL The mobile goes into this mode when the BS has allocated a channel to a transaction mode circuit, and has no traffic exchange on this channel frames. A channel with exchanges of signalling in absence of traffic for frame numbers ranging from 1 to 17 Tetra frames circuit mode is called FACCH (Fast Associated Control CHannel) channel. A channel with frames signage for Tetra 18 frame number circuit mode is called channel SACCH (Slow Associated Control CHannel).

8.2.4. SIGNALING AND PACKET MODE HALF SLOT / FULL SLOT A mobile mode "Incoming packet" Half Slot makes signalling block on one of the two as timeslots uplink channel under the supervision of the BS. A mobile "Incoming packet" Full Slot mode emits signalling blocks on any of the uplink channel under the supervision of the BS timeslot. The Exchange diagram below shall be established with the following configuration: La BS is configured in MCCH only (normal mode) is the MS@a mobile mode "signalling and package" on the MCCH (he is a signaling message to transmit to the BS) are @b and @c mobile Idle state (they listen to the MCCH)

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Downlink ( BS => MS )

Uplink ( MS => BS )

SCH TX and ALOHA allocation on sub slot 1.1 and allocation of sub slot 1.2 for MS@b response

1

2

3.1 3 4.1 4.2

t

1.1

3

1.2

Random Access use by MS@a MS@b response

2.1

4

2.2

Response to MS@a and allocation slot 1 for MS@c response

1

3.1 3.2 4.1

2

4.2

MS@c response

1

3

2.1 2.2

4

3.1 1

3.2 4.1

2

4.2

3

4

8.3. TRAFIC MODE OPERATION 8.3.1. NORMAL TRAFIC MODE The BS has allocated to the mobile channel for a voice transaction or data circuit mode. Logical channel used must be the TCH channel for voice frames or data exchanged on Tetra 1 frames to 18 circuit mode. 18 Frames are exclusive to the beacon frames.

8.3.2. PREMPTIF TRAFIC MODE The mobile works the same way as a normal "traffic" mode. There besides the possibility to issue or receive on Tetra 1 frames to 17 normally dedicated to the traffic signal blocks (blocks traffic are replaced by signalling by the entity issuing blocks and are therefore lost). The logical channel associated with a block warning issued or received instead a block traffic is called STCH (CHannel STealing).

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BS(MCCH timeslot 1) Downlink ( TX ) MN4 FN1

FN2

FN3

FN4

FN5

FN6

FN7

FN8

FN9

FN10

FN11

FN12

FN13

FN14

FN15

FN16

FN17

FN18 MN5 FN1ETELM

1 2 3 4 1 2 3 4 1 2 3 4 1 2 3 4 1 2 3 4 1 2 3 4 1 2 3 4 1 2 3 4 1 2 3 4 1 2 3 4 1 2 3 4 1 2 3 4 1 2 3 4 1 2 3 4 1 2 3 4 1 2 3 4 1 2 3 4 1 2 3 4 1 2

Uplink ( RX )

Mode Traffic

MS monoslot Uplink ( TX )

ALOHA Demande de mise en com TCH duplex

1 1 2 2 FN1 Avis de traitement d'appel 3 3 4 4 1 1 2 2 Assignation de mise en com TCH FN2 3 3 Timeslot 2 downlink et uplink 4 4 1 1 Acquittement par préemtion STCH 2 2 + début d'émission TCH ( half slot ) FN3 3 3 Bloc TCH downlink ( Full slot ) 4 4 1 1 Bloc TCH uplink ( Full slot ) 2 2 FN4 3 3 Bloc TCH downlink ( Full slot ) 4 4 1 1 Bloc TCH uplink ( Full slot ) 2 2 FN5 3 3 4 4 1 1 : 2 2 FN6 3 3 4 4 : 1 1 2 2 FN7 3 : 3 4 4 1 1 2 2 FN8 3 3 TCH Half slot + préemption STCH Dw 4 4 1 1 TCH Half slot + preemtion STCH Up 2 2 FN9 3 3 TCH Full slot Dw 4 4 1 1 TCH Full slot Up 2 2 FN10 3 3 : 4 4 1 1 2 2 FN11 : 3 3 4 4 1 1 : 2 2 FN12 3 3 : 4 4 1 1 2 2 : FN13 3 3 4 4 : 1 1 2 2 FN14 3 3 : 4 4 1 1 2 2 : FN15 3 3 4 4 1 1 2 2 FN16 3 3 TCH Full slot Dw 4 4 1 1 TCH Full slot Up 2 2 FN17 3 3 Opportunité de signalisation ACCH 4 4 downlink 1 Opportunité de signalisation ACCH uplink 1 2 2 FN18 3 3 4 4 theoretical TETRA training copyright

MN4

FN1

FN2

FN3

FN4

FN5

FN6

FN7

FN8

FN9

FN10

FN11

FN12

FN13

FN14

FN15

FN16

FN17

FN18

Downlink ( RX ) 1 2 3 4 1 2 3 4 1 2 3 4 1 2 3 4 1 2 3 4 1 2 3 4 1 2 3 4 1 2 3 4 1 2 3 4 1 2 3 4 1 2 3 4 1 2 3 4 1 2 3 4 1 2 3 4 1 2 3 4 1 2 3 4 1 2 3 4 1 2 3 4 1 pageFN1 902

FN1

FN2

FN3

FN4

FN5

FN6

FN7

FN8

FN9

FN10

FN11

FN12

FN13

FN14

FN15

FN16

FN17

FN18 MN5

8.4. HALF / FULL DUPLEX OPERATION There are two types of mobile: Mobile does that in half duplex mobile operating in full-duplex... this distinction relates to the physical possibilities of hardware, they is not directly related to functional opportunities

8.4.1. HALF DUPLEX OPERATION There are two types of mobile: Mobile does that in half duplex mobile operating in full-duplex... this distinction relates to the physical possibilities of hardware, they is not directly related to functional opportunities:

Tx

Tx

Tx

Tx

UPLINK 1

2

3

4

1

2

3

4

1

Rx

2

3

4

1

Rx

2

3

4

1

2

Rx

DOWNLINK 1

2

3

4

1

2

3

4

1

2

3

4

3

Rx to Tx switching time

4

Tx to Rx switching time

With this arrangement, mobile half duplex are therefore capable of carrying out in full duplex, both signs for voice traffic exchanges or data circuit mode. It belongs to the infrastructure (who knows if a mobile is half or full-duplex) do not transmit data to a mobile during the slot where he is supposed to be broadcast and during the adjacent slot.

8.4.2. FULL DUPLEX MOBILE These mobile are able to make and receive simultaneously; previous restrictions do their shall not apply and they may issue on several contiguous slots.

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8.4.3. SLOW and FAST SWITCHING In the previous case, the mobile is switches emission receipt and vice versa, with a full slot between emission periods and periods of receipt time: is the slow switching. Some mobile are able to switch issue receipt and vice versa in a time virtually nil; they are then able to send and receive in adjacent slot time.

Tx

Tx

Tx

Rx Rx

8.4.4. CHANNEL CHANGE Another strong constraint standard imposes on mobile (half or full-duplex) you can change the frequency channel in less than a slot (11 milliseconds). This feature allows a mobile respond after a channel, change order in the same slot held that where he had received this order, account flows offset.

8.5. MULTISLOT OPERATION It is possible to 'group' several TETRA slot for a same chemistry between the infrasrtucture and a mobile time. This function allows you to have a transmission rate multiplied. Association of time slot can be on the same carrier. Multislot is possible in various conditions, according to mobile capabilities: Mobile with duplexor These mobiles integrates a real duplexor and separate Tx and Rx circuits; they may transmit and r eceive in the same time and there is no limitation to implement multislots. Mobiles with fast switching These mobiles may transmit and receive in consecutive time slots One may • Transmit over two time slots and receive over the two others • Transmit over one time slot and receive over three time slots with unbalanced duplex procedure • Transmit over three time slots and receivre over one time slot with unbalanced duplex procedure • Transmit and receive over up to four time slots with half duplex procedure Mobiles with slow switching These mobiles can’t offer multislots with duplex procedure Example:

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Tx

Tx

Rx

Tx

Rx

3 Time slot Multislot downlink with a false duplex mobile: there is more than one time slot available on the way back (uplink)

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8.6. ENERGY SAVING MODE This mode of operation enables the motive of asleep for a long time to save his power; it is based on an appointment to wake up: when he is in power saving mode, a mobile lulls n time slot and wakes up to receive a particular slot time. This mode of operation is for instance a MCCH or a SCCH mobile, it assumes that the mobile calendar remains synchronized during sleep. This mode of operation is negotiated between the mobile and infrastructure: the mobile makes a request to enter into this mode and infrastructure responds it with a group of power-saving, and a starting point; seven groups of economies modes are defined :

Economy group

Sleeping time

EG1 EG2 EG3 EG4 EG5

Sleeping frames number 1 2 5 8 17

EG6 EG7

71 359

4 seconds 20,5 seconds

57 millisec. 114 millisec. 285 millisec. 456 millisec. 1 second

remarks

corresponds to the minimum base stations mode Minimum mode divided by 4 Minimum mode divided by 20

When a mobile cell exchange energy saving mode, it can keep this economy, view with the same characteristics, provided that it ensures the proper alignment of its calendar with that of its new cell (sync time slot numbering of frames and multitrames); this alignment should be automated where all cells in a single LA must be synchronized. Low power mode is immediately stopped in the following cases: • mobile is returned on a different signaling channel • mobile receives a call to one any of its addresses (individual or group) or a transfer of data (advanced link) to start • the mobile wants to transmit a mobile signal changes Mobile returns to power saving mode in the following cases • it is on the MCCH • it has nothing more to transmit

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8.7. DIRECT MODE (DMO) Direct mode allows mobile devices to communicate with each other, without going through an infrastructure. Direct mode is not supported by all TETRA terminals. Some terminals have mode 'dual watch' for which they work mode DMO while continuing to listen to any signal from the infrastructure; they are thus able to answer a call transmitted by the infrastructure while they were placed in DMO mode. DMO uses one frequency (not a couple) with 25 KHz width

8.7.1. MAIN PRINCIPLE DMO mode uses similar exchanges as for TMP but one terminal acts as a base station; it is the master: it broadcast its own rhythm (especially its frame period) and all other terminals must synchronise to it. A DMO chanel may support up to 2 duplex communications (noted A and B) or 4 half duplex communications .

Tx A

Tx A

CHANEL A duplex

Rx A

Rx A Tx B

CHANEL B duplex

Tx A

Rx A

Tx B

Rx B

Tx B

Rx B

Rx B

8.7.2. DMO REPEATER The DMO repeaters to relay a communication on a time slot TETRA, between two terminals in communication DMO. In General, a DMO Repeater can operate only on a single communication both (repetition of a single time slot). This function is supported by some mobile.

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8.7.3. DMO / TMO GATEWAY TMO/DMO gateway to relay communication between TETRA (TMO mode) infrastructure and other mobile; typically, this is a mobile mounted on to a vehicle which relay to a portable scales of this mobile without sufficient coverage of infrastructure. This function is performed on a single communication both.

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9. NETWORKS ARCHITECTURE

9.1. RADIO ARCHITECTURE Previously, modes of operation of the BS mentioned depending on the density of traffic in a network, another important aspect concerns the distribution of BS, which is intimately linked to the previous appearance. 9.1.1. HIGH DENSITY TRAFIC NETWORK Many radio channels are necessary; it is spread. The question arises of whether it is better to have many sites of short-range or a lesser number of sites, each with many more BS and more far-reaching. A first approach of this aspect was effected under the single corner optimization "density" over the air on one channel, without taking into account all factors whose effects are listed below:

TETRA NETWORK WITH HIGH TRAFIC DENSITY

Hertzian density (spectrum optimisation) roaming Multisite open channel without synchronous operation Multisite open channel with synchronous operation Security in case of radio site failure capacity of significant mobilization of resources at a given point Antena coupling Fixed link costs Logistic cost Infrastructure cost

Large number of small sites

Small number of large radio sites

High by reusing frequencies with limited power cells Large number (disavantage) Very low efficiency

low Low number (advazntage) Low efficiency

efficient

efficient

high low

low high

no high high

Very difficult low low identical

There are also add "quantization" effect of to TETRA:, in case of strong global traffic density, it is almost unnecessary to decrease the size of the cells below that three or four communications by site, amount that corresponds to an elementary BS traffic density. Of course, for sites to multiple BS, they work in extended mode.

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9.1.2. THREE ANTENNAS COMPROMISE FOR GIGH DENSITY TRAFIC This provision is to bring together, in a single site, three sites normally infrastructure equipment almost independent and to connect them to a directive antenna opening on the third space. This solution has many advantages, and even if it is not always optimal, it is never far from these optima. GSM also deliberately systématisé this provision.

With an ideal sharing space on three antennas, these antennas gain increases the scope of the site of a factor in (3 and total number of infrastructure equipment is the same).

EQUAL AREAS

This three antennas provision offers the following features: • Spectrum efficiency: almost as optimal as the solution to many small sites • roaming: almost as interesting that large sites because the path of mobiles is rarely a circle centered on site • security site equipment failure: less bad than for large capacity radio sites • mobilization at a given point : means • antenna coupling: no if the total number of carriers remains less than three • open channel with synchronous: advantageous but without interest • open channel without synchronous: disadvantageous (characteristic without consequence for the GSM but important for TETRA)

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9.1.3. LOW DENSITY TRAFIC NETWORKS Low traffic density networks are quite frequent, especially in the area where it is important to ensure coverage throughout the territory - even in the most remote locations - even to what site equipment does routes no communication security during its entire life. Of course, for this type of network, it is not question to have a cellular approach and it will always seek to minimize the number of sites by choosing the best places (those providing maximum coverage). The problem therefore appears differently and is sought primarily to increase coverage of sites and then find a process to minimize the number of channels.Avec TETRA, l’augmentation des performances d’un site passe par le diversité réception pour améliorer la liaison montante et par l’augmentation de puissance rayonnée pour améliorer la liaison descendante. Found a model three - or four - antennas that shows strong similarity with the system to three antennas and three cases of high-density traffic; base stations devices is substantially identical: • three receivers: they are instance on three separate frequencies for the case of high density and fitted in diversity on the same frequency for the case of low traffic density • three transmitters (or the equivalent of three transmitters) instance on separate frequencies for the case of heavy traffic densities and coupled low densities of traffic on the same channel for the case. For these networks with low traffic density, TETRA architectures provide an essential characteristic by ad hoc radio resource mobilization capacity: indeed, having a BS in a place to offer capacity mobilization of 4 communications here need - analog or similar (TETRAPOLE,..) must be increased by four investment infrastructure to provide the same result. .

9.2. GENERAL ARCHITECTURE OF A TETRA NETWORK The TETRA standard does not architecture network or sub sets infrastructure: it gives a TETRA network interface specifications (air, interface with an external network interface...). The network architecture and the cut in as functional sets is the responsibility of the master of industrial.

Other TETRA networks

Air Interface

ISI

AI

RESEAU TETRA

MS

No standard inside

PEI

(mobile)

RTCP PABX

LI LS

Listening interface

Wired station

NORMALISE

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Inside a TETRA network, there are large functional equipments • Base stations • Base station controlers • switch • dispatching • administration • … There are no standard between these equipments.

Common architectures can be classified into three categories:: • Centralized with dedicated links: a central switch is connected to ase stations through structured links (dedicated links): it can be doubled for redundancy • Centralized with IP links: a central switch pilots bases stations through an IP networks – the switch may be doubled at any point of the IP network • architecture that have no switch. site radio site radio

site radio

site radio

site radio site radio

site radio

Sw

NMS

NMS

Sw

site radio

site radio

IP network

IP network

PABX PSTN

IP network

PABX PSTN

dispatch

gateway dispatch

serveur PABX PSTN

serveur dispatch

NMS

serveur

CENTRALISED 1 Switch liens Dedicated vers sites linksstructurés to radio sites

IP CENTRALISED > = 1 Switch IP links to radio sites

NON CENTRALIZED 0 Switch IP links to radio sites

9.2.1. NON CENTRALIZED NETWORKS (FULL IP) Radio sites are able to directly manage communications; they communicate through the IP network. Interfaces with other systems (PBX,..) are performed through gateways connected anywhere on the IP network. With this architecture, when a site collects information (enrollment, appeal,), he knows not priori where route, it passes therefore to all sites. Each site and receives all information submitted by all other sites and retains those concerning mobile are registered on this site. This architecture is very flexible and allows to trivialize any device. On the other hand, it imposes a limitation: indeed, incoming traffic on a site is directly linked to traffic total network, not only traffic actually handled by this site; therefore, this traffic increases very quickly, if the network believes, even if the number of mobile

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managed by site remains constant. Given the limited transmission links capacity to sites, and given the limited capacity of inbound traffic real-time processing, this type of network is in practice restricted to 8, exceptionally 16 sites .. Non concerned site radio

site radio

Non concerned site radio Incoming trafic is not related to the radio trafic managed on the site but related to the whole trafic of the network

site radio

IP network

9.2.2. CENTRALIZED NETWORKS WITH DEDICATED LINKS

These networks are made up of a central switch connected to the various radio through dedicated links (digital links to Nx64Kb/s in General) sites. This architecture is much more rigid than previous architecture but it is not a limitation to the size of the network; switch serves as the 'filter' and only transmit to a radio single traffic required to this site.

9.2.3. CENTRALIZED IP NETWORKS This architecture is obtained by replacing dedicated between switch and radio architecture centrally by links IP site links. Traffic between switch and radio site is selective for each site and there is no limitation of capacity linked to decentralized networks. With this provision, the switch can be placed anywhere on the IP network. Can even have multiple switch different address - radio site seeking to be 'logger' on a switch with a preferential order. That this provision of benefits, include: • Securing by redundancy: multiple switch are placed on the network; normally, radio sites located on the preferential switch - he's taking hand' network; failure of this switch, it stops responding and radio sites will stay on the second preferred site. Redundancy is automatically provided with the advantage to have the switch in remote places (which is not directly possible with dedicated link architecture to be plaçé to the side of the 'normal' switch redundancy switch). • Auto split network in several under independent networks in the event of IP network failure Normally, all traffic from a site is addressed to the current switch on the network, and if necessary is switch forwards traffic to one or more other sites.

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B site radio

site radio

site radio

A

serveur

dispatch

IP NETWORK

recorder

Mobile/dispatching communication PABX PSTN

SWITCH

A frequent provision is to route traffic between devices involved in a communication directly: switch manages communications and, at the beginning of each, it gives the address of the other each equipment or other equipment to the or which traffic should directly be dispatched during the entire communication.

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B site radio

site radio

site radio

A

serveur

dispatch

IP NETWORK

recorder

AT the beginning of the communication, the switch gives indication for direct routing between radio sites

PABX PSTN

SWITCH

This provision allows theoretically reduce total traffic on the IP network. In practice, this method is very effective for point-to-point communications.. but very bad for multipoint communications; in fact, instead of reducing traffic, it increase proportionately to the square of the number of devices concerned. Thus, in professional networks, there are many group involving multiple sites and/or communications must be saved and/or communications for which one or more items dispatching should be listening in third party communications.

9.2.4. REDUNDANCY WITH CENTRALIZED NETWORKS Looking at where full redundancy with duplicate units here. In the case of a structured links network, several SW may be used in redundancy on the network with or without switching links, depending on the organization network. In link, the SW can be placed at any location on the network; a single SW is master on the network. The system works as follows: - Each SW IP network broadcasts a message indicating priority level living. Each BS and each device connected to the network selects the active SW on the network and with the highest priority each of these registers on the SW equipment that it has selected. Thus, to make a master SW, simply assign a higher priority. This arrangement allows you to build networks that can be split in as independent networks in the case of network failure IP; these networks are 'autocicatrisant' where they replenished automatically of IP network reconnection

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BS BS BS

BS

BS

BS

Links switching

SW A

SW A

SW B

STAR NETWORK

SW B

DAISY CHAIN NETWORK No requirement for links switching

REDUNDANCY WITH DEDICATED LINKS

BS

BS

BS BS

IP network other equipements SW A SW B

SW A broadcasts an information indicating it has the highest priority. Equipments receiving informations from SW A and SW B register to SWA.

REDUNDANCY WITH IP LINKS

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BS

BS

BS BS

IP network Other equipments SW A SW B

In case when IP network is spreaded into two parts, the network automatically is divided into two independant TETRA networks, each of them controlled by a SW.

Split and healing with IP links

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9.3. SOFTWARE ARCHITECTURE Software architecture provides different levels of processing and distribution of tasks. This architecture is frozen by the standard, detailed rules for the implementation of this architecture are completely free.

9.3.1. LEVELS STACK The diagram on the following page shows this architecture and stacking features. There are the first three levels: for an OSI pyramid with : • Physical layer with modiulation, filtering, ramping,.. functions • Layer 2 divided into two sub layers • MAC layer – with two parts : • lower MAC with coding, scrambling, interleaving, encryption,.. • upper MAC which mainly manages time slot allocations • lower LLC layer including basib link and advanced link • layer 3 divided into two sub layers : • lower layer 3 inclusding data transfer management, registration , internal ressources management and configuration information broadcasting. • Upper layer 3 including mobility management and specific protocols to external interfaces (circuit or packet oriented). Between these layers, there are the following software interfaces:: • Physical interface dic=vided into two sub interface : • TP_SAP which corresponds to data interface • TPC_SAP which corresponds to control interface (frequency, power,..) • Interface between layer 2 and layer 3 with 3 junctions : • A junction dedicated to signaling with mobiles • A junction dedicated to information broadcast • A control junction • Interface to external systems via different junctions Two other important interfaces are : • « U-PLANE » junction which corresponds to audio compressed signals • « C-PLANE » junction which corresponds to any signaling

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9.3.2. MAPPING FUNCTION TO PHYSICAL EQUIPMENTS As already mentioned, functions in different devices implementation choice is completely free; the following diagram gives an idea of the different possible options:

TNX

C_PLANE

TLX..

U_PLANE

TMX....

TMV..

TP..

antenna SW

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9.4. FIXED LINKS ARCHITECTURE Except in the case of automatic relay networks, infrastructure equipment are usually interrelated by digital links (for analog transmission media presence, should place all necessary to return to the previous case modem); there are two types of links: • 'Structured' links for which data are arranged to the queue and whose good throughput is equal to the on line data rate • 'Unstructured' links (IP type) in which data are transmitted as they arise and which must be with data rate much more than this strictly required Of course, when a duct in a limited throughput (case of the air interface), should be to structured link; however, when a duct is not limited in throughput, it processing equipment prefer to use an informal mode for exchanging messages. Links between BS or BSC and switch is in the air interface extension are naturally willing to be treated rather structured while links between switch and dispatching or data processing centre will be instead of unstructured type. This arrangement is not rigid, but often is an arrangement of land availability because radio sites placed in point above are not equipped with high-speed lines (links are therefore created - or leased with the lowest rates possible) while central equipment (switch, dispatching, processing center) often enjoy an environment of high-speed networks. Dedicated link Non dedicated link (IP,UDP) Radio site Radio site

Radio site

Network mangement

PABX

IP network

Radio site

Switch

IP network

API

PABX

API dispatch dispatch

Full IP

Mixed : dedicated links to base stations and IP for other equipments

Any arrangement is therefore permitted, provided that it complies with a few basic rules, in particular that do not pass in structured (IP) on a low flow - duct so if average throughput required between two devices is substantially equal to the capacity of the link, the IP transmission organization is to outlaw.

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9.4.1. DATA RATE The throughput should be is function junction deported by this link. Reported to the pyramid of treatments, we see that this rate is 36 KB/s at the TP junction; roughly there is a minimum of next to junctions TMX, TLX and this rate rises gently for superior junctions. If the string includes the voice decompressors, this rate rises dramatically (256 Kbps + signaling) vocodeur 300

rate Kb/s Rate for 4 channels ( 1 TETRA channe)

36

TP

TMV

TMX

TLX + U_PLANE

C_PLANE + U_PLANE

C_PLANE + MIC

Lower throughput point must be chosen preferentially to deal with the longer lines and many - that is to say either rows SW - BS or SW - BSC lines. The above mentioned rates are average rates should take account of the fact that Crete throughput may be markedly higher based on multiplexing used to route 4 routes of a BS; indeed, the more delicate constraint concerns long signs towards data transmission: anticipated longer packets are 2 Kbytes; two cases are then to consider : • either signage uses a fixed time manner with the voice multiplexed duct, therefore uses a rate well below the speed of the link: in this case, there is no discomfort to the voice but the packet transmission is very long - unnecessarily long if there's no voice communication. Example: 64 Kbps link is divided into 4 x 8 Kbps for the voice and 32 Kbps for signalling: package provides 250 milliseconds for transmission • Either signage uses the full flow of the link and, in this case, the voice might be greatly embarrassed. Example: 64 Kbps link is used in full flow; the packet does more than 125 milliseconds for passed - but, during this time, 2400 bit voice will have been lost or need to be buffered. • Either link uses a duct structured with a statistical multiplexing giving priority to the voice and, in this case, none of the previous two disadvantages is fear and can even reduce the throughput of the link • Either link is informal and, in this case the link rate should be considerably higher than the average flow to allow routing of long data along with the voice.

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9.4.2. MULTIPLEX OF SEVERAL BASE STATION ON A DEDICATED LINK When used with BSC, they are number one by radio site and control, each of them, all these BS on their site. Traffic on the link between a BSC and switch to which it is attached is substantially equivalent to the sum of the BS from trades; indeed, only inter BS on the same site traffic would be to subtract traffic between this site and switch - but the link must be sized for the highest traffic, i.e. for traffic type PABX / mobile, and the rule will apply (on the other hand, it is often desirable to pass traffic on the switch, monosite do for listening purposes). The sizing of the link between a site and switch to which it is attached is therefore independent of the presence of a BSC. Functionally, this link is the equivalent of a multiplex each BS traffic and architecture is a star. On certain sections, this multiplex can resume traffic to another site. Hardware architecture is a string but functional architecture is a star.

Site A BS

SWITCH

BS

Site B

BS

BS

BS

BS

Ex : 2Mb/s

Physical architecture : daisy chain

Site A BS

BS

Site B

BS

BS

BS

BS

SWITCH

Functional architecture : star

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9.4.3. DEDICATED LINKS SECURISATION There are two types of secure connections: • security by a permanent • security emergency link failover Securing by failover proceeds by binding the link rescue (manual or automatic) switching. Failover causes the connection with all the effects that this may cause more or less long outage (cut communication,...). However, this solution may be very interesting in the following cases:le lien principal est cher à l’investissement et peu cher à l’exploitation • link main is reliable • emergency link is inexpensive investment and expensive operation. In these circumstances, binding is quiesced little frequently a dear link; the more typical case is a wireless beam rescued by digital dial (type ISDN).

Permanent security is to have two links in parallel continuous. In this case, information are issued simultaneously on the two links at both ends and received one of the two links: there is a function 'And' l ' issue and a function "Or" delivery.

AND

OR

Link A

Extrémity 1

Extrémity 2 AND

OR Link B

9.4.4. RING NETWORK Ring networks consist of a rebouclée Garland; this Loopback provides redundancy allowing overcome the failure of any of the links in the link of the Garland. Functionally, the system reverts to have a star with each virtual link BS/Switch by almost opposite paths security architecture.

Site 1

Site 2

OR

AND

BS

SWITCH AND

OR

Site 4

This architecture is very specific problems regarding the synchronization of sites by links

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9.5. CLOCK ARCHITECTURE - SYNCHRONISATION 9.5.1. TETRA CLOCKS STACK The following table shows the hierarchy of clocks used in TETRA system; it is particularly interesting to evaluate opportunities for synchronization with other systems using different signals.

SIGNAL binary symbol time slot frame multiframe

frequency 36 K 18 K 70,5 Hz 17,64 Hz 0,98 Hz

period 27 microsec. 55,55 microsec. 14,2 millisec. 56,7 millisec 1,02 sec..

division

Total division

2 255 4 18

2 510 2040 36720

hyperframe

0,016 Hz

61,2 seconds

60

2.203.200

remarks

périod = 17 x 480 x 125 microsec.

Related to 8KHz PCM clock

9.5.2. SYNCHRONISATION REQUIREMENTS The standard application required that all sub sets a TETRA network infrastructure work synchronously. This requirement is in fact not always necessary in all cases and the need for synchronization depends on the use and configuration of the network. The study of these requirements can understand and apprehend any (and very common) clock problems on the ground. There are three types of synchronization: • radio synchronization flow information • carriers synchronization (sync low-level) • synchronization of calendars (synchro high-level) The following table gives the requirements for each type of synchronization on the air interface according to different types of use

BS with synchronous transmission No BS connection trafic TCH/F Between TCH/x BS ou signaling SW/BS hand-over

Carriers synchronisation √

Low level synchronisation √

High level synchronisation √

√ √

√

√

√

.. Thus, a synchronization default may have no effect in some contexts operating

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9.5.3. SYNCHRONISATION VECTORS TETRA - network equipment BS, BSC and SW should be synchronized between them; to do this, they must hold their local clock to an external signal that can come either from a link that their are connected, or a similar external reference for all such as GPS however clock, all synchronizations are not possible and the following table shows the most common opportunities:

Radio carriers synchronisation oui oui oui non

GPS clock V11 link E1 link IP link

Data rate synchronisation difficile oui oui non

Calendars synchronisation oui oui oui difficile

9.5.4. SYNCHRONISATION THROUGH DEDICATED LINK Links connect either switch between them, the switch and the BS or BSC; they contribute actively to the synchronization process. There are two types of structured links: • links which impose their clocks – (typical V11 link) • the links are transparent to clocks – most of E1 links (but not any of them)

H1 B1 H2 B2

H1 B1

2 Mb/s G703

H2 B2

Transparent clocks

H B1 H B2

V11/X24 – imposed clocks

B1 H B2

These two types of links are also found using modem on analog line - must be particularly wary of 'imposed clock' mode because, in this case, it is one of the two modem driver link - its accuracy is largely insufficient local clock. It is possible to make a transparent link from a link on which clock is imposed by the operator by a specific technique to as use potential throughput and regenerate each end receipt, the clock as it is issued at the other end (type G703) clocks

.

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Ho H < Ho

H reconstituée

B

B .... only one transmission way is drawn

.... This technique remains fragile and often leads to the phase jitter whose effects can be devastating, especially for synchronizing radio carriers. ... in total, there are three types of links (link transparent to clocks, link to imposed clocks and link with regenerated clocks) for digital interfaces between TETRA subsets.

9.5.4.1.NON SYNCHRONISATION LINK EFFECT Either two digital links to close but not synchronized clocks:

H1 B

H2 FIFO

B’

Interconnection equipment may have a memory buffer on the binary path (memory type FIFO). This memory allows you to collect related variations debit clocks H1 and H2; however, the problem remains around if the average flow of these clocks is not strictly identical: at a time, it will miss a bit, either have a bit too. For example, binary transmission will corrupt exactly equal to the offset average of H1 and H2 clocks pace, regardless of the length of the FIFO. In some cases, this deterioration has no significance. It is for the transmission of signs which are not permanent, and the issue is directly rhythmed by the clock output. In the case of permanent binary transmission (data circuit-based transmission) should therefore errors at a rate exactly equal to the average relative offset of clocks. In the case of the voice transmission, an average relative offset also produces errors that result in any noises more or less important; however, it is possible to significantly reduce these effects by the implementation of justificatio techniquesn : • positive justification: there is a sample speech too: it deletes and, possibly, on smooth adjacent samples; • negative justification, it creates a further sample interpolating with adjacent samples. This technique allows you to connect digital telephone connections arriving so non-synchronized on a TETRA network; however, the operation is not guaranteed for transmission of data or signage.

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9.5.4.2.DEDICATED LINKS SYNCHRONISATION The previous considerations show that it is necessary to synchronize all links a TETRA network between them: • either by using links already synchronized between them • either by use of links to higher throughput and clock recovery Thus, a single link V11 is used in a network, if him to drive across the network. If two links transfix are used on a network, they must be synchronized between them. Typically, wireline operators "snap" their transfix links to a very stable and very precise national clock; in this case, all transfix links are synchronized between them and any can be referenced; attention however to transfix links "of campaign" carried out by the commissioning of two modem to broadband on an analog line, without any connection with the national network: this type of line may be satisfactory for simple wholly inadequate but it needs for a telecommunication network. Links in G703 are usually no problem in fact render to an end the clock it provides them to another. Particular attention must still be increased use of certain types of top-level multiplexing.

The following diagram gives an example of network with all its links and its vectors synchronization:

SW 1

Site B

V11

Site A

microwave 2Mb/s

Href E1 2Mb/s SW 2 V11 Site C Href

9.5.5. GPS SYNCHRONISATION A GPS receiver to sattellite (s), is a fixed rate of 1 second with the order of 100-nanosecond precision provides; it provides also a calendar (usually in the form of a series - NMEA protocol or owner message) information giving GMT time. This information is sufficient to ensure the synchronization of TETRA sites.

9.5.5.1.LOW LEVEL SYNCHRONISATION Marking the second signal is directly usable to enslave a TETRA base station reference oscillator; this signal accuracy being 10 - 7 (100 nanoseconds per second) is compatible with tolerance sought on the radio bearer. The main problem occurs when the GPS receiver is more satellites (what happens regularly to anywhere on the globe, even if the antenna is very clear) - coverage should be while the drift of the oscillator site remains within the limits during the duration of a 'hole' coverage (this time may be more than a few minutes).

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9.5.5.2.HIGH LEVEL SYNCHRONISATION

GPS calendar is rythmé to 1 second, while the TETRA calendar is rythmé 1,02 seconds - which leads to a few difficulties. The period of coincidence weft / second is 17 seconds corresponding to 300 frames however, a resynchonisation frames is not sufficient to the extent where TETRA full calendar maintained by mobile and infrastructure account until the hypertrame A hypertrame includes 60 x 18 = 1.080 frames Coincidence hypertrame/second period is of 306 seconds (5 minutes 06 seconds) or 50 hypertrames equivalent to 300 multitrames or 5,400 frames. Resynchronization GPS cannot intervene at best only every 5 minutes.

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9.6. DATA BASE ARCHITECTURE The structure and the functions associated with databases will be separate presentations (see chapters), what matters here is the General description, location of the databases and trade between these ba flows

9.6.1. DATA BASE CONTENT The master database on a network is that of subscribers of the network (fixed, mobile terminals, dispatching,..). This database includes the following: • Terminal identities • Personnal identity • Identity of assignd and atteched groups • Terminal characteristics • simplex/duplex • mono/multi slot • mono/multi carriers • audio equipment • end to end encryption • circuit mode data • SCLNP data • CONP data • Air interface encryption • linéarisation with carrier change • multi channel TETRA • advanced link • minimum mode • signaling over specific carrier • version of TETRA standard • .. • rights allowed to the terminal • allowed area • call types and called parties allowed • allowed services and parameters of these services • ... • Messages for the terminal • Audio messages • Data messages • Current status of the terminal • Network and Radio site localisation • Current status (idle, communication,..) • .....

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The identities of the terminal include its own identity, its membership to different groups, its assigned identity... The identities of the terminal include its own identity, its membership to different groups, its assigned identity... by the operator but declared by the terminal him even at the time of its inclusion. The rights of the terminal cover areas where he can make and receive calls, the call type it can send or receive, correspondents types with which he can talk... The courier terminal cover its voice and its 'data' message. The terminal State covers its geographical location (location on a site) and its State power (communication, pending,...) The TETRA standard contains no indication on the establishment of these databases. A given mobile may be listed that in one of the databases to the same network (outside); this database is called attachment for this terminal database

9.6.2. VISITOR AND FOREIGN MOBILES The standard does not directly difference between mobile visitor and mobile foreign; normally : • a visitor mobile is a mobile managed by the same operator but that changes network relative to its original - or as network network according to the organisation of the operator. • a foreign mobile is a mobile managed by another operator. Standard speaks of mobile visitor: a visitor mobile is a mobile not listed in the database of the network or the sub network when it flies on this network or this under network; this introduction does that by going to view the database where is listed mobile; thus, standard makes no distinction depending on the need to fetch these data in the same structure (same operator, directly interconnected networks) or in another structure . This difference appears as an operator uses a centralized database or distributed databases.

9.6.3. VISITORS AND FOREIGN MOBILE DATA BASE When a mobile fits in an area where it is unknown, the system will search for information about this Subscriber in a place, in the same network or another network and recreates a temporary local database for this mobile - is the visitor (or foreign) database. This temporary database will be destroyed when the mobile permanently leaves the area. During all the time where the mobile is visitor in an area, its visitor database will be updated; it is also important that its original database is kept aware of some changes; there is therefore exchanges between the original database and the database temporary visitor, these exchanges are shown schematically below:

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VDB VISITORS DATA BASE HDB HOME DATA BASE

Transmitted by mobile

From operator

Transmitted by mobile

caracteristics identities

caracteristics

rights

identities rights

status

messages status

TRAFIC

Several arrangements can simplify (or complicate) mechanisms regarding visitor databases or foreign: • to priori confidence: the network receive a visitor or a foreigner agrees immediately if it meets certain criteria, without waiting to have the database attach this mobile response elements • authentication: this mechanism (described in the following paragraphs) can be applied to mobile to mobile visitors residents; it allows you to verify the exact identity of mobile. • default rights: rights allocated to mobile visitors - and foreign - let alone are not necessarily the same as those in its original network

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9.6.4. DATA BASE LOCATION As already mentioned, the standard leaves freedom of establishment of databases; there are two main degrees of freedom in the choice: • the presence of a parent database unique on a network or multiple distributed databases • the ability to recreate locally, at BSC or BS girls database to reduce access time and to ensure a gradient loses the link mode. For a network with a single switch, the mother database is unique and directly connected to the switch; only freedom is in use or not of daughter databases in the BS or BSC. The presence of girls databases does not really decrease volume traded on the link between the SW supporting the mother database, and the BSC or the BS that supports the daughter database; indeed: • without the daughter database, any relative to the mobile transaction involves an inquiry and/or an update of the mother database • with the daugtherl, the mother DB database must be updated with any transaction regarding the mobile. Furthermore, with fall nack mode, the presence of a local daugther database is interesting that during the moments following link; for some time beyond cut, daughter database often becomes very lapse. Finally, the presence of a daughter database does not solve the problem of visitors in fall back mode (and then they will be very many), should therefore adopt a strategy for these mobile (of type to priori trust). Therefore, the presence of a daughter database is really interesting by gains access times it can get. For multiswitch networks, it is possible only with a single database system connected to a switch determined; in this case, reducing access time, it is almost necessary daughter databases in each switch, either in each BSC yet; this kind of provision is therefore unusable for large networks. The alternative is to have a database switch, and attach each mobile subscriber to one and only one of these databases.

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9.7. NETWORKS WITHOUT LINKS AND SWITCH Base stations may be available in version 'automatic relay' no nécéssitant or switch links; they route of mobile traffic / mobile or mobile / basic radio. They have the following characteristics: • No need for synchronisation • Presence of an internal database (Elementary) These relays can be extended with special radio which can offer dispatching function and can relay telephone communications ; this last feature is made possible by establishing duplex link with the mobile - that is to say that they occupy 2 channels (2 time slot) for a duplex communication with mobile while one channel is sufficient for the same communication phone in case of a network with link and switch.

RTCP PEI

data

TETRA radio terminal

Automatic TETRA relay

MOBILE

FIXED radio dispatching

Fixed radio base is made up around a standard radio equipped standard junction PEI terminal. Complete networking from several automatic relay is possible, but such networks are always performance significantly lower than those obtained with the same number of base stations connected to a switch. In General, these networks use a separate by relay bearer (while in analog, it is common to use several relay on the same frequency); possible utilization of time between the relay share mode however would circumvent this restriction (at the cost of technical stunts not envisaged today). In the case of using a separate carrier by relay networks, it is necessary to have basic radio in relays, including a terminal by carrier: it is not possible to have a single orderable Terminal frequency because it must be able to work simultaneously on multiple frequencies. Radio databases become real capable to routethe communication and maintain their own databases switch.

RTCP

PEI

data PEI

PEI

TETRA radio terminal TETRA radio terminal

Antenna coupling

TETRA radio terminal

dispatching

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9.8. RADIO SITE FALL BACK MODE When TETRA site, normally connected to a switch is isolated due to cut the link, it may enter fall back mode to continue to route local traffic. It is necessary however to use this capability with great care - see delete in some cases, the cure is worse than the disease. N isolated radio site may offer following services : • Accept or refuse mobile registration • Call between mobiles and/or groups under its coverage area • Messages between mobiles and/or groups under its coverage area • … If the rest of the network is still operational, mobile have interest to seek to register on fully operational rather than on the sites in fall back mode in order to take benefit from the whole offered services – this is specially sensitive for communication with between mobiles and dispatch stations when they are out of the radio site coverage In order to prevent such situation, radio site in fall back mode must broadcast an information indicating the fall back mode to mobiles able to register on another radio site. Some terminals do not process this information. The second problem with fall back mode occurs at the time of the reconnection of the site on his switch and update the database at this time. Thus, in the case of a mobile registered on a radio site in fall back mode and coming back to a fully operative radio site, the local database of the site in fall back mode have an information about the mobile registration which is not the same as in the general network data base. A way to avhas the information that mobile is responsible then only the General database has switch contrary information (oid such a problem is to perform registration request over the whole mobile fleet after any fall back mode.

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10. DISPATCHING

10.1. DEFINITION and ROLE of a DISPATCHING A dispatch is a set of fixed operator positions managing communications with the mobile fleets. The dispatching may: • Receive calls from mobiles • issuing calls to a mobile or mobile group • listen / intercept calls • allow calls • merge several communications • manage ambiance listening • assign dynamic groups • …. Own dispatch functions cover all respect to the distribution tasks between operators dispatch positions; these functions are not seen from the network attached to the dispatching,When a mobile calls its dispatching, he does not know the operator positions to be reached In some simple networks, dispatching is integrated in the transmission network; in more complex cases, and for a better trivialization equipment interfaces and devices, dispatching is functionally and physically separated from th transmission network..

10.2. CENTRALISED AND NON CENTRALIZED ARCHITECTURE The oldest of the dispatching architecture includes a central switch connected to any dispatch station in a star way. This unit provides the distribution of tasks between operators,; operators workstations have little autonomy and their rights are directed from the control unit (distinction between station controller and Headquarters,..). The networking architecture have no central switch and possibilities of each dispatch station is defined by a set of soft parameters and by some access control peocess. Signaling and voice are transmitted on the LAN, generally • Voice is transmitted with UDP • Signaling is transmitted with TCP/IP •

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Star architcture

Radio SWITCH

Dispatching switch

Non centralized architecture

Radio SWITCH

LAN

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Non centralized architecture is with a lot of advantages : • Equipments are standard (with reduced price) • Configuration is easily changed • Dispatch station may be remotely used by using standard LAN technologies • MMI (man machine interface) may be optimized to merge communication functions ith other applications (example of AVL display and the possibility to perform a call by mobile designation on the map) • … Tasks distribution between dispatch stations is made by a unique software loaded into each dispatch station. Specialisation is obtained by using passwords ; in some case, rights may be transmitted from one dispatch station to another. Dispatch stations may manage other applications in the same time and the software architecture is as follow :

IP

VOIP Audio Interface

Sound board

MICRO, LS

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API Application Application

TETRA signaling Signaling Interface

MMI

SCREEN, KEYBOARD, MOUSE,…,…

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10.3. VOICE OVER IP and TETRA There are many methods of transmission of voice over IP; each of these methods must choose formats Exchange audio blocks between two possibilities: • Voice transmitted with the TETRA compressed form • Voice transitted with ‘linear’ form as PCM .. other format are avoided in order to avoid to use several different CODEC. Transmission with compressed TETRA form has the advantage of reducing the size of exchanges on the local network; however, it implies the presence of a TETRA vocoder in each workstation. Transmission with uncompressed form is much more gourmet in exchanges on the local network, however, it is easiest to implement and offer greater opportunities for both conferences - in fact, these methods are implemented by summons devices and broadcast which necessarily working on not compressed formats. Unlike other types of data transmission over LAN, transmission of voice over IP does not suffer delays or significant loss rate, under penalty of a rapid degradation of the intelligibility of the signal; accordingly and figure (transmission as compressed or uncompressed) in all cases, the voice should be a priority, which can be obtained by one or more of the following methods: • Oversizing the LAN • Limitation for long data exchanges over the same LAN as used by audio • Use of the preserve bandwith technology • Use of a separate LAN for audio

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11. EXCHANGES OVER OTHER INTERFACES

11.1. ISI INTERFACE The ISI (Inter System Interface) interface defines the connection between two TETRA networks; the scope of this interface is very broad as it can apply between any communication network. ISI interface is with 3 levels • Level 1 defines services independently from any implementation • Level 2 defines functional possibilities and exchanges flows • Level 3 defines signaling protocol

11.1.1. ISI OFFERED SERVICES 11.1.1.1.MOBILES ROAMING In General, a mobile attached to a particular SW (home SW) and registered as a visitor to another (previous visited SW) switch to change the cell and register on a third (visited SW) SW.)

Home SW HDB

ISI

ISI

Previous visited SW aVDB

New visited SW nVDB

When a mobile roams from one network to another, following exchanges are transmitted over ISI : • Registration request from the new visited SW to the home SW (exactly the home data base) • Response from the home data base with indication about: • Allowed services for this mobile • Authentification parameters • Attached ans assigned groups • Upgrade of the home data base localisation indication • Cancel the registration on the previous visited SW

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11.1.1.2.INDIVIDUAL AND GROUP COMMUNICATIONS With TETRA, group communications are automatically supported by base stations where at least one mobile of the group is registered. The group is declared in a network (home network for the group) - the switch of this ntwork manages the group communication – even if there are no more mobiles of this group under its control (all mobiles have migrated). Thus, there are three SW types: • The SW manging the communication (home SW fotr the group) • The SW initiating the communication and involved in this communocation • The SW(s) involved in the communication without being the initiator

Home SW Manages the communication ISI Initiator SW (and involved)

ISI ISI ISI

Involved SW

Involved SW Involved SW

For individual calls, there are only two involved SW

11.1.2. ISI ADRESS AND ROUTING PROCESSI Any message tranmitted over an ISI interface must have a SW as the destination adress • Messages sent to a home SW are routed by any transit SW according to a predefined routing table • Messages sent to a visited SW different from the home SW have an adress wich is the location of the mobile in its home data base.

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11.2. LINE INTERFACE This interface is defined in the TETRA standard; it uses dedicated wired link between SW and dispatch station. Unfortunatly, most of the dispatch stations are now connected with IP and the line interface is not used.

11.3. PABX – PSTN INTERFACE These interfaces are the telephone standard ones (S0,T0,T2,..) Call establishment from mobile to telephone (PABX or PSTN) and call establishement from PABX to mobile is without any difficulty. In the case of PSTN to mobile, it could be more complex with two different cases. • PSTN connection is achieved either directly or through a PABX and direct arrival selection is available: one public phone number is allocated for any of the TETRA mobiles. Call establishement is direct. • PSTN connection is achieved through a PABX but there is no direct arrival selection available: in that case, telephone to mobile calls are with two steps: first step, the PABX is called with a public phone number over the PSTN and when the connection is established, the number of the called mobile is dialed.

11.4. DATA TRANSMISSION INTERFACES Several data interfaces are defined by the TETRA standard. However, all these interfaces are with dedicated link between the SW and the data serveur. Now, one prefer to use IP technologies and all these interfacs are not in use.

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11.5. PEI INTERFACE 11.5.1. GENERAL PRESENTATION The PEI interface (Peripheral Equipment Interface) is used to connect radio mobiles to on board application(s). throught this interface one may : • Send and receive data messages – SDS and/or packet data • Send and receive data in circuit mode • Transmit, receive and manage voice calls • Access to general information from mobile (example : radio status, registration status, RSSI,..) The main goals with PEI are • To offer a standard on board interface between any mobile and any application. • To minimize the communication functions to be achieved by the API • To be compatible with most of other equivalent systems (GSM, mobitex,..) Physical interface is a serial one, similar to V24 and V28 and without trafic control (hardware as RTS/CTS – or software as Xon/Xoff). It is with 3 wires only. Three protocol types are supported :

TETRA PEI

AT Commands • Dcircuit mode • SDS • Radio configuration • radio informations

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Packet data • IP version 4 • IP version 6 • ISO CLNS • X 25

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Remote control • Audio communication control • SDS • Radio configuration • Radio informations • Supplementary services • Circuit mode data transmission

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11.5.2. PHYSICAL INTERFACE The port is a 3 wires with a 9 or 25 connector sub-D type or with a RJ11/RJ45.one

Circuit number

103 102 104 101

signal

Tx data masse Rx data earth (if available)

abréviation

TxD SG RxD PG

sub-D 9 25 4 points points pôles 3 2 1 5 7 2 2 3 3 screen screen +1

RJ11/RJ45 6 pôles 2 3 4

8 pôles 3 4 5

10 pôles 4 5 6

As default set up, the format for transmission is asynchronous, 8 bit, 1 start, 1 stop, LSB first. The data rate could be up to 64 Kb/s When power on, data rate must be 9600 b/s. rate change may be programmed from this basis or an automatic rate detector may be used.

11.5.3. COMMAND and DATA MODE At any given time, the junction between the mobile and the terminal is either in command mode, or in data mode: • Command mode: the mobile transmits and receives commands. Two sub modes are distinguished according to if the ris or not an on going communication with the mobile. • Data mode : the mobile transmits and receives usefull data with two sub modes : • Transparent data sub mode ( typical for circuit mode) • PPP sub mode (packet protocole) data are recorded in a FIFO inside the mobile for radio transmission and received data from radio are sent to the terminal with packet format Switching from command mode to data mode is made by transmission, from the terminal of ATA, ATD or ATO commands Switching from data mode to command mode is made by sending, from the terminal a break sequence or, if managed, by puting off the DTR control signal.

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11.5.4. AT COMMANDS AT commands are mostly used with wired modem ; they are according to V25 standard ; they are also used by GSM There are two types of commands • Normal commands as described in V25 spec. • Extended commands as decribed in V25 ter spec. Extended commandes are noted with a + signa t the beginning of the command. Extended commands are transmitted from terminal to radio mobile and may access to three types of functions : • +CMDi = xx : write command number i with parameterx xxx • +CMDi = ? : test of command number ide la commande numéro i ; ce test est utilisé pour connaître le format, le type et la plage des paramètres à prendre en compte • +CMDi ? : read parameters of commands numer i

example of command line: ATCMD1 CMD2 = 12 ; + CMD1 ; + CMD2=,,15 : + CMD2 ? ; + CMD2= ?

Header of the command line

Set parameter

Extended command

Parameter may be ommitted

Read command to get the parameters

Test of the command

end

responses : +CMD2 :3,0,15,’’TETRA’’ Response to the command +CMD2 ? ;parameters in ASCII form are admitted

+CMD2 : (0-3),(0-1),(0-12,15),(‘’TETRA’’,’’IRA’’) Response to the command +CMD2= ? ; it indicates the range of possible values for any parameter

OK Final result

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BASIC AT COMMAND COMMAND

Mandatory/ Option

TETRA USE

Z(value) &F(value) I(value) D(x,x,x..) T P A H(value) 0(value) S0 = (value)

M M O M M M M M M M

S3 = (value) S4 = (value) S5 = (value) S6 = (value) S7 = (value) S8 = (value) S10 = (value) L (value) M (value)

M M M M M M M M M

Reset the terminal and use of the default parameters Defult parameters as factory ones Specific information request Call request (dialing a list of numbers) To dual frequencies dailing, non used To pulse dailing not used Response to a call Hook when called Give order to the terminal to switch into data mode, value = 0 Number to ring tones befire hook. Value = 0 indicates that there is no automatic response Command line end Header for a response Line header pause – not used May be ignored May be ignored May be ignored Not used Not used

EXTENDED AT COMMANDS COMMAND +IPR = (value) +ICF = (format, parity) + IFC = (by TE, by MT) +ILRR = (value) +GMI ou +CGMI + GMM ou + CGMM +GMR ou + CGMR +GSN ou + CGSN +GOI +GCAP +GCI = (T.35) +CSCS = (value) +CSTI = (value)

+CBSI = (circuit(encrytion, communication type)

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Mandatory/ Optionnel

TETRA USE

O O O O M

Data rate 0 = automatic detect Character format : 3,3 = 8 bit, 1 stop, no parity Flow regulation on junction Give the mode to set up the rate Ask for radio terminal manufacturer identification

M

Ask for radio terminal model identification

M

Ask for radio terminal version identification

O

Ask for radio terminal serial number

O M O

Ask parameters of X208 standard used Ask for radio terminal possibility – in this case, response is : +CTETRA Set country code to be used Set alphabet to be used Set adress type to be used, associated with a ‘D’ command for dialing. Value = 0 short TETRA numberi address = 1 TETRA identity (SSI) = 2 full TETRA identity (TSI) = 3 external identity Set, after daililng, characteristics of the requested communication circuit = 0 doded audio (preserve for future) = 1 : audio ao non protected data7,2 Kb/s

M

M

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+CDCC = (value)

M

+CEER

M

+CSDS = (service)

M

+CNMI = (mode(my(bm(ds(bfr)))

M

+CMGS = (da,toa,oa,length,)

M

+CMGL +CMGD = (index) +CMGR = (index) +CNUM +CREG

M M M M M

+CPAS

M

+CBC +CSQ

+WS45 = (n)

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M

= 2 : 4,8 Kb/s interleaving 1 = 3 : 4,8 Kb/s interleaving 4 = 4 : 4,8 Kb/s interleaving 8 = 5 : 2,4 Kb/s, interleaving 1 = 3 : 2,4 Kb/s interleaving 4 = 4 : 2,4 Kb/s interleaving 8 encrytion = 0 no end to end encryption = 1 ens to ens encryption Communication type = 0 point to point = 1 point to multipoint Set the requested capacity as for cicuit mode or for datq packet mode. When this command is issued as test, the response is the radio terminal capacity Value = 0 : 1 time slot = 1 : 2 time slot = 2 : 3 time slot = 3 : 4 time slot This is a request to the radio terminal, for the reason of the last fail to call - returned test must not exceed 2048 caracters and must not contain 0 ou OK sequence. Set (or inform) available SDS services = 0 SDS = 1 precoded status messages = 128..specific, proprietary Indicates how to receive messages = 0, write into a buffer and erase eldest messages in case of overflow = 1 :reject new messages in case of terminal link failure = 2 :route to the terminal if the link to the terminal is available and, if not, write into buffer = 3 : directly route to the terminal Send a message da : destination adress toa adress type oa message length Request received messages list Reset messages writen into ‘index’ Read messages writen into index and erase it Request TETRA mobile number With test , this command gives information about mobile registration. With command, it allows or not mobile registration Request mobile status, as response : = 0 mobile ready = 1 mobile non ready to receive order from the radio terminal = 2 non known status = 3 ringed mobile (but ready to accept orders) = 4 mobile involved in a communication but ready to receive orders = 5 idle Request battery load indication Ask for radio link rrssi ; as response : 0 - 113 dBm or less 1 - 111 dBm 2.. 30 -109 à -50 dBm 31 - 51 dBm or more 99 not known ber : 0 < 0,01 % 1 from 0,01 to 0,1 % 2 from 0,1 to 0,5 % 3 from 0,5 to 1% 4 from 1 to 2% 5 from 2 to 4 % 6 from 4 to 8 % 7 > 8% Select data mode 0 character transparent mode 4 point to point protocol

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11.5.5. PPP MODE (Point to Point Protocol)

In order to simplify data transmission over PEI, a driver may be developped to be used by software people non TETRA and/or PEI familiar. It is according to following schematic ::

PL_OPEN req PL_OPEN conf PL_CLOSE req PEIapplication

PL_CLOSE ind PL_TEST req

PEI Interface

Driver PPP

PL_TEST ind PL_REPORT ind PL_UNITDATA req PL_UNITDATA ind

Different internal parameters to the driver are used to adapt it to several cases • Internet Protocol version 4 • Van Jacobson Compressed TCP/IP • Van Jacobson Uncompressed TCP/IP • IP6 Header Compression • Internet Protocol version 6 • Internet Protocol Control Protocol • IPv6 Control Protocol • Link Control Protocol • TETRA Network Protocol type 1 • TNP1 Control Protocol

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12. ADRESS / NUMBERING

TETRA does offer large adress different facilities.

12.1. GENERAL TETRA ADRESS This is the complete adress of a TETRA mobile equipment – it is unique, named TSI, as following :

TOTAL 48 bit MCC Country code 10 bit

MNC Network code 14 bit

SSI Short adress 24 bit

ITSI : individual adress ATSI : assigned adress GTSI : group adress USSI : visitor adress (mixed as wanted by operator)

3 digit CCTT X121 France = 208 ( 0D0 hexa)

• Individual adress names a unique mobile • Group adress names a set of mobiles which have common features – group adress may be ‘static’ – that is fixed inside a mobile – or dynamic, that is downloaded from infrastructure. A mobile may be with any group number at the same time. • Assigned adress is an individual adress which is downloaded from the infrastructure to the mobile. • Visitor adress is an assigned adress to a mobile coming from another network and accepted in the network.

Exchanges over air interface are according to following schematic :

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Infrastructure

mobile

@ ITSI, ASSI, (v)ASSI, USSI (preference ) @ ISSI, ASSI, GSSI, USSI

Only for initial registration

12.2. COUNTRY CODE These codes have been defined internationally by UIT which is from United Nation GREECE NETHERLAND BELGIUM FRANCE MONACO ANDORA SPAIN HUNGARY BOSNIE CROATIE YOUGOSLAVIE ITALY VATICAN ROMANIA SWITZERLAND TCHEQUE (république) SLOVAQUE (république) AUSTRALIA UK DENMARK SUEDE NORVEGE FINLAND LITUANIA (république) LATVIA ESTONIE RUSSIA UKRAINE BELARUS (république) MOLDOVA (république) POLAND DEUTCHLAND GIBRALTAR PORTUGAL LUXEMBOURG IRLAND

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202 204 206 208 212 213 214 216 218 219 220 222 225 226 228 230 231 232 234 238 240 242 244 246 247 248 250 255 257 259 260 262 266 268 270 272

JAMAIQUE GUADELOUPE BARBADE ANTIGUA et BARBUDA CAYMAN (iles) VIERGES/BRITANNIQUES (îles) BERMUDE GRENADE MONTSERRAT SAINT KITTS ET NEVIS SAINTE LUCIE SAINT VINCENT ANTILLES NEERLANDAISES ARUBA BAHAMAS ANGUILLA DOMINIQUE CUBA DOMINICAINE (république) HAITI (république) TRINITE et TOBAGO TURKS et CAICOS (îles) AZERBADJAN AZAKSTAN INDIA PAKISTAN AFGHANISTAN SRI LANKA MYANMAR (Birmanie) LIBAN JORDANIA SYRIE IRAQ KOWEIT ARABIE SAOUDITE YEMEN (république)

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338 340 342 344 346 348 350 352 354 356 358 360 362 363 364 365 366 368 370 372 374 376 400 401 404 410 412 413 414 415 416 417 418 419 420 421

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ICELAND ALBANIE MALTE CHIPRE (république) GEORGIE ARMENIA BULGARIA TURQUIE FEROE GROENLAND SAINT MARIN (république) SLOVENIE (république) MACEDOINE LIECHTENSTEIN CANADA ST PIERRE et MIQUELON UNITED STATES PORTO RICO VIERGES/AMERICAINES (îles) MEXIQUE CHINA (République) TAIWAN, Chine COREE (Rép.Dém.Pop. de) BANGLADESH MALDIVES (République) COREE (République) MALAISIA AUSTRALIA INDONESIA (République) PHILIPPINES (République) THAILANDE SINGAPOUR (République) BRUNEI NEW ZELAND GUAM NAURU (république) PAPOUASIE NOUVELLE GUINEE TONGA SALOMON VANUATU (république) FIDJI (République) WALLIS et FUTUNA SAMOA-AMERICAINES NOUVELLE CALEDONIE POLYNESIE FRANCAISE COOK (îles) SAMOA AMERICAINES MICRONESIE EGYPTE ALGERIA MAROCO TUNISIE LIBIA GAMBIE (République) SENEGAL MAURITANIE MALI GUINEE

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274 276 278 280 282 283 284 286 288 290 292 293 294 295 302 308 310 330 332 334 460 466 467 470 472 480 502 505 510 515 520 525 528 530 534 535 536 537 539 540 541 542 543 544 545 546 547 548 549 550 602 603 604 605 606 607 608 609 610 611

OMAN EMIRATES ISRAEL BAHREIN QATAR MONGOLIE NEPAL EMIRATS ARABES UNIS (Abu-Dhabi) EMIRATS ARABES UNIS (Dubai) IRAN OUBEKISTAN TADJIKISTAN TURKMENISTAN JAPON COREE (république) VIET NAM HONGKONG MACAU CAMBODGE LAOS GUINEE EQUATORIALE REPUBLIQUE GABONESE CONGO (République) ZAIRE (République) ANGOLA (République) GUINEE BISSAU (République) SEYCHELLES (République) SOUDAN (République) RWANDA ETHIOPIE SOMALIE DJIBOUTI (République) KENYA (République) TANZANIE OUGANDA (République) BURUNDI (République) MOZAMBIQUE (République) ZAMBIE (République) MADAGASCAR (République) REUNION ZIMBABWE (République) NAMIBIE (République) MALAWI LESOTHO BOTSWANA (République) SWAZILAND COMORES AFRIQUE DU SUD (République) BELIZE GUATEMALA LE SALVADOR (République) HONDURAS (République) NICARAGUA COSTA RICA PANAMA (République) PEROU ARGENTINE BRAZIL CHILIE COLOMBIE(République)

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422 424 425 426 427 428 429 430 431 432 434 436 438 440 450 452 453 455 456 457 627 628 629 630 631 632 633 634 635 636 637 638 639 640 641 642 643 645 646 647 648 649 650 651 652 653 654 655 702 704 706 708 710 712 714 716 722 724 730 732

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COTE D’IVOIRE BURKINA FASO NIGER (république) TOGO (République) BENIN (Répulique) MAURITANIE (République) LIBERIA (République) SIERRA LEONE GHANA NIGERIA (Rép. Fédérale) CHAD (République) REPUBLIQUE CENTRAFRICAINE CAMEROUN (République) CAP-VERT (République) SAO TOME-ET-PRINCIPE (R.D )

612 613 614 615 616 617 618 619 620 621 622 623 624 625 626

VENEZUELA (République) BOLIVIE (République) GUYANE EQUAYEUR GUYANE (Départ, Français) PARAGUAY (République) SURINAME (République) URUGUAY

734 736 738 740 742 744 746 748

12.3. TETRA GROUPS A group is a set of TETRA equipments each of them with a different individual adress. A group is associated to a set of characteristics defining its way to use. A group may include different TETRA terminal types : as example, a group may include handportables and some dispatch stations. While group characteristics are with wide range and a lot of possibilities, it is of the most importance to use the right words, as defined in the norm, not to be confused. It is possible – and usefull in some case- to define different groups with the same terminals set. By this way, one may perform a group call to the same parties with different call characteristics according the called number. Example : the same set of 10 handportables corresponds to group 23 and group 123. The 123 group is declared with a lower priority and 23 with a higher one. A calling party may select the call priority to the same user group by selecting 23 or 123.

Affected group : a Tetra terminal may be affected simultaneously to several groups. Such equipment is open to communication when receiving a call to any of the affected group. Static group : a group wich is fixed programmed inside the equipment. .

Dynamic group : a group wich is dowloaded inside the Tetra terminal by the infrastructure. Downloading dynamic groups is performed by the infrastructure when the group is created, deleted or modified and when a terminal is turned on. By this way, if some chage have been made during the iddle state of a terminal, this last is automatically updated when it registers. Dynamic groups may be created, modified or deleted by an external application connected to the network. Such application may run over a dispatch station or any more complex application. . Typical example of dynamic groups : • Set up a group of users for a specific mission ; the mission is generally time limited. • Urban transport: a bus as affected to a transport line. The line is declared as a dynamic group what is used to perform calls to any bus affected to this line in case of some need. • Airport : a plane is affected to a flight number. Many people are working around the affected plane before take off and after landing. These mobiles and handportables are affected to the flight number, what is conveneient to manage the flight.

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Closed group : a closed group is a group which may be called only by terminals owning to this group. A special mention is made for telephone and a group may be closed to tel and open to other users (in that case, the group may be reached from any Tetra terminal but not from a telephone set).

Open group : contrary of closed group. Attached group : each terminal have, at any moment one and only one attached group. This group is one of the affected group (static or dynamic – be carefull, some terminal do not support dynamic group for attachment). The attached group (some time named ‘default group’) is used to issue a call from the terminal when it is not involved in any other communication, only by depressing the PTT. • When a terminal belonging to several groups (affected groups) and receive a call to one of this groups, it is opened and may transmit by depressing its PTT. • When a terminal (not involved in a communication) dials a group number and depress its PTT, the call is performed to the selected group. • When a terminal not involved in a communication depress its PTT without numbering, its automatically performs a group call to its attached group. Attachment is very usefull for a lot of users. That allows to a group of terminals to communicate between them only by depressing the PTT, as for talky walky. They believe to be alone on the radio channel (in fact, the radio channel is dynamically allocated by the infrastructure). There are several ways to attach a group to a terminal. • Attached group is selected manually by the user in the list of its affected group. • Attached group is downloaded by infrastrucure upon directives issued by an external application and/or by a dispatcher. When the attached group is selected by the terminal itself, infrastructure must be aware of this selection in order to update its data base ‘ and the application data base). This function is automatically achieved by the terminal with automatic transmission of the selected attached group to the infrastructure each time there is a change.

Scanned group : a terminal may be affected to several different groups, it may receive a call to one of this groups when involved in another communication. If the group is scanned, the terminal is aware of this new incoming call. Infrastructure manages the scanning by transmistting the call on each ongoing communication involving a terminal belonging to the scanned group. Priority scanned group : a scanned group is declared with a priority level. When a terminal involved in a communication receives a scanned group call, it automatically switches to the incoming communication if the scanned group is with a higher pririty than the ongoing one.

Acknowlege group :when the infrastructure transmits an acknowlege group call, it monitors the terminals wich have been joined and makes a report. This is achieved by a special procedure wich polls terminals during the begining of the communication , without any indication to the terminals.

Group with priority over individual : when a terminal involved in an individual communication (with another terminal or with telephone) receives a group call with hihger pririty over individual, it automatically releases the individual communication and enters the group one. Group without priority over individual : when a terminal involved in a group without priority over individual receives an incoming individual call, it automatically leaves the group communication (but don’t release it if it is not the ‘owner’) and enters the individual one. Group without priority over individual : in that case, the incoming call does not release the ongoing communication. .

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Listening group : it is a defined set of terminals wich are systematically opened for listening any predefined communications. If the listening group is defined to monitor individual call, the infrastructure manage the individual communication and open a second group one to transmit to the listerner group audio exchange during the individual communication . Dispatcher group – dispatching: A set of dispatch stations managing the same fleet is named ‘dispatching’. There could be several dispatching connected to the same Tetra network (example police dispatching and fire brigades dispatching). Each dispatch station is with its one and unique adresse. The dispatching have also an address wich is a group address similar to mobile group address. By this way, a mobile may reach either a selected dispatch station or the dispatching – in that second case, all dispatch stations belongin to the dispatching receive the call and the first of it hanging up takes the preseance over the communication; the incoming call is then automatically rub out of other dispatch stations.

. .

12.4. VISITORS Visitors are radio terminals owning to another TETRA network (in general a distant one without radio coverage overlapping) and used on the network. The other Tetra network is with a different MCC/MNC code. – the case of Tetra subnetworks sharing the same MCC/MNC code is different and is described in another §. Obviously a visitor can be accepted only if it has been previously agreed between the management of the two networks. An accepted visitor may transmit and receive calls and data. With limitation, groups may be also visitors groups. For being a visitor, a radio terminal must: - Be programmed with signaling frequency channels of the visited network - Be programmed with MCC/MNC code of the visited network - Support the visitor functions A visitor can’t use its own adress on a visited network. For the two networks have different numbering plans and, without care, it same address may be used by the different networks. In order to solve this problem, following process is used: - When a visitor wants to register on the visited network, it transmits its full adress with indication of its originated MCC/MNC code. - The visited network check if the terminal may be or not accepted. - If accepted, the visited infrastructure download into the terminal a specific visitor adress wich is a unique one, from a dedicated range of it own adressing plan. - Any further exchanges between the visitor and the visited infrastructure refers to the allocated visitor address. - Any incoming call to the visitor is translated into the corresponding visitor adress by the infrastructure. - The visitor user never know its visitor adress and always refer to the numbering plan of its origin network numbering plan.

12.5. OTHER TETRA ADRESSES 12.5.1. SHORT NUMBER (SNA) Short numbers are with 10 bit instead of the 24 bit of a SSI.

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This possibility is out of interest whilen any mobile have its own and specific short number memory, very easy to use. Nevertheless, there is a big interest to preserve short number addresses for data serveurs connected to TETRA networks. By using such address, each message may take benefit of 14 bit more for payload – that increase data transmission efficiency from mobile to data serveur and from data serveur to mobile. - See also § ‘supplementary services’

12.5.2. COMPLETE IDENTITY (TEI) This is the serial number of the equipment – it is unique and made as follow :

TOTAL 60 bit - 15 digit Agreement code TAC 6 digit

Manufacturer code

Serial number

preserve

2 digit

6 digit

1 digit

Given by th regulator

12.5.3. BASE STATION IDENTITY This identity is with the color code allocated to the radio site ; it made with 30 bits according to :

TOTAL 30 bit MCC Country code 10 bit

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12.5.4. EVENT LABEL ADRESS This adress mode is mainly used for mobile polling. The polling party (data serveur) transmits requests with SDS to a mobile named by its standard SSI adress associated with a request number 10 bit length, managed by the data serveur (the event label). The polled mobile sends back its response the event label reference instead of its own expeditor adress. At the total, question are longer over the air interface ( by adding the event label information) but reponses are shorter while expeditor addresses are replaced by events labels – that is downlink traffic is increased while uplink is decreased.

12.6. ADRESSES DOWNLOADING AND UPLOADING The infrastructure may assign individual adresses (ASSI) and also group adresses through the set of following procedures :

12.6.1. ADDING AN ADRESS GROUP The infrastructure maya dd one or several group adresses to a given mobile ; this last may accept or refuse such modification with an indication in its response.

MOBILE

Air interface

BS

Data base

Add to the list add @ITSI, GSSI

Accepted or rejected

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12.6.2. GROUP ADRESS SUPPRESS This is the reverse from the preceding procedure – but the mobile c’ant refuse such suppression.

MOBILE

Air Interface

BS

Data base

Suppress from the list suppress @ITSI, GSSIs

accept

Suppress ack

A similar prodedure is used to suppress all group adresses inside a given mobile, without any list of these groups. At any time, the infrastructure may ask to a mobile its group list.

MOBILE

Air Interface

Data base

BS

List request request @ITSI

List of the groups

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12.7. ADRESS FIELD TRANSMISSION • SSI adress (24 bit). It indicates a called party in the same network • SSI adress + extension adress (24 bit), the etension may indicate another network • SSI adress + extension adress (24 bit), + external number (24 bit), the external number may indicate a phone number • Short number address (SNA – 10 bit) this address is one affected to a specific equipment of the network.

12.8. NUMBERING Adressing plan and numbering plan are different : numberig plan is what is seen by a user and there is an equipment to locally translate a number to an adress. An numbering plan used in a network may be different for any equipment of this network while the adress plan is unique. As there are many different telecom networks, it is impossible to normalize numbering plans ; nevertheless, it is recommended to use some common principles for any user may not be completly disturbed by using different networks. These recommandations have been issued by ETSI for any telecom system (not only TETRA).

12.8.1. HEADER NUMBER From a mobile, one may often reach several different networks. In that case, it is recommended the network will be designated by the first digit dialed on the keyboard. That limits the number of networks reachable from a terminal by 10 – what is sufficient for a normal user. When a terminal equipment may reach only one network, the header number may be ommitted.

12.8.2. NUMBERING IN ITS OWN NETWORK Such numbering restricts to SSI the used adresses on the TETRAair interface (for calling and called parties). These adresses are 24 bit long, which could be expressed a a number from 0 up to 16 777 215 – that means more than 7 digits. It is recommended to never exceed 7 digits for the user. As result, number in the range 10.000.000 to 16.777.215 can’t be ued by an operator.

12.8.2.1.PREDEFINED SHORT ADRESS The mobile have a SSI number with 7 digits named : DT1 DT2 DT3 DT4 DT5 DT6 DT7. The mobile have a recorded 7 digit number in its awn memory, named: DF1 DF2 DF3 DF4 DF5 DF6 DF7. When a user dial number on its keyboard, the dialed number is mixed with the predefined number to form the called address as follow:

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predefined number recorded inside the terminalinal

DF1 DF2 DF3 DF4 DF5 DF6 DF7 D1

D2

D3

DF1 DF2 DF3 DF4 D1

D2

D3

number dailed by the operator

SSI adress

Decimal/binary converter

SSI 24 bit

Called adress

Th number of digit to be dialed by the operator may be fixed or free or variable inside given range. If the predefined number is 000000000, the process is the same as the zéro left insert process.

12.8.2.2.RELATIVE SHORT ADRESS This procedure is the same as the previous one but the predefined number is exactly the SSI adress of the mobile.

Mobile number

DT1 DT2 DT3 DT1 DT5 DT6 DT7 D2

D3

DT1 DT2 DT3 DT4 DT5 D2

D3

Dialed number Called number

Decimal/binary converter

Called adress

SSI 24 bit

12.8.2.3.INTERNAL SHORT NUMBERS This used the internzal table of a terminal which is recorded by the operator to design shortly some full numbers frequently used. Downloading and uploading such agenda from and to a terminal is not specified by TETRA.

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12.8.3. NUMBERING OUTSIDE THE NETWORK A mbile which want to call a party not in the same TETRA network must issue the call with the full ITSI adress by using the extension fiels (MNI = MCC + MNC,= 24 bit )

12.8.3.1.PREDEFINED NETWORK The called network must be programmed inside the terminal (no manual input)

Predefined network code (MCC,MNC)

DT1 DT2 DT3 DT4 DT5 D2

D3

Decimal/binary converter

Extension field

Called SSI 24 bit

12.8.3.2.NETWORK SELECTED BY THE USER In this mode, the numbering plan must include an exact number N of digit to be dialed to designate the called party inside its network. Following rules apply : • SSI Called party is made with predefined adress method • The 4 digit at the left to the firs N dialed digit are used as MNC • Other digits, if they exist, are used as MCC

N

D1

Cointry code (MCC)

D2

D3

D4

Network code (MNC)

D5

D6

D7

DT1 DT2 DT3 DT4 DT5 D6

D7

Decimal/binary converter

Extension field

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12.8.4. SHORT NUMBER ADRESSING 10 bit short number adress may be used by TETRA (see supplementary services). Selection of one of these adress may be made with dialing 3 digits. When a mobile using such facility registers as a visitor in another network, it may ask for doxnloading the short number adress table of its own network in the visited network; for its temporary use.

12.8.5. EXTERNAL CALLS

12.8.5.1.NORMAL PABX CALL The PABX is declared with a specific SSI identity inside the network of it it is connected. This identity is programed inside the terminal and the call is as follow :

D1

MCC

D23 D24

PABX adress in the network

MNC

Extension field

Called SSI 24 bit

External number (24 éléments)

12.8.5.2.INTEGRATED PABX CALL Several PBX nay be interconnected together to form a unique phone network and there are several connection between different TETRA equipments and different PABX.

TEL. NETWORK PABX

PABX

connection

connection

PABX

connection

TETRA

TETRA

TETRA

equipment

equipment

equipment

TETRA NETWORK

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In that configuration, it is possible to route directly a call to the TEL. network by using the special SSI code: 16 777 184 This is outside the 7digit range. The so interconnected PABX are named E164 compatible

12.8.5.3.CALL TO ISDN NETWORK It is the same principle as previously but the special SSI number Le principe est le même que précédemment mais le numéro particulier est alors : 16 777 185 (également inaccessible par numérotation à 7 chiffres).

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12.8.6. VPN (VIRTUAL PRIVATE NETWORK) VPN functions allows to different fleet to share the network and to be managed independently from other fleets. VPN implies : • The numbering plan may be splitted into different subranges • Each subrange may be managed independently • Each subrange have a unique prefix (in general the lowest address of the subrange) • Subrange prefix mut not been known by users

9.999.999

3.999

fleet 3

Préfixe 3 3.000

Any segment may include • Dispatch stations • Dispatch groups • Radio mobiles • Static groups • Dynamic groups • Data serveurs • Tel.sets • ….

2.999

fleet 2

Préfixe 2 2.000 1.999

fleet 1

Préfixe 1 1.000 999

X

0

Example: VPN with constant subrange of 1000 numbers

On the air interface, full addresses with subrange prefix are used; in order prefix are not seen by users, terminals must • Hide the prefix • Add the prefix for any outgoing call All terminals on the market have not these possibilities wich have to be programmed inside the terminal. . Relative adressing process may be used to implement VPN ; this process is as follow : • The terminal have its own 7 digits individual adress • When the user dial a number on its keyboard, the terminal automatically add a prefix wich is the first digit of the individual adress, missing to reach the full 7 digit.

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Example : 3

Terminal number

2

5

9

Number dialed by the operator ( 3 digits)

3

Number transmitted by the terminal

2

5

9

6

7

1

2

3

4

2

3

4

12.8.7. DIRECT MODE NUMBERING Direct mode calls are only if the frequency is known by both party. Frequency selection maybe coupled to a numbering plan. Direct mode numbering is identical as the general one ; however, there are some restriction according to following table.

numbering

MS / MS call

Inside the network .... predefined short Relative short To a predefined network Inside the visited network To a designated network

Call through Call through type 1 repeater type 2 repeater

√ √ √ √ √ √

√ √ √ √ √ √

Call throught DMO gateway

√ √ √ √ √ √

√ √ √ √ √ √ √ √ √

Short number adressing PABX network ISDN network

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13. REGISTRATION, AUTHENTIFICATION

13.1. REGISTRATION 13.1.1. IMPLICITE REGISTRATION A network may be set in order not to need registration (network with one site as example). Thid characteristic is broadcasted by infrastructure.

13.1.2. MULTIPLE REGISTRATION In that case, the infrastructure do not erase old registration during a predefined period or forever. The infrastructure keeps memory of any cells where a mobile have been located. This function is specific for one operator.

13.1.3. NORMAL REGISTRATION This procedure is trigerred by the mobile when it changes from one cell to another or when it is powered on. The registration request message is transmitted with ISSI address. The infrastructure may accept or reject the request.

MOBILE

Air Interface

BS

Data base

registration @ISSI Location update reject

accept Registration accepted

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13.1.4. REGISTRATION WITH ASSIGNMENT The infrastructure may take benefit of the registration of a mobile to download an assigned adress (ASSI) to this mobile.

MOBILE

Air interface

BS

Data base

registration@ISSI Update location

Registration accepted and ASSI downloaded

Accept + ASSI

13.1.5. FOREIGN REGISTRATION The registration request from a foreign mobile is immediatly recognized with the USSI adress inside this request.

MOBILE

Air interface

BS

Visitors data base

Home Data base

registration @USSI Location update Parameters request

rejet

reject reject rejet Accept + parameters Registration accepted + assignations v(ASSI) et vGSSI)

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13.2. DEREGISTRATION Infrastructure may ask to mobile to deregister when they are powered off or when they change their adentity (mobLe réseau peut demander aux mobiles de se désinscrire lorsqu’ils changent d’identité (individuelle ou de groupe) oile and/or group). This characteristic is broadcasted by infrastructure. Deregistration is a one way procedure and is not decured by ack.

MOBILE

Air interface

BS

Data base

Detach@ITSI update

Deregistration is used by infrastructure to speed up call forward on non reachable or no response – forwarding is directly provided without waiting for mobile response.

13.3. ACTIVATION / DESACTIVATION The infrastructure may, at any time, put a mobile in an inoperative mode for a temporary time or definitivly. It also may reactivate a mobile which have been teporary descativated. A mobile definitively desctivated can’t be reactivated (return to an autorised center) All these procedure are one way:

MOBILE

Air Interface

BS

Data base

Temporary desctivation désactivation

réactivation réactivation

Permanent Désactivation permanente

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13.4. AUTHENTIFICATION Authentification is a check procedure of the mobile equipment; it is absolutly not related to any operator authentification. This procedure request to the mobile to transmit its complete serial number (TEI). Furthermore, authentification may be used for encryption, it permits in this case to transmit secondary encryption key to the mobile.

13.4.1. SIMPLE AUTHENTIFICATION Authetification procedure may be triggered, at any miment by infrastructure.

MOBILE

Air interface

BS

Autehntification request

Data base

Autentification request

Serial number Response with serial number

13.4.2. AUTHENTIFICATION WITH REGISTRATION Authentification process may be joined to any of the registration procedures.

MOBILE

Air interface

Registration request @ISSI Authentification request

Serial number Registration accepted

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Data base

Localisation update

Authentification request Authentification response

accept

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For visitor mobiles, the complete procedure is as follow :

MOBILE

Air interface

BS

registration @USSI

assign v(ASSI))

Registration @v(ASSI),ITSI

Visitor data base

Home data base

Location update

Adress assignment v(ASSI)

Location update

Authentification request

Authentification request

Request parameters

Parameters and TEI

Serial number Authentification response

Location update

Registration accepted Registration accepted + assign v(ASSI), v(GSSI)

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14. AUDIO AND CIRCUIT MODE SERVICES

14.1. INTRA NETWORK SELECTIVE CALL 14.1.1. GENERAL CHARACTERISTICS Selective communications aretwo ways, point to point betxeen a calling party and a called party. Communication may be achieved with duplex mode or with half duplex mode – this mode is negociated between infrastructure and the terminals. The mode must be half duplex if only one of these party ask for it. Communication may or may not be encrypted. Calling party or called party may break the communication. During the communication, a transmitting terminal may also transmit data without any audio disturbance, by using the STCH. Contrary to analog radio, infrastructure may transmit data to the mobile even if its last is transmitting – especially, the infrastructure may stop mobile transmission. Selective communications may be established : • Either with direct mode : a short ring is broadcasted on the called mobile and the communication is immidiatly achieved – that is the calling party may speak and he is listened by the called party. • Or with hook mode: the called party is ringed until the called operator kook (by depressing th green key) or until the calling party breaks the request or by time out.

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14.1.2. MONOSITE CALL , DIRECT MODE WITHOUT FREQUENCY CHANGE:

time

calling Tx Rx U_SETUP

1 2

3

2

3

D_CALL_PROC

4 1

2

4

3

1

2

4 1

2

4 1 L2_ACK

1

4 1

2

D_CONNECT

3 STCH mac-data

2 3

1

4

2

U_CONNECT 4

4

2

3

D_SETUP

2

1 4 1

2

2

4 1

D_CONNECT

2

4 1

2 3

L2_ACK

3 1

Channel assignement

1

1

3

3

1

D_INFO

2

2

230 ms

4

1

4 1

called Tx Rx

1

3

3 100 ms

BS Rx Tx

3

2 3

2

4

3

1

1

2 3

2

4

2

4

3

1

3

1

2

STCH nul

late

2

4 1

TCH

early

3

2

TCH

Procedure is th same for audio call or for circuit mode data call, as follow : • Calling mobile transmits the call request with an ALOHA access, on the MCCH ( or on the SCCH if previously assigned) - message U_SETUP, half a time slot • Infrastructure responds with an acknowledge (D_CALL PROCEDING) and, simultaneously sends the call to the called mobile over the last radio site where the called mobile have been registered • Called mobile is ringed and trasmits an acknowledge (U_CONNECT) • Inffrastructure transmits to both parties, a message indicating to go on communication on an allocated time slot. • Each party transmits back an acknowledge on the assigned channel (assigned time slot) – 2 time slot with the example • Infrastructure transmits to the calling party a message indicating the begining of the communication on he allocated channel • Calling mobile transmits the audio signal just after transmission of a signaling stealing message (STCH) • Infrastructure repeats preceeding messages to the called party

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For a cicuit mode data call, the channel assignment may be achieved : • Either early : in that case, the channel assignment is indicated with messages D_SETUP et D_CALL _PROCEDING • Or late: the channel assignement is indicated inside the D_CONNECT message For an audio call, channel assignement is made only in late form .. in any case, a mobile receiving a channel assignment must immediatly connect on the indicated channel. Any call establishement indicates a maximum time allowed for this communication. After this time out, any mobile must come back to the common signaling channel.in the idle state.

14.1.3. SELECTIVE CALL, DIRECT WITH FREQUENCY CHANGE The procedure is identical to the preceeding one but a linearisation phasis is introduced for both parties.

time

calling

BS U_SETUP

1

100 ms

called

1

4

1

4

2

3

2

3

2

3

3

1

4

2

4

1

3

1

2

4

2

3

1

4

2

4

2

4

2

1 2

3

1

3

1 2

3

D_CALL_PROC

1

D_INFO

2 U_CONNECT 4 1

1

4

2

1

3

230 ms

3

1

4

2

2

1

3

2

4

D_CONNECT

1

1

2

4

2

1

3

1

3

2

4

2

4

3

1

3

1

2

Channel change CLCH

4 3

D_CONNECT

TCH

4

1

3

STCH mac-data

2

1

L2_ACK

2 3

D_SETUP

STCH nul

2

TCH

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14.1.4. MONOSITE CALL, HOOK MODE WITHOUT FREQUENCY CHANGE

Procedur eis as follow :

calling

infrastructure

called

Chnnel assignment

U_SETUP D_SETUP D_CALL_PROC U_ALERT

early

D_ALERT ring Autres messages

Autres messages

normal

U_CONNECT

D_CONNECT

hook late

D_CONNECT

For data transmission circuit mode, channel assignment may be • Early – when the call request is received • Or normal , during the time the called party is ringed • Or late when the called party hook For audio communication, channel assignment must be with late mode.

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14.2. INDIVIDUAL CALLS BETWEEN DIFFERENT NETWORKS Communications between different networks may hapen as soon as the callin party and the called party are nor under the same radio network with different situations : • Calling and called parties decalred in the same network • The calling party is under its own network coverage and the called party is a visitor of another network • The called party is under its own network coverage and the calleing party is a visitor of another network • The calling party and the called party are under the coverage of two different visited networks. • Calling and called parties are not declared in the same network • Calling and called parties are under their home network coverage • Calling or called party are visitors on different networks. From the mobile side, the call establishment procedure is exactly the same as this provided for calls in the same network – from the infrastructure side, process is different. Following general principles are used : • The switch of the network where is located the calling party is the manager of the communication. • The communication control is transferred to another switch in case when the calling party changes to another network. • Call establishment is managed according to localisation data recorded in the database of the called party and not according to visitor data base indications.

14.2.1. BASIC PROCESS Any mobile have its own data base inthe network where it is declared. One important information of this data base is the last location where the mobile have been registered. This information is updated only y switchs of any connected network when it accepts a registration of this mobile. The switch of a calling party takes into account the network reference of the called party (MCC and MNC of the called party) Then there are two ways to proceed: • The forward method • The rerouting method

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14.2.2. REROUTING CALL PROCESS The initiating switch sends the call request to the home network of the called party. The home data base location (last location) of the called party is interrogated. If the called party is located in its home network, the call request is immediately routed to the last radio site of this network. If the called party is located to another network, the home switch rejects the call request from the initiating switch with an indication of the new location of the called party. The initiating switch may send a new call request directly to the designated network.

SW B (called party home data base)

SW A (originating SW )

SW C (Called SW)

A calling B called

the procedure is as follow: B Home SW MS B

A SW MS A

Home SW MS A

SETUP req ind

MIGRATION req ind

SETUP req ind RELEASE resp conf

RELEASE req ind

INFORM 1 req ind

INFORM 1 resp conf

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C SW MS B

14.2.1. FORWARD CALL PROCESS The initiating switch sends the call request to the home network of the called party. The home data base location (last location) of the called party is interrogated. If the called party is located in its home network, the call request is immediately routed to the last radio site of this network. If the called party is located to another network, the home switch reroutes the call request to the switch of the network where is located the called party.

SW B SW A (originating SW )

(called party home data base)

SW C (Called SW)

A calling B called

14.2.2. TROMBONE DETECTION Trombone situation is this one when the called mobile is visitor inside the network of the calling party.. The procedure makes a loop for the database of the called party send back an information from the calling network indicating it is a visitor of its own. When the calling network receives a trombone indication as reponse, it looks its own visitor database to recover the location ( radio site) of the called party and broadcasts the call on this site. This procedure avoids a communication over a loop with wasting link ressources and possibly degrading the quality of services (transmission time,..).

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14.3. GROUP CALLS INSIDE A NETWORK A group communication is bidirectionnal, point to multipoint between a calling party and severals called prarties. Calling and called parties may be a TETRA terminal, a dispatch station and, in some case a telephone set. The group may mix these different types of parties. Group members share a common predefined number which is the group number and which is used to performe the group call. A terminal (radio or wired) may be assigned to a group : • Statiically and permanent (programmed inside terminal or with a SIM card + declaration in the infrastructure administration) • Dynamically by an authorized operator The group call is realized with the only group adress (GSSI) and there are no response from mobiles. The procedure is optimized in order to minimize callestablishement time. When mobiles are with different cell coverages, the call is performed only on radio site where mobiles owning to the group are registered and only on these sites. This process avoids to allocate frequencies over radio sites when it is not necessary. If the group includes wired terminals, call establishement for these equipments may be longer than for radio (typicall 500 milliseconds for radio equipments) – especiallly in case of a phone set with hook time. Any group communication have a unique ‘owner’. At the begininf, the owner is the initiator of the communication (the calling party) – then he may transfert its right to another group member involved in the communication. Only the owner of a group communication may break it – but the system by time out. A group communication need only one trafic channel per involved radio site. Group communications are with half duplex and involved parties must use the PTT command to talk. In case of a wired equipment, the PTT command may be implemented or omitted – in this last case, the communication is achieves with half duplex mode with radio terminals and duplex mode with wired terminals. Group communications may or may not be crypted. There are several different group call types : • Normal group call : the call is directly broadcasted. • Acknwolege group call: after the call is broadcasted, the infrastructure polls each of the group member to know if they have been reached; the polling is made during communication without any information to the mobile operators. • Acknowlege group call with conformation : this is an acknowlege group call as but the call is really established only if some conditions are fullfilled about the mobile responses. Group call and acknowlege group call procedure are according to following schematic (dot lines are for acknowledge group calls) :

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calling

infrastructure

called

Channel assignment

U_SETUP D_SETUP

early

D_CALL_PROC D_CONNECT

late D_INFO

D_INFO

U_INFO

Channel assignment may be early or late for group circuit mode data call but only withe late mode for audio group call.

14.3.1. PTT MANAGEMENT PTT command is used for any half duplex communication (selective audio or circuit mode data call, group audio or circuit data call). The PTT command does not directly put the radio terminal in transmit mode – it is a request to the infrastructure to get the permission to transmit. At any time, the nfrastructure allows only one terminal to transmit – that ensures there are never several mobiles simultaneously transmitting and interfering themselves. This reqiuest is transmitted with a U_TX DEMAND message; at the beginning of the communication, this request may be directly transmitted with the call request. When the infrastructure allows a mobile for transmission, it sends a D_TX GRANTED message to this mobile which responds with a D_INFO message. Generally, the infrastructure allows immediately transmission permission if nobody is transmitting when the request is received. • If the request is received when another mobile is transmitting, the infrastructure may : • Either reject the request with a specific indication in the D_TX GRANTED message or records this request in a file, waiting for the end of the ongoing transmission – this is the ‘queuing mode’ – in that case, the mobile must not resend the request before being authorized. The infrastructure may, at any moment, ask to a transmitting mobile to stop this transmission with a D_TX_WAIT message. A mobile may request a high priority request to transmit with a U_TXDEMAND message with a specified priority level ; The infrastructaure may or not, according to different priorities, stop the ongoing transmission and grant the Tx permission to the new mobile. Such process is generally longer than the process to grant th the Tx permission in nomal way while, the U_TXDEMAND message is transmitted only during the 18 frame. When a mobile stops transmission, it sends a U_TX_CEASED message ; this message is resent to other mobiles with a D_TX_CEASED message this last message may be ommitted in case when the infrastructure directly allow another mobile to transmit.if he was in the waiting list.

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Mobile A

infra

Mobile B

Channel assignment (audio)

Channel assignment (circuit data)

U_TX CEASED

D_TX CEASED

D_TX CEASED

U_TXDEMAND

D_INFO

D_TX GRANTED

U_TXDEMAND (prioritaire) D_TXGRANTED

D_TX INTERUPT

Any transmission authorization from infrastructure is with a maximum time and any authorizes mobile may stop its transmission at the end o this time and send a U_TX CEASED message. Channel allocation is permanent for circuit data mode group communication but may be broken for audio group communication.

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14.3.2. END OF COMMUNICATION

14.3.2.1.END OF COMMUNICATION FROM MOBILE For a selective call, any of the involved parties (calling and called) may break the communication. For group communication, only the owner of the communication may break it.

infrastructure

A Mobile

Channel assignment

B Mobile

U_DISCONNECT D_DISCONNECT D_RELEASE

U_RELEASE

May be allocated to another communication

14.3.2.2.END OF COMMUNICATION FROM INFRASTRUCTURE The infrastructure may break a communication at any moment – such process may be triggered when receiveing a highest priority call request without radio ressources available or by a time out. This end is initiated by issuing a D_RELEASE message indicating the reason of the break.

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14.3.3. TRUNKING AND QUASI TRUNKING MODES Trunking mode with group communications may be used in order to get a little more simultaneous communication than available trafic channels by taking benefit of the ‘blanks’ during some half duplex communications. Statistically, it has been demonstrated that about 20% of time is wasted during half duplex communications – that is time without anybody pressing its PTT. Such trunking is achieved by very late allocation of the trafic channel – that is to allocate only when the T xis granted to one mobile. With this process, there is a risk in case when no channel is available just at the time a Tx is requested from a mobile. This mode must be used only in case of radio site with large number of channels to take benefit of the statistic effects :Theoretical gain may reach 20% only if there is a minimum of 5 trafic channels simultaneously used with half duplex audio communications ; these statistics are very dependant upon the user behavior. In order to minimize risk with trunking mode, one may use the ‘quasi trunking’ mode; it is a trunking mode but with a dead time added after each of PTT release : the communication is broken only after this time out.

Mobile A

infrastructure

Mobile B

Channel assignment

U_TX CEASED D_TX CEASED

D_TX CEASED

U_TXDEMAND D_INFO

D_TX GRANTED

U_TX CEASED D_TX CEASED

D_TX CEASED

Hold time

QUASI TRUNKING D_TX CEASED

D_TX CEASED

U_TXDEMAND D_INFO

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After sending the D_TX CEASED message from infrastructure, if there is no mobile asking for transmission after the hold time, the infrastructure transmits a second D_TX CEASED message with indication of ressource release.

14.3.4. BROADCAST CALL Broadcast calls are one way group call – that is only the calling party may transmit and called mobiles can’t respond. These communications are strictly identical as normal group communications, the transmission restriction is managed by mobiles.

14.3.5. OPEN CHANNEL CALL Open channels call are managed as normal group call by infrastructure ; for mobiles, the difference is because each time the PTT command is depressed while the mobile is not involved in a call, a call set up is automatically requested by this mobile for the ‘attached’ group. As call establishement is short, there is, for a user, no significant difference between normal PTT during the communication with the attached group and the attached group call or call again – as result, if ressources are enough, the user working on its attached group feels to use a dedicated channel as per analog radio.

14.4. INTER NETWORKS GROUP CALL A group call is an inter networks group call as soon as one or more mobiles belonging to the group is visitor of a network. One separates: • The network where one mobile is initiating the communication (originating SW) • The network where the group is declared (Home SW) • The network(s) where mobile(s) belonging to the group are visitor(s) (participating SW) .. with all possible combinations : • The originating SW may be the home SW • The originating SW may also be a participating SW (the calling mobile is visitor of a network where other mobiles belonging to the group are also visitors) • The home SW may not be a participating SW ( all mobiles belonging to the group are out of the home network). • The home network may be a partivcipating network • Participating networks may be only originating and / or home network(s). Furthrmore, it is possible to merge several groups declared in different networks – this case is out of this scope.

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SW C (Called SW)

SW B (Group Home data base)

SW A (originating SW )

appelé

SW C (Called SW)

calling

called

14.4.1. BASIC PROCESS It is the home SW which manages the communication, even if it is not participating. (this is different from selective call ) – the management includes the call establishment, the PTT manngement and the call release. In case when the calling party is migrating to another network, there is no change of manging SW.

14.4.2. PARTIAL GROUP When a group call is requested, the home SW of this group make a list of any network involved ( any network where one ore more group’s members are registered).and to transmit the call request to these networks. It may be that some of these networks are overloaded and/or they do not allow, at this moment, ressource allocation for an external request – in that case, some of the mobiles belonging to the group can’t be joined. This is a ‘partial’ group. According to the network, a partial group may be accpted or rejected – that is, if it is rejected, the group communication is refused if all the group member can’t be joined. As a network may be overloaded during limited time, it may transmit an information to the requesting network indicating there is some delay. The communication may be established without this network then extended as soon as tressources are available.

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15. MOBILITY

15.1. DIFFERENT CELL CHANGE CASES There are two mobility types : • Mobility with network change (migrating) • Mobility inside a network with cell change (roaming/hand over) A mobile normally registerd on a cell permanently evaluates the possibility to go with another cell of the same network ; in case when it does not find any signaling TETRA channel of this network , it looks for other networks in order to register as a visitor. There are different cases of cell change : • Non declared reselection: the mobile is not involved in a communication or in a specific procedure at the time it changes cell. • Non annouced reselection : the mobile does not need (or can’t) to declare the change before this change – example a mobile listening a group communication • Type 3 annouced reselection : the mobile is not multislot and have not the possibility to listen to signaling channels when it is on a trafic channel ; the mobile is obliged to break the communication to listen signaling channels and to reselect a cell. After reselection, it request to the infrastructure to resume the communication. • Type 2 annouced reeselection : the mobile is with multislot and may reselect during a communication. The infrastructure can’t directly and shortly switch a communication from a TCH of one site to another TCH on another site. • Type 1 annouced reselection: it is the perfect hand over : the mobile select another cell and ask to the infrastructure for a change with new cell indication. The infrastructure switchs the communication on the new cell without any interrupt. Any mobile must support minimum : • Non declared reselection • Non annouced reselection • Type 3 annouced reselection .. type 1 and 2 are option for mobiles. The infrastructur does not know the reselection modes supported by a mobile. Mobiles know reselection modes supported by infrastructure thanks to the broadcasted messages. They also know the surrounding cells of the cell where they are registered with the broadcasted messages. It must only reselect a cell wich is indicated in the broadcasted messages.

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Reselection mode choice is made by the mobile according to following schematic :

partial

no

Neighbour cells knowlege

Initial selection no yes

Radio link broken

Informations about neighbouring cells List of valid cells and the best cell identified wich is different from the registration cell

Non annouced reselection

yes no

Open with a selective audio or circuit data communication

Non declared reselection

no

selective

yes

Type 1 or 2 annouced reselection

Neighbouring cells scanned

yes

Radio link broken

Selective or group call establishment

group

Non annouced reselection

Is terminal allowed for transmission

no

yes

no

yes

Type 3 annouced reselection

The selected neighour cell is checked

yes

Resélection non annoncée

no

Type 3 annouced reselection

Type 1 or 2 annouced reselection

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15.1.1. NON DECLARED RESELECTION Following phases are successivly activated: • The mobile declares internaly that it is not possible to transmit or receive signalisations. • If no neighbouring cell is selected, it starts scanning to get one. • The mobile select a cell only after checking any scanning possibility • The mobile switchs over the MCCH of the selected cell • If the selected cell requests registration, the mobile registers to this new cell • If registration is refused, the mobile request a registration to another cell of the list; if it is the end of this list, it restarts from the first and stops any on going transaction. • If it is accepted by a cell or if no registration is required, the mobile declares signaling link with infrastructure on operation.

15.1.2. NON ANNOUCED RESELECTION Non annouced reselection is always triggered by radio link failure, either during a communication or when the mobile do not get all informations about surrounding cells. At the first, the process is identical as for non declared reselection. Then, after reselection success (by registration in the new cell) the mobile transmits immediatly a request to restore the communication previously stopped with indication of the cell wich is just leaved (MCC,MNC,LA) The infrastructure is theoretically able to recover the communication and to switch it over the new cell. In case of success the mobile is informed on the signaling channel of the new cell and receives the information about the channel assigned by the infrastructure on the new cell to resume the communication. As soon as the reselection is effective, a mobile may resume any data transmission (but circuit data communication) by retransmitting any transaction wich is not acknowlege.

15.1.3. TYPE 3 ANNOUCED RESELECTION Type 3 reselection could be only with two conditions : • A neighbour cell have been selected from the list of declared neighbour cell broadcasted by infrasructure • The radio link with present cell may be used even with low level signals The mobile transmits first to the infrastructure a message indicating its intention to change. The infrastructure send back either an order for immediate change or an order to wait. In this last case, the mobile wait for a change message. If this order is not received after a fixed time – or if the radio link is broken during this time – the mobile makes the change. Then, the proces, is identical as non annouced reselection (registration to the new cell and request for call restoration).

15.1.1. TYPE 2 ANNOUCED RESELECTION Type 1 and 2 are requested by the mobile with same form; it is the infrastructure which choices between type 1 or 2 reselection. Type 2 is selected if infrastructure does not support – or can’t achieve – type 1 reselection. In that case, the infrastructure responds Type 1 is not possible and the reselection will be of type 3

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15.1.1. TYPE 1 ANNOUCED RESELECTION The mobile is able to listen neigbouring cells wich have been declared by infrastructure (broadcasted informations on the present cell) and to select one of them with right service level, right radio link quality and right capacity to register the mobile. When the link quality with the present cell is decreasing, lower than the expected qlink quality with the selected cell and sufficient to exchange signalisations, the mobiles transmits a cell change request with the indication of the selected cell. The infrastructure acknowledge the request and manage the change with time slot assignment over the new cell. When all is ready, the infrastructure tr ansmits to the mobile an order to change to the new cell with the channel assignment. The mobile immediately change frequency and time slot and recover exactly its communication on this channel.

15.1.2. RESELECTION DURING HALF DUPLEX COMMUNICATIONS For hal duplex communication, the mobile prefer to reselect a cell not during transmission but just after the PTT is released.

15.2. MOBILE MECANISMS FOR RESELECTION 15.2.1. SCANNING The scanning is used to evaluate the radio link quality with a base station ; it could be achieved according to one of the three following mode :

15.2.1.1.FOREGROUND MODE The mobile, in idle state on a cell : • Changes frequency to listen neighbour cell • Synchronises and decodes BNCH – if no BNCH is received after 5 seconds, back to the origin channel. • Measures radio field (RSSI) and evaluates C2 • Back to the original channel

15.2.1.2.BACKGROUND MODE : Ths mode is used when the mobile wants to evaluate the link quality with a neigbouring cell and, without breaking the link with the present cell. The mobile looks for synchronization and perform field measurement as for foreground mode. It decodes BSCH and BNCH to evaluate C2 parameter. The mobile must record any information about the TETRA calendar for each of the listened cell in order to be able to synchronise immediatly in case of cell change and to speed up the whole scanning process to update all the C parameters every 10 seconds.

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15.2.1.3.INTERRUPT MODE This mode is identical as the foreground but the mobile is involved in a communication over the present cell and must interupt it to evalaute the C parameter of an adjacent cell.

15.2.2. MONITORING Monitoring is a continuous evaluation of the links to cells designated as neighbour of the present cell. Procedure is according to background mode and a measure is declared as valid with minimum 10 seconds.

15.2.3. RANKING The ranking is the permanent ipdate of the list of the neigbouring cells broadcasted by present cell.

15.2.4. LINK QUALITY MEASUREMENT At any time, following parameters are broadcasted by each cell ; • RXLEV_ACCESS_MIN : minimum level to be received by a mobile in a cell • MS_TXPWR_MAX_CELL : maximum power allowed for mobile transmission in the cell From these parameters, a mobile permanently evaluate the ‘C’ quantity according to :

C = RRSI - RXLEV_ACCESS_MIN - Max ( 0, MS_TXPWR_MAX_CELL - PMS) ... PMS is the maximum RF power the mobile may transmit. This C parameter evaluates the margin gain (in dB) of the link, corrected by the power margin of the mobile. The C parameter is noted : • C1 for the present cell • C2 for the best neigbouring cell If RXLEV_ACCESS_MIN and MS_TXPWR_MAX_CELL parameters are unknown for a cell, the mobile takes the value of these parameters in the present cell.

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15.2.5. MOBILITY PARAMETERS A lot of parameters are taken into account by a mobile for cell reselection. Four of them describe reselection thresholds in conjunction with RX_LEVEL_MIN. Two types of reselection are to be considered : • A fast reselection wich allows to reselect a new cell in case of fast loss of the radio link with the present cell (reselection is necessary) • A slow reselection wich allows a mobile to select the best cell (resélection is not necessary but optimises the process) Fast reselection is with 3 conditions: • Link quality with present cell, evaluated with C1 parameter, goes down to a level (FAST_RESELECT_THREHOLD) during 5 seconds • Link quality with new cell, evaluated with C2 parameter, is higher than a level added to an hysteresis (FAST_RESELECT_THREHOLD + FAST_RESELECT_HYSTERESIS) • No cell reselection occurred during the past 15 seconds Slow reselection is with 3 conditions: • Link quality with present cell, as evaluated by C1, goes down to a level (SLOW_RESELECT_THREHOLD_ABOVE FAST + FAST_RESELECT_THREHOLD) during 5 seconds • Link quality with the new cell, as evaluated by C2, is higher than the quality of the link with the present cell C1 added to a certain quantity :( SLOW_RESELECT_HYSTERESIS) • No cell reselection occurred during the past 15 seconds The four parameters FAST_RESELECT_THREHOLD, FAST_RESELECT_HYSTERESIS, SLOW_RESELECT_THREHOLD_ABOVE FAST, SLOW_RESELECT_HYSTERESIS are in a range of 30 dB with 2 dB steps.

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RSSI RSSI received on the present cell d’origine

RSSI received on the new cell

FAST_RESELECT_THREHOLD + FAST_RESELECT_HYSTERESIS

FAST_RESELECT_THREHOL D

RX_LEVEL _MIN of present cell RX_LEVEL_MIN of new cell

FAST RESELECTION

RSSI

RSSI received on the new cell

RSSI received on the present cell d’origine

SLOW_RESELECT_HYSTERESIS + ∆ RX_LEVEL_MIN

SLOW_RESELECT_THREHOL D

Niveau min Rx cellule d’origine

∆ RX_LEVEL_MIN

Niveau min Rx nouvelle cellule

SLOW RESELECTION

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15.3. CELL CHANGE WITHOUT CALL RESTORATION When a mobile is not involved in a communication, there is no circuit restoration. The mobile reqiests registration on the new selected cell – the process is different according to if the cells belong to the same network or not. • When the two cells are in the same network, this network only update its data base (update of the mobiole location) – home data base if the mobile belongs to the network and visitor data base in the contrary; il this last case, the cell change is not notified to the mobile’s home data base. • When the new cell is in another network, two cases are separated : • The new cell is in the home network of the mobile – that is the mobile come back to its home network. In that case, there is only an update of the home data base. • The new cell in not in the home network ; severals options are possible : • Acceptance by the home network : the home network is interconnected with the new network and this last ask to the home network if it may or not accept the mobile. • Acceptance with authentification : this case is identical to the preceding one but before clearance, the home network request an authentification procedure. • A priori confidence : the networks are interconnected, the new network accepts the mobile without clearance from the home network but update the home network about the mobile location. Later, if the home network refuse the migration, it transmits a request to the new network to reject the mobile. • Programmed confidence : the networks are not interconnected – or the link between the network is broken and the new network accept or reject the mobile according to a predefined table and or some predefined rules takinf into account any parameter as : • Contracts cetween operators • Preserved cell for visitors and residents • Restriction when the new network is overloaded • ...

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•

15.4. CELL CHANGE DURING INDIVIDUAL COMMUNICATION 15.4.1. ROAMING WITH CIRCUIT RESTORATION The mobile was involved in an individual communication before the cell change. In that case, there is always a nregistration of the mobile on the new cell – but with type 1 annouced reselection procedure.

15.4.2. MIGRATING WITH CIRCUIT RESTORATION The mobile was involved in an individual communication before the cell and the network change ; there is registration of the mobile on the new cell of the new network : after this procedure, the restoration is achieved according to one of the two following possibiliites

15.4.2.1.FORWARD MODE RESTORATION

MOBILE A

When mobile B migrates from network 2 to network 3, the network 2 set up a connexion to bound ntworks 1 and 3

SW 1

SW 3

SW 2

V MOBILE B

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15.4.2.2.REROUTING MODE RESTORATION

MOBILE A

When mobile B migrates from network 2 to network 3, the network 1 set up a circuit to network 3 and release the connexion with network 2

SW 1

SW 2

SW 3

V MOBILE B

15.4.2.3.TROMBONE DETECTION During forward mode migration, there could be some trombone. Such situations must be avoided and any network must detect theses situations. When its detected, a rerouting procedure must be achieved to solve the problem.

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15.5. CELL CHANGE DURING GROUP COMMUNICATION When a mobile belonging to a group and involved ina communication of this group changes cell, the infrastructure must perform the communication continuity for this mobile, whatever this obile is transmitting or receiving and whatever this mobile is or not the master of the communication.

15.5.1. ROAMING OF A RESIDENT DURING A GROUP COMMUNICATION When the mobile and the group are resident of the network, the process is as follow : • If the new cell was previously involved in the group communication ( that is there is a minimum 1 other mobile of the group in the area of the wew cell) the infrastructure must route the mobile to the same channel as previously used. • If the new cell was not involved in the group communication, the infrastructure must open a channel for this communication on this new channel and routes the mobile to it. • In any case, the infrastructure must look if there is one mobile of the group left in the cell leaved n by the mobile – if there is no more mobile belonging to the group in this cell, the channel allocated on thi cell must be released.

15.5.2. ROAMING OF A VISITOR DURING GROUP COMMUNICATION The visitor is with an assigned adress and the group is also with a visitor assigne group adress. The roaming is achieved by the network exactly as in the previous case of resident roaming, only by taking into account visitor addresses instead of resident addresses.

15.5.3. MIGRATING OF A MOBILE DURING GROUP COMMUNICATION The home swith of the group manages the cell change and indicates the change to the new network. • If this new network was previously involved in the same communication, it manages itself the extension on a new cell (if necessary) • If this network was not previously invoved in the communication, it must set up the connexion with the new cell. The network wich is leaved by the mobile must check if there is one remaining mobile of the group in its area – if no, it must release all connexions related to the communication.

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16. SUPPLEMENTARY SERVICES About thirty supplementary services are normalized ; each of the mis fully described and there may be interferences between these services. TETRA standard lists some of these interferences but this list in non exhaustive. All these services are with general commin requirements: • The infrastructure must broadcasted, on request, if a service is or not available. • The operator of the network may activate or desactivate any service • The infrastructure must indicate reasons when it rejects service request from a mobile. Any service (all telecom services and not only TETRA services) must be looked through three different points of view for any comparison and/or evaluation. • Authorized user(s) they manage the service by seting up • Parameters of the invoked service • Rules to know if a mobile may be beneficiary or affected by the service • Beneficiary user(s) they may invoke the service • Affected user(s) Example 1 : ambiance listening Authorized defines who, when and what condition one may listen a mobile Beneficiary are people authorized to liste other mobiles Affected are listened mobiles Exemple 2 : call forward Authorized user defines the calls to be forwarded Beneficiary users are the called party the call of hi mis forwarded Affected user is the user who receives the forwarded call The second example is well suited to understand the importance of such classification: if, as example, one equipment is specified authorized users = operator Beneficiary users = mobiles Affected users = mobiles … that means A mobile can’t program himself the forward party A dispatch station can’t be forwarded A mobile can’t be forwarded to dispatch station A mobile can’t be forwarded to telephone …..

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16.1. LIST SEARCH CALL This service allows to set up a list of terminals with some order who may be called for a special purpose. When the service is invoked, the infrastructure looks for the first terminal of the list and call him; without response, it calls the second and so on.. Authorized users may create, delete and modify the list. List declaration is with the number (adress) associated to the list and the terminal adresses. In case when no terminal from the list may be reached, the infrastructure sends back a service reject to the ucalling party with the reason of it (all terminals busy as example). A list can’t include a dynamic group A list can’t be inconditionally forwarded A list search call may include some area restriction – in that case, only mobiles of the list registered in the designated radio area are called. A list search call may with premptive priority The list search call may be restricted according to the calling party but can’t be restricted according to called parties.

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16.2. CALL DIVERSION Call diversion allows a user involved in a communication to call a third party ; all the parties enter into a group ommunication. The third party may be any :( mobile, dispatch station, telephone set, group) restrictions may be implemented specifically and are not defined in the norm. In a selective call, call diversion may be triggered by the calling or by the called party. The party who performs the call diversion is the owner of the group communication. In a group call, call diversion may be triggered by the owner of this communication. Following table describe all situations:

second call

Indicvidual call Group call appel de groupe acquitté Broadcast group call

Original call Individual call

Group call

Acknowlege group call Group call Acknowlege group call Non allowed

Group call Group call Group call Non allowed

Acknowlege group call Acknowlege group call Group call Acknowlege group call Non allowed

Braodcast group call Broadcast group call Group call Broadcast group call Broadcast group c

At the begining of the communication after call diversion, a signal is broadcasted to users to inform them another party enters the communication.

16.3. INCONDITIONAL CALL FORWARD This service activated for a terminal equipment automatically routes any incoming call to this termina to another terminal. The terminal who is beneficiary of this service keeps any of its facilities to issue calls.

16.4. CALL FORWARD ON BUSY This service is identical as previous one but the call forward is performed only if the called party is busy.(involved in another communication).

16.5. CALL FORWARD ON NO RESPONSE The call is forwarded only if the called party do not hook after a fixed time in hook mode call.

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16.6. CALL FORWARD ON NON REACHABLE The call is forwarded if the called party is not registered on the network or if there is no radio link between the infrastructure and the terminal. This service is theoretically only for mobile terminals while wired terminal are always reachable. The called terminal may issue another call but, in this case, that means the radio link is recovered that is the terminal is reachable.

16.1. VOICE MESSAGING In many cases, call forwar on busy, no reply and not reachable are programmed to a voice messaging – as for the GSM. Usage of it is simple and it implies SDS messages to prevent any user about the number of pending messages.

16.2. CALL AUTHORIZED BY DISPATCHER This service allows a dispatcher to check and to establish communications between two parties who are normally non authorized to call themself. Autorisation may take into account any parameter as : • Calling profile • Type of calls • Called party • Areas • …. If a mobile to mobile call involves two different authorisations (one for the calling party and one for the called party) with two different dispatchers, only one of these autorisation must be performed by the system. When a dispatcher authorizes a communication, this autorisation may apply if the called party is forwarded to a third party. Preemptive priority calls must not be concerned by autorisation. Autorisation by dispatcher cancels any incoming or outgoing restriction for a terminal.

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16.3. INCOMING CALL BARING This service do not allow calls according to different characteristics wich may be : • Any of the incoming call for a mobile • Any of the incoming call from outside of the network • Any call from a list of identified users • Any call from a list of identified networks • Any incoming group call • ..

16.4. OUTGOING CALL BARING This service is the inverse from the preceding ; it forbids call from a user according to the call type : • Either any party • Either call outside of the network • Either call to PSTN • Either call using defined intersystem links • Either call outside of a fleet • Either call outside of a defined area • Either some call with defined characteristics (as example circuit mode data call) • Either call to defined terminald or groups • ...

16.5. CALL REPORT When a selective call can’t be established for any reason, the call report service gives an indication to the calling party with two possibilities : • If the called barty can’t be reached for it is busy, the call report service invoked by the calling party triggers transmission of the missed call indication to the called party as soon as it is free and before a fixed amount of time. • If the called party can’t be reached because the infrasctructure does not reach it, the call report service invoked by the calling party triggers the transmission of the missed call indication as soon as the called party will be again active on the network before a fixed amount of time.

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16.6. SECOND CALL This service displays on a terminal (radio or wired) the incoming calls when this terminal is already involved in another communication. The terminal may • Either ignore the second call • Or reject this second call • Or accept this second call The second call indication is displayed durin a maximum predefined time, it includes the priority level of this second call and the procedure is different according to the on going communication type.

16.6.1. CALLED PARTY INVOLVED ON A SELECTIVE COMMUNICATION If the called paty ends its communication during the time the second call is displayed, this second call is automatically processed as normally from the end of the first communication. The called party may also put the first call in a hold state.

16.6.2. CALLED PARTY INVOLVED IN A GROUP COMMUNICATION WICH HAS NOT BEEN INITIATED BY HIM The called party may leave the group communication to answer the second call ; the group communication is not altered for other group members.

16.6.3. :CALLED PARTY INVOLVED IN A GROUP COMMUNICATION INITIATED BY HIM In that case, if the called partywant to access to the second call, he must first either release the group communication, or transfert the control of it to another group member.

16.6.4. CALLING PARTY IN THE SAME GROUP The situation when the called party and the calling party are in the same group and a second call is issued betwenn then, that means either the calling party had not been reached by the group call. In that case the late entry service must apply or the calling party wants to have a selective communication out of the ongoing group communication. For this reason and in case when the infrastructure does not know exactly the group members, the second call service must be processed by infrastructure.

16.6.5. SECOND CALL IGNORED BY THE CALLED PARTY After the fixed time to display the second call indication and without callin party acceptance, the display is suppressed and the calling party is informed of the reject.

16.6.6. SECOND CALL REJECTED .. same effect as previous case.

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16.6.7. LACK OF RESSOURCE If the called party accepts the second call while there is not enough ressource to establish the communication, an error message is displayed on the called terminal wich may accepta gain this second call during all the time the second call is displayed.

16.7. CALLING LINE IDENTIFICATION PRESE NTATION This service displays the identity of the calling party on the called terminal with sufficient accuracy in order the called party may call back the calling party.

16.8. CONNECTED LINE IDENTIFICATION PRESENTATION This service displays the identity of the real called party on the calling terminal wxhile the connected party may be different from the called party – in case of call forward as example). This indication must be accurate enough to perform another call.

16.9. CALLING/CONNECTED LINE IDENTIFICATION RESTRICTION This service do not allow the two preceding services (red list).

16.10.ADVICE OF CHARGE Charging may be very complex – especially with group communication and charging rules are out of the scope of TETRA standard. In case when charging is achieved by any way, the advice of charge service displays according to case: • An indication at the end of the communication • An indication during the communication • An indication when the call is established

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16.11.CALL HOLD Communication hold is achieved by this service, for individual or group calls.wich have not been initiated by this terminal. Maximum number of calls hols by a terminal is fixed by the system.

16.11.1.INDIVIDUAL CALL HOLD The call hold may be from the calling or the called party; the effects are : • A release of the ressources occupied by the on going communication • A display, on the non invoking call hold terminal, of an indication of this hold. When a communication is hold, any of the two parties may release this communication by the normal procedure. Both parties of an hold communication are considered as busy from the infrastructure. When a user have hold several communication, he may resume it selectivly – if the infrastructure have no ressource at this moment, it indicates it and the communication remains on hold ; it may be resumed later.

16.11.2.MULTIPOINT CALL HOLD Only the owner of a multipoint communication may invoke the call hold for this communication. Parties involved in this communication are informed of the call hold and they may go on communication without the owner of the communication. The party invoking the call haold is considered as busy from the infrastructure and hem ay issue any other call. The infrastructure go on managing the multipoint communication as if i twas not on hold. When a terminal in a call hold is called with a higher priority call ; the communication on hold is released for this terminal and the new communication is established. – this is for selective calls and group calls.

16.12.CALL COMPLETION ON BUSY SUBSCRIBER When a calling party A try to reach a party B wich is busy, he may invoke the call completion on busy subscriber service. As soon as the called party is clear, the infrastructure automatically call both party. This service is time limited. If the called party B is forwarded to C, and if C is busy, the infrastructure waits for the first call release (from B or C) to perform the service. If the original communication have an area restriction and if party B goes out of the allowed area during the waiting time, the completion is cancelled and the calling party is informed.

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16.13.CALL COMPLETION ON NO REPLY This service triggers periodically a call to the non replying terminal during a time limited period or until there is a reply. Parameters of this service are the period time and the maximum time for this service; they are fixed in the infrastructure.

16.14.SHORT NUMBER ADRESSING This service is related to short adresses of the network; it is not related to any short number used inside any terminal equipment. Authorized users may define this service with: • The list of the short number adresses on the network • For each short adress, the list of supplementary services available. • For each short address, the list of beneficiary usersles adresses abrégées du réseau

16.15.PRIORITY CALL Each call request includes a prority level. There are 8 priority level (one have to add 8 more priorities with premptive level). The priority is used when call request are store in the waiting list (so priorities have no effect if the network is unloaded). It is also displayed on the called terminal(s). The infrastructure may ‘correct’ priorities according to its own rules.

16.16.CALL RETENTION PRIORITY Any TETRA communication have a priority information named CRV. It is used in case of lack of ressources to know what communication must be released to set up a premptive priority call. In case when CRV are equal, the eldest communication is released first. Aythorized user(s) may assign CRV to some users or user groups.

16.17.PREEMPTIVE PRIORITY CALL This service is only used in case when the network have not enough ressources. It releases the lowest CRV communication (the eldest of them if there are many) in order to get ressources for a highest priority request call. Premptive priority call may be transmitted by a mobile, even if it is not registered on the network. The called party is included in the call request. • If the called party is already involved in a selective call : • If the on going communication is with a highest priority, the new request is rejected

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• In the contrary, an preemptive priority indication is displayed to the called party and an alarm is transmitted to other parties involved in the ongoing communication • After a fixed time (from 0 to 10 seconds) the ongoing communication is released and the highesqt priority communication is established. • If the called party is already involved in a group communication : • If he is not the owner of the communication, he is only isolated from the group and the highest priority communication is established while other group members may go on their communication (but if it have not been prempted in case of lack of ressource). • If he is the owner of the communication, this communication is released.

16.18.DISCRETE LISTENING Discrete listening offers the possibility to benficiary user(s) to listen some communications woyhout ny indication to the listened users. As option, the listener may be authorized to enter into a listened communicztion and to break it. This service needs: • Listened groups must be clearly defined • Anciliary functions reltive to come into a communication and to release it must be clearly dfined • Beneficiary user(s) must be clearly defined • Listener must be registered and authentified • Listener must invoke the service and indicate when they live it.

16.19.AMBIANCE LISTENING A « control point » (CP) may control a terminal (MS or LS) with a special communication type, without any action from this terminal. Ambiance listening does not restrict any of the possibilities of the terminal to send or to receive a call. A mobile may be set in ambiance listening if it is already involved in a call. Any audio call or any packet data request from a terminal in ambiance listening mode cancels this mode. If the terminal is already in ambiance listening (from another benficiary user) the invoking party receives a busy indication and, according to the network, may join or not the on going ambiance listening. – in this case, an indication is sent to others listeners. This service may b used only by some designed and authentified people. In a lot of case, the service may be activated for one terminal only after a distress call from this user.

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16.20.TALKING PARTY IDENTIFICATION This service allows to know, at any moment during a group communication who is speaking. The talking party identity is transmitted with PTT signaling. For individual calls, the talking party is always the calling party. In case when the call is forwarded, the talking party identity is the identity of the terminal really depressing its PTT. Talking party identification is not active for user(s) beneficiary of the calling/connected line identification restriction service.

16.21.AREA SELECTION This service allows the authorized user(s) to define, for any mobile/and or group the area where they may take benefit of the TETRA services. One may define, as example: • Any TETRA network • The home network • The visited network(s) • The cell • The cell and the adjacent cells • A specific area • … A call under area selection may be submitted to dispatcher authorization.

16.22.LATE ENTRY By this service, the infrastructure periodically transmits group call when they are active. This signaling is transmitted over commonsignaling channels in order to reach mobiles not in a trafic channel. A mobile belonging to a group may be out of coverage or powered off or involved in another communication during a call establishment for this group. When the mobile is again ready to receive the call (power on or moving to a coverage area or communication release), it automatically joins the group communication as soon as this last is not finished. This service is defined for any group with • The group identity • The period of recall

16.23.TRANSFER OF CONTROL Any group communication have one and only one owner ; this last have unique rights as this to release the communication.

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At the first, the owner of a group communication is the initiator of this communication (calling party) – the owner may transfer his rights to another group member involved in the communication by the service ‘transfert of control’. The transfer is realized with indication of the new owner identity; the infrastructure may accept or reject the transfer; in case of acceptance, the transfer is notified to both parties. According to the network, charge transfer may or may not be with transfer of control.

16.24.DYNAMIC GROUP ASSIGNMENT An authorized user may create, edit or suppress a group from any party (individual terminals, group,..) and use a group adress to name it. Short number adresses and lists (for least search call) can’t be included in a dynamic group. After any creation, mofification or deletion of a dynamic group, any group member is informed about it. Dynamic group can’t be included in a list for search list calls. Dynamic assignements are individually notified for each of the concerned terminals: if the terminal is reachable at the time of the modification, it is immediatly updated ; if it is non reachable at this moment, the infrastructure wait for the next registration of this terminal to inform it.

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16.25.INTERFERENCES BETWEEN SUPPLEMENTARY SERVICES 1 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29

Lis search call Include call Call forward unconditional Cll forward on busy Call forward on no reply Call forward on not reachable Call authorized by dispatcher Barring of incoming calls Barring of outgoing calls Call report Second call Callinfg line identification Conected line identificzation Calling/connected line identification restriction Call hold Call completion on busy subscriber Call completion on no reply Short number adress Priority call Preemptivr priority call Advice of charge Discrete listening Ambiance listening Talking party identification Are selection Late entry Transfer of control Dynamic group assignment Call retention priority

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17. DATA SERVICES TETRA standard V+ D defines three types ofdata transmissions :

• Cicuit mode data • IP packet mode data • Short Data Sercice (SDS)

17.1. CIRCUIT MODE 17.1.1. DESCRIPTION With this mode, the infrastructure set up a link from one point to another point or to other points by allocating radio ressources during the whole time of the data communication. The resource allocation is allocated after negociation between infrastructure and terminals as for an audio call.

17.1.2. AVAILABLE DATA RATES Available data rates for circuits mode are ; • Protected mode without interleaving :  7.2 kbit/s 14.2 kbit/s 21.6 kbit/s and 28.8 kbit/s • Low protection with short interleaving:  4.8 kbit/s 9.6 kbit/s 14.4 kbit/s and 19.2 kbit/s • High protection with short interleaving:  2.4 kbit/s 4.8 kbit/s 7.2 kbit/s et 9.6 kbit/s • Low protection with medium interleaving :  4.8 kbit/s 9.6 kbit/s 14.4 kbit/s et 19.2 kbit/s • High protection with medium interleaving  2.4 kbit/s 4.8 kbit/s 7.2 kbit/s et 9.6 kbit/s • Low protection long interleaving  4.8 kbit/s 9.6 kbit/s 14.4 kbit/s et 19.2 kbit/s • High protection and long interleaving  2.4 kbit/s 4.8 kbit/s 7.2 kbit/s et 9.6 kbit/s Following table indicates the time slot number required indifferent cases : Data rate ( kbit/s ) Timeslot number ( 1 carrier ) 7.2 non protected 14.4 non protected 21.6 non protected 28.8 non protected 4.8 low protection short interleaving 9.6 low protection short interleaving 14.4 low protection short interleaving

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19.2 low protection short interleaving 2.4 high protection short interleaving 4.8 high protection short interleaving 7.2 high protection short interleaving 9.6 high protection short interleaving 4.8 low protection medium interleaving 9.6 low protection medium interleaving 14.4 low protection medium interleaving 19.2 low protection medium interleaving 2.4 high protection medium interleaving 4.8 high protection medium interleaving 7.2 high protection medium interleaving 9.6 high protection medium interleaving 4.8 low protection long interleaving t long 9.6 low protection interleaving long 14.4 low rotection long interleaving 19.2 low protection long interleaving 2.4 high protection long interleaving 4.8 high protection long interleaving 7.2 high protection long interleaving 9.6 high protection long entrelacement

4 1 2 3 4 1 2 3 4 1 2 3 4 1 2 3 4 1 2 3 4

1 1 1 1 1 4 4 4 4 4 4 4 4 8 8 8 8 8 8 8 8

When a circuit mode call request is received with a given data rate, according to available ressources and calling and called party declared possibilities, the infrastructure may : • Either set up the communication with required data rate • Or refuse the communication • Or set up a communication with a different data rate :  for unprotected data  If the requested data rate was 28.8kbit/s, the infrastructure may offer 21.6 kbit/s or 14.4 kbit/s or 7.2 kbit/s  If the required data rate was 21.6kbit/s, the infrastructure may offer 14.4 kbit/s or 7.2 kbit/s  If the required data rate was 14.4kbit/s,the infrastructure l'infra may offer 7.2 kbit/s  for data with low protection  If the required data rate was 19.2kbit/s, the infrastructure may offerr 14.4 kbit/s ou 9.6 kbit/s or 4.8 kbit/s  If the required data rate was 14.4 kbit/s, the infrastructure may offer 9.6 kbit/s ou 4.8 kbit/s  If the required data rate was 9.6 kbit/s, the infrastucture may offer 4.8 kbit/s  If the long interleaving was required, the infrastructure may offer medium or short interleaving  If the medium interleaving was required, the infrastructure may offer short interleaving  for data with high protection :  If the required data rate was 9.6kbit/s, the infrastructure may offer 7.2 kbit/s ou 4.8 kbit/s ou encore 2.4 kbit/s  If the required data rate was 7.2 kbit/s, the infrastructure may offer 4.8 kbit/s ou 2.4 kbit/s  If the required data rate was 4.8 kbit/s, the infrastructure may offer 2.4 kbit/s  If the long interleaving was required, the infrastructure may offer medium or short interleaving  If the medium interleaving was required, the infrastructure may offer short interleaving

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17.2. SDS DATA 17.2.1. Description SDS (Short Data Service) offer following services

• • • •

Transmission and reception of short individual messages Transmission and reception of short group messages Transmission and reception of short user defined messages (status) Transmission and reception of short user dfined messages (status)

17.2.2. CAPACITY There are 4 SDS classes • Type 1 SDS : fixed length 16 bit • Type 2 SDS : fixed length 32 bit • Type 3 SDS : fixed length 64 bit • Type 4 SDS : variable length from 0 to 2047 bit Blocs representative of SDS are exchanged over common signaling channels or, trafic channels if one party ins involved in a communication (audio or data). When SDS are transmitted over MCCH or SCCH, the number of time slot needed is according to following table :

SDS type 1 ( 16 useful bit) SDS type 2 ( 32 useful bit) SDS type 3 ( 64 useful bit) SDS type 4 ( 2047 useful bit)

DOWNLINK 1 half slot

8 slots

1 half slot

1 half slot + 8 slots

UPLINK ALOHA access

ALOHA access Preserved access

17.2.3. FLASH MESSAGES Normal SDS messages received by a terminal are stored in the memory of this terminal and an indication is displayed on the home page to show any pending message in the memory. In some case, it is useful not to store the received SDS message but to display it directly: it is the ‘flash message’. These are transmitted exactly as a standart SDS but with one bit difference in the header. Flash message are automatically erased with an action from the user. Flash messages are well suited to MMI with real time functionalities.

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17.3. PACKET DATA MODE

17.3.1. DESCRIPTION Packet data are exchanged over the air interface on logical signaling channels. There are three types of packet data sevices : • " Connection Oriented Packet Data Service " - CONP • " Connectionless Packet Data Service " - SCLNP • " Packet IP " CONP is a service wich transfer X25 packet data from a source node to a destination node by using the ISO8348/8878/8208 protocol. It set up and release dynamically logical connections or virtual circuits between users. SCLNP transfer a data packet from a source node to a destination node without circuit connection. It may be used either with FULL mode ( data transfer + all other specific TETRA facilities),or in SLIM mode ( data transfer + some specific TETRA facilities). SCLNP offers up to 2048 bytes transfer with specific facilities : • priority ( SLIM andt FULL ) • under adressing ( SLIM and FULL ) • datation ( FULL only ) • broadcast ( FULL only under operator control ) • area selection ( FULL only under operator control ) • packet recording ( FULL only under operator control ) CONP an SCLNP are now rarely used, compared to IP packet data mode.

17.3.2. PACKET IP DATA MODE Packet IP data mode offers direct exchange of packet as usually used by softwares between mobiles or between a mobile and serveur(s) directly connected to the infrastucture. An IP packet is transmitted according to : • The transaction is initialised by infrastructure over a common signaling channel (MCCH or SCCH). • This initial procedure is realized with opening an advanced link over a physical channel selected by the infrastructure. • The packet is transmitted with advanced link • The packet is transmitted with or without two types of compression  Header compression  Data compression • When there is no more packet to transmit, - and after some time out – the advanced link is desctivated. IP packet transmission is realized in circuit mode with the high efficiency of the advance link. TETRA standard distinguish different mobile classes according to their possibilities to handle IP packet mode in the same time as other facilities. • A – parallel : the mobile may simultaneously offer IP packet data mode and circuit mode and SDS transmission ; it accepts circuit mode and SDS when it is in the REAY state. • B – alterned : the mobile can’t manage circuit mode and IP packet data mode in the same time. It may accept SDS transmissions and circuit mode establishment signaling when it is in the READY state but it can’t start itself the circuit mode.

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• • • •

C – IP dual mode : the mobile can’t support call establishment circuit mode signalisations ( and circuit mode itself) when it is in packet mode ( status READY) – nevertheless, it may accepts SDS data. D – IP dual mode restricted : the mobile can’t accept any SDS or circuit data call set up signalisation when it is in packet data mode, status READY E – IP and SDS only: the mobile do not support circuit mode F – IP only

17.4. INTEFACES TO TERMINALS Access from a terminal is through the standard PEI interface (Peripheric Equipment Interface ). Between a central equipment and a mobile terminal, following protocols are available:

17.4.1. DATA SERVICE ACCESS FOR CIRCUIT MODE AND SDS Terminal Equipement

Terminal Mobile

Application AT Commands Other levels

V24

V24

CMCE MLE AI 2

AI 1

RT The protocol is based upon AT commands..such protocol is also intensively used between a terminal equipment and a wired modem; irt is also used with GSM, what offers some compatibility level with applications developed for GSM.

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17.4.2. PACKET DATA SERVICE ACCESS : Equipement Terminal

Terminal Mobile IP Signalisation + Relayage ou SCLNP ou X25PLP Convergence MLE PEI DLL AI 2 ( PPP )

IP or SCLNP or X25PLP PEI DLL ( PPP )

V24

V24

AI 1

R1

PPP : specifique point to point protocol IP : Internet Protocol

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18. ENCRYPTION

Enccryption itself is a very simple process wich transform a binary stream to another one with same length according to an algoritm and a key. The key management is often more difficult to handle. There several types of algoritm and keys are either private (one identical key between users) or public (two keys per subscriber : one public for transmission and one private for reception).

18.1. END TO END ENCRYPTION The whole link betwenn two users is protected ; encryption is done inside terminal equipments (radio or wired).

compressor

SW

compressor

BS

Air interface encryption End to end encryption

End to end encrypotion is difficult to implement with audio compressor while an audio signal must be encrypted after the compressor and not before. Encryption defined with TETRA standard deals only with air interface ; end to end encryption may be realized according to IEE standard.

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18.2. PUBLIC AND PRIVATE KEYS There are two types of keys for encryption:

18.2.1. PRIVATE KEYS Private keys are simple and efficient : users who want to exchange information confidentially share the same key wich is used to encode and to decode messages. The key may be specific to an equipment or from an user authentification or from a SIM card. The same key is used from encoding and decoding data. Keys may be different according to communication type. Group communications may be protected with different keys qccording to the group and these keys are different from keys used for selective communications. Group keys must be downloaded to an equipment in case when it is remotely assigned to a group and after check of its own individual key.

18.2.2. PUBLIC KEYS These keys are more complex ; they are used only since a short time. The priciple is as follow : Each user have two different keys : one for encryption, wich is public and one for decoding wich is private. The public key is known everywhere and anybody who want to transmit confidentially a message to somebody get the public key of the destination user and encrypt data with this key. The destination user is the only one to know the reverse key of the preceeding and useit to decode the message. It is not possible to find the reverse key from the orginal one.

Public key KP

Inverse key (private)

ALGORITHM

ALGORITHM

table

Clé déduite Kd

decryption

encryption Message to transmit

Encrypted message

Message as original

Public keys are not used by TETRA standart - only private keys process are defined

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18.3. AIR INTERFACE ENCRYPTION Air interface encryption is realized by combining, bit to bit, data to be encrypted and a encrytion sequence wich is made from a KSG ( Key Stream Generator) ; Such process don’t use any memory effect, what avoid error propagation (sensitivity for radio link). Encryption is made at the higher MAC level; it affects any signaling and audio message but don’t affect headers and adresses.

18.3.1. KEY STREAM GENERATOR The key stream generator is with an algoritm, a key and an initial value ; it produces n bit per time slot named KSS(0), KSS(1), .. KSS(n-1), the largest value for n is 432, it is obtained for TCH 7.2 non protected channel. Bit generated by the key stream generator are added modulo 2(exclusive or) with data. If the number of bit to be encrypted is less than the number of bit generated by the KSG, remaining bit from the KSG are not used. Information about channel allocation are not encryted – same for fill bit. Following diagram show the process for a full time slot encrytion and for half time slot encryption.

MAC header

TM-SDU1

MAC header

TM-SDU1

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Fill bit

KSS1

KSS2

KSS1(0)

clear

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Time slot n

encrypted

Time slot n + 1

FULL TIME SLOT ENCRYPTION

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MAC TM-SDU1 header

MAC TM-SDU1 header Fill bit KSS2

KSS1

KSS2(0)

KSS1(0)

clear

encrypted

Fill bit

clear

encrypted

Time slot n

HALF TIME SLOT ENCRYTION Process is the same for downlink as for uplink

18.3.2. NUMBER AND PARAMETERS FOR KSG Different key stream generators may be used. TETRA standart makes provision for 16 : 8 for standart algoritm and 8 for propriatary ones. Initial value (noted IV) must be periodically changed in order to avoid ‘replay’ technologies ; it contains 29 bit noted IV(0).... IV(28) according to frame number and following rules : • The first two bit are same as time slot number (0 to 3) • following 5 bit are same as frame number (1 to 18) • following 6 bit are multiframe number (1 to 60) • following 15 bit are hyperframe extension number ( 0 to 32767) • last bit is equal to 0 for downlink and 1 for uplink encryption may be according to :

key

Encrytion stream KSG

Initial value

Clear text

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18.3.3. KEYS Several different keys are used according to trafic type. Information about the key in use are transmitted in clear form in the MAC header. SCK key (secondary key) : at a given time, a switch have one and only one SCK key wich is used for any non selectiv trafic and for selectiv trafic to non authentified mobiles. DCK key (dérivated) :it is used with any uplink trafic and for any selective downlink trafic to authentified users MGCK key (group modified) : it is specific for each group and is used to encryt any trafic of this group ; it is made from two keys : • GCK key (group) specific for each group • CCK key (common) spécific for each radio site

18.3.4. ENCRYTION TYPE Several types of encryption level are distinguished : type 1 : no encrytion. Authentification but terminal identities are verified during registration type 2 : encrytion with SCK key type 3 : authentification procedure is used and DCK keys are exchanged between terminal and infrastructure during this procedure. Thanks to this key, a terminal may find the common key (CCK) and, from it, find MGCK key for each of the groups it belongs. Whatever be the encrytion level, distress calls are without authentification.

18.4. AUTHENTIFICATION OF A USER BY INFRASTRUCTURE The key stream generator uses an algoritm A and a key K

key K

Algorithm A

Authentification is a procedure wich allow to a party to check if the other party share the same key as itself. This procedure must be realized without transmission of the key itself and and realized in order to avoid replay – that is a record by an intruder of the data exchanges and a replay of it without knowlege of the content of these data. Authentification is realized by transmitting a non encrypted bit stream. This bit stream is encrypted by the terminal to be authentified and sent back. By comparing the two stream, the nitiating party knows if the key used by the relote terminal is the same as its own.

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Random stream K

K

A

A

=

By extension of this procedure, it is possible to transmit, in the same time as authentification, a derived key (noted DK)

Ramdom stream S1 K

K

A

A

Ramdom stream S2

B

B

DK

DK =

Authentification check if a remote terminal share the same key ; this last may be • Either hard programmed inside the terminal • Or programmed on a SIM card • Or elaborated from a dialing • Or elaborated from a PIN code • Or any combination of these methods

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18.4.1. AUTHENTIFICATION OF AN INFRASTRUCTURE FROM A TERMINAL A terminal may check if the infrastructure where it is registerd is the right one (and not an infrastructure controlled by enemy) that is achieved by an authentificaztion process wich is the reverse as the preceding one.

18.4.2. MUTUAL AUTHENTIFICATION Authentification of the terminal by the infrastructure and authentification of the infrastructure by the terminal may be performy the infrastructure or by the terminal. A derived key DK is transmitted during this double process.

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