05 Rn20225en20gln0 Optimization Featuresrg30

BSSOPT 2G Radio Network Optimization Principles (RG30)

Features for Optimization

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Objectives At the end of this chapter participants will be able to

• identify the features that can be useful in the optimization process

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Contents of BSSOPT • Introduction to optimization – What is network optimization – What should be taken into account when starting network optimization?

• Assessment – Current network situation

• KPIs and Measurements – Measurement tables and KPIs

• Finding optimization solutions and verification – Maximum gain in limited time and investments – Optimization tasks, implementations, solutions

• Recommended Optimization Features – NSN recommended optimization features

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Optimization Features – Table of Contents

• The features that can be considered for optimization can be divided in the following categories: – Traffic – Interference – Capacity management – (E)GPRS

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Traffic Features

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Optimization Features - Traffic • Features to improve traffic handling are needed when the traffic handling based on the strongest signal is not performing adequately. • Example features that can be used for traffic handling are the following: – – – – – – –

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Umbrella CBCCH (Common BCCH) Traffic reason HO DFCA (Dynamic Frequency & Channel Allocation) DADL/B (Direct Access to Desired Layer/Band) Soft channel capacity Traffic handling to 3G/LTE

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Optimization Features - Traffic Common BCCH (1) • • • •

Combines signaling channels Combines traffic channels and improves trunking gain Tighter reuse of the non-BCCH frequency band Quality improvement due to decreased number of handovers

CBCCH Example BTS 1, 900 layer, BCCH frequency band BTS 2, 1800 layer, non BCCH frequency band

GSM 900 BCCH, SDCCH GSM 900, TCH GSM 1800, TCH

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Traffic can be pushed to the other layer based on  Load  Signal level  PBGT

Optimization Features - Traffic Common BCCH (2)

Existing BTS parameters are divided into: • Common segment specific parameters • BTS specific parameters

BTS specific parameters

Segment specific parameters

SEGMENT

BCF

BCF

BTS

BTS

GSM 1800 900 BCCH GSM 900 1800

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GSM 1800 900

Optimization Features - Traffic handling Umbrella between 2 cells

Note! HO area

cellA

cellA

These 2 cells can also be located in the same site. cellB

When the signal is better than the umbrella threshold (for example AUCL= -80dB) => Traffic will be pushed to other cell cellB

Dominance area is now bigger HOs back to cellA • PBGT (should be adjusted higher) • Level • Quality 9

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Interference Features

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Optimization Features - Interference • Interference handling is needed when its levels in a cell or site are high and thus performance and network quality are reduced. • Optimization to improve interference levels can be performed using the following NSN features: – AMR FR / HR (can also be used for capacity management) – AMR Progressive Power Control – Advanced Multilayer Handling AMH and Direct Access to Desired – – – – – 11

Layer/Band DADLB (also for capacity management) Single Antenna Interference Cancellation SAIC and Downlink Advanced Receiver Performance DARP Dynamic Frequency and Channel Allocation DFCA Frequency Hopping Energy optimized TCH allocation (RG20) (E)GPRS Downlink Power Control (RG20)

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Optimization Features – Interference AMR FR / HR AMR Full Rate (AMR Quality & Coverage) – AMR FR increases Spectral Efficiency (EFL) – AMR FR increases indoor signal strength – AMR FR increases the effective cell size

AMR Half Rate (AMR Capacity) – AMR enables the usage of half-rate  more users without decreasing voice quality Handover

AMR Half Rate 7.4

5.9

4.75

12.2

7.95

Handover Link adaption

AMR Full Rate 12

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4.75

Optimization Features – Interference SAIC / DARP (1) SAIC = Single Antenna Interference Cancellation Generic term for a receiver algorithm in a handset utilising one antenna Nokia’s phase 1 SAIC is a proprietary algorithm

DARP = Downlink Advanced Receiver Performance 3GPP standardized 2G feature utilising SAIC and uplink signalling Introduced in Rel-6 as release independent feature • Can be introduced to terminals supporting earlier 3GPP releases Nokia’s phase 2 SAIC is a 3GPP compliant DARP feature 13

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Optimization Features – Interference (RG30) SAIC / VAMOS MS Hi, ... … Hi, I’m SAIC…

Mobile station types naming convention  SAIC is a generic term for the algorithm that

suppresses interference in a single antenna Non-SAIC receiver (Single Antenna Interference MS Cancellation)  SAIC was standardized originally in 3GPP Rel.6 DARP and terminals having SAIC algorithm on board MS and signaling their SAIC-capability to the network were officially named DARP phase1 (Downlink Advanced Receiver Performance)  currently MS SAIC-capability is 3GPP release independent feature SAIC-capable  in 3GPP terminology, DARP phase1 MS signals MS its capability to the network, while MS referred to as SAIC does not have to indicate its capability

Hi, I’m VAMOS I … ... I’m better than SAIC since I can use new TSCs 

 VAMOS I MS supports new training sequences

that have been optimized for simultaneous use in OSC mode and hence provides link gains over legacy TSCs  VAMOS II MS supports new training sequences and utilizes advanced receiver providing further link gains over VAMOS I or SAIC. It supports also Shifted SACCH functionality.

VAMOS I MS

 Note: in most of NSN materials the term “SAIC MS” refers to a mobile that have SAIC capability and indicates it to the network 14

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Hi, I wish I could tell you that I’m SAIC, but…

VAMOS II MS

Hi, I’m VAMOS II … … I’m even better than VAMOS I 

Optimization Features – Interference (RG30) SAIC / VAMOS MS

• Features provides support for new types of handsets: VAMOS-1 and VAMOS-2. • New Training Sequence Codes were defined and standardized in 3GPP for VAMOS mobiles in order to improve their link level performance when paired in OSC mode. VAMOS-2 additionally utilizes joint detection method/successive interference cancellation to retrieve the desired signal out of composite channel. • New TSCs were introduced in such a way that for each legacy TSC there is a new TSC and the cross-correlation properties of such pair is optimized to assure its orthogonal properties • Features work on top of RG20/25 features DHR/DFR with limited number of changes in RRM mechanism in comparison with pre-RG30 OSC implementation

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OSC support for VAMOS handsets (RG30)

- OSC support for VAMOS handsets – major changes in RRM: - once at least one VAMOS mobile is paired in OSC mode, new TSC has to be assigned for one of the mobile in this pair; the second mobile will use legacy TSC - the TSC pairs are fixed in such a way that for one legacy TSC (from so called TSC set 1) there is only one counterpart new TSC (from new TSC set 2) to be used for the paired mobile – this TSC has the same number as the counterpart legacy one

- VAMOS pairs (i.e. OSC pairs where at least one of the mobile is VAMOS capable) could be prioritized over non-VAMOS pairs (i.e. where neither of the mobiles is VAMOS capable) in order to boost the penetration of new TSCs and hence increase the link performance of such pairs and consequently reduce the overall interference level in the network - DFCA algorithm is updated and made aware of new TSC set - TSC pairing rule for VAMOS case has to be respected by DFCA algorithm - new C/I target and soft blocking values for VAMOS DHR and VAMOS DFR are introduced

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AQPSK support with VAMOS-2 handsets (RG30)

- AQPSK support with VAMOS-2 handsets – major changes in RRM: - non-SAIC mobiles are allowed to be paired with another mobiles (in both DHR and DFR mode) – if the second mobile in this pair is VAMOS-2 capable - Without this feature non-SAIC mobiles are excluded from any DHR/DFR pairing actions

- in case of VAMOS-2/non-SAIC pairing asymmetrical AQPSK modulation is applied in DL direction in such a way that subchannel with higher power is assigned to non-SAIC mobile and sub-channel with lower power is assgined to VAMOS-2 mobile - AQPSK modulation loss for both candidates has to be taken into account in the power budget calculation prior to the actual pairing to assure that both MSs will survive more severe radio conditions after the pairing (caused by interferences from the other sub-channel and sub-channel power imbalance) - Modulation loss is also taken into account in the DFCA algorithm

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Optimization Features – Interference SAIC Modulations: GMSK

8-PSK

In today's GSM networks the vast amount of traffic is using GMSK modulation

FR, HR and EFR speech AMR speech GPRS EDGE (MCS1-4) Control channel EDGE (MCS5-9)

SAIC is a digital signal processing technique that uses the correlation properties of a GMSK modulated signal to perform an active cancellation of the interfering signals

Neighbor BTS

GMSK modulated interferers  SAIC gain Own cell

fc

8-PSK modulated interferer  No SAIC gain / No loss Gain on both synchronized and non-synchronized networks

Serving BTS

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Optimization Features – Interference

DFCA – (Dynamic Frequency & Channel Allocation) Random FH TRX 1

BCCH

TRX 2

Random FH over a fixed frequency list

TRX 3 TRX 4

DFCA TRX 1

Loose interference control

•

Relies on random spreading of the interference

BCCH Cyclic FH over individually selected frequency lists and MAIOs for each connection

TRX 2 TRX 3 TRX 4

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C/I > C/I target

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Accurate interference control (C/I estimations)

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Each connection is assigned with the most suitable radio channel (MA list, MAIO, TSL)

Optimization Features – Interference Energy optimized TCH allocation (1) • RG10 provided a wide range of Energy Efficiency solutions • Through this RG20 feature, the BTS power consumption can be further • • •

•

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reduced by allocating the most power demanding MSs to the BCCH TRX (which is always at the maximum power) Allocation to the BCCH TRX is based upon the Downlink received signal level information The improved power management achieved reduces the level of interference in the Downlink and consequently may also decrease the call drop rate Transmit Power reductions of 1.5 to 2.5dB are anticipated, leading to a possible Power Consumption improvement of around 10%  OPEX savings The gain is greatest for lower to medium TRX loading levels (up to approximately 60% TRX loading). For increasing loads, the influence of the feature and consequently the gain, reduces

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Optimization Features – Interference Energy optimized TCH allocation (2)

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Capacity Management Features

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Optimization Features – Capacity Management • Capacity Management is the process where network capacity is increased through the use of features that enable more efficient use of the existing hardware capacity. • Example of new RG30 features that can be used to optimize capacity are: – – – –

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OSC Double Half Rate with SAIC MS OSC Full Rate with SAIC MS Circuit Switched Dynamic Abis Pool Local switching for Packet Abis

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Optimization Features – Capacity Management OSC Half Rate with SAIC MS (1) Doubled Channel Capacity for Voice with legacy SAIC+AMR Handsets through applying “4G technology” in the 2G BTS • Low cross-correlation Training Sequence Pair • • • •

Q

enables multiplexing of OSC UL/DL Sub-channels Downlink uses QPSK modulation with each subchannel detectable in SAIC MS as normal GMSK Uplink based on V-MIMO applied for normal GMSK OSC can be applied for TCH/HR to provide 4x HR Channels per radio timeslot ~ “Double Half Rate” Fewer TRX (+ related hardware) are required for OSC: – 4 OSC TRXs may provide capacity equiv. ~ 6..8 TRXs – Reduced combining losses  Fewer required Sites – Energy Efficient solution, reducing the total BTS

(User-A, User-B) (1,1)

(0,1)

I (0,0)

(1,0)

HR HR

FR ~8 dB

DHR DHR DHR DHR

~12 dB

power

TRX

User-A User-B 24

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V-MIMO Receiver

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Deciphering Deciphering

Decoding Decoding

Abis

C/I

Optimization Features – Capacity Management OSC Half Rate with SAIC MS (2)

Radio Resource Aspects for OSC

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Two Subscribers to be paired into the same radio resource – Preferably with similar link budget (up to ~40dB window) – DFCA functions of the BSC may be employed for optimal pairing – Combining OSC with DFCA results in a further improved DHR utilization

• Power Control in DL for two Subscribers sharing QPSK constellation – Maximum power of the two users is used

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A Virtual TRX is provided via OSC – Dynamically allocated Abis resources

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Optimization Features – Capacity Management Circuit Switched Dynamic Abis Pool (CSDAP) (1) • 2 x 8kbit/s Abis Timeslots are required to support the paired OSC Half Rate Calls (OSC-0 and OSC-1) with OSC Half Rate with SAIC MS

• It is not efficient to simply double the fixed transmission capacity for each Radio Timeslot since the extra capacity is only necessary during higher loading; when OSC is activated

• Thus, practically, either: – A Packet Abis (over TDM or over IP/Ethernet) Solution or – The Circuit Switched Dynamic Abis Pool (CSDAP) feature is required to support the additional Abis capacity

• Circuit Switched Dynamic Abis Pool offers the possibility to create and manage common transmission pool(s) - shared capacity - for OSC Half Rate Calls within the BCF 26

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Optimization Features – Capacity Management Circuit Switched Dynamic Abis Pool (CSDAP) (2)

Efficient management of OSC Abis capacity requirements.

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(E)GPRS Features

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Optimization Features - (E)GPRS Example of (E)GPRS features: – – – – – – – – – – – – – 29

NCCR, NACC EDA (Extended Dynamic Allocation) HMC (High Multislot Classes) Extended cell for (E)GPRS Dynamic Scheduling for Ext UL TBF PCU pooling DL DC Territory Procedures (RG20) TRX specific link adaptation for DLDC (RG20) Smart Resource Adaptation (RG20) Adjustable TBF Multiplexing Density (RG20) Enhanced Packet Scheduling (RG30) Admission control for EGPRS (RG30) Intersystem NCCR for LTE (RG30)

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Optimization Features – (E)GPRS Network Controlled Cell Reselection (NCCR)

• NCCR (Network Controlled Cell Reselection) enables the network to control the resource allocation when the MS performs the cell reselection. • NCCR is an optional feature in Nokia BSC. Operator can enable/disable the feature on BSC level. • Network Control Mode (NCM) defines how cell re-selection is performed: Cell border with default values

GPRS

EDGE

BTS

EDGE

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Cell border with default values

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Packet Transfer Mode

EDGE • Offset 24 dB when going from EDGE to BTS GPRS cell • Offset -12 dB when going from GPRS to EDGE cell

EDGE

Result: EDGE MS does not enter GPRS cell.

Optimization Features – (E)GPRS Network Assisted Cell Change (NACC) NACC shortens the cell reselection in two ways: • Sending neighbour cell system information on PACCH to MS in packet transfer mode while it is camped on the serving cell • By supporting PACKET SI STATUS procedure in a target cell Cell Reselection Delays Two-phase access, Inter-RA, Inter-PCU Nokia 6230i

NC0 = “normal” cell reselection 6 38% drop in outage times

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Time(s)

4

Application Outage Data Outage Cell Outage

3

2

1

0

NC0

NC0 + NACC

Network Control Mode

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Optimization Features – (E)GPRS Extended dynamic allocation (EDA) Peak uplink throughput doubled to 236.8 Kbps with 4 slots

Extended Dynamic Allocation increases GPRS/EDGE peak uplink throughput to 236.8 Kbps

• Without EDA, 1 DL timeslot is needed for each UL timeslot • With EDA, 1 DL timeslot can control multiple UL timeslots

With Class 1-12 mobiles, no EDA

Peak uplink throughput 350

– Maximum 4+1, 3+2 timeslots DL+UL

300 250

– Maximum 1+4, 2+3 timeslots DL+UL

200

With High Multislot mobiles and EDA – Maximum 2+4, 3+3 Timeslots DL+UL

kbit/s

With Class 1-12 mobiles and EDA

S11.5 S12

150 100 50 0 GPRS

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GPRS CS3/4

EDGE

Optimization Features – (E)GPRS High Multislot Classes (HMC) Supports 3GPP Release 5 High Multislot Mobiles • Multi Slot Class 30 ... 45 Mobiles • Maximum (Sum = 6): 5+1, 4+2

High Multislot Classes increases GPRS/EDGE peak downlink throughput to 296 Kbps

Timeslots DL+UL • With Extended Dynamic Allocation also: 2+4, 3+3 Timeslots DL+UL 350 300

Peak downlink throughput

250

kbit/s

Increased Downlink data rates • Improved Video streaming • Faster Web content browsing • Faster mail attachment download

200

S11.5 S12

150 100 50 0 GPRS

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GPRS CS3/4

EDGE

Optimization Features – (E)GPRS DL DC Territory Procedures Enables DL DC with reduced PCU Resources TRX 1 (BCCH)

•

•

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CCCH SDCCHSDCCH

PS

PS

PS

PS

PS

TRX 2

CS

CS

CS

CS

PS

PS

PS

PS

TRX 3

CS

CS

CS

CS

CS

CS

CS

CS

TRX 4

CS

CS

CS

CS

CS

CS

CS

CS

Territory enhances dynamically to another carrier due to DL DC allocation, if CS traffic load allows it, because CS has priority over PS.

Enhances the Territory Handling procedure such that by default an operator is able to maintain a smaller PS Territory, which may then be extended upon request - when a Downlink Dual Carrier (DL DC) capable terminal enters the packet transfer state Currently the default PS Territory (across the two TRX) may be downgraded due to CS traffic loading, but it cannot be automatically upgraded for the DL DC MSs © Nokia Siemens Networks

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Optimization Features – (E)GPRS Enhanced Packet Scheduling • Specifies how the BSC behaves when the BSS PFC procedures are enabled and how the 3GPP Release 99 QoS attributes are used in the PCU. • The BSS PFC is a standardized procedure that enables the transfer and negotiation of QoS parameters between SGSN and the PCU. The packet flow identifier (PFI) field is used to indicate which packet flow a given logical link control packet data unit (LLC PDU) belongs to. • Each packet flow has an Aggregate BSS QoS Profile (ABQP) of its own which defines a set of QoS parameters that determine the QoS requirements of a given packet flow. • The PFI field thus links the LLC PDU to the correct QoS parameter set. - It allows the operator to provide service differentiation to the mobiles based on the Release 99 QoS attributes. • The adjustable scheduling weights used in this feature allows the operator to determine how PCU shares the radio resources among the users with different QoS attributes, See next slide! 35

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Optimization Features – (E)GPRS Admission Control for EGPRS • Allows the operator to do QoS differentiation for GPRS and EGPRS subscribers at temporary block flow (TBF) establishment in such a manner that low priority TBFs are more easily rejected in high traffic load situations than high priority TBFs -> high priority subscribers are more likely getting service in congestion situation than low priority subscribers.

• The idea of the Admission Control for EGPRS feature is to block some new TBFs at TBF establishment in high traffic load situation, rather than admitting all TBFs in and dropping some ongoing TBFs in case of congestion.

• This increases the probability that the already admitted subscribers are able to complete their data transfer successfully and thus less radio resources are wasted on uncompleted data transfers.

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Optimization Features – (E)GPRS Intersystem NCCR for LTE • This feature provides the possibility for the network to order a cell reselection from GSM to LTE instead of the autonomous selection done by the mobile station (MS) itself. Based upon this feature, the network decides when the MS should change the cell and what the target cell should be. • Parameter: LTE NCCR Enabled. The values are 0 (Disabled), 1 (Coverage based Inter System NCCR for LTE) or 2 (Coverage and service based Inter System NCCR for LTE). • The criterion for the Inter System NCCR to LTE (Coverage based) is as below: (Signal level of the target cell > LTE NCCR quality threshold) and (Priority of Target cell > priority of serving cell). • The criterion for the Inter System NCCR to LTE (Service based) is as below. (Signal level of the target cell > LTE NCCR quality threshold).

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