Ul Rssi Ericsson

UMTS UL Interference E. Eter

Possible Causes for UL interference

Too high UL RSSI (>-100 dbm) can be caused by:     

External sources of uplink interference Inter-mod product Incorrect plumbing Parameter TMA ulGain setting does not match the real TMA gain Faulty devices along the Rx path  Loose Connectors  Tight Cable Bends

High UL RSSI caused by external interference has significant impact on UL capacity and coverage of a cell.

2

UL RTWP (Ericsson) Antenna

UL RSSI pmAverageRSSI is measured in the RU power sensor. The result is translated to dBm at the Rx reference point by the factor K_dBM. K_dBm = (RUG – FUG) + FAtt – TMAG

Rx Reference Point

Where, FAtt is the Attenuation antenna feeder cable and TMAG is the TMA Total Gain RUG and FUG are internal to the NodeB

TMA

TMAG FAtt

NodeB K_dBm

FUG

FU

RUG

RU RU

Feeder attenuation and TMA Gain are provided by site configuration. So it’s important the loss FAtt and gain TMAG are accurate.

Power Sensor

pmAverageRSSI

Next 3 slides show how to input the TMA gain and feeder attenuation In the OSS element manager

3

TMA Gain

4

Feeder Attenuation and delays

5

Feeder Attenuation and delays

6

pmAverageRssi

7

Ericsson Uplink RSSI Measurement pmAverageRssi  UL RSSI counter can be checked through either RBS Performance Statistics counter pmAverageRssi. It can be read by Business Object or Prospect.

8

UL Interference Monitoring A macro was developed to graph ( see figure below) and flag any cell that has a RTWP at least 2dB greater or less than the mean RTWP for all cells in a given RNC. A daily summary for the worst performing sectors will be available on NetTrack (Ericsson and Lucent ). Ericsson Measured Interference 40000

30000 25000 20000

CNU3007A

15000 10000 5000 0

-1 < 08 11 0 . -1 5..- dB 06 10 m . -1 5..- 8 dB 04 10 m . -1 5..- 6 dB 02 10 m . -1 5..- 4 dB 00 10 m .5 2 . d -9 .- 10 Bm 8. 0 5 d -9 ..-9 Bm 6. 8 5 d -9 ..-9 Bm 4. 6 5 d -9 ..-9 Bm 2. 4 5 d -9 ..-9 Bm 0. 2 5 d -8 ..-9 Bm 8. 0 5 d -8 ..-8 Bm 6. 8 5 d -8 ..-8 Bm 4. 6 5 d -8 ..-8 Bm 2. 4 5 d -8 ..-8 Bm 0. 2 5. d .-8 Bm 0 dB m

Number of Samples

35000

Signal Level

9

How to identify the cause of high UL RSSI In case one or two sectors of a site has high UL RSSI

Antenna

Rx Reference Point

 Swap antenna feeders between good and bad sectors on RBS cabinet top.

A

TMA

 Wait for the next ROP and check the UL RSSI. NodeB



If the high interference stays with the antenna: - then it may be external interference or TMA (A) - otherwise check the FU/RU. (B)

FU

B

 Use spectrum analyzer to detect external interference sources Too low UL RSSI (<-110 dbm) will cause PRACH preamble detection problem because UE uses too low power to access the site. It may also cause UL synch loss drop call if the initial power of the Radio Link is too low during handover.

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RU RU Power Sensor

pmAverageRSSI

LUCENT Uplink RSSI Measurement RTWP VS.RF.Rtwp.LE110 to VS.RF.Rtwp.GT90 Description • The measurement provides a distribution of the Received Total Wideband Power(RTWP) within the granularity period. • The RTWP provides separate counters on a 1dB step size in the typical range used for detailed evaluation. This range is -110 dBm to 90 dBm. • Trigger condition For every 100 ms sampling period the mean RTWP value for the sampling period will be calculated and the appropriate counter incremented. The ranges are defined as listed: 11

LUCENT 1. TMA equipped and controlled by the Node B 2. No TMA equipped

12

TMA equipped Node B The reference point for RTWP is at the TMA input port (antenna side of the TMA). For this configuration RTWP is computed by adding the Rx Path Gain (consisting of the Node B's internal path gain plus the external path gain) to the RSSI measured at the radio's receiver. The external path gain (between the reference point and the Node B's External Antenna Connector (EAC)) is the combination of the Rx Gain data contained in the associated TTLNA Descriptor plus that contained in the Antenna Path Descriptor. RTWP reference point

TTLNA

Feeder Cable

Filter panel

Filter panel attenuator

Cable to Radio

824 MHz

Total Gain (dB)

12.00

-3.00

-0.15

30.50 13

-8.00

-0.70

30.65

No TMA equipped NodeB The reference point for RTWP is the Node B's External Antenna Connector (EAC). In this case RTWP is computed by adding the RSSI measured at the radio to the Node B's internal path gain. The Antenna Path Descriptor's Rx Gain parameters are set to zero.

RTWP reference point

_

LNA

Variable Attenuator

1:3 Splitter

Cable to radio

Total NodeB Filter

Gain (dB)

38.00

-3.00

-7.00 14

-1.60

26.40

Other Cases • There are variants of the "TMA equipped but NOT controlled by the Node B" scenario described in Configuration 2, above. For example, there are certain RxAIT configurations in Cingular's network where RxAIT is equipped without the presence of TMA. In some cases the RxAIT components appear to the Node B as the equivalent of a TMA in the external path. Similarly, there are configurations where the Nokia GSM base station hosts the Rx path. For this case the path through the host GSM base station and antenna system appears as a TMA equivalent.

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