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 (