rssi

1 (6) Technical Support Punlarp Maipaiboon 11 April 2005 RX antenna supervision by comparing RSSI

The purpose of this feature is to monitor the Rx antenna condition. Rx antennas can be monitored for major problems by taking a long-term average of the difference between the Main Rx RSSI and the Div Rx RSSI. This feature provides continuous antenna supervision for the BTSs, which have main and diversity in use. It also offers an alternative solution for Tx monitoring in cells that use duplexing. This detects, for example, antennas with poor VSWR and inadequate feeders.

The monitoring is based on the principle that all received bursts, where the Rx level of main or diversity branch is above the defined limit value (-95dBm), are accepted as samples and used in the averaging process. The differences of the TRXs connected to the same antennas are counted up, and the average difference per main and diversity antennas is calculated. If the difference is above the threshold (default value 10 dB), an alarm is activated. For the Nokia PrimeSite base station, the Rx branch difference is calculated separately per TRX. The threshold default value of 10 dB can be changed by a parameter at the BSC between 5-64. The functionality of the feature can be disabled by using the maximum value.

It is still possible that both antennas are damaged simultaneously and the difference algorithm cannot detect the fault. For this reason, the BTS also observes the assignment and handover success rate per antenna. Excessive failures are detected by Bias-T unit, and an SWR alarm is raised.

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In case of alarm: 1 Check if the LNA is installed at the Diversity RX. If yes ignore alarm or adjust the parameter RXD 2 If no LNA installed at Diversity RX go to 2.1

2 (6) Technical Support Punlarp Maipaiboon 11 April 2005 2.1 To investigate, connect to BTS remotely by Remote BTS Manager open the RSSI comparison

value in Supervision menu to get the compared result. Example: *************************** RSSI Comparision Values *************************** Newest values: TRX ID Ant 1 Ant 2 Ant 3 Ant 4 Diff. Rel. Diff. --------------------------------------------------------------------- Sector 13 TRX 1 -84 -85 n/a n/a 1 0.00 TRX 2 -84 -85 n/a n/a 1 0.00 TRX 3 -84 -87 n/a n/a 3 0.00 TRX 4 -84 -84 n/a n/a 0 0.00 Avg. Diff. 1.25 Sector 14 TRX 5 -84 -84 n/a n/a 0 -0.67 TRX 6 -85 -84 n/a n/a 1 -0.67 TRX 7 -84 -84 n/a n/a 0 -0.67 TRX 8 -86 -86 n/a n/a 0 2.00 Avg. Diff. 0.25 Sector 15 TRX 9 -85 -85 n/a n/a 0 1.00 TRX 10 -84 -85 n/a n/a 1 -0.50 TRX 11 -85 -84 n/a n/a 1 -0.50 Avg. Diff. 0.67 Antenna Ant:1 Ant:2 TRX 1 -84 -85 1 TRX 2 -84 -85 1 Avg. Diff. 1.00 Antenna Ant:2 Ant:1 TRX 3 -84 -87 3 TRX 4 -84 -84 0 Avg. Diff. 1.50 Antenna Ant:3 Ant:4 TRX 5 -84 -84 0 TRX 6 -85 -84 1 Avg. Diff. 0.50 Antenna Ant:4 Ant:3 TRX 7 -84 -84 0 TRX 8 -86 -86 0 Avg. Diff. 0.00 Antenna Ant:5 Ant:6

3 (6) Technical Support Punlarp Maipaiboon 11 April 2005 TRX 9 -85 -85 0 TRX 10 -84 -85 1 Avg. Diff. 0.50 Reliable values: TRX ID Ant 1 Ant 2 Ant 3 Ant 4 Diff. Rel. Diff. --------------------------------------------------------------------- Sector 13 TRX 1 -84 -85 n/a n/a 1 0.00 TRX 2 -84 -85 n/a n/a 1 0.00 TRX 3 -84 -87 n/a n/a 3 0.00 TRX 4 -84 -84 n/a n/a 0 0.00 Avg. Diff. 1.25 Sector 14 TRX 5 -84 -84 n/a n/a 0 -0.67 TRX 6 -85 -84 n/a n/a 1 -0.67 TRX 7 -84 -84 n/a n/a 0 -0.67 TRX 8 -86 -86 n/a n/a 0 2.00 Avg. Diff. 0.25 Sector 15 TRX 9 -85 -85 n/a n/a 0 1.00 TRX 10 -84 -85 n/a n/a 1 -0.50 TRX 11 -85 -84 n/a n/a 1 -0.50 Avg. Diff. 0.67 Antenna Ant:1 Ant:2 TRX 1 -84 -85 1 TRX 2 -84 -85 1 Avg. Diff. 1.00 Antenna Ant:2 Ant:1 TRX 3 -84 -87 3 TRX 4 -84 -84 0 Avg. Diff. 1.50 Antenna Ant:3 Ant:4 TRX 5 -84 -84 0 TRX 6 -85 -84 1 Avg. Diff. 0.50 Antenna Ant:4 Ant:3 TRX 7 -84 -84 0 TRX 8 -86 -86 0 Avg. Diff. 0.00 Antenna Ant:5 Ant:6 TRX 9 -85 -85 0 TRX 10 -84 -85 1 Avg. Diff. 0.50

4 (6) Technical Support Punlarp Maipaiboon 11 April 2005 The following are the example of possible case:

1. Cable (1) failed Newest values: TRX ID Ant 1 Ant 2 Ant 3 Ant 4 Diff. Rel. Diff. --------------------------------------------------------------------- Sector 13 TRX 1 -104 -85 n/a n/a 19 0.00 TRX 2 -104 -85 n/a n/a 19 0.00 TRX 3 -84 -104 n/a n/a 20 0.00 TRX 4 -84 -104 n/a n/a 20 0.00 Avg. Diff. 19.5

2. Cable (2) failed Newest values: TRX ID Ant 1 Ant 2 Ant 3 Ant 4 Diff. Rel. Diff. --------------------------------------------------------------------- Sector 13 TRX 1 -84 -104 n/a n/a 20 0.00 TRX 2 -84 -104 n/a n/a 20 0.00 TRX 3 -104 -84 n/a n/a 20 0.00 TRX 4 -104 -84 n/a n/a 20 0.00 Avg. Diff. 20



5 (6) Technical Support Punlarp Maipaiboon 11 April 2005





6 (6) Technical Support Punlarp Maipaiboon 11 April 2005

9. No any cable failed but one feeder and/or antenna have VSWR better that another or vice versa, alarm can be activated.

Newest values: TRX ID Ant 1 Ant 2 Ant 3 Ant 4 Diff. Rel. Diff. --------------------------------------------------------------------- Sector 13 TRX 1 -82 -94 n/a n/a 12 0.00 TRX 2 -82 -94 n/a n/a 12 0.00 TRX 3 -93 -82 n/a n/a 11 0.00 TRX 4 -93 -82 n/a n/a 11 0.00 Avg. Diff. 11.5

For the case(9) if measure the Ant1 and Ant2 with Site Master, the VSWR for both are acceptable but one is quite better than another. In this case the problem cab be the connector or Feeder jumper etc.

However if cable (1) and (2) are failed simultaneously alarm will

not generate because there is no diffence between them. In case RSSI comparison result show that RX cable like cable number (3)(4)(5)(6)(7)(8)… failed, this fall can be confirm by perform TRX test remotely.

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