Operation Guide - RX Path Imbalance

OPERATION GUIDE: RX PATH IMBALANCE REASON This problem is created because there is a difference between the signal strength levels of the path A and path B in the reception part of the RBS that exceeds the limits defined by the Define RX Path Imbalance Parameters in the OMT. The supervision of this fault is based on measurements over a long period; hence the fault does not cease as soon as the fault is corrected. Actions are to be taken by 1. Field Team 2. NPM Team

ACTIONS: FIELD TEAM Check configured data 1. Check the defined RX path invariance limits using the Define RX Path Imbalance Parameters function in the OMT for the faulty antenna system. 2. Check the number of samples (should be 7000) and threshold (60). 3. Use Document below to redefine samples or threshold if required

46679007-Define-R X-Path-Imbalance.docx

Using OMT monitor RX The RX imbalance monitor must be used to verify the correction of the fault. After waiting for 5 min, the output will come. If the result is 0 dB then perfect, however, if the delta signal strength A-B is 1. (-) negative then it means the problem is with Branch A. 2. (+) positive then it means the problem is with Branch B. If the delta signal strength A-B exceeds +/- 6 dB, the alarm will be raised. Procedure to monitor the RX Imbalance is below

1. In the OMT select “Maintenance” , “Monitor” and select the RX Imbalance for the TRX carrying a traffic. 2. The Average delta signal strength A-B and Number of samples A-B will be shown in the window and the monitor will update every 5 minutes. Check physical connections based on the result from Monitoring 1. Check the RX cables, Jumpers, feeders, cable connections inside and outside the cabinet and antennas, for example, with Antenna System SWR tests. 2. Open and reconnect all internal RF Coaxial cable. 3. Check and tighten all feeder system connection. 4. When the fault is corrected, reset the TRU to cease the fault immediately. 5. Test the possibility of antenna fault, and replace if required Notes 1. 2G cannot handle AISG. 2. If incorrect UL/DL attenuation and delay is set for the sharing path between RUSs an imbalance will result in the system. 3. When TMA/ATMA is in use the gain is set manually for the 2G-side. If this is not done an imbalance will occur. This is mainly for tri-band Antennas.

ACTIONS: NPM TEAM Check MRR results 1. MRR shows RXlev imbalance between Path A and B 2. Diversity supervision shows Rx Lev imbalance between path A and B 3. Rx Diversity Monitor shows Rx Lev imbalance between path A and B Check if Configuration Issue Sometimes after site issues have been resolved there isn’t sufficient samples to cease the alarm and the alarm remains pending. In those cases, it has been suggested that increasing samples via CS traffic may be used. Before performing this, Network Performance Management team has to confirm that all KPIs (accessibility, retainability) are fine. We could increase the number of samples i.e. CS traffic, in the CHGR where the alarm was observed in order to cease the same. Following changes were suggested in order to increase CS traffic in CHGR > >

CSPSALLOC as CSFIRSTPSNOPRF CSPSPRIO as CSPRIO

>

NUMREQEGPRSBPC value to 0 in CHGR0 and same value to updated in CHGR1.

If no alarms are observed after changing the configuration then it clearly shows the configuration fault (not HW/SW fault).