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Drop reasons due to bad quality on downl

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  • #60937

    Below is the scenario I am facing:
    1. In order to have more BCCH freq and the hopping frequency set was reduced from 21 freq to 18 freq.
    2. Implementation was successful and no general degradation was noticed.
    3. However one particular cell’s TCH drop performance degraded at the same time of implementation; main reasons are drops due to bad quality on downlink.
    Since the degradation was not general across the network what is the cause for this particular cell and what can be changed to reduce its drop rate.
    Thank you so much.



    Could you please share the main KPIs for that site ? (TCH drop%, HO qual%, CSSR) before and after the modification.

    To improve the DL Qual in case of SFH, the strategyis to reduce the overlapping coverage between surrounding cells and this cell.

    Therefore, try downtilting / re-azimuthing the neighbours’antennas. You can also tilt the “bad” cell, in order to reduce its coverage, as long as the coverage is still satisfying for your planning.

    Other “soft” solutions : activate DL/UL power control and DL/UL DTX. If those are already activated, try enhancing the power control thresholds. Put them 3 or 4dB lower.
    Reduce the HO MARGIN, so that the MS will go to the best serving cell faster. For ex: instead of HO_M = 5dB, try 3dB… but on the other hand you must increase the averaging window.

    Finally, you can remove TRX’s in the bad cell and in the cells around, to reduce the radio frequency load. And activate HR, to balance the capacity loss.



    Hi Eric4u.
    You can replan its frequency and observe.Also,check if there is any H/W issue.I think if you have used some AFP tool(not real time based),u need o check your physical database too(Azimuth mainly or cable swap)


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