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DL Quality improvement

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  • #68591 Reply
    Aman
    Guest

    Hi can anybody tell how to improve DL quality at BBH level in an NSN system

    #68592 Reply
    pix
    Guest

    – remove TCH interferences (co channels)
    – activate DL Power control and DL DTX in the whole area (= not in the cell only, but all the neighbours), for all codecs.
    – ensure first-ring neighbours is well defined and MS can do the HO at the right time.

    DL Quality is not an issue if it is less than 5, in case of BBH. Indeed, if less than 5, it does not impact the voice quality that much.

    Set your DL PC to reach an avg dl quality of about 3. With such settings, the interference/noise level of your network will be reduced greatly.

    Cheers
    pix

    #68593 Reply
    Aman
    Guest

    Hi Pix

    DL power control is enabled and DL DTX is also enabled.
    Power control settings are also OK.
    Still maximum cells are having DL quality between 90 and 95 while it should be more than 95.
    We are missing something somewhere but do not know what.
    Can you please tell about enabling DL DTX at MSC
    What should be the value of parameter DL DTX DISABLED BY MSC

    Currently it is OFF and DL DTX is ON at BSC

    #68594 Reply
    Aman
    Guest

    Also as a field observation DL Quality is getting degraded more during hopping. We are using 1*1 frequency hopping.

    #68595 Reply
    pix
    Guest

    aman,

    keep in mind that with SFH 1×1, the acceptable quality is located between 0 and 5, not 0 and 4. So if you see 95% between 0 and 5, then you are fine.

    DTX DL DISABLED = OFF indicates that the DTX is NOT disabled, so that sounds about right to me.

    Quality improvement will be reached if you increase HR usage (that reduces the RF load), and if you increase the downtilt / reduce antenna height.
    SFH1x1 is very sensitive to antenna design, you must reduce cell coverage as much as possible. That’s why doing the “exit” HO asap is important as well.

    Regards
    pix

    #68596 Reply
    Aman
    Guest

    Hi Pix

    We are taking between 0 and 5 only.

    Yet in Full rate quality is deteriorated more than in half rate.

    Can turning on TFO help?

    #68597 Reply
    pix
    Guest

    hi,

    no, TFO will not have any effect on RXQUAL, it will “only” improve the voice quality.
    RXQUAL is the rate of errors on the radio link, nothing else. The only way to improve this RXQUAL is to reduce interference. The codecs, the TFO, the AMR, etc, should not have an effect on RXQUAL. On the other hand, frequency hopping, power control, dtx, vamos, frequency planning, frequency load, antenna, combiner, bts sensitivity, etc, have an effect on RXQUAL (= all “physical” features)

    FR and HR should suffer both from the same RXQUAL. But FR will decode the signal into “speech frame” when rxqual is poor more succesfully than half-rate.

    I don’t know why you are seeing rxqual on HR better than rxqual on FR. Probably a statistical effect ? Perhaps HR calls are established on BCCH frequencies more often ? I have no good explanation… 🙂

    IMO, you should focus on:
    – worst cells
    – PC & HO thresholds

    Sorry, i’m not very helpful, but your problem is “vast” and very specific to your network…

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