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Deradation in DL Quality with AMR

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  • #59284 Reply

    AMR has been implemented in one of our major cities and there is degrdation in DL Quality with AMR implementation. Total no of samples in RXQUAL 0 were about 81% before implementation which have reduced to around 74% after AMR implementation incresing DL Quality Handovers for city level.
    Strange thing is that there is no degrdation in uplink.
    Vendor is Alcatel (B9).ACS for AMR FR is (12200,7950,5900) while for AMR HR (7950,5900,5150,4750).
    Any reasons for this degrdation as everything is same as before i.e Frequency plan , database (except AMR parameter changes) ,hardware??

    #59285 Reply

    dear this is normal when you have AMR because this speech codec make your call at bad rx quality but the ms sending measurement report to network that the radio condition is bad so trying to trigger ho so in order to eliminate this problem there are L_RX_QUAL_THRESHOLD TO AMR SO YOU HAVE TO CHECK YOUR SEETTING IF THEY THE SAME AS NON AMR YOU HAVE TO CHANGE IT TO LOWER THAN NON AMR

    #59286 Reply

    I think that there is more to it, first of all there is drastic increase in Half Rate traffic for BSCs as there are more than 500,000 HO attempts per day with cause 27 and there are very few attempts with cause 26 that is from HR to FR.
    I think DL Quality degrdation is linked to this increase in HR traffic .

    and these very high number of attempts with cause 27 are because of very high values for Offset_CA_High and Offset_CA_Normal which are currently set to value 45 (4.5).

    #59287 Reply


    I don’t really have time to explain, but later i will 🙂
    So the thing is : if RXQUAL = 0, then the cause AMR FR –> AMR HR is detected (because the threshold is “0”). So most of MS AMR will actually be in “AMR HR” rather than AMR FR.

    Perhaps the bad RXQUAL average values are due to this also… AMR HR provides less protection than AMR FR.


    #59288 Reply

    you are right, this channel adaptation from FR to HR is causing this increase in HR traffic and hence degradation in DL Quality.
    Only confusion is that there is no degrdation in UL Quality as total number of samples in RXQUAL 0 are 87% after the implementation which are same as before.

    #59289 Reply

    After the implementation of AMR as soon as DTX was enabled for both AMR FR and HR, Downlink Interference Handovers have increased for all the cells.

    What can be the possible reasons???

Viewing 6 posts - 1 through 6 (of 6 total)
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