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TCH drops due to high utilization

  • This topic has 8 replies, 1 voice, and was last updated 9 years ago by pix.
Viewing 9 posts - 1 through 9 (of 9 total)
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  • #67664 Reply
    Saurabh
    Guest

    I want to know whether there can be TCH drops due to high utilization in a cell or not. How do we justify this?

    #67665 Reply
    pix
    Guest

    hi,

    high load in a cell means that neighbour cells are probably highly loaded as well…
    If that’s the case, then it means all frequencies are highly utilized, which means the C/I degrades, which leads to more drops.

    I would say the increase in drops is about +30% to +50% compared to non-busy hours.

    If neighbours are not loaded, then I would assume that one of the TRX which is usually not used during low-load starts to take more traffic during the busy hour. Bad luck : this trx is either faulty or uses a frequency which is “dirtier” than the ones used in the other TRXs.

    Let le know if that helps,

    Cheers
    pix

    #67666 Reply
    Aman
    Guest

    Hi Pix
    What Could be the reason if TCH Drops degrade in the whole BSC in peak hour. Also cells in which they degrade are not common.

    #67667 Reply
    pix
    Guest

    aman,

    what do you mean by “not common” ?

    here are my first guesses :

    – bsc overload
    – tc overload
    – peak hour = in-car calls = highly mobile subscribers = lots of HO –> call drop rate must degrade
    – high frequency usage = high interference
    – …?

    what is the cause of drops ?

    cheers
    pix

    #67668 Reply
    Aman
    Guest

    Hi Pix
    Cause of Drops is not clear.Drops come randomly and majoraly are pegged in TCH_RF_Fail
    In afternoon with almost same traffic we do not observed any drops.
    But in evening i.e. in peak hour lot of drops are observed. And Most of the BSCs having such problem belong to same MSS.
    Earlier their seemed to problem in SYNC.Every time we changed the clock source,we got improvement in drops. But now we have dedicated SSU for clock generation.So there is no problem of clock as well.

    by common cells I mean that suppose there are 100 cells having TCH Drop>2% on day1, then on day2 there are completely different cells having high Drop.Hardly 10-15 cells are common

    One of the facts i agree with you is that, yes there are lot of handovers in peak hour and more than 50% of them are due to poor down link quality.

    Please suggest.

    #67669 Reply
    pix
    Guest

    ok.
    can you give me an example for one cell ?

    during the afternoon
    – call drop rate = ?
    – tch erlang = ?
    – ho qual (ul + dl) = ?

    during the evening
    – call drop rate = ?
    – tch erlang = ?
    – ho qual (ul + dl) = ?

    you know what you could do : show the hourly evolution of total tch erlang for the whole MSC and see if the CDR suddenly increase as soon as a certain value is reached ?
    that would prove that the msc is overloading..

    -> do the same graph per BSC.

    finally : are you using frequency hopping SFH ? or BBH ?

    cheers
    pix

    #67670 Reply
    Saurabh
    Guest

    Hi,
    I am facing issues in cells where neighbors are not congested & also this phenomenon is very common, so can’t assume the TRX faulty for all cases.

    #67671 Reply
    Aman
    Guest

    Hi Pix
    the analysis was done but it fails at some points because on certain days, the KPIs get normal by themselves.
    so the question arises why MSC is not getting overloaded during that days…nd there is no traffic dip on that days

    there is something that we are missing out…but do not know what…

    #67672 Reply
    pix
    Guest

    hi aman,

    ok, that’s good, but I need you to answer my previous post…

    also – you have done the analysis per BSC and per MSC ?
    what about “per TC” ?

    regards
    pix

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