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SDCCH drops

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  • #52422

    I work with BTS 240XL-II SIEMENS and radiant system composed by dual band/dual polarized antennas (800MHz & 1900MHz) (2TRX per antenna port). When we need to use more than 4TRX’s, we use an extension rack and an extension antenna, many times this antenna is “similar” to the main one only in technical especifications but not in radiation patterns and that’s the point where the problem begins : I have experienced SDCCH drops at rates of about 6-8% in this cases when the sector has neighbour with another one in other Location Area. Call Setup Fail and TCH Drop rates remain normal and less than 2%, SMS traffic reduces at 20% of its usual load. Anybody in this forum has an explanation for this problem?


    problem in antenna patterns would only generate SDCCH assignment failures or TCH assignment failures (well, sometimes the SDCCH assignment failures are counted into the SDCCH drops, by some vendors, check your formula)

    sdcch drop between LAC’s occurs because of poor coverage at the border, so the Location Update is started but dropped due to poor radio conditions. try increasing your Cell Reselection Hysteresis and Temporary Offset (i.e. 12dB)and Penalty Time (i.e. 40s).

    did you activate SDCCH handovers ? (disable them, by default)

    you can also perform a drivetest/abis to see exactly what is the cause of the problem.


    Hi all
    i am working on a Network with Nokia, Ericsson and Siemens vendors. i am trying to unify main KPI on a netwrok level ( combining all 3 vendors) but i found many differences between each vendor’s KPIs ( radio kpi), Nokia taking into account System point of view and Ericsson taking Customer point of view KPIs. i have a question especially regarding SDCCH Drop Call in Nokia. we experience high SDCCH drop in nokia area compared to Ericsson or siemens. and 99% of SDCCH are due to radio reason ( SDCCH Fail Radio cause). the problem is that this includes also failures before even the SDCCH is completly assigned to MS ( before getting EST IND from MS).
    Do you know any other Nokia formulae that counts only drops after Establish indication
    thanks for support and help


    hello.. i am a newbie…

    in Siemens BTS240XL, if you need to use more that 4TRX’s per sector, you can use an extension rack and you can connect an extension rack to main rack by using selic & can bus cable. No need an extension antenna. except you upgrade your GSM with add DCS site on this GSM site..

    About the degradation of KPI, maybe you can check the performance of hardware or the frequnecy



    Hi putu..
    on that scenario, we also need a specified hardware for Siemens product called FDUAMCO. It allows you to create up to 8 TRX per sector.


    what is difference b/w hysteresis and offset.

    Baba Ibatien Traoré

    what is the solution of high SDCCH Drop due to other reasons?


    I have a problem with micro site in SIEMENS vendor.This sites have a high SDCCH DROP Rate.Please help me about this.please tell me how to set values of T200 in micro and macro site. TX


    SET “TRP=0″(TRX priority in TCH allocation)


    SDCCCH drops, high CE util

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