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SDCCH drop rate

Viewing 15 posts - 1 through 15 (of 18 total)
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  • #45152

    Hi RF,

    How can I resolve the SDCCH drop rate problem in my area since no congestion problem both on SDCCH and RTCH.


    check on the frequency


    Hi to All,

    How about SD Assign Fail, what parameters should I look on or to tunned? Anyone could reply to my query would appreciate very much



    SD Assignment Failure is either:
    – congestion (but that’s not considered as a failure, strictly speaking)
    – radio problems
    – hardware problems (abis, trx…)

    If it’s not congestion or hardware, then it’s a radio issue:

    1- Coverage ? does this cell has a huge coverage ? then you can’t do anything unless increasing the RX LEV ACCESS MIN from -104dBm to -100dBm for instance, or reducing the TIMING ADVANCE LIMIT.

    2- Interference ? Try changing the frequency. Try putting the SDCCH timeslot on another TRX.

    I noticed high sdcch failure rate (50%) for sites using abis over satellite. Can’t do anything about this, so far (need to go drive-tests there one day…)


    If TCH Drop is high could be suspected hardware ( TRU , DXU ) if RF losses increased . If MISC Drop increased suspected link .

    I’m also having same problem with SDCCH Drop. There is no congestion issue. But the MISC DRop increased too much.

    Any Idea

    Rahul Godse

    While doing drive test, we found that, same BCCH is observed on TEMS neighbour window with small Rxlev dffrence.
    Neighbour window
    BCCH Rxlev
    611 -74
    611 -76
    why this Rxlev diffrence is for same BCCH ?


    Normally, SD high drop rate problem is caused by :
    – above 4%. Hardware failure, either BTS or transmission >> replace the most problematic module even no alarm appears
    – Specific User, massive SMS usage >> above 8% drop rate. In the case, you can figure out the problem by applying CDR(Record on specific cell). It also accompanies with massive SDCCH load.
    – Imperfect Frequency Assignment >> 1% to 4% drop rate. Of course, co- or adj- channel interference can cause the problem. But you also have to care about the “Too Close BCCH assignment”. The MS usually can not correctly detect the right BSIC if there are two neighbours with the same BCCH. It’s ocassionally error detected. Try to change a new BCCH !!


    Hi ,
    have one query as below:

    we have ultra and metro sites on same mast(Tower) to reduce congetion but in this case we get rx_level below site are same, in this case there is ping pong is happining want to know solution for same. in idle aas well as dedicated mode.

    if we activate C2 para. in NOKIA system than its for dynamic users but what is the solution for static users in idle mode??


    C2 is only for subscribers in Idle Mode. It will help keeping subs within the “lower layer” cell.

    During a call, you have to use specific handovers algo, which prevent power-budget HO from lower to upper cell, and force HO from upper to lower cell. This HO (umbrella-mini) is also depending on traffic load on both cell.

    Tell us how it goes…


    hello facing huge call drop and congestion problem also call setup time is huge………couldn’t find any issue with either BTS or BSC hardware……….any idea….

    Da Architect

    Hello Pix,

    I am facing (as you previously mentioned)SDCCH ASSIGNMENT FAILURE 50% for sites using abis over VSAT. how did you solve this problem?

    Best Regards


    Hi rahul
    Some say it is bug in tems, but i think it is reflected signal strength, which tems is measuring.


    Hello Da architect,

    50% sdcch assign failure is NORMAL for VSAT sites. There is no way to solve this abnorbality. However, keep in mind that this situation does not affect the end user !


    I have worked with so many VSAT sites but what you are telling about SDCCH failures will be 50% in VSAT is not true.


    Are we talking about SDCCH assignement failure, not SDCCH drop, yeah ?

    If so, in alcatel, we measure a lot of SAFR in VSAT cells, but without impact to users. I don’t know for other vendor though… Just sharing my experience.

    How do you improve SAFR in your VSAT cells ? Special timers or parameters settings ?


Viewing 15 posts - 1 through 15 (of 18 total)
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