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SDCCH dimensioning for HR environment

Viewing 15 posts - 1 through 15 (of 155 total)
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  • #35463

    How to dimensioning SDCCH channel for network with HR 30% ?


    what is this HR 30% means ?


    HR penetration.
    The system use Dynamic HR allocation. We use the threshold at mean that when the next call coming the system will check if the idle TCH is less than 30% of total TCH in that cell.So the call will be assign with HR instead of FR.


    Dear wisa, this is the best i can find in my documentation bout Dynamic HR Allocation, i know this is not answer your question, but maybe we can discuss bout this, what kinda switch/BSC do u use ? maybe we can find more things to discuss

    Dynamic HR Allocation
    This feature optimises the usage of capacity when the traffic load is high, whilst it offers the best possible speech quality when the traffic load is low. This is achieved by changing the channel rate of a connection in accordance with the traffic load in the cell. At high traffic load TCH/HR is allocated and at low traffic load TCH/FR is allocated.

    The threshold for traffic load, parameter TLDTH, is defined by the operator. This parameter is defined as a percentage value, set per BSC, indicating the number of idle TCH/FR per total number of deblocked TCH/FR.

    Depending on the traffic load condition the two following cases occur:

    When the number of available TCH/FR in the cell is above the threshold value, FR resource types will have precedence over HR resource types at allocation.
    When the number of available TCH/FR in the cell is below or equal the threshold value, HR resource types will have precedence over FR resource types at allocation.
    At assignment, a change of priority order of preferred channel rate is only allowed if the MS has dual rate capability. At handover, a change of priority order of preferred channel rate is only allowed if the MS has dual rate capability and if the MSC allows changes between full rate and half rate also after the first channel allocation request.

    Within the GSM 900 band, the number of idle full rate channels is determined based on the status of the parameter for available GSM 900 bands, ERBANDSINCLUDED. If the parameter is set to OFF, then only idle full rate P-channels are considered. If the parameter is set to ON, then all idle full rate channels in all available GSM 900 bands are considered.


    Could you tell me how we can reduce SDCCH drops? And how to find out SDCCH drop reason in Ericsson BSC?


    HR usage was not so popular till some time ago due to the degradation in speech quality. Do you know of instances, say networks, where AMR (Adaptive multi rate speech codec)has been implemented with HR to improve upon the speech quality?

    Another question, at what point in the TRX configuration, like single TRX or multi TRX per cell is HR allocation preferred?


    sdcch drop reasons in Ericsson BSC could be find from counter that already defined in BSC, these are some :
    – excessive Timing Advance
    – low Signal strength
    – Baq Quality
    – Others

    in order to reduce SDCCH drop, u must find the relevant problems


    Does SDDCH is useable all allong the speech communication ?


    SDCCH is only used for the call set-up procedure, once this is successful, a TCH is assinged if available and the SDCCH is released


    I have a problem of low call setup success rate and high SDCCH drop, when i see the counters i don’t find any problems of interferences or bad quality (UL and DL). the cells have a good HO_Better cell and low TCH drop!!!

    Paritosh Rai

    How Dynamic SDCCH wrk in Ericssion system.

    Mohammad Yasin

    Hi Jacob
    Please Tell me which vendor equipment you are using.I have an idea about Nokia Equipments.




    Also got some SDCCH in Nokia equipment (BTS/BSC). UL/DL levels is -70?-85. UL/DL qual is 98%/97%. SDCCH drops is 20% (approx 5 drops/hour). Site is in tunnel on a LAC border. Do you have any ideas? Statistics could be better, but not that bad…

    regards, Marcel

    Mohammad Yasin

    Hi Marcel,

    Can you please tell me the value of RLT (Radio Link Timeout) and the no. of SDCCH configured in the cell are normal or more than normal.


    this is right that HR allocation affect the SDCCH dimentioning.
    But i ask about itis effect on PCH capacity. because i know there is optimum point between the SDCCH load & PCH load.
    so i think this point will be change after HR implement & new related SDCCH dimentioning.
    Please more clarification.
    Best Regards.

Viewing 15 posts - 1 through 15 (of 155 total)
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