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SDCCH congestion

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  • #68297
    slim omrane


    Please to clarify that point :

    In case on SDCCH congestion , Is there a repetition of channel request?Only in case of location update and call reestablishment allowed?
    The KPI SDCCH_congestion rate is thus wrong because it contains redunduncy?

    Please the link for 3GPP clarification


    hi slim,

    if the sdcch is congested, the BSS will behave accordingly to your setting “Enable Immediate Assignment Reject”.
    If “ImmAssRej” = DISABLE then the MS will repeat the Channel Request almost immediately
    If “ImmAssRej” = ENABLE then the MS will repeat the Channel Request only “WI_xx” ms later, which provides more chance for a SDCCH channel to be available.

    The MS can send up to MAX_RETRANS+1 channel requests.

    Yes, the SDCCH Congestion is artificially increased by retransmission. However, if you activate the “ImmAssRej”, you can apply the formula:
    SDCCH_Cong – Imm_Ass_Rej / Channel_Request

    As a result, you are counting only the last congestion failure. If the SDCCH is setup at the 3rd attempt :
    SDCCH Cong = 3
    Imm Ass Rej = 3
    –> sdcch cong rate = 0%

    I hope it makes sense… please test the formula carefully because I don’t remember having tried it.
    (i didn’t care much about artificial SDCCH congestion.. it should always be zero IMO… really and artificially !)


    SDCCH congestion

    Thanks Pix,
    Further clarifications please:
    The SDCCH requests are repeated till max retrans+1 whatever is the type of the service needed (LU,SMS,call establishment)?

    In case of LU,it will stop retransmissions by max retrans+1 or it will do another cycle?

    Please the link of 3GPP doc for repetition of SDCCH requets in case of SDCCH cong


    yes, retransmission works for any kind of request.

    Location update will indeed start a new cycle, because the MS has to do the LU anyway.

    44.018 -> the channel request procedure

    23.122 -> the location update process (i’m not sure whether they say how long to launch a new cycle in this doc).


Viewing 4 posts - 1 through 4 (of 4 total)
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