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High Random Access Failure rate

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  • #50108 Reply

    Hi Vinod,
    The actual RACH failure is only due to collision of RACHs since any subscriber can think of starting a call/sending sms at any time so probibility of collisions are high in RACH phase. But it would not be pegged in any stat at any vendor.

    The RACH failure which is pegged at some vendors is the RACH failure detected after reception of a RACH.
    This failure can be due to CRC check fail of this received RACH, UL level below set threshold. Distance exceeds TA limit.

    #50109 Reply

    Hi Pix,
    I cant help but overlook that there is a serious issue with the formula of SDCCH_assign_unsuccess_rate ( SDNAUR )as MC149 seems added and then subtracted..
    Is it just for the easy of understanding also what are the failures that are counted in [MC148 – MC01 – MC02 – MC149] as they are neither blocking not, Channel not available nor is it MS_Access. So what is it due to.

    Also I dont think RACH discards due to CRC failure, too low UL Level and Dist_limit are pegged at Alcatel.

    #50110 Reply

    hello mania,

    SDCCH_assign_unsuccess_rate =

    SDCCH_assign_cong + SDCCH_assign_fail BSS + SDCCH_assign_fail_Radio


    SDCCH_assign_request = MC04 + MC148
    SDCCH_assign_cong = MC04
    SDCCH_assign_fail_BSS = MC148 – (MC01 + MC02 + MC149)
    SDCCH_assign_fail_radio = MC149

    The Requests is actually the number of “allocations” (mc148) + number of “congestions” (mc04). This is an approximation…
    The failures_BSS are the difference between the allocations and the success + failures_radio. All the allocations that do not become success or fail_radio, then you might wonder what happened to them. We count them as “fail BSS”.

    Let me know if you have any doubt.

    RACH failures are not counted in alcatel, that’s correct.

    #50111 Reply

    Can someone tell me the reason of CSV Access failure ????

    Either it is RF reason or RNC reason…

    #50112 Reply
    Boniphace Meshacky

    hey friends i have a question on how MAIO is applicable in frequencies planning, in case you may found MAIO is out of given range what can you do to solve this problem

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