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SD blocked

Viewing 14 posts - 1 through 14 (of 14 total)
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  • #55431 Reply
    rkb
    Guest

    I have found blocked call(SD block) in TEMS log file.
    The layer 3 message was ‘missing immediate assignment’ while the MS requested channel(AGCH) (in the call attempt retry).
    After 2 retry (as by the max_retransmission parameter)the call was blocked.and the layer 3 message was ‘No immediate assignment’.
    What does that layer 3 messages mean?Does it mean to any specific cause for that Block?
    I know that thats a SD block.But I couldnt find the reason for that block.There supposed to be no SD blocking.

    #55432 Reply
    rkb
    Guest

    why there was no immediate assignment command from the bts after ms requested for channel by RACH?..what may be the cause?..

    #55433 Reply
    Pix
    Guest

    This is normal,

    In case the SDCCH channels are all busy (= high sdcch congestion rate), then the BTS doesn’t have to reply to the MS.
    The MS will then retry by itself, by sending a second and then a third CHANNEL REQUEST.

    This is a standard mode of operation.

    There is feature called “immediate assignment reject” that can be activated, so the BTS will send a message (IMMEDIATE ASSIGNMENT REJECT). This is not mandatory though. It works better this way though (generates less sdcch congestion), so I usually recommend to activate it.

    #55434 Reply
    rkb
    Guest

    hi Pix,
    Other then SD Congestion,is there any other reason which may cause bts doesnt have to reply to ms?
    Because,I found no SD congestion for that cell fom the statistics.

    “There is feature called “immediate assignment reject” that can be activated, so the BTS will send a message (IMMEDIATE ASSIGNMENT REJECT).”
    thats mean we have to enable this feature to get “immediate assignment reject” in case of SD congestion?

    #55435 Reply
    Pix
    Guest

    hi,

    other possibility: the BTS never received the channel request in the first place. A problem of poor path balance (problem of UL reception), or just bad coverage ?
    Or interference on the UL BCCH?

    for the 2nd question: yes

    #55436 Reply
    TNS
    Guest

    Hi, Pix.

    If the MS request is filtered using RACH_TA_FILTER is there any specific message via air interface?

    BR

    #55437 Reply
    Pix
    Guest

    TNS,
    No DL message at all.
    The MS will retry MAX_RETRANS times to send a CH_REQUEST but there’ll never be an answer from the BTS.

    #55438 Reply
    TNS
    Guest

    Yes, I know it…
    So it’s another possibility (for answer of the main case )…

    BR

    #55439 Reply
    Pix
    Guest

    Oh, ok, i got it now. the question mark threw me off the scent 🙂

    #55440 Reply
    TNS
    Guest

    HI, Pix

    I was almost sure, so it was a question.
    After you confirmation it was a “conclusion”.
    (I know it = I knew it – my mystake ).

    BR

    #55441 Reply
    Pix
    Guest

    We are getting to a serious degree of subtlety here… 🙂

    #55442 Reply
    mnr
    Guest

    immediate assignment

    #55443 Reply
    GSM ENTHUSIAST
    Guest

    the missing immediate assignment would definetely mean there was no sd allocated.This could be due to more reasons other than blocked SD.simply put,an sd assignment failure.could be due to a lack of sd resources,radio issues,TX issues between BSC and BTS…etc

    #55444 Reply
    Rachael
    Guest

    how many call attempt retry is possible before call block?

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