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PS Assignment Failure ratio is high

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  • #67006 Reply
    Alonewolves
    Guest

    Hi everyone;

    My question is related to PS side.

    i have noticed that some cell have high PS assignment failure ratio.

    here is the observation points:

    1- everyday the same cells suffering from the problem

    2- Those Cells suffer this problem for some period . not whole day , ie. between 13:00 to 15:00 and 20:00 to 21:00

    3- i am sure there is GPRS/EDGE trafic on cell, i have check GPRS/EDGE Throughput daily basis

    4- PS Assignment Failure ratio is %100 for mention period.

    5-EDAP configuration are correct and TRXS and sectors are GPRS/EDGE enabled, cross-connection are properly configured. Traffic manager is ok.
    ( all setting are correct because sectors gives gprs/edge services , i can see PS throughputs )

    6- BTS is Nokia Ultrasite Software Version 7.0

    What do you advise , what to check to troubleshoot the problem.

    Regards.

    #67007 Reply
    alonewolves
    Guest

    Hello,

    Any suggestion ? looking forward hearing you soon

    #67008 Reply
    pix
    Guest

    hi alonewolves,

    when failure is 100%, the problem always come from a faulty HW.

    Now, i don’t know Nokia systems, but you might want to check the PCU (packet control unit) congestion or processor overload. Under extreme stress, I assume defense mechanisms are activated (tbf assign reject?). Also, maybe it’s your BTS processing unit that’s overloaded.

    I have no other suggestions… check interfaces congestions as well (ater, abis, Gb)

    I don’t think the core network (SGSN) could be the problem here.

    Again, i would say that’s either a BTS or a PCU HW problem.

    Regards
    pix

    #67009 Reply
    Alonewılves
    Guest

    Dear all,

    Although Nowadays i don’t have any cell that has %100 PS assignment failure rate,
    but a cell has high PS Assign. Failure rate every day changng from %30 to %50

    Accourding to formula :

    PS_ASSIGNMENT_FAILURE_RATE =
    1- (The number of the PACKET_IMMEDIATE_ASSIGNMENT messages/The number of packet channel requests on CCCH)

    in CELL-1 NACK for ps assignment message is “0”,

    so i confused in here
    if NACK for PS assign. message is 0 ,
    accourding to formula PS failure rate needed to be 0 as well

    Site has 3 Cells,
    Cell 1 and 2 share the same EDAP pool,
    Sector 3 has individual EDAP pool,

    i have expected to have similar PS assignment problem for cell 2, which shares EDAP pool with cell 1,
    Cell-2 does not have this kind of problem. i assume that problem is in the BTS side.

    Could you please comment on this isuue ,

    Here some additional information regarding to Cell
    No Congestion On:
    Control Channels
    Gb link
    Related Frame Relay has little congestion
    EDAP has congestion but almost the same rate with other cells’
    Default and dedicated GPRS values are the same for all cells.

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