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sdcch cong in low traffic !!

Viewing 12 posts - 1 through 12 (of 12 total)
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  • #47835 Reply
    akefa
    Guest

    Hi guys

    if I have the following:

    1) 2 sdcch/8
    2) 4.17 sdcch traffic
    3) 104 sdcch availability (adaptive configuration)

    and

    4) 18% sdcch conjestion !!

    could any body justify the congestion? any possible scinario?

    br
    akefa

    #47836 Reply
    NK
    Guest

    It can be due to phantom RACH. try to change timer T3101 to lower value.

    regards,
    NK

    #47837 Reply
    akefa
    Guest

    Hi NK,

    regarding the timer you mentioned, is it in Ericsson? coul you plz justify why decreasing this timer may solve the problem.

    #47838 Reply
    NK
    Guest

    Hi! Akefa,

    I am using Siemens. Phantom RACH is one of the reasons for SDCCH congestion. When BSC gives immediate Assignment message for SDCCH via RACH, BSC runs T3101. If timer the dedicated channel is not
    established before T3101 expires, the allocated channel is released.
    This scenario can e.g. occur if noise on the radio is decoded as
    RACH access (“phantom RACH”) by mistake.
    If this is a case, setting a long time for it means long time to wait for SDCCH response from MS which does not exist. This gives lower Traffic but SDCCH congestion.

    If this a case, I hope decreasing it will solve the problem.

    regards,
    NK

    #47839 Reply
    akefa
    Guest

    NK

    It is clear, thank you. Your info was clear like the sun, quite like the moon

    I will try to play with this timer and see the effects. I will call this timer the layers discover (phantom RACH are big layers 🙂

    I already made a soft reset for the site and every thing back to normal for the last 3 days. Therefore, the phantom RACH 🙂 here maybe due to hardware.

    #47840 Reply
    akefa
    Guest

    Hi NK

    Actually i have been told that i can not play with this timer, it is fixed !!

    (ericsson)

    #47841 Reply
    akefa
    Guest

    Hi Pix and NK

    t3101 is the timer of IMMEDIATE CHANNEL ASSIGMENT so is not related to the sdcch ! immediate assignment means the MS’s will be assigned a signaling channel directly from TCH, and hence the word “direct” came. i am confused because you are talking about sdcch. plz you can read the definition of the immediate assignment or t3101 again !

    once you answer, I have more to say regarding the issue.

    take care

    #47842 Reply
    NK
    Guest

    Hi! Akefa,

    Immediate assignment means SDCCH if assignment type is “Early Assignment(EA)” type and TCH if assignment type is “Very Early Assignment(VEA)”. Most of the opeartor use “Early Assignment” so that TCH can effectively use. I hope that your type is EA.

    If timer T3101 is fixed in your network, I think it is optimized value. SDCCH congestion may be due to another reason.

    regards,
    NK

    #47843 Reply
    Tounsi
    Guest

    Hi all,
    Please anyone can tell me the difference between immediate assignment and normal assignment ?
    Also, Is there other kinds of assignment ?
    Regards

    #47844 Reply
    pix
    Guest

    hello Tounsi,

    the immediate assignment is the message sent from BSC -> BTS and BTS -> MS during a normal assignment. This message is sent on AGCH, and describe the physical address of the SDCCH subchannel that is going to welcome the call. Once the MS gets this info, it will move to this SDCCH subchannel.

    A normal assignment means a “call setup”, in opposite to handover assignment. It is also written “NA”.

    Regards,

    #47845 Reply
    Rami
    Guest

    Dear akefa,
    Check RACH Busy Threshold, MAX RETRANS, LAC border

    Good Luck

    #47846 Reply
    Nur
    Guest

    Dip is not comming into service
    problem is below,dip is showing abl & rdi fault.

    Could anybody advice me what should i do..

Viewing 12 posts - 1 through 12 (of 12 total)
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