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SD drop

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  • #59494 Reply
    agz
    Guest

    hey guys,
    I have a cell which is in a LAC boundary and has an SD drop of more than 15%.The main utilization of SD in the cell is for location update and is around 90%.I have audited the frequency and increased the reselect hysteresis.But still there is no use.plz letmme kno if there is any other soln for this.Out of this,Timer T3101 expired drop is 3.27%

    #59495 Reply
    Pix
    Guest

    It seems to be a recurrent problem in many networks. You can try investigating it by performing A interface traces with a protocol analyzer (K15, Atellia, etc).

    It could be due to only one faulty MS, or a specific brand of faulty MS, or some faulty behaviour from the NSS –> by checking the trace you will see if the problem occurs always at the same DTAP message (authentication, ciphering, or TMSI reallocation, whatever…).

    A failure in the BSS could also cause this, but I assume you have checked all interferences + all BTS hardware ?

    #59496 Reply
    agz
    Guest

    s…i hv chckd all interferences and hardware..no probs in that..the cell which I hv mentioned is firing @ buildings and I have incresed the power control level..hv increased the cell reselect hysteresis as well to reduce the LU..bt in vain…

    #59497 Reply
    Bijoy
    Guest

    Hi Agz
    Can you shift the LAC boundary?
    Look,T3101 expiry indicates either interference or poor link balance,you need to check that also.You can also try to increase the timer T3212(periodic LU timer).Try increasing the timer T200 to reduce SDCCH drop.If SDCCH HO is enabled,disable it & check

    #59498 Reply
    agz
    Guest

    Hi Bijoy,
    T200S is 1000ms and is unique thruout the network…i cant shift the LAC boundary as the adjacent BSC’s LAC is in another MSS.AS i hv mentioned b4 i hv check d ND reports and neither interference nor path imbalance is found..hw is perfect..

    #59499 Reply
    Bijoy
    Guest

    Which counter is contributing the most?Is it SDCCH_RADIO_FAIL?

    #59500 Reply
    agz
    Guest

    BOTH RADIO FAIL&ABIS_FAIL

    #59501 Reply
    Bijoy
    Guest

    Ok agz
    Now nswer the following
    1.Is HR Traffic too high in this cell?
    2.What is the Cell configuration & Carried Traffic?
    3.How many SDCCH have been defined in the cell?Have you defined more than 1 SDCCH on any TRX having 16KBPS LAPD?
    4.What is the LAPD signalling bit rate of the TRX’s in the cell?
    5.Is the cell configured on a single BCSU?
    6.Has the BCSU capacity of this BSC reached 90%?
    7.Is Soft Channel Capacity enabled in this BSC?
    8.Is dynamic SDCCH enabled in BSC?
    9.Is there any alarm “LAPD Message Distribution problem” on any of the LAPD link in this cell?

    #59502 Reply
    agz
    Guest

    sure..bijoy,
    1.No such HR TRAFFIC IN THE CELL.
    2.4 TRX CELL AND TRAFFIC ARND 7 ERLANGS DURING BBH.
    3.4 SDCCH+1SDCCB.NO..
    4.ALL THE TRXS ARE HAVING 32Kbps signalling.
    5.No.the Trxs are configured on three BCSUs.
    6.YUP.
    7.YUP.
    8.YUP.
    9.NOPE.

    #59503 Reply
    Bijoy
    Guest

    Remove all TCHD from the cell n check.Also try to re-create the TRX’s in the least loaded BCSU.Also check there is no errors in the PCM

    #59504 Reply
    agz
    Guest

    Bijoy,
    Here all the BCSUs r loaded heavily so I wont b able 2 do that..
    Also,I found another interesting stuff in this cell…whenever I am shifting SD in the cell,those Trxs r getting pathloss.Sterday I added one sd in a trx,wn i chkd the hardware report today that Trx is having pathloss ..wt cud be the reason…
    Cn u xplain in detail abt d removal of TCHD,..hw will dt affect in SD drop.

    #59505 Reply
    Bijoy
    Guest

    Agz
    It means that the MRs of SDCCH have higher path loss,maybe the users are on the cell border.Once TCH is assigned pathloss gets reduced either by Link adaptation of AMR or by PC.since SDCCH holding period is short,maybe PC doesn’t gets enough time to take care of pathloss.

    By removing the TCHDs,I was just trying to offload the BCSU’s a bit.I think you will be having high T3101 expiry and ghost RACH also

    #59506 Reply
    agz
    Guest

    yup..I have mentioned that in my first post

    #59507 Reply
    agz
    Guest

    even i thot lik dt and changd the PC threshold level both DL and UL by 5dB in the cell..bt in vain…

    #59508 Reply
    Bijoy
    Guest

    what is the average RX level & Rx Qual of the cell.I think it is a coverage issue.

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