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GSM Nortel SDCCH Failed Assigment Rate

Viewing 11 posts - 1 through 11 (of 11 total)
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  • #56760 Reply
    m@u
    Guest

    Hi gurus,
    My network is experiencing extrange high SDCCH Failed Assigment Rates that appear only for some hours during the day and only at some cells.

    I checked the reasons for SDCCH disconnections and some high values at those hours are “SCCP disconnection” and “T200 Timeout”. Does anyone know what could be the reason for this? or happened to you before?

    It would be really good if this forum could allow some screenshots or to attache jpegs to show the statistics.

    Please help me.

    Regards,

    #56761 Reply
    Pix
    Guest

    I’m not a motorola expert, so i’m just sharing a thought 🙂
    T200 and SCCP are on two different interfaces.. T200 is probably linked to the LapD of the Abis (or Air), and the SCCP to the A/Atermux interface.

    Having a failure on both sides but without impacting the ongoing TCH calls would point towards a BSC signalling board failure ?

    Do you know the cause of the SCCP disconnection? There are probably some counters counting the different possibilities.

    #56762 Reply
    m@u
    Guest

    Hi Pix,
    Thanks for your answer, but today I found some other things.
    I was wrong, the reasons of the SDCCH disconnections were only for the SDCCH drops, but I figure out that the drops didn’t increase, so as you said the SCCP and T200 are the reasons for the drops. (I’ll look on that after solving this problem)

    On the other hand I noticed the SDCCH Failed Assigment Rate is calculed by SDCCH Seizures/SDCCH Attempts*100%

    Also comparing the counters when the cell was having problems and when it was not, I realized that the counter that measures the Expiration of the T3101 (set at 3 seconds) increased from 1 when it was OK to 707 when it was with problems. For this comparison I only selected one hour (12:00) at mid day.

    On the other hand checking the notifications of the Site I found that the following alarm appeared at the BTS (cell) level:

    Fault number : (1266) BLOCKAGE OF RADIO CHANNEL(S) IN FREE STATE
    radAnoChln : (
    transceiverId : 0
    channelId : 1
    subChanId : 0)
    (
    transceiverId : 0
    channelId : 1
    subChanId : 1)
    (
    transceiverId : 0
    channelId : 1
    subChanId : 3)
    (
    transceiverId : 0
    channelId : 1
    subChanId : 4)

    indicating the TRX0 where the BCCH (TS0) and SDCCH/8 (TS1) are defined.
    and some subchannels of the SDCCH8.

    Reading about this fault, says that the RadioResourseSupervision measures the channels on BUSY and FREE state but do not understand what is the reason yet. I’ll investigate.

    If any of you guys have experienced this before please guide me.

    BR.

    #56763 Reply
    SpiT
    Guest

    m@u
    regarding those Establish Failures,
    can you put a bit more information, from what you are getting on this two counters
    1163/17 and 1163/0 ?

    anyway, if t200 expirations are way high, you can try to isolate if there is any trx wich is adding the mayority of them, and seek for hw issues.

    on sccp discs, is more complex, it could be from abis issues to bad setting paging parameters.

    the alarm is simple and inutil (i think), just said that the listed subchanns were free after X time. ( where X is the hours you have defined on radresfreetimer)

    spit

    #56764 Reply
    Pix
    Guest

    M@u,

    SDCCH assignment unsuccesses are usually due to:
    Congestion
    Interference
    Poor coverage
    Hardware failures

    Since the counter is counting a timer expiry, I’d go for bad coverage and faulty hardware first.
    Can you check the path balance of trx 1 ? Could you try reallocating the BCCH and SDCCH to another TRX ?

    #56765 Reply
    Tanvir
    Guest

    Hi experts,

    We r using Motorola H2 Macro BTS. In one of the site sector 3 is giving high SD drops. I have checked the IOI, DL & UL BER but didn’t get any problem.

    Hardware’s have been checked twice.
    What could be the reason of sudden rise of SDCCH drops.

    Your support is required.

    Regards,
    Tanvir

    #56766 Reply
    Gabriela
    Guest

    Hey m@u, do you have some Nortel documentation about the main parameters for optimization. I am a 22 years old girl, fresh graduated and I am having an interview to get a job with Claro (operator in GT) and they have Nortel equipment. So I want to make a good impression and get the job. You can email me at gabysosa@msn.com

    I will realy, appreciate it, I have searched in many places and cant find any docs!

    #56767 Reply
    Gabriela
    Guest

    Hi m@u, can you please help me.

    #56768 Reply
    Nancy
    Guest

    Some cells have sudden sdcch congestion for like an hour or two with increased in attempts, yet sdcchs are 100% available. Kindly assist.

    BR

    #56769 Reply
    G
    Guest

    Hi nancy, is that SDCCH congestion during the BH??

    #56770 Reply
    Junior
    Guest

    Would you be kind enough to explain t200 timeout on the nortel equipt.

Viewing 11 posts - 1 through 11 (of 11 total)
Reply To: GSM Nortel SDCCH Failed Assigment Rate
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