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Silence Problem

Viewing 15 posts - 1 through 15 (of 20 total)
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  • #43706 Reply
    Abdel
    Guest

    Hi everybody,
    I am a telecom technician and I got a problem in my GSM network, we use both 900MHZ and 1800MHZ. The problem is the call is silent for a while then it becomes ok then silence then ok, sometimes silence will not stop, and then you have to cut the call and call it again. Usually this silence caused one way communication, may be you are transmitting but not recieving and the caller can hear you well but you can’t. Any idea what this problem is related to, can it interference, also we use adjacent frequancies,not in the BCCH but in TCHs.

    #43707 Reply
    Madhu
    Guest

    To Abdel

    1)The call mute can be because of Interference.
    2)Poor RX_LEVEL
    3)BAD transmission

    Regards
    Madhu

    #43708 Reply
    t28
    Guest

    hello abdel,

    I agree with madhu, my advice is…
    go to the field, do many MOC, if you find mute call, perform force handover to another site. if mute call is still continuing, it is trans (I mean NSS) problem, for example with echo-cancellers, if problem disappear you should check HW & frequencies on cell where you established MOC…
    what dou you think about it ???

    #43709 Reply
    Riz
    Guest

    Hi,

    This is a very comman problem. It’s ‘coz of multiple reasons. See any call is basically a circuit or channel. I.e:
    Call(Circuit made of this call) =

    TRX-TS,KSW-TS,GPROC-TS,TS-on the E1 port at site ==> TS-E1 port at BSC –> ksw-TS-> TS at E1 port going towards transcoder ==> ts- e1 transcoder-> KSW-TS ==> MSC E1 Pool (physical cables).

    [
    TS = time slot / channel of trx or ksw or gproc or E1 link.

    gproc= proccessor at site,bsc,xcdr.

    ksw= kilo port switch== multiplexer high way, distributing the ch/TS to/from E1 port to their correct destination(tS/CH on E1 port, trx, gproc .). It is inside site, BSC, transcoder.

    E1= 32(30) 64kbps channels (=2Mbps) port. It is a serial to parallel – wise versa converter.

    ]

    So problem could be at any of these parts of the complete circuit.

    CIRCUIT = RCI + CIC

    RCI= trx-ts,site e1 etc. radio part.
    CIC= bsc to msc via trascoder.

    But generally you find problems in :-

    1) Hardware problem at site-bts.
    OR
    2) E1 link(32 chs/ TS) cross connection at any of these interface.

    1:- Hardware problem:- E.g: In motorola system, we get RCI Alarms for one/more TS of one/more TRX. This indicates us that we have “mute” problem. The problem could be at any of above.
    But we try to reset the trx.
    If multiple such alarm comes, & if there is a common factor , e.g a common E1 link(port), we try to reset this MMS(MSI) -E1 port.
    This may clear the ALARM; BUT wait if the alarm reccurs(i.e. when the same circuit being used again), means the problem still exists.

    If by analysis we are pretty sure we try to replace the faulty dev(trx or e1-port).

    2:- TRANSMISSION GUY PROBLEM:- The links(E1-32 chns) might have been cross-connected, means- call-circuit of one goes to other. This’s totally meaning less hence no-audio problem.

    Confirm which is the ch/ts of which E1. Ask the transmission team to check at these interfaces. Site-ddf, bsc-ddf, msc-ddf. DDF=distribition frame(like cable hub- a mess!).

    You can Also do drive test of the area to confirm the cells, trx, cics with this problem.

    Also you can enable call-trace (CTP) on the affected area(during busy hour), hoping you capture the faulty circuit.
    !!But one warning if you enable a BSC-Level trace for say 1/2 hour without setting maximum calls, a BSC may be making more than 5000 calls per half hour. Associated ctp huge data transfer&proccessing from BSC -TO-OMC, might make the BSP(Master proceessor at BSC utilised 100%) -ineffect loading the BSC & STATS not coming in the OMC. Or worse BSC proccessor getting reset= BSC getting reset ===> YOU ARE FIRED.

    But cell level trace are harmless, even for bsc-level trace set the max calls at

    #43710 Reply
    Riz- contd.
    Guest

    But cell level trace are harmless, even for bsc-level trace set the max calls at

    #43711 Reply
    Abdel
    Guest

    Hi guys,
    There is no CIC problem at all, I thought CIC can cause one way communications, I saw this before, the problem i have got here is in my network, you call somebody then may be you chat for seconds and then silence will start, if you wait you can hear his voice again or silence will continue, based on my experience i don’t think this is a CIC problem.
    This problem usually happens in our largest city. We have got a lot of adjacent frequancies not the BCCH but a lot of adjacent TCH frequancies, Therefore can this be the cause?

    #43712 Reply
    Boko
    Guest

    Hi Abdel,
    Are you sure that there aren’t a lot of handovers (for example due to Quality) and you are in one cell?
    As you know durring handover speech is substituted using some algorithm with last good received speech frame. In some vendors it is the same one but each next is more silenced and after certain time it is only silence.
    Otherwise is sounds as equipment problem. Noise reduction, echo cancelers (GSM-GSM), transcoders etc.

    #43713 Reply
    shelton
    Guest

    which components of the BSC communicate with those of the BTS.

    #43714 Reply
    Mania
    Guest

    Hi Abdel,
    Tell me which vendor you are working on then the problem may be specific and known to that network.
    The case you specified can be because of two reasons.
    1. Get a DT done and see if this happens after intra cell HO if so there might be mapping issue of that TRX. but your explaination shows that this is less probable.
    2. Check if DTX_HR and AMR are enabled on that city. and confirm vendor. Issue might be with the decoding of SID frames there.

    Do reply with Vendor, DTX and AMR information.

    #43715 Reply
    koko
    Guest

    Hi Abdel,
    mostly silence call/blank voice was due to transmsion problem not in radio part and defined as normal call.
    if the problem occured due to transmisiion problem, try to conduct verticality check in Abis and Ater. check every single port/slots which have problem. u can query and localize problem from BSC log in ftp data.
    after u do it, u can localize which port or slot which have problem, then do troubleshooting with instalation team…

    might help.

    #43716 Reply
    Ayat
    Guest

    Hello

    Ericsson has a KPI named as

    Silence/One-Way Transmission,

    0–1%,Speech Quality

    so could you explain to me??

    #43717 Reply
    Bob
    Guest

    There is a very poor possibility, Do you use VAD service? how much AF has been considered in ur net(Activity Factor in your network)- If handover and interference is ok mean Radio ok , if you have problem in all bss the problem can be related to Core too.

    #43718 Reply
    shelton
    Guest

    Hmacro2 Bts signals “wrong fibre connection” on CTUs & requires for the site to b deleted & created again for the CTUs to work & they drop again to & signal “wrong fibre connection”.

    What cpould b th problem

    #43719 Reply
    K.K.Nath
    Guest

    Hi Abdel

    There are so many co BSIC-BCCH in neighbors list.Pls check the problem after removing the co BSIC-BCCH

    #43720 Reply
    shelton
    Guest

    K.K Nath
    do u mean i have to audit th BSC

Viewing 15 posts - 1 through 15 (of 20 total)
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