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NW Release

Viewing 15 posts - 1 through 15 (of 16 total)
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  • #53709 Reply
    ms
    Guest

    In a recent drive test, our objetive was to find out a high Call Setup time problem.

    What I found was, in some calls, all the Call Setup handshaking it’s ok until the Channel Asignment. The problem was, the Alerting msg never was received, and 28segs after the Channel Request msg, there is a Disconnect msg from the network (NW Initiated Release).

    Could it be a signaling congestion problem (SS7) ?

    BR.

    #53710 Reply
    pix
    Guest

    i leave that question to NSS gurus…

    but let’s focus on the BSS part:
    in the drivetest, you should see (in case of originated call)
    (…)
    sdcch:authentication request/response
    sdcch:ciphering mode cmd/cmp
    sdcch:setup (ul)
    sdcch:call proceeding (dl)
    sdcch:assignment cmd (dl)
    tch:sabm (ul)
    tch:UA (dl)
    tch:assignment complete (ul)
    tch:alerting (dl)
    (…)

    there is no channel assignment on the air interface. the alerting will come after the MS has sent the assignment complete.

    #53711 Reply
    ms
    Guest

    Pix, that´s what I was trying to say.

    The handshaking in that cases is this:

    sdcch:authentication request/response
    sdcch:ciphering mode cmd/cmp
    sdcch:setup (ul)
    sdcch:call proceeding (dl)
    sdcch:assignment cmd (dl)
    tch:sabm (ul)
    tch:UA (dl)
    tch:assignment complete (ul)
    tch:disconnect (dl) -this is the Network Release I mentioned –

    It’s almost the same you mentioned, but there’s no Alerting msg.

    In that cases, there’s only 20seg between the Ch. Request and Disconnect.

    BR.

    #53712 Reply
    pix
    Guest

    this problem is going to be counted as a call drop in the BSS (= TCH drop). do you see a huge amount of drops in those cells ?

    do you see a radio problem in your drivetest ?

    i can guess your answers, so at least it proves that it really looks like a BSS/NSS misunderstanding… have you tried performing some traces on the A interface ? do you see the assignment complete ? do you see the alerting ?

    could you check with NSS engineer if they could trace the issue within the MSC ?

    #53713 Reply
    ms
    Guest

    Pix,

    The drive test was performed using a 90sec. call, and after that, a redial (almost 100 Call Setups sequences).

    This problem was found on 26% of the Call Setups, in different cells, but the same LA.

    In that cases, the handshiking was as follows:

    UL Channel Request
    DL Immediate Assignment
    UL SABM-CMD
    DL Ciphering Mode Command
    UL Ciphering Mode Complete
    UL Setup
    DL Identity Request
    UL Identity Response
    DL Call Proceeding
    DL Assignment Command
    UL Assignment Complete
    UL SABM-CMD
    DL Disconnect (20 sec. after Ch. Req.)
    UL Release (Call End – NW Initiated Release)
    DL Release Complete
    DL Channel Release
    UL DISC-CMD
    DL UA-RSP

    So, there is an Assignment Complete msg, but there’s no Alerting msg.

    We ask MSC administrators in order to ask for a signaling trace.

    #53714 Reply
    pix
    Guest

    thx ms for the great details, i’m amazed by this value of 26% !!

    Sorry, i said something incorrect before : You will not see call drops in your QoS : the disconnect is a normal release, not counted as a drop.

    I can’t check right now, but it could be interesting to see what kind of information is contained in the “assignment complete”, or in the “alerting”. Perhaps there is something related to a new feature that was activated not long ago, and that is not understand by either the BSS or the NSS. But really, it’s just a guess.

    Regards,
    Pix

    #53715 Reply
    Pan
    Guest

    Dear Ms! Perhaps you must to search your Alert on destination side? What kind of call is it? MOC or MMC? Is destination number within PLMN or PSTN? In latter case: Is your PSTN completely digital network or there are many analog exchanges in PSTN? Tell your NSS engineer to analyse the trace record on E-interface between your MSC and PSTN if destination number is located within PSTN.

    #53716 Reply
    Pan
    Guest

    and else.. What is the cause value in disconnect message?

    #53717 Reply
    ms
    Guest

    Pan & Pix,

    The destination number is within PSTN.

    Pix, the Assignment Complete msg is as follows:
    ————————
    MS2
    Assignment Complete
    Time: 12:21:16.54
    Frame number: 2194570
    Skip indicator : 0
    Protocol discriminator : (6) Radio resources management messages
    Message type : 41
    RR cause
    Value : (0) Normal event
    ————————

    There’s no Alerting msg in this cases, and this is the main problem (after the Assignment, we receive a Relesease from the Network).

    The Disconnect msg from the Networks is as follows:

    ———————–
    Transaction identifier : 8
    Protocol discriminator : (3) Call control; call related SS messages
    Message type : 37
    Cause
    Coding standard : (3) Standard defined for the GSM PLMNS
    Location : (2) public network serving the local user
    cause value : (31) Normal, unspecified
    ———————–

    Tomorrow we’re going to perform a Drive Test, but in this case it’ll be complemented with a MSS trace, so I’ll keep you posted.

    BR.

    #53718 Reply
    Ayat
    Guest

    Dear , All

    I am responsible to monitor the KPI for each office. During the three last months we launched the CRBT service, and during the monitor processing I notice some value in Call drop rate (%).
    We connect to CRBT service center By GMSC (Gateway) BSC…. VMSC,,,,,, GMSC,,, CRBT.
    We found High call drop rate in GMSC office, but this value with no sense, because according to our customer this service are ok.

    The reason was:

    After normal signaling interact, if called number has CRBT service, VMSC send IAM(include called number xxxxxxxxxxxxxxxxx),SAM to CRBT by GMSC,and CRBT return ACM,ANM back to VMSC.

    Now you can hear color ring. Before called party answer, you or called party release call , release cause value is “normal, unspecified” and GMSC think it as call drop rate.

    Why call release cause ???

    Could you help me to simplified this reason

    #53719 Reply
    ms
    Guest

    Hi all,

    Finally, the problem was fixed.

    We talked with core administrators, and the problem was a malfunction in a SS7 signaling E1.

    When the mobile sent the Setup msg, there was no response from de network, because of lack of signaling frames.

    Best Regards,

    ms

    #53720 Reply
    sonny
    Guest

    Any Idea what cause Blocked Call with this?

    MS1
    Disconnect

    Time: 10:58:26.95
    Transaction identifier : 8
    Protocol discriminator : (3) Call control; call related SS messages
    Message type : 37
    Cause
    Coding standard : (3) Standard defined for the GSM PLMNS
    Location : (2) public network serving the local user
    cause value : (41) Temporary failure

    Message dump (Hex):
    83 25 02 E2 A9

    MS Tick: 903237

    MS1
    Time: 10:58:26.95

    Blocked Call
    Block type: No Alerting or Connect
    CC Cause:Temporary failure
    , call time: 266 ms

    #53721 Reply
    anh
    Guest

    MS1 call MS2 (same network).
    MS1 has:
    Channel Request
    Immediate Assignment
    Setup
    Call Proceeding
    Assignment Command
    Assignment Complete
    Alerting (DL)
    Call Setup
    Disconnect
    (Setup time~18.5s)
    while MS2 has no Call Attemp (no Channel Request, just Cell Reselection).
    In this case, call failed.
    Anyone let me know the cause and solution.
    Disconnect msg:
    Time: 09:27:11.98
    Frame number: 372727

    MsgCtrlOperation :
    Transaction identifier : 8
    Protocol discriminator : (3) Call control; call related SS messages
    Message type : 37
    Cause
    Coding standard : (3) Standard defined for the GSM PLMNS
    Location : (0) user
    cause value : (16) Normal call clearing

    #53722 Reply
    vivek anand
    Guest

    Call blocked due to no alerting and connecting.plz suggest the cause or reason and how to solve

    #53723 Reply
    Mohamed Riad
    Guest

    Datalink Failure
    DL Event: N200_Timeout
    SAPI: 0

Viewing 15 posts - 1 through 15 (of 16 total)
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