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Handover

Viewing 15 posts - 1 through 15 (of 27 total)
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  • #47171 Reply
    Rajiv Gujral
    Guest

    Hello all,

    Im facing handover problems in many cell especially Inter BSC handovers and in the trace im getting “Hanodver Failure RR Cause: Protocol Error” or “Timer Expired”.
    If anyone can help me out in solving the problem.

    Regards
    Rajiv

    #47172 Reply
    Pix
    Guest

    Possible causes :

    1. Channel type combination not supported or invalid data
    rate;

    2. or CIC is present for SDCCH connection;

    3. or CIC is missing for a TCH connection;

    4. or Cell identifier for target cell is not present for a Multicell
    BSS;

    5. or IE identifier is inconsistent (i.e. missing mandatory
    field, Encryption Information, Classmark Information 1 or
    2, or Cell Identifier (Serving cell));

    6. or erroneous IE contents (Encryption Information);

    7. or only one among OIEs “Group Call Reference” and
    “Talker Flag” ist present

    #47173 Reply
    Pix
    Guest

    I can’t post my answer…

    #47174 Reply
    Pix
    Guest

    By comparing the HO REQUIRED, HO REQUEST and HO COMMAND (and more) on each side, you should be able to detect exactly where is located your problem.

    As for the timer expiry : which timer ? If you know which timer is expiring, you will know which message the MSC or BSC is waiting and not receiving. And you’ll know exactly what is going wrong.

    External HO problems are very interesting to solve, because you must work with QoS, OMC and NSS people.

    #47175 Reply
    Indranil
    Guest

    Pix,

    Pls clarify the point
    ” or only one among OIEs “Group Call Reference” and
    “Talker Flag” ist present” as it is not clear to me.

    I am waiting for ur reply.

    Cheers//

    #47176 Reply
    Pix
    Guest

    i think it is in regards with “group calls”, which i doubt is widely used…

    #47177 Reply
    Rajiv Gujral
    Guest

    Dear Pix,

    If u can explain me from where in can check “invalid data rate” or “Cell identifier for target cell is not present for a Multicell
    BSS”. In trace its only “Timer Expired” im getting and no other info(no details regarding which timer is, and on which end it is expiring). Also plz let me know from where will i start to solve this problem.

    #47178 Reply
    Tomar
    Guest

    Hi Rajiv Gujral,
    Please check message flows for your vendor. You could find witch timer is expired. I saw sometimes, that for Siemens equipment, if expires timer T7, there is problem with wrong definition of CGI in source/target BSC/MSC. It is possible to see in counters.
    That my recommendation: At firs check if there are right definitions of handovers. Not only in BSC (target cells), but also in MSC (outer cells) in both directions.
    BR Tomar

    #47179 Reply
    pix
    Guest

    yes, exactly, check the message flows, for outgoing HO (for the serving BSC) and incoming HO (for the target BSC).

    You can find the message associated to which timer.

    In the same way, you can associate QoS Counters to the message flow. Check where is the discrepancy in the QoS counters, and you’ll see exactly which message is missing.

    That will lead you to the equipment which is not performing its job correcly (and which wasn’t configured properly 🙂 )

    #47180 Reply
    JIC
    Guest

    Hi Pix,
    In our network we have a problem with inter BSC handovers, we tried to do TEMs drives and we have isolated 1 BSCs which is giving us inter BSC Handover problems. Iam getting T200 expiry

    #47181 Reply
    Emmanuel
    Guest

    Dear All,

    We recently integrated an iBSC to an existing one. The vendor is ZTE, we defined external cells to the new BSC and they are handing over to it quite well, but the iBSC is not handing over to these cells.

    Can anyone please help me in resolving this issue as it is resulting to high drop calls and even bad speech quality as the MS while driving cannot handover to the adjacent cells?

    Thanks for your suggestions.

    Emmanuel.

    #47182 Reply
    pix
    Guest

    hello,

    if external cells are correctly defined, then it’s a mismatch between the BSC and the MSC.

    ZTE -> external cells is not working, it means:
    1/ either the iBSC does not manage to “contact” these cells -> HO COMMAND is not sent to the MS. HO is not triggered, there is no HO failure.

    2/ the iBSC understands those cells are neighbors, a HO CMD is sent to the MS, but the MS cannot access the external cells. HO FAILURE occurs.

    Which case is it ?
    Case 1 i suppose ?
    therefore you should perform an A INTERFACE trace. Do you see a HO REQUIRED from iBSC to MSC ?
    do you see a HO REQUEST from MSC to target BSC ?
    and so on…
    find where is the “missing” message. If the HO REQUIRED is missing, it means the problem is in the iBSC.
    if the HO REQUEST is missing, the problem lies in the MSC.

    Initial check, before traces:
    in OMCR ZTE, the external cells are defined
    in MSC, the neighbor cells of iBSC are well defined.

    Regards,
    Pix

    #47183 Reply
    Emmanuel
    Guest

    Pix,

    Thanks you very much for the suggestions.

    The scenario is case 1.

    External cells are defined in both BSCs and the MSC as neighbours.

    I did dedicated mode drive test with the call originated from the test site while the A interface signaling trace was runnnig. We will analyze the log file and I will update this forum on findings.

    Thanks once again for the support.

    #47184 Reply
    pix
    Guest

    ok, thanks 🙂

    #47185 Reply
    Emmanuel
    Guest

    Pix,

    The result of the trace shows that there is no “HO required” message from the iBSC to MSC, meaning the issue is the iBSC…..I am a little bit stuck here.

    Please let me know the next step.

    Thanks a lot.

    /Emmanuel.

Viewing 15 posts - 1 through 15 (of 27 total)
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