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Inter-MSC Handover fail rate

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  • #53647 Reply


    We encounter a problem of inter-MSC high handover fail rate. there is a lot of attempts but 100% fail rate.
    Please, what we need to check in such case ? we work on Nokia BSS.


    #53648 Reply

    1) check that the external neighbor cells are correctly defined in the OMC-R’s

    2) check that within each MSC, the external LAC and external cell are correctly defined. check adresses, etc.

    the problem certainly lies in the MSC’s, not in the OMCR’s.

    are both ways failing, or only one direction ?

    #53649 Reply

    hi spart,
    i got a same problem ,there are high number of ho failure for interMSC

    but i have a strange pattern, for example from MSC A to MSC B, there’s no problem, but if the MSC B to MSC A, the problem occured.

    I have checked the external LAC ( has been created ) , the routing ( use same routing way )

    can any body help me to solve this ?

    same with spart, we use Nokia BSS and Nokia NSS.

    #53650 Reply


    in such cases, even though you have already performed the verifications, it’s still probably a problem in MSC B.

    If there is no initial HO requests, check that target cell is well defined in the serving OMCR.
    If there is a “external” HO request from the serving BSC (from MSC B), but there is no HO execution (no ho command), then it means the MSC B is “stopping” the HO from hapening. Perhaps because it can’t find the target MSC, or the target cell.

    IMO, you should check again the MSC B…

    #53651 Reply

    hi pix

    yes i agree with you, i am very sure the problem is come from the core side, due to the ho failure distribute to many cells at the border site between two MSC. we have many handover attempt with low success.

    The verification from BSS side / OMCR has been done, and nothing wrong with this side.

    so do you have any idea, what kind of parameter should checked ?

    #53652 Reply

    i don’t know anything about MSC… I’m a pure BSS engineer 🙂
    but if you have attempts, it proves that the problem comes from core network, 99.9% sure about that.

    #53653 Reply

    check network lac on each msc.

    #53654 Reply

    Hi Spart,
    I want to add something to this discussion. If u get detailed stats on interMSC HO, analyse them. For eg. if the HO rate from MSCB to MSCA is poor then check for the outgoing HO attempts of MSCB and incoming HO attempts of MSCA. With this u can come to an approx conclusion in which MSC the analysis has to be made. Normally in one node the failure will be high. If success rate is high in MSCA i/g it means there might be problem in MSCB where the definitions of cells of MSCA are not proper.

    A good solution is to check all the internal & external neighbor definitions in all MSC and BSC nodes.


    #53655 Reply

    U can also check the BSSMAP request receive timer, or IAM/ACM timer. 🙂

    #53656 Reply

    Dear all,

    i have migrated some sites from BSCA to BSCB, Both BSCs belong to the same MSCA. When HO requests come from MSCB to MSCA, they are failed. kindly any one can guide me what parameters should be checked to resolve this issue.

    #53657 Reply


    You must investigate further by looking at all the messages that should be sent and received in case of inter MSC HO.

    Find out which message is not received, by which equipment, and you’ll see where is the misconf.

    Here are the interfaces you should monitor :
    Air interface (with drive test)
    A interface (with protocol anlyser or with BSS or NSS stats)
    MSC-MSC interface (with prot analyser or with NSS stats)


    #53658 Reply

    (1)When MSC A receives Handover Required from BSC A , MSC A Should be able to Recognize this CGI,LAI are controlling by which MSC. (2) MSC B receives MAP Prepar Handover Request from MSC A , now MSC B knows which LAC and CGI are targeted,MSC B requests VLR to provide Handover Num or MSHON, at the same time MSCB asks Targeted BSC to please provide required Resources(3)BSC sends ACK also VLR Send MSHON(4) MSCB sends back MSHON to MSCA (5)MSC A now Sends IAM message to MSCB and the…
    the best way to find out what is problem is to see which cause code you receive- as a brief summery–> MSCA should knows CGI and LAC of Target Cell which controlling by which MSC it is very important ,–> MSC-A should be able to analyzing MSHON sent form MSC-B to sends IAM message- check who abnormally terminated the Handover ,most properly it is MSC A
    Hope it come in use

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