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No handover after call waiting!!

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  • #53325 Reply

    Dear All

    We are facing a strange problem as explained below:

    “Party-A” is making conversation with “Party-B” and “Party-C” makes call to “Party-A”. If Party-C disconnects the call after hearing the “Call waiting” announcement or system releases the call saying “No Answer” to party-C, after that NO HANDOVER ATTEMPT is made by the Party-A during the rest of the entire call untill it gets dropped due to bad quality.

    According to our observation problem is something related with the “RELEASE of WAITING CALL” which toggles the handover algorithm to stop.

    Any suggestions pls!!!

    #53326 Reply

    hello arpan,

    NO HANDOVER ATTEMPT made by party-A ? It doesn’t sound like anything i know…
    I assume you’re looking at a drivetest tool, at the “event” screen ?

    Could you rather check the layer-3 messages ? That will give us more details about what’s really happening.
    Is there a HO COMMAND in downlink for example ?

    did this problem happen all the time on different MS, or did it just happen once ?
    does it happen also when the call is in a cell with good quality, and a HO shouldn’t take place ?

    It’s incredible that the Handover algorithm (located in the BSC) is impacted by DTAP messages which are transparently routed between MSC and MS.


    #53327 Reply

    Dear Pix..

    The problem was analyzed both in Drive-test and system trace. It happens for every call that get call in waiting. There is No HO Command in downlink. It is observed that the MS of Party A couldn’t get out from the cell in which it got the call from Party-C, although it was getting very good signal level from other cells. This is resulting in call drop & por quality.


    #53328 Reply

    Arpan, i think you’ve won the award of the most interesting issue of the year.

    no K12 logs? no L3 messages?

    if 100% reproducible go in lab that will be my only suggestion.

    Hope you’ll find the solution and share with us

    #53329 Reply

    hi arpan,

    I’m a bit confused about the “NO HANDOVER COMMAND”. You mean the BSC doesn’t send a HO CMD to the MS, right ?

    Because the msg “NO HO CMD” doesn’t exist. Sorry if i sound stupid, it’s just confusing 🙂

    So BSC doesn’t send the msg, even though the radio conditions should lead to a HO.

    On the opposite, if the MS wasn’t being called before, while being already busy, under the same radio conditions, the BSC would send a HO CMD.

    If that’s what you’re observing, then yes, this should be investigated in a lab… what are the vendors of the MSC and BSC ?

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