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Handover

  • This topic has 25 replies, 1 voice, and was last updated 13 years ago by paraHO.
Viewing 11 posts - 16 through 26 (of 26 total)
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  • #51470 Reply
    paraHO
    Guest

    Yes Pix there are many different HO Fail causes it just narrowing down the cause number/s. I put 2 to see if they were right..

    #51471 Reply
    pix
    Guest

    ha ok, sorry, i didn’t see it was a question.

    for the example below, the probable cause will be “radio link failure” or ” reversion to old channel”.
    But as far as i can see, all the handover failure causes on A interface trace are “abnormal”. I think the vendor can put which ever cause he wants, it’s not mandatory to put the cause that corresponds to the problem : the MSC does not care about the cause of the failure.

    note: i’m just talking about A interface.

    #51472 Reply
    MKT
    Guest

    What is the relation between following:

    BA list
    Neighbour List(OMCR/BSC)
    SI5 list and SI2 list differs with eachother or not?

    Someone has told me that if a BCCH is present in BA list then that BCCH will be a part of measurements reports and handover attempts can take place on that BCCH. But it might be possible that the same BCCH is not defined as the adjacency, and thus a handover failure.

    Please clear the doubt.

    Regards

    #51473 Reply
    Bilal
    Guest

    Hi MKT,

    It may differ from vendor to vendor. In Ericsson we have 3 different lists :

    1- Active Mode BA List
    2- Idle Mode BA List
    3- Neighbor list.

    Active Mode BA list is sent in SI5 and it tells the MS which BCCHs should be measured in dedicated mode and reported back.Idle mode BA List is sent in SI2 and tells the MS which BCCHs should be measured in Idle Mode for cell reselection. Neighbor list is in BSC and not sent to MS, it is used for handover decisions. Logically every neighbor BCCH should be part of active mode BA list otherwise there will be no handover. If a BCCH is part of Active BA List and is not defined as a neighbor, it will be reported in measurement reports but will be discarded and no handover command will be sent. If BCCH of a neighbor is not part of active BA list then it wont be measured by MS and hence no handover 🙂

    #51474 Reply
    MKT
    Guest

    So the summary is:

    BA list is obtained from SI5.

    SI5 is obtained from BCCH of
    serving cell.

    Measurements are done on frequencies present in the BA in list.

    Measurement reports are send to BSC.

    BSC after analysing measurement reports shortlists a BETTER carrier.

    After that if this BETTER carrier is ALSO present in NEIGHBOUR LIST then handover command is given to MS.

    After that MS performs an handover attempt.

    Result may be:
    Handover successful
    or
    Handover Failure(for reasons as discussed earlier).

    Kindly confirm the above!

    #51475 Reply
    MKT
    Guest

    One thing more.

    CAN an RF person involved with the post processing of drive test log files say that…

    “The following handover failure was due to the reason they were not defined as neighbours in BSC/OMCR.”

    Regards

    #51476 Reply
    paraHO
    Guest

    MKT you want short answers but your conclusions are not clear..

    There are many sys_info just like at standard (GSM0408 etc). The two BA lists you discuss here:

    BA(BCCH) sys_info 2/bis/ter
    BA(SDCCH) sys_info 5/bis/ter
    BA SIM (as in SIM card)

    if ignore the BA SIM, are the two what you saying?

    #51477 Reply
    MKT
    Guest

    A frequency in the BA list but not in the neigbour list. Let us take the case:

    Case 1:

    BSC finds that the frequency is a better candidate for handover.
    Then BSC checks the neigbour list for the reported BSIC. And BSC doesnot find the said BSIC in the neighbour list. Hence no handover command message will be sent to MS.

    Drawback: You looses a possible good candidate.

    Case 2:
    BSC finds that the frequency is a better candidate for handover.
    Then BSC doesnot performs the neigbour list check.Handover command message will be sent to MS.
    After that BSC performs the neighbour list check and founds that BSIC is not the neighbour. But until now it is too late. The handover command message has already been sent to MS.

    Advantage: The MS attempts HO and fails. You have a easy way to find out the best candidate which is being missed or a missing neighbour.

    So…

    Is it possible to configure the HO sequence/settings according to the need.

    regards

    Note: Practical data is available where it is shown in the TEMS log files that HO fails are due to missing definations of neighbours.
    Hence it is sure that HO command is being given by the BSC inspite of the fact that a BSIC is not a neighbour.

    #51478 Reply
    Bilal
    Guest

    Hi MKT,

    One correction please: SI5 is sent on SACCH not BCCH.

    Answer to your question: In normal case i.e. no co-BCCH/BSIC No, he can’t say that “handover failure due to missing definition in BSC” because as we discussed there would be no Handover Command in the first place.

    But remember missing neighbor can indirectly cause a Handover failure or call drop. In this case handover may be attempted to a defined neighbor which is not the ‘best’ cell at that location and it may fail due to bad quality or low signal strength. If BCCH of missing neighbor is in Active BA list, you will easily be able to detect it from DT logs.

    #51479 Reply
    kuuku2
    Guest

    having problems with 900 and 1800 not handing over to each other. It keep moving from site to site too. Sometimes, the handover goes bad overnight and gets better without anything work on it.
    who has experience a thing like this before

    #51480 Reply
    paraHO
    Guest

    MKT I just note correction please from earlier should be BA(SACCH) -my typing error in hurry this morning, sorry.

    BA(BCCH) sys_info 2/bis/ter
    BA(SACCH) sys_info 5/bis/ter
    BA SIM (as in SIM card)

Viewing 11 posts - 16 through 26 (of 26 total)
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