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LAC IDENTIFICATION

Viewing 11 posts - 1 through 11 (of 11 total)
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  • #61468 Reply
    LAC
    Guest

    Hi experts, my ? at lac boundary how ms knows the neighbour lac during reselction

    #61469 Reply
    SHELDON
    Guest

    Hi LAC,

    The LAC of the serving and neighbouring cells are sent as part of the System Information, thus, the MS always knows whether the neighbouring cell is in the same LAC as the serving cell or not.

    Regards,

    SHELDON

    #61470 Reply
    Pix
    Guest

    Sheldon,

    The LAC from the neighbour cell is sent in the S.I. from the current serving cell or is it sent in the S.I. from the neighbour BCCH ?
    I used to think the MS listened to the neighbour BCCH’s SI sometimes and retrieved the LAC, CRO, TO, PT (etc.) from there, but… as soon as I say it, it sounds impossible. It is probable that the serving is broadcasting all this already… what do you think ?

    Cheers,
    pix

    #61471 Reply
    SHELDON
    Guest

    Hi Pix,

    I initially thought the neighbour LACs were sent as part of the serving cell’s system information, but after a little research (after your observation/question), I now believe they’re sent on the neighbours’ SI.

    The only LAC info in the SI is found in SI TYPEs 3&4, and this gives info about the LAC of ONLY one cell (the serving cell).

    The MS also reads the system information of the six strongest neighbouring cells at least once every 30 seconds( at least to decode the BSIC), and I’m sure it can read the neighbour’s LAC and other parameters during this time.

    Let me know what you think.

    Regards,

    SHELDON

    #61472 Reply
    pix
    Guest

    sheldon,

    ok, we both converge towards the same thinking… that’s a good sign we are getting closer to the truth ๐Ÿ™‚

    …but during dedicated mode, the MS barely have time to decode the BSIC of neighbour cells… how can it decode “all” SI messages of the six strongest cells ??

    I’ll try to investigate this too from my side, let’s meet here tomorrow ๐Ÿ™‚

    cheers
    pix

    #61473 Reply
    SHELDON
    Guest

    Hi Pix,

    Thnx for your post, and sorry for my late reply.

    Actually I haven’t found anything new concerning the dedicated mode. However, I was just thinking…does the MS still need to decode the SI of the neighbours in dedicated mode? I’m asking this because in dedicated mode, the locating is handled by the BSC, which already ‘knows’ all the cell parameters.

    Thus, if the mobile needs to do a handover, the only thing it needs to report to the BSC is the neighbour’s BCCH(and maybe BSIC?). I’m not saying this on any authority, just a feeling.

    In Idle mode, it’s the MS which handles the cell selection and reselection, thus, it needs to read the SI of the neighbours as well.

    Plz let me know if you’ve found anything new.

    Regards,

    SHELDON

    #61474 Reply
    pix
    Guest

    sheldon,

    it makes sense ๐Ÿ™‚ didn’t have time to check the 3GPP yet…

    pix

    #61475 Reply
    Bijoy
    Guest

    Hi Pix,Sheldon,LAC
    The MS doesn’t know anything about the neighbour’s LAC or other parameters neither during cell reselection or HO.What the MS does is to simply report the neighbour BCCH(if in the cells BA list) & decoded BSIC alongwith its Rx_Lev(If BSIC is decoded and redecoded) to the BSC.

    Br\\
    Bijoy

    #61476 Reply
    Pix
    Guest

    Hello Bijoy,

    so how does the MS knows that the neighbour belongs to another LAC, and how does it know CRO, TO and PT (and CRH) values for this specific neighbour ?

    #61477 Reply
    Bijoy
    Guest

    Sorry Pix
    Did I wrote cell reselection????I cant beleive.!!!!

    Gross mistake.
    Hang me till death!!!!

    #61478 Reply
    Bijoy
    Guest

    Regarding Cell reselection,
    The MS shall attempt to decode the BCCH data block that contains the parameters affecting cell reselection for each
    of the 6 strongest non-serving cell BCCH carriers at least every 5 minutes, if the parameters affecting cell
    reselection have not been provided by the network in the serving cell.
    When the MS recognizes that a new BCCH carrier has become one of the 6 strongest, the BCCH data shall be
    decoded for the new carrier within 30 seconds, if the information is not already available.

    Br\\
    Bijoy

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