Generic selectors
Exact matches only
Search in title
Search in content
Post Type Selectors

Uplink Quality & Inter BSS Handover

Viewing 4 posts - 1 through 4 (of 4 total)
  • Author
    Posts
  • 12th January 2011 at 22:35 #65509
    engaom
    Guest

    Dear Experts;

    I just want to share with you this case and your reply is highly appreciated.

    The case is that I have to cells neighbor to each other and the inter BSS handovers sometimes fail causing call drop during DT (in both directions).

    Here is the investigation steps that I did:
    1- Tune the handover margin from the source cell to the target to fast the handovers (No Effect)

    2-Frequency tuning.(No Effect)

    3- From BSS call traces I found the following:
    1- Very bad uplink on the target Cell
    3-the msc trigger the handover to the target cell correctly and all messages between BSCs occurs until
    T200 Expiry (so L2 connection not established).

    Finally;do think that the uplink is the main cause of this issue; specially that I disabled the Uplink power control on the target cell and the Uplink Quality improved or mainly disappeared

    Thanks & Regards

    13th January 2011 at 16:40 #65510
    Pix
    Guest

    Hi Engaom,

    During the DT, Which layer 3 messages does the MS receive ?

    The HO Command ?

    If no : then problem in your MSC database.

    If yes : then resume reading…

    Look inside this HO command :
    you should see the frequency and TS of the target cell on which the MS should connect.
    Are they correct ? Is it indeed the target cell towards which the MS should go ?

    If yes : then it means the MS tries to connect to the right cell, but with wrong parameters.
    On top of my head:
    1/ problem of clock in the target cell ?
    2/ problem of ciphering ? are both sides using the same ciphering mode ? (A5/1 ? A5/0 ? A5/3 ?)

    Cheers
    pix
    Regards
    pix

    14th January 2011 at 13:20 #65511
    engaom
    Guest

    Thank Pix “great Expert”

    After check both BSCs have the same ciphering Alg A5/1

    Regarding Target cell; I got the which is the target cell

    “SYNCH CHANNEL MESSAGE”
    ========================
    MS1
    Synch Channel Information

    Time : 12:34:02.04
    Vendor Header
    ARFCN : 58 (E-GSM)
    FrameOffset : 174078
    QuarterBitOffset : 914
    BSIC : 4-6
    T1 : 824
    T2 : 8
    T3′ : 0
    spare : 0
    Message dump (Hex):
    99 9C 20 00

    Fianlly;there is no something clear about the clocking

    Thanks & Regards

    14th January 2011 at 18:59 #65512
    pix
    Guest

    hi,

    the synch message does not show any problem, IMO. Could you copy & paste the content of the HO COMMAND received by the MS in DL in the serving cell, and the contents of the CHANNEL REQUESTs sent just after from MS to the target cell ?

    Thanks,
    Pix

  • Author
    Posts
Viewing 4 posts - 1 through 4 (of 4 total)
  • The forum ‘Telecom Design’ is closed to new topics and replies.