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SDCCH Assignment Failures

Viewing 7 posts - 16 through 22 (of 22 total)
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  • #50266 Reply
    GMN
    Guest

    Dear Pix
    Ghost RACH requst can lead to sdcch drop or not?and when HLR check the channel request is fake or not?

    #50267 Reply
    Mak
    Guest

    In my point of view

    Ghost Rach Lead to SD blocking.

    #50268 Reply
    Tarun Ahuja
    Guest

    Can anyone update on whether there is any standard/specification which tells how many GHOST RACH in how much time are acceptable in any bts system??

    #50269 Reply
    pix
    Guest

    hi,

    3GPP TS45.005 p.42:
    For a BTS on a RACH or PRACH with a random RF input, the overall reception performance shall be such that less than 0,02 % of frames are assessed to be error free.

    So random noise should be decoded as a noise for 99.98% of the time
    0.02% of the noise could be understood as a request, by mistake.

    There are 51 RACH-blocks in 240ms (approx)
    so that’s 765,000 RACH blocks / hour
    0.02% * 765,000 = 153 ghost rach per hour are “accepted” by 3GPP. In other words, if a BTS is located in an area without any traffic (anechoic room, for example), the number of ghost RACH self-generated should be less than 153 / hour.

    regards
    pix

    #50270 Reply
    BHT
    Guest

    Dear PIX,
    Can you please shed some light on that matter that for a request to be considered as RACH it should GMSK modulated & BSIC needs to be decoded to consider it as RACH request.
    It means Ghost rach should happen only in rare cases.
    Looking for your reply.
    Thanks
    BR,
    BHT

    #50271 Reply
    ABC
    Guest

    is anybody got break through to the SD blocking due to ghost RACH /Faulty MS

    #50272 Reply
    pix
    Guest

    BHT,

    sory, i missed your post.
    Rach requests do not contain the BSIC.
    Yes, they are GMSK modulated. But that doesn’t allow noise detection. EM Noise could “sound” like a GMSK signal.

    Yes, Ghost RACH are rare, if they are just noise. But sometimes, some equipments generates a signal which is exactly containing a sequence of 900MHz phase modulated symbols. In this casse, it is decoded as a RACH.

    Regards
    pix

Viewing 7 posts - 16 through 22 (of 22 total)
Reply To: SDCCH Assignment Failures
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