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Undecoded SACCH using F.Hopping

Viewing 13 posts - 1 through 13 (of 13 total)
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  • #53275 Reply
    mariano
    Guest

    Hi!

    I’d like to know if drops using freq. hopping due to co-ch or adj interference are because of bad C/I over all the hopping channels.

    For ex. in TEMS, I’ve a cell using FH over 5 channels. Several ‘Undecoded SACCH msj’ are displayed before drop occurs.

    BR

    #53276 Reply
    pix
    Guest

    hello,

    what are the 5 channels ?

    your assumption is good : it is correct to say that there is probably a bad C/I on about 3 frequencies in this list. Maybe not all frequencies though… this is not necessary.

    regards,
    pix

    #53277 Reply
    peyo
    Guest

    You’re using base band hopping, right?

    in BBH Tch in use is moving from TRX to TRX. SACCH are from FACH which are stolen for TCH so they are moving to. Of course all what can interfer with TCH (co-chan, interference) will interfer with SACCH. which can be a first point for investigation.

    You also have strong dependencies with Antennas system. If for any reason antenna path on TRX1 has less loss than antenna path on TRX2 then there will be TCH effect (so SACH effect) .

    What i’ll do is stop frequency hopping and try to find any HW issue (TCH losses, BER..)

    #53278 Reply
    Pix
    Guest

    peyo,

    some corrections…

    Baseband hopping is not necessarily moving from TRX to TRX. In alcatel, the BBH is “synthetized” : the TCH remains on the same TRX, and the frequency changes each TDMA frame.

    The SACCH, FACCH and TCH are three different channels, each located on the TCH multiframe.
    FACCH is stolen from TCH bursts on demand.
    SACCH is regularly sent on timeslot 12 of the TCH mframe.

    regards,
    pix

    #53279 Reply
    mariano
    Guest

    Yes, pix, usually the cells are using synthetized FH.

    In particular, this cell is from Ericsson, but in the network coexists both Siemens and Ericsson.

    BR,

    mariano.

    #53280 Reply
    pix
    Guest

    mariano,

    you cannot do SFH on only 5 frequencies.. even if you have just one hopping TRX, you’d need at least 6 or 7 frequencies to achieve good quality (in SFH1x1).

    in 1×3, with 5 frequencies, you could have just one hopping TRX max.

    could you write down the radio configuration of this cell, exactly ?

    regards,
    pix

    #53281 Reply
    Blitz
    Guest

    Dear Pix,
    In our network, we have no problem with configuration 2/2/2 for sites
    using SFH system. Because each freq is hopping in MOBALOC, the more you allocate freq for MOBALOC the better you can get quality (C/I) for your network.

    #53282 Reply
    pix
    Guest

    blitz,

    that’s exactly what i said. if you use only 5 frequencies in your MOBALLOC, that’s not enough and you’ll suffer from bad quality.

    the more the better.

    the rule (in sfh1x1) is to have :
    no of freq = 8.3 * no of TRX’s

    regards
    pix

    #53283 Reply
    blitz
    Guest

    thanks pix, I thought 5 frequencies you said was for TRX configuration.

    #53284 Reply
    jack
    Guest

    dear mariano
    can you tell me where in TEMS you found this message( layer 3 or ,,,,,)

    #53285 Reply
    mariano
    Guest

    jack,

    This messages are under ‘Error Reports’.

    Presentation -> Signaling -> Error Reports

    BR.

    #53286 Reply
    Peyo
    Guest

    Pix,

    you’re no longer using cavity combining block in alcatel BSS?

    #53287 Reply
    Eagle
    Guest

    Im using huawei equip anf RF hoping and im geting the same error

Viewing 13 posts - 1 through 13 (of 13 total)
Reply To: Undecoded SACCH using F.Hopping
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