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Reversion to old channel

Viewing 8 posts - 1 through 8 (of 8 total)
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  • #44173 Reply


    we’ve a lot of assfailri_roc(assignment failure-reversion to old channel) which causes a LOW call setup in my network.How do you fix this problem??

    #44174 Reply

    Do you mean this for normal cells?
    Usually this means that the BTS cannot receive the SABM message that the phone sends on the TCH channel.
    Do you have repeated assignment feature?
    In some cases this could double the number of assignment fails with cause “roc”.

    #44175 Reply

    Thank you Boko.

    In some cells this is repeated from as far as 3months back,and it is being investigated and in some cases its once-off but very high.
    My problem is that this persist and we are unable to pinpoint and eliminate the causes of this “roc” once and for all or should I say what equipment can be appropriate to locate and fix this defaults.

    #44176 Reply

    One way it could happen is if you have different tipes of CU or whatever it is called by the vendor. For example on BCCH one could have EDGE CU which is with higher power for GSM but the rest TRX with normal amplifiers. If by any reason you have difference between TRX with the SDCCH and the one where the TCH were allocated there you have a problem. Also for common BCCH.
    You should use an analyzer to see where the TCH for the call was allocated

    #44177 Reply

    Thanks Boko

    I think you have a point there about the mixing of Trx’s-I’m going to investigate this.Also the point pertaining to the analyser is a problem to us because we dont have it working,will make a plan.I will update you the progress.

    #44178 Reply


    Check if you have increase of DL Quality HO, decrease of mean TCH holding time, increase of SDCCH MHT. Also stop hopping and check if the traffic on one of the trx’s is significatly less than the others. This should lead you to the problem. It could be connected to software bug or a patch implementation.


    #44179 Reply

    HI Boko

    It seems you have quite detailed knowledge of the problem.

    I am on nokia system, similar term here is “Return to Old”. i had a similar problem in some cells(scatered). Can you suggest how should you go about troubleshooting the cells.

    The max contribution for handovers in my case was DL Int(30%), then DL Qual(6%), Then other reasons were normal(Power budget-30%).


    #44180 Reply

    Usually you should try to find out when this starts. Then check for any changes in the network that day. Usually there is the problem. I am not familiar with Nokia systems (counters and parameters) but here in the forum I saw some guys with detailed knowledge. I hope they can help you.


Viewing 8 posts - 1 through 8 (of 8 total)
Reply To: Reversion to old channel
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