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SDCCH dimensioning for HR environment

Viewing 15 posts - 121 through 135 (of 155 total)
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  • #35583

    Hi Ristre,

    I just found this rule to be checked :

    T_GSL_Ack (BSC) > T200 (GSL) * (1 + N200 (GSL))

    N200_GSL (BSC) : Maximum number of re-transmissions on a GSL link.
    T_GSL_ACK (MFS) : Supervision of MFS acknowledgements on BSCGP.
    T200_GSL : Supervision of acknowledgements on the GSL link.



    I have problem in understanding how Timing alingnment is done on the abis interface for the Trau frames in UPLINK ,and DOWNLINK direction,for different codec scheme frames(FR,HR,AMR).Can anybody send me a trace of trau frames on abis interface .
    with warm regards..


    frequency hopping
    Hello, all
    ould you explain what is frequency hopping in as simple as that ( i need to understand tht by use sample way ) thanks


    Half rate
    Hello all
    Why we use Half rate tech. although it has disadvantage .
    in our network we use HR we are going to disable it to know what is the effect of HR on our network.


    Hi All,

    Please tell me what would be the effect of Ghost RACH to Paging Load and AGCH Load.
    Also, what would be the effect in the SD resource?


    hello zeus,

    ghost rach will trigger allocation of an SDCCH at the BSC side.

    the following msg will be sent over abis:
    channel required
    channel activation
    channel activation acknoledge
    immediate assignment command

    and finally, on the air interface : immediate assignment command, from BTS to the MS (on AGCH).

    Ghost RACH increases AGCH load and increase the number of SDCCH allocated by BSC (after the channel required, the BSC books a SDCCH channel)

    So ghost rach can also lead to SDCCH congestion.

    NO impact on PCH.



    Hi all,
    can somebody tell me how the Ghost RACH are originated in the system.


    From the same place ghost are originating from… nobody really knows 🙂

    It could be one of the following:
    BTS internal equipments generating electromagnetic disturbances
    External radars (army for instance)
    External electromagnetic devices (alarms systems, remote controls…)
    Other network operators (from other countries)
    Atmospheric disturbances, and so on…

    Favorite answer : generated by the BTS itself…

    Yogesh Choudhari


    I am working on G1800 network, and we are using Nokia equipment for front end and also for back end ( NSS). My n/w is having high SDCCH failure rate.

    When i see the reason for SD failures on clear code level, I got a high count of clear code on Establishment indication message corruption.

    Can this be a result of wrong POC parameter tunning, if no then can anybody tell me the other possible reason.


    What is POC ?

    so you’re measuring a high SDCCH failure rate on “all” cells, during each hour of a day, every day of a week ?

    Is it related to the amount of traffic in your network ? (for instance, during the night, there is no traffic, so you don’t see sdcch failure, do you ?)

    If the failures happen all the time, even when there is no traffic, you might be getting some country wide interference (another operator ?).. or possibly some problem with other sites collocated on the same pole (did you co-locate your gsm900 sites with dcs1800 sites ?)

    If the failures only happen when TCH traffic is occurring, then you can investigate parameters settings (i’m thinking about timers and repetition of RACH…)

    Just giving some leads, about BSS side. I’ve got no knowledge about NSS side.


    Yogesh Choudhari

    Thanks Pix for reply and sorry for giving reply so late.

    POC is power control parameter.

    In our network we are observing this problem sevearly during network busy hours i.e. when traffic is huge. For RACH we have done some fine tunning on RACH repetation and the multifram spread slots. But it is not giving any improvement.
    Can you please share something on timer level.
    We have some amount of SD fail because of T3101 expirory also


    Hi there,

    The power control will not affect your SDCCH assignment success.

    Exactly, how much is your “SDCCH ASSIGNMENT FAILURE RATE” ? (in average for your GSM1800 cells)

    Regarding other answers, i’ll have to study which timers are used during this phase. To simplify the problem:

    your BSC is getting a “CHANNEL REQUIRED”, then sends a “CHANNEL ACTIVATION” to the BTS, then receives a “CHANNEL ACTIVATION ACKNOLEDGMENT”.

    Next step : the BSC is sending the IMMEDIATE ASSIGNMENT COMMAND, directly to the MS.

    It is at that point that you measure a failure : the MS doesn’t answer the assignment command, or, if it does receive it, it is the BTS that doesn’t receive the SABM from the MS.

    If messages are not received, it means either the BTS or the MS stop listening… so there might be a timer expiry. Check T3122 / T3120 / T3101… those are the timers that are quite obvious, but there might be additional timers somewhere… I’ll look for it when i have more time. But i think you can quickly find your answer about timers in the 3GPP documentation.

    Check 3GPP TS 04.08 “mobile radio interface layer 3 specifications”, especially the chapter 3.3 “RR connection establishment”.


    Please tell about these KPI:
    Utilization of VLR

    We have of course 3 MSC


    How can we reduce PCH load, if on complete network how or for a single sector too?


    Anyone knows how FLP works? Does is need BSS sync.


Viewing 15 posts - 121 through 135 (of 155 total)
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