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RACH overload on Abis

Viewing 15 posts - 1 through 15 (of 20 total)
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  • #52823 Reply
    james
    Guest

    hello
    can any body help me about RACH oveload on Abis

    #52824 Reply
    pix
    Guest

    RACH is a random access channel, on the air interface. it cannot “overload the abis”…

    maybe you mean there are too many channel requests on your abis ? that’s strange, because normally this is not a cause of problem, the number of channel requests in a site is less than the number of paging.

    Anyway, you could just increase the amount of bandwidth dedicated for the RSL of the BCCH TRX.

    #52825 Reply
    james
    Guest

    pix
    thanks but also i would like the reason for this overload and is there any thing in point view of RF to do it like Downtilt change radio parameter

    #52826 Reply
    pix
    Guest

    hi James,

    but the fact that the RACH cannot overload the Abis should point out that I don’t really understand your problem.

    How do you measure this overload ? Any QoS indicators that reflect this issue ?
    What are the impacts of this overload ?

    #52827 Reply
    james
    Guest

    dear
    I have this indicator to indicate the (CCCH load indication)which define if the valus of RACH overload is small is greatly effect the Abis and f this indicator vlaue is to big may BSC will not procced with this site normally .

    #52828 Reply
    pix
    Guest

    RACH overload is a load on the Air interface, not the Abis interface. It is alcatel B9, isn’t it ?

    If the RACH is overloaded it doesn’t mean your RSL on the Abis is overloaded. You should check the Abis congestion instead.

    But if you think the RACH is congested, then you should check your S and TX_INT parameters. Are they set at the correct values ?
    You can activate the immediate assignment reject feature, to avoid RACH “channel requests” repetitions.

    You can perhaps play with AGCH queue parameters (if this is alcatel, then you don’t have access to those, i think)

    And perhaps your RACH is overloaded due to GPRS ? Can you check the number of PS channel requests and the number of CS channel requests ?

    #52829 Reply
    james
    Guest

    we area using Ericsson, i would like to know what is “S”, If I don’t play with this parameters is there any other parameter and if the cell is overshooting you don’t think that may be the coverage overshooting limiting can effect this load

    #52830 Reply
    pix
    Guest

    frankly, i doubt that this overload is “real”. I think it is a parameters mistake. So, yes, you can downtilt the cell : you will loose coverage, you will loose traffic. Loosing traffic = subscribers out of coverage = loosing money. Your boss and your subscribers are going to be very happy about that 🙂

    I don’t know hat’s the name of the S parameter.. can you check your dictionnary of parameters and search for all parameters related to Channel Requests ?

    #52831 Reply
    Abdel
    Guest

    I am getting the same RACH overload alarm in several cells, i checked the cell parameters and i found out there is a RACH LOAD indication threshold (RLIT) which is 60%, so i think this is just a notification to know that ur RACH reached 60%. What do u think guys?

    #52832 Reply
    Abdel
    Guest

    In this notification RACH overload, I think we need to increase the CCCH channels so we can get an extra 51 RACH timeslots in non combined and 21 in combined BCCH, it is just a notifcation that the RACH load has reached peak capacity.60%

    #52833 Reply
    Pix
    Guest

    Abdel,

    Check your S and TX_INTEGER (3GPP TS 04.18), they could reduce the number of retransmissions of channel request.
    Also, you can try to activate the “Immediate Assignment Reject” mechanism.

    #52834 Reply
    Ayat
    Guest

    hello,

    what is the TA (time advance)

    what are the range of TA from ==TA=0 to TA=63.

    plz more explantion are needs

    #52835 Reply
    Pix
    Guest

    TA is the distance between MS and BTS.

    unit is “550m”.

    TA = 1 means Distance = 550m
    TA = 2 –> = 1100m
    TA = 3 –> = 1650m

    TA = 10 –> = 5500m
    TA = 20 –> 11000m
    etc etc

    #52836 Reply
    MSG
    Guest

    does “Rach overl load” affect by repeater?

    #52837 Reply
    safar
    Guest

    Hi pix,

    in eric maxta is the hard limit and talim is soft limit

    so if i reduce maxta from 32 to 10 then if cell has good coverage after 10 maxta and user will be there at 10 maxta then inspite of good coverage but limitation of maxta limit will it latch on it(i mean when he is trying to set up call from idle mode) ?

Viewing 15 posts - 1 through 15 (of 20 total)
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