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Project + doubts

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  • #67837


    I´m involved in a project for GSM. The idea is to provide the transport for a GSM operator via our IP satellite links. They have the GSM network and we have the satellite network to transport their calls. I have a lot of information but I´m not sure if I´m using it in a right way to make the link budge for each one of the sites. For example: i think that the maximum capacity is given for the amount of TRXs and that each TRX is about 128kbps. Is that correct? Could something help me to clarify this kind of answers?




    no problem
    each TRX = 128kpbs
    but you must add some high level signalling on top of that:
    per group of 4 TRX full rate, add 64kbps. If the group does nto contain 4 TRX, then you must also count 64kbps.

    for ex, one BTS with a total of 12 TRX = 8*128kbps + 3x64kbps

    one BTS with a total of 13 TRX
    8*128kbps + 4*64kbps

    if a TRX is supposed to carry half rate, then it will count for 2 TRX within a “group of 4” signalling. In other words, 2 HR TRX require 64kbps of signalling.

    one BTS with 12 TRX, 6 of them being “HR” and 6 being “FR”
    8*128kbps + 3*64 + 2*64
    2*64 because 3 groups of 2 HR TRX

    3*64 because 2 groups of FR TRX : group 1 = 4 TRX, group 2 = 2 TRX.

    I hope that helps… 🙂




    Thank you very much for your usefull explanation.
    I have other question. Our customer sent us a form with a information for each one of the sites. For example:

    BTS A -> 3 TRXs capacity
    BTS B -> 4 TRXs capacity

    So, my doubt is if in the GSM world the total capacity for the example would be:

    Total = 7 TRXs


    Total = 7 (in one direction) + 7 TRXs (in the other direction) = 14 TRXs

    I hope you can understand my doubt. I don´t know if 7 TRXs would be the total capacity or if I must to consider other 7 TRXs plus for the other direction of the traffic.

    Sorry for this silly questions but I´m new in the GSM world.

    Thanks in advance!


    not silly at all.
    the day you stop asking question is the day you are being silly…

    1 TRX will use 128kbps in each direction, in UL and in DL.

    so 7 TRX = 7*128kbps in ul + 7*128kbps in DL.

    + the signalling, which also goes in both direction.

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