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TRU count

Viewing 15 posts - 1 through 15 (of 19 total)
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  • #35847

    I would like know the # of TRU installed on a network.
    i would like this ifomation per
    SITE/BSC and across the whole network. has anyone got a formula for this


    i also want to know

    Nguyen (

    Plz kindly advise what is TRU ? Plz describe yr question more detailed.

    Lee Ann

    TRU – GSM transceiver. 8 talk channels (TCH’s) per transceiver. My network has 1st 4 channels defined for DATA (DCH) on first TRU.


    Ok, I know, this is sometime called TRX or RTF.

    What do you mean a formula for the # of TRU per SITE/BSC? I think you cannot use a formula for calculating this # of TRU, it is per network and depends on your demand.

    Or do you mean “cell planning” ?


    Yes want to cell plan


    yes there is a target number of TRU’s wwhich need to be installed on the network. At teh moment I do not have a way of knowing if we are meeting that target. so i want a count of the TRU on the network, soo i can know how close we are to target.

    Nguyen (

    To determine the # of TRUs you need, first to have to know the number of the subscriber the cell will serve (by mean of statistic data or forecast, for example 1000 subscribers), and the average traffic per subscriber (for example 20mErl/sub).

    Hence you will calculate the total traffic that the cell must offer:

    1000sub * 20mE/sub = 20 Erlang

    Suppose that your cell will work at blocking probability GOS=1%.

    From here you will have the total traffic channel the cell must provide:

    TCHs = 30

    You know that 1TRU = 8TCHs, so you will need 4 TRUs for this cell.

    After having the # of TRUs, you have to calculate the # of SDCCHs, and so on.

    If you have more information, pls contact me and describe you problem more detailed, I will try to support you.



    hi Nguyen,
    What do you mean that total traffic channels in one cell?
    only traffic or whole??
    I ask for 1 TRU 8 channels or
    for 1 TRU 7 Channels ??


    Sorry, but I have not understood your question so clearly.

    The calculation I have made is for 1 cell. Each TRU has 8 channels (8 timeslots). The 1st TRU in the cell caries the BCCH (on the 1st timeslot), so 1st TRU may provide 7 traffic channels. Other TRUs in a cell (if any) provide 8 traffic channels per each.

    Pls advise if it is not the answer for your question.



    Hi Sadie,

    yes your BSC will have a limitation on the number of cells and TRU/TRX you can define for that BSC which ever is reached first .
    It is the Hardware Limitation of your BSC. These kind of information you can get by checking which is the utilised elements in the Data File information in your BSC.

    In ERICSSON system you can see the number of cell used and defined by SAAEP for sae 298. Similarly there exists SAE for other elements


    hi Sadie,

    ref your initial question there are a number of things to factor.At the start of the network rollout a certain number of sites and hence TRUs (radios) will have been budgeted for. However this is theoretical and (99% of the time) inadequate.

    Also as stated by Sheetanshu a number of BSCs will have been calculated and will limit the amount of TRUs that can be supported. This usually affects things later on depending on traffic take up.

    On a site basis then there are limits from the vendors on how many TRUs can be configured. high capacity (traffic) sites usually configured as 12/12/12 for example which is a total of 36 TRUs. Low traffic sites (rural) may only have one TRU (1/0/0). This assumes a standard 3 sectored site and no co located BTS.

    Bottom line is that as the network grows and traffic increases/decreases then individual sites SHOULD be optimised to have the required number of TRUs for the amount of traffic it is taking. This can be done from network stats (usually BSC/BTS monitoring). These can be applied to the erlang table for the required GOS and the number of TRUs can be worked out.

    Calculation of number of TRUs per BSC should be done very carefully as the traffic for a BSC does not relate geographically to where that traffic is.

    Also as each TRU has a frequency then obviously the less used the better from an interference point of view. Also financially the physical TRU costs money AND so does the features (ie hopping implementstion etc).

    Hope this helps a little


    Hi Sheetanshu,

    It seems that you are working in BSC-Ericsson AXE System.Can you list important SAEs in BSC and their Main Information.

    I am working in MSC-AXE.

    Pls can you give me a mail at

    I have some more doubts about MO,MOG,TG…related things.


    Can u tell me, that in a live GSM/CDMA network
    1) Acceptable percentage drop calls
    2) acceptable % of Access failure
    3) acceptable % of Handove/handoff
    3) acceptable % of Loacation update

    ARE U READY to TAKE Challenge….



    What is the corelation between TRXs and the number of simultaneous voice channels? Is it 8 simultaneous voice calls for every TRX? For e.g. if I have 6 TRXs does it mean, I have 48 simultaneous lines?? Then based of the 48 lines, can I back out the total busy hour erlangs I can support for a given GOS (say e.g.2%)??

    Also, what role does the frequency/spectral capacity play in determining the number of simultaneous lines/voice calls?

    Thanks for the help,

Viewing 15 posts - 1 through 15 (of 19 total)
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