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mapping of E1 channels

Viewing 15 posts - 31 through 45 (of 55 total)
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  • #48288
    manoj shrestha

    Can anybody help me to calculate the bandwidth occupied on E1 say if the site is configured with only one trx, when the tranmission on the Abis interface is ip based.


    Hi all,
    I would like to know the Abis configuration if we have 1 + 2 PDTCH in Um interface.
    is it still possible with 15 : 1 configuration?
    Can anyone explain to me this?


    Muhammad Atif

    Does any one who can guid me which standard deals with mapping of TRX an an E1 ?



    1+2 PDTCH are mapped/defined on TRX on Um interface.
    E1 are on Abis interface, so thereis no mapping of PDTCH on E1.
    It is the timeslots that you give for EDGE services that are mapped on Abis E1s and that is customer specific.

    correct me if im wrong.




    All radio timeslots are mapped to equivalent throughput on the Abis.

    For example :
    1 TCH = 1 Abis nibble
    1 PDCH = n Abis nibble (PDCH throughput can range from 8kb/s to 59kb/s so need more than 1 nibble to carry all that !)

    As a rule of thumb:
    4 TRX require 1 ABIS TS to signalling
    1 TRX require 2 ABIS TS for data (TCH & PDCH)
    And for PDCH, you can define additional ABIS TS to allow bigger throughputs to users & allow more users at the same time.

    1 BTS 3 cells at 4 TRX each = 3 + 24 = 27 ABIS TS for sig + TCH.
    You can add 4 ABIS TS for EGPRS, to fill up the whole 31 ABIS TS available.



    Thanks Pix,

    Abis ts for data is not fixed, it can vary as per vendor specs or to increase throughput.
    there is no one to one correlation b/w PDTCH on Um n Abis ts for data on Abis E1.
    (correct me if im wrong)

    one doubt in ur explanation as im not familiar with these terms.

    1 Abis TS = 1 Abis nibble??
    wat i understood is,
    1 Abis TS is 64kbps ts on Abis E1
    1 Abis nibble is 16kbps ts i.e 1/4 of 1 Abis TS.


    I agree with all you just said 🙂

    abis TS = 64kbps
    abis Nibble = 16kbps

    PDCH is carried over n abis Nibbles.
    The abis nibbles that carry the PDCHs are called “GCH” (in ALU).



    so if thats the case, 1 TRX = 1 Abis nibble?


    I wrote
    “1 TRX require 2 ABIS TS”

    Why do you say 1 nibble ?

    1 TRX carries 8 radio TS.
    Each radio TS (16kbps) is connected to 1 ABIS nibble (16kbps).
    Therefore, 1 TRX = 8 radio TS = 8 Abis Nibble = 2 Abis TS.

    Read slowly 🙂

    You know, I just found out that an easy way to compute how many Abis TS are needed for a BTS (the minimum number, that is).
    # of Abis TS = 2.25 x # of TRX

    It took me years to finally discover this simple method. Dumb & Dumber & Pix (the Dumbest).


    sorry pix, what i mean is

    1 TRX = 1 Abis nibble for signalling – 16kpbs(LAPD).


    If we have 7 16kbps TRX and one 64kbps TRX then how we can calculate by this formula

    # of Abis TS = 2.25 x # of TRX

    Does we take no of TRX 7 or 8


    The formula is based on the assumption that the RSL (signalling) for 1 TRX is only 16kbps in average.

    So you can locate 4 TRX into one Abis Timeslot (there is multiplexing and dynamic sharing of the 64kbps : each TRX could go up to 64kbps if other TRXs are not sending RSL at that time)

    Amman, your case does not follow the assumption.



    hi Pix,

    U wrote that “there is multiplexing and dynamic sharing of the 64kbps : each TRX could go up to 64kbps if other TRXs are not sending RSL at that time”.

    can u explain this as wat i understand this 16 kbps is dedicated for that particular TRX.
    is there any case/feature in which this sharing happens or its default.


    It is not default… Every time you create a BTS, you must choose where and how you carry your RSLs over the Abis. Several possibilities (depending on vendors)
    – each RSL gets static 16kbps
    – each RSL gets static 32 kbps
    – each RSL gets static 64kbps (i think it exists, i’m not sure)
    – 4 RSL share 64kbps (dynamic)
    – 2 RSL share 64 kbps (dynamic)

    Most common conf is the dynamic 4RSL/64kbps
    It is just that the 4 RSL of 4 TRXs are multiplexed over a shared capacity of 64kbps.
    Each one is not statically allocated 16kbps : the sharing is dynamically computed, depending on needs of each RSL.


    Sardar Khaleeq uz Zaman

    Hi everyone,

    Can any body tell me the full capacity and spare capacity of

    1. BTS
    2. ABIS Interface
    3. A Interface
    4. Ater Interface

    & what physical links are used in these interfaces i-e (frame relay, microwave, ATM, X.25 etc)…

    can anybody send me the pdf or docs of these.


Viewing 15 posts - 31 through 45 (of 55 total)
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