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mapping of E1 channels

Viewing 15 posts - 1 through 15 (of 55 total)
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  • #48258

    How many TRX can be connected in one E1?
    each TRX needs 2 E1 time slots ( 64*2= 128 kbps )
    each TRX needs needs 16 kbps for signalling , so 4 TRX can fit in 1 E1 time slot
    so for 4/4/4 configuration 24 E1 time slots for actual voice traffic and 3 E1 time slots for signalling.
    0 time slot for synchronization and 16th time slot for O&M link .

    So, 24+3+2 = 29 time slots are occupied . We are left with only 3 E1 time slots . I can put one more TRX , again occupying 2 E1 time slots and the last one for signalling out of which 48 kbps is still free.
    So , all in all we can connect 13 TRX at max with 1:4 multiplexing .

    But , I have connected 14 TRX in one E1 in Nortel System .
    And at the most we can connect 15 TRX in one E1 with LAPD concentrated mode 2 .

    But I could not justify more than 13 TRX in one E1 logically.
    pls explain.

    1. What is 1:4 mulitplexing ?
    2. What is 1:1 multiplexing in which we can at max 10 TRX at max( correct me if wrong )
    3. What is LAPD concentrated mode 2?
    4. Is it important that only 16th E1 time slot should be given for O& M link ?

    Karen Thompson

    Hi Ravi,

    Signalling TSLs depends on the vendor systems you are using. But in general 1 TRX takes 2 TSLs on a E1.

    Motorola has combined signalling while Nokia has seperated TRX signalling and many more.

    1:4 & 4:1 multiplexing/de takes place in transcoder.

    16th TSLs for signalling is worldwide with PSTN networks and hence we use the same, as we do interconnect with PSTN.

    Let me know if you require more information.



    hi karen

    we need two E1 time slots for one trx ( 64*2 = 128 kbps )____- ok

    as u told that motorola has combined the signalling …….
    …..combined with ___ the two time slots in which the actual data is being transfered i.e in the same 128kbps only ??????

    If it is like this that the trx signalling is adjusted in the two time slots only , then 2*15 trx = 30 E1 channels .
    We can connect 15 trx in one E1 ( of course 0 ts given for synchro & 16 for O&M link )__________– I want to know with which protocol it is configured _______ Is it LAPD concentrated mode 2 ?

    And still some questions u will find in my previous post that I am still looking for ______ pls have a look again to my previous post /


    Karen Thompson

    It is vendor specific, Motorola has combined 64K (or more) known as RSL for every site and Nokia has this signalling distributed for every TRX and finally OMU.

    With motorola you can go upto 14 TRX (0-SYNC, 1-RSL, 16-O&M, 29 remaining so you can connect 14 TRXs max).

    What equipment do you work on ?? and what technology 2G or 3G.



    dear karen

    what is RSL ? I don’t know …. pls explain…….?? Also pls explain how With motorola you can go upto 14 TRX (0-SYNC, 1-RSL, 16-O&M, 29 remaining so you can connect 14 TRXs max….????

    pls explain about the signalling especially RSL ?/

    secondly u told that we can connect 14 trx in motorola …… which BTS is it ……. I have worked on H-1, H-2 & HM types …. I couldn’t find connecting more than 12 trx in one BTS ????

    I have worked with Motorola BTS , Nortel BTS and ZTE …..
    I am working with 2.75G tech.

    1. What is 1:4 mulitplexing ?
    2. What is 1:1 multiplexing in which we can at max 10 TRX at max( correct me if wrong )
    3. What is LAPD concentrated mode 2?


    Hello Raji,

    I don’t want to be rude, but if you don’t know what is the RSL on the ABIS, I don’t think the answers to your initial questions will ever satisfy you 🙂

    RSL is the physical channel that carries the signalling of ONE trx (SACCH and SDCCH, if there are SDCCH on the TRX)

    Now the whole purpose is to use ABIS as much as possibl for TCH. So we need to multiplex several RSL together as much as possible, and even multiplex them with OML. Of course, by doing so, you reduce the capacity for RSL, risking some ABIS congestion.

    So those are the possible solutions (ts = 1 64kbps on the abis):
    1. No multiplexing
    1 OML = 1 ts
    1 RSL = 1 ts
    1 TRX = 2 ts

    2. Static Mx
    1 OML = 1ts
    1 RSL = 0.25 ts (16kbps) (only one config : 4 RSL will be put on one ts)
    1 TRX = 2 ts

    3. 64kb/s statistical Mx
    1 OML + 4 RSL = 64 kbps (one RSL can use up to 64kbps if the 3 others don’t use their bandwidth. Contrarily to the static mx, where 1 RSL cannot use more than 16 kbps)
    1 TRX = 2 ts

    4. 16kb/s statistical Mx
    this is a particular configuration : each radio TS0 of each TRX must carry the BCCH or a SDCCH. No TCH allowed on TS0 !!
    1 TRX = 1.75ts
    OML+RSL = 0.25 ts (for the first TRX)
    RSL = 0.25 ts (for the other TRX’s)

    So with the solution “16kb/s statistical mx”, a cell with 4 TRX will use only 8 abis ts
    0 – SYNC
    1 … 31 = 15 TRX + 1 abis ts unused.

    Finally, even if one BTS cannot use 14 TRX, one ABIS link can be shared by several BTS

    FYI, an alcatel bts can go up to 24 trx 🙂 French rocks !!

    Md Sarfraz Iqbal

    What is TRX signalling,TCH why it is used,what is OMU in terms of Nokia BTS.What is the power consumption of one trx.


    Dear Karen,

    In Ericsson RBS 2206 how many TRXs maximum can be configured.



    hi sir
    i want to know about motorola bts installation.units used in bts & there much operating power,current and voltage needs to bts.


    Well i need some information.Basically 1 E1 means that we have an IF cable coming from one dish.If we have ,for example,8+8+8 configuration that means total of 24 trx and 48 time slots will be required.So we will be needing two E1s for this.So here,two E1s means that two IF cables coming from 2 Different dishes.Am i correct?



    i don’t have any experience with dishes, but i guess you’re talking about PDH/SDH ? Well, i know that one dish can carry much more than only one E1, but i don’t know physically what is an IF.
    It’s just a matter of capacity : 1 E1 = 2Mb/s. How much is 1 IF ?

    PIX ,

    IF(intermediate frequency) cables are the cables that are connected between the microwave dishes and BTS.


    dear all…

    what is OML?
    I work with OSS Nokia
    I still confuse about OML faulty

    thanks 4 all

    Ahmed S. Anwar

    what does TRX stands for??


    In Motorola BSS
    we used 1 RSL(1 Abis TS) per 1 BTS
    and 1 CTU(TRX) per 1 RTF(2 Abis TS)

    Try to compute
    1E1(Abis) = 32 TS – 1 TS(sync. TS0)
    You have 31 TS to use in abis.
    1 TS for RSL and 30 TS for RTF

    1 Abis maximum 1BTS with 15 CTU(TRX)

Viewing 15 posts - 1 through 15 (of 55 total)
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