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Preferred BCCH TRX

Viewing 8 posts - 1 through 8 (of 8 total)
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  • #51109 Reply

    Hi all,

    What is the reason/advantage for specifying a TRX in a cell as Preferred. As it is seen that in case of failure of this(Preferred) TRX the BCCH do shift to other TRX but an alarm is generated in BSC that BCCH is not at Preferred TRX.


    For a cell having 3 TRX we can have a combiner for TRX1 and TRX 2, while the output of TRX3 can be fed directly to the Duplexer without the need of combiner. So in this case if BCCH is to be mapped then will it be wise to choose the TRX3 or not?
    Choosing TRX3(the one without combiner) can provide us extra coverage(since of extra 3 dB power then other two in same cell).
    In case of TCH allotment do we have any option in BSC to define the priority among the TCH allotment TRX wise. or Do BSc has the intelligence to allot the TCH on the basis of TA or power control.



    #51110 Reply

    Hi Mazin,

    1. It is useful to declare a “preferred” TRX, in order to favourize TCH allocation on this specific TRX. This option is usually chosen to force GPRS on BCCH TRX first.

    2. Regarding the alarm, i don’t know.

    3. In your example, the TRX 3 will have a power reduced by 3dB, in order for this cell to have all its TRX providing the same power at BTS output. This is called power leveling.

    4. The TCH allocation is favourized by the PREFERENCE MARK, as you stated above. This is a TRX parameter you can change in the OMC-R.

    — note : there is few more questions that might interest you :
    – “how the BSC maps the logical TRX and the physical TRX ?”. Because the TRX 1 in your cell might not be the 1st TRX in your BTS, physically.
    There is an algorithm for this, so the BCCH is usually the TRX with highest EDGE power, etc…

    – “is there any priority in the allocation of a TCH, if the PREF MARK is set to 0 on all TRX ?”. will the TCH be allocated on last TRX ? first TRX ? but which TS ? there is an algorithm in the BSC, that will allocate TCH on full rate TRX normal power, then dual rate TRX normal power, then full rate high power, then dual rate high power, and so on.
    For PDCH allocation, this is usually done in the reverse order.

    #51111 Reply

    Power leveling? This is new to me.
    Can you please tell that how the control unit of BTS or the which unit of BTS takes the decision to do the power leveling. I mean how does BTS came to know that the BCCH signal of a cell or sector is getting radiated with more power then the TCH TRX of that cell. I mean whether it is done on sensing the cabling present or some other mean. Though doing this by sensing the cabling seems to be an easier way but i doubt whether this is only the sole criteria or something else must be taken into picture. As all the TRX’s in a cell most of the time differs in the terms of their output power and same also depends up to certain extent on aging of TRX.

    Please give the source info for POWER LEVELING.

    #51112 Reply


    Are you sure that the concept of POWER LEVELING exits.


    #51113 Reply

    it’s more than a concept, it is the default mechanism in the BTS :
    at the BTS output, all TRX should be measured with the same TX power.

    It can be disabled since B9, in alcatel, and it implies the use of concentric cells. I don’t know about other vendors.

    #51114 Reply
    Askari (Mani)

    Dear MKT,
    Perhaps the best means of over-comming this problem is to use a combiner for the third TRE as well. else if it becomes the BCCH there might be serious problems. Different footprints of different radios resulting in low CE of hopping radios effecting CSSR and Low HSR.
    Else you can have power based zones in the cell. making the extra-combiner TREs inner zone.

    #51115 Reply

    Team can someone help me to know , if it’s possible to have TRX preference on Ericsson cells like for Alcatel ?
    If yes , how ?

    #51116 Reply


    we have alot of sites are off completely for long time , i try to check the alarm history , i found most of them have “Cell interruption alarm” for all the cells ..Probable Cause is Equipment Malfunction. Specific Problem 1. The site to which the cell belongs is lost.
    2. The cell BCCH frequency is faulty. could you explain to me .. if the the problem in BCCH and the BCCh in TRX1 .. can i chanage the configuration

Viewing 8 posts - 1 through 8 (of 8 total)
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