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Two BCCH in one Sector…..?

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    BCCH during Idle Mode is different with BCCH in Dedicated Mode, but they have the same Cell ID. However, this event is not consistent because there were times that the BCCH in Idle Mode is same when in Dedicated mode. What is happening?


    Hi Onigece,

    BCCH is the frequency of the TRX0

    In dedicated mode, you are not on the bCCH frequency, but on one of the TCH frequencies, which may be equal to the BCCH freq (if tCH on trX0 too), or different (if TCH on TRX > 0)




    Hi pix,

    Thanks! We will send a request of cell’s parameter to RNO in time, to verify if the BCCH showing in dedicated mode belongs to one of its TRXs(non-bcch).

    Got another question though, does phone still monitor or read messages on TS0(of bcch frequency) whenever it is in dedicated mode.

    By the way Im using Nemo testphone and on the interface you can see the serving BCCH and cell ID in idle or dedicated mode. This is the first time i encountered such event, on other sites i walktested, the BCCH in dedicated mode is same as in the idle mode.



    ok, so if it is specifically stated “BCCH” in Nemo, it is indeed the BCCH frequency of the current serving cell, and not its “TCH” frequency. the TCH freq (or TCH ARFCN) is probably shown somewhere else in the interface.

    A standard MS may or may not listen to the BCCH of its serving cell. There is no need to listen to it, as all the required signalling info are transmitted over the SACCH (which is located on the current TCH).
    However some operator can set parameters so that MS are forced to measure the BCCH freq, as if it were a BCCH neighbour (a little tricky AND not needed, as I said above).
    The NEMO MS might have specific software, and therefore might listen continuously to the BCCH freq, in order to provide BCCH RXLEV along with the TCH RXLEV.

    In your case, if the BCCH freq is different than the one you expect, then I suspect that you are not in the cell you think you are. During call setup, the MS goes from IDLE to DEDICATED MODE. However, if the serving cell is congested, the MS is handover immediately to a neighbour cell, which becomes the new serving cell. The bcch is therefore different. This HO during Call Setup is called “DIRECTED RETRY”. The MS is on SDCCH of CELL A and if cell A is congested, it is HO on a TCH of CELL B. Directed Retry is a HO from SDCCH A to TCH B.



    It seems that is the case. And maybe the CI is not updating whenever Directed Retry SDCCH(cell A) to TCH (cell B) happens.
    How about ‘concentric cell’ configuration, do the concentric cells have same CI? I havent tackled this topic though.


    Concentric cell is one cell (one Cid) with two groups of TCH : TCH900 and TCH 1800. However, there is only one BCCH : the BCCH 900.

    Basically, there is one and only one BCCH per cell id.


    Hi Pix,

    Thanks, it helped a lot.



    please! Anyone know how to obtain the traffic in erlang due to the FACH state and the URA state… both belong to the RRC connection mode.

    thank you very much!

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