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BCCH Failure

Viewing 15 posts - 1 through 15 (of 84 total)
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  • #36613 Reply
    Scot
    Guest

    Hi All,

    Lets say there are TWO TRXs in a Sector.And First TRX Contains BCCH and SDCCH/8.

    In the Second TRX all 8 TS are used for TCH Purpose.

    A call is going on in TRX2.
    If suddenly TRX1 Fails what will happen.The condition is there is no other Sectors nearby and no other BTS.

    Call will be maintained or not ?

    Rgds

    Scot

    #36614 Reply
    Chefo
    Guest

    I think that this failure would not affect the calls on TRX2, unless they are not on timeslots 0 and 1, because the signalisation during dedicated mode is using SACCH which is on the same TS as the TCH.
    After the fail of TRX1 the BCCH and SDCCH will be trasferred immediatly to TRX2.
    I hope it is helpfull to you.

    #36615 Reply
    Transfering…?
    Guest

    “TRX1 the BCCH and SDCCH will be trasferred immediatly to TRX2 “-Is this is a OPERATOR SETTING or DEFAULT System Setting in GSM ?

    Rgds

    Scot

    #36616 Reply
    gyanendra
    Guest

    hi Scot/Chefo

    I agree with chefo that there will be no effect on the calls on TRX2 but do not agree with limitation of TS 0 & 1. Chefo u forgot that in case of BCCH shift the whole ARFCN gets shited to 2nd TRX. so in that case there won’t be any non bcch ARFCN & hence calls that were earlier on non bcch TRX will be dropped.

    Lastly the fascility that BCCH always remains active in a cell by shifting to some other TRX in case of a HW failure is a vendor provided fascility.

    Hope this clears all ur doubts.

    #36617 Reply
    Chefo
    Guest

    Sorry for the desinformation i gived to you.
    Please, disregard my first message.
    I have recent experience with Alcatel equipment, and the procedure in case of fault BCCH TRX lasts for 2 to 3 minutes, during which the calls on TRX2 are disconnected and the frequency is changed to the BCCH ARFCN.
    Maybe with other vendors the procedure is different, i don’t know…
    Regards
    Chefo

    #36618 Reply
    Scot
    Guest

    Hi gyanendra&chefo,

    Thanks guys for clearing this.

    Rgds

    Scot

    #36619 Reply
    AlexSh
    Guest

    swithching TRXs in case of BCCH TRX fail, as I know, is a vendor dependent feature. aslo u can lock BCCH TRX, all traffic on it will be lost but other TRXs in this sector remains working and will handle traffic

    #36620 Reply
    Pradeep Singh
    Guest

    hi all,
    If BCCH is always present in the TS0 of all frequency bands.what is the need of BCCH ARFCN when BCCH is available in all ARFCNs.
    On the other time slots of BCCH ARFCN, other logical channels and traffic channel can also be transmitted. Is there ant special significance of the term BCCH ARFCN ?

    #36621 Reply
    Chefo
    Guest

    Pradeep Singh,
    The BCCH is located only on TS0 on BCCH frequency of the sector. The other frequencies in the sector are for traffic purposes only and do not carry BCCH signaling.
    Regards.

    #36622 Reply
    sam
    Guest

    suppose there are 8 trx,then how sdcch, bcch and tch will placed in 64 timeslots. how do we plan for bcch and sdcch requirement?

    #36623 Reply
    Chefo
    Guest

    Sam,
    The BCCH is located allways on TSL0 on the TRX carried BCCH frequency. The SDCCHs allocation is depending on the vendor’s requirements, but generally it is recommended to be placed on the BCCH ARFCN but this is not mandatory. The number of the SDCCHs depends on that what is the number of TCHs in the cell, full-rate or half-rate, what is the type and location of the cell in the network and many more. There are tables from which you can dfine the initial number of SDCCHs and after performance measurements you can tune it.

    #36624 Reply
    sam
    Guest

    thanks chefo,

    but please tell me how many sdcch we have to allot for half / full rate considering my example of 8 trx. can u send me the table which u have written about.

    thanks again ur reply.
    sam.

    #36625 Reply
    monem
    Guest

    Thanks all for this clarification.
    BCCH must be on the lower freq in case of fixed allocation.
    BCCH ARFCN carrier known as the Beacon of sector (for access, signaling & control function).
    FOR channel dimensioning we can use different method but as standard (BCCH & SDCCH on Ts0 of carrier (combined mode) for cell with low signaling load. OR BCCH on Ts0 & SDCCH on Ts1, for significant high load on signaling.
    But we can allocate more Ts for SDCCH for further high signaling load.
    Further more for half rate TCH the SDCCH will be more than Full rate, Because the call set up, SMS, Fax, HO,LA update registration & other signaling will increase by increasing of calls & so you allocate more SDDCH for this load by fixed or auto allocation according to the vendor system.
    Regards.

    #36626 Reply
    Chefo
    Guest

    Sam,
    for a cell with 8 TRXs you should define 3 TSL as SDCCH(8) if you are using Full-Rate or 5 TSL as SDCCH(8) if it is Half-Rate. But keep in mind that this is only initialy defined values. After some measurements you may need to increase the number of the SDCCH channels. I have no idea about the traffic model of the network where this cell is located.
    Monem,
    Generally you are right, the bcch frequency band is not mandatory located on the lowest frequencies, it depends on the planning strategy.

    regards
    Chefo

    #36627 Reply
    monem
    Guest

    thanks chefo for replaying.
    i thinks the measurement which define the SDCCH are call model(measured holding time for events using SDCCH) & moreover SDCCH/TCH load ratio, allowed GoS for (SDCCH,TCH) and effect of PCH capacity.
    But kindely i need to know about HO load & is it have any effect on SDCCH dimentioning and call model.
    Also how half rate is implement in cell (fixed OR dynamic by SACCH)and which is better.
    Best Regards.

Viewing 15 posts - 1 through 15 (of 84 total)
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