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PLMN Configuration

Viewing 6 posts - 1 through 6 (of 6 total)
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  • #38279

    Hi Guys,

    Another question !

    I read somewhere that for a MO to MO call in the HPLMN the VMSCA extends the call to a designated GMSC that does the HLR querying for routing info for B and extends the call to VMSCB.

    Is this the usual configuration in most PLMNs or are they usually set up so that the VMSCA does the routing query itself????

    Your thoughts please ..

    Kind Regards



    hi,all GSM system using same method of call setup only the system names differ…


    Hi SSharma,

    MO Call Doesnt Matter where it goes,First it is processed by Presently Serving MSC.

    MT Call doesnt matter where it comes from it should come through GMSC.This is as per GSM Standard.



    Hi Waleed/S.Vijay,
    Thanks for the replies.

    So just to confirm are you guys suggesting that an MO call (i need to confirm this) will be handeled first by the serving MSC which would pass it to a GMSC or does the serving MSC usually act as the GMSC itself ???? I am asking as I need to know the usual way most networks are setup.

    Also, do GSM networks usually implement optimal routing where an MSC in A parties GSM network is able to interrogate B parties HLR and route directly to B parties VMSC ??

    Kind Regards



    Hi Sanjeev,

    It is possible to have Optimal Routing.Now there are lot of products for this.

    But first clear your doubts in Normal MO Call and MT Call.

    MO Call :

    MS in MSC-1 (Serving )

    MS A —> MSC -1 =As per B-Number The can be routed to


    In case if it is Mobile Number the B-No is analysed first.

    Note this VV Important : “If the MSC Founds that the B-Number is belongs to same PLMN then it will route to GMSC ” as per Routing program.GMSC May integrated or may be in some other Place.
    Only if the B-Number belongs to same network.This is found out in B-Number ANALYSIS..etc..etc..ok

    If the B-Number belongs to some other PLMN network then the call may go through Direct Route between Serving MSC amd Other PLMN or Through PSTN ( In India ).

    MT Call :

    MT Call scene starts whenevr a call reaches GMSC.It may come from PSTN Other PLMN or Integarted MSC or From Same PLMN MSC Through Inter MSC Links.
    Then onwards MT Call scene starts up.

    Understand them Separately.Never Mix Them.



    Hi S.Vijay,

    I think your explanation has cleared my doubts .. so I really appreciate you help 🙂 Thanks.

    BTW – Any idea if in case of conditional call forwarding at the VMSC/VLR the GMSC is sent an indication? Which may result in T_BUSY or T_NO_ANSWER being triggered ?????

    Kind Regards


Viewing 6 posts - 1 through 6 (of 6 total)
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