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What is BSIC?

Viewing 15 posts - 16 through 30 (of 35 total)
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  • #35827
    Dimapl
    Guest

    Hi Nguyen,
    Thank you for the information about inter-PLMN handover. When performing inter-PLMN handover MS gets registered in VPLMN first, doesn’t it? Does it imply that core-MSC changes at the inter-PLMN handover?

    #35828
    Nguyen
    Guest

    Hi Dimapl,

    What do you mean in the “Does it imply that core-MSC changes at the inter-PLMN handover?” phrase? Sorry for my stupid English!

    I think when the MS moves from its HPLMN to another PLMN, the roaming subscription check must be performed first. Hence the MS cannot maintain the call in progress. In other words, the “inter-PLMN handover” terminology does not exist.

    Is this right? Plz give your opinion.

    By the way, could you tell me what GSM specs about Roaming procedure.

    Thanks/Brgds

    #35829
    Atul
    Guest

    Hello!!
    This is a nice place for discussion. Lot of technical interaction going on. Was searching thru Google on AXE810 and found this forum. Just been thru the “Switch Planning for GSM” thread and then going thru this one.
    I think the GSM specifications do not describe the handovers between cells of different PLMNs. Please correct me if I am wrong. If it exists, it should be similar to Inter-MSC handover except for the fact that roaming check feature of the visiting MS would have to be done which need not be done for Inter-MSC handover because here it is generally assumed that both the MSCs would be of the same PLMN.
    Nguyen>>> What Diampl probably means is that if MSC A(core MSC) of HPLMN was handling the call and then Inter-PLMN handover takes place to MSC B of VPLMN. Would MSC A be completely out of picture now ? Well, in case of Inter MSC handovers, that’s how it happens.
    Diampl >>> I feel if Inter-PLMN handovers do exist then the same should be the case here too. Core MSC A should be out of picture. But could you please tell me what happens to CDRs during the Inter MSC handovers. Would both the MSCs generate CDRs for their portion of call handling.
    One more silly doubt now after going thru this thread. Let us consider a scenerio where a MS in speech phase moves to an area with a different LAC but within the same MSC area. Handover takes place. It is said that handover would be done first and then LU would take place. Will the LU be done during the speech phase over FACCH or will it happen after call termination.

    Regards.

    #35830
    Nguyen
    Guest

    Hi Atul,

    Thank you for your contribution to this thread.

    In the case of inter-MSC handover, MSC-A is the switching element. All call control (including CDR and signaling) remains in MSC-A for the entire duration of the connection, this is called the anchor principle, and of course the connection between MSC-A and MSC-B is maintained during this time. After the call is finished, all data related to MS from VLR-A is tranfered to MSC-B by mean of MAP messages. MSC-A cannot be out of the picture.

    The LU will be executed only after the end of the call.

    Brgds.

    #35831
    Atul
    Guest

    Hi Nguyen,
    It was a pleasure.
    I quickly went thru the GSM Rec 03.09 version 7.0.0 release 1998 on Handover procedures. It says, after Handover from MSC-A to MSC-B, the connection between MSC-A and MSC-B is released. I think anchor and relay MSCs are the names given for understanding the scenerios.
    When you say LU will be executed after the end of call, I assume you are meaning after the speech phase is over.
    Main components of LU are TMSI and LAI. VLR-B, HLR and SIM card of MS must be updated and VLR-A cleared. While the call is in speech phase and the handover has been completed, I think VLR-B should be updated with the LAI,HLR of MS must have the VLR-B number. I feel this is necessary coz if a call lands on MS while he has moved from MSC-A to MSC-B and is still in speech phase and the LU has not yet been done then the HLR of MS will show the presence of MS in VLR-A and VLR-A will have the old LAI and the response to the calling party would be that the MS is not answering the call(this would also be improper utilization of PCH in VLR-A area). Whereas, actually he is busy in VLR-B area. But if the VLR-B and HLR of MS are updated during speech phase immediately after handover, any caller to this MS will hear the announcement that the subscriber is busy. But don’t know what the GSM recs say.
    Another thing is updating the SIM of MS. New TMSI and LAI should be given to MS. When will this be done? I feel this info can be exchanged over FACCH during speech phase but not sure. Any member familiar with this scenerio may please contribute.
    And yes, roaming subscription checks of MS for Inter PLMN(even if it exists) shouldn’t be an issue. The handover request would first have been received by MSC-A of HPLMN. Right at this moment before communicating with MSC-B of VPLMN, the MSC-A can find out from HLR of MS(or may be keeping such records already within VLR-A) whether the MS has Inter PLMN roaming subscription(MSC-A by now knows the area/operator where the MS is heading to). If yes then it proceeds to call MSC-B. Now if roaming agreements are in place between MSC-A and MSC-B of different PLMNs, then MSC-B will accept the handover request of MSC-A. Well, I have just tried to apply logic to the above scenerio, not read these in GSM Recs. In case of error, please correct me.
    Regards.

    #35832
    Nguyen
    Guest

    Hi Atul,

    The inter-MSC handover can be divided into 3 cases:

    1) Basic inter-MSC handover, where MS is handed over from MSC-A to MSC-B.
    2) Subsequent inter-MSC handover, where MS is handed over from MSC-B to MSC-B’.
    3) Subsequent inter-MSC handback, where MS is handed back from MSC-B to MSC-A.

    In the case 1 and 2, the MSC-A controls the call and maintains the connection from MSC-A to MSC-B or MSC-B’ during all time of the call. Only in the case 3, the MSC-A will release the connection between MSC-A and MSC-B after handover procedure.

    I could confirm that the LU can only be executed after the call is finished. In the scenario you have mentioned, the busy announcement is not the problem as the MS may have the Call Waiting subscription. However, plz be noted that the LU procedure is performed via SDCCH, not by SACCH nor FACCH. Hence the LU can be performed only after the end of the call. Updating the SIM of the MS with new TMSI and LAI will be processed simultaneously with the LU procedure.

    About inter-PLMN handover, I have no new idea yet.

    Brgds.

    #35833
    Atul
    Guest

    You are right Nguyen!!
    Actually, I had read thru the GSM specs very quickly(one should never do that) and missed out the most important part. It clearly says, “MSC-A shall retain overall call control until the call is cleared by the fixed subscriber or the MS and there is no further
    call control functions to be performed (e.g. servicing waiting calls, echo cancellers)”.
    I knew LU takes place over SDCCH but my above misconception was causing the confusion in my mind.
    Many many thanks for clarification.
    Regards.

    #35834
    Nguyen
    Guest

    Hi all,

    Interesting that I have found the spec about inter-PLMN handover. It is 3GPP TS 22.129. However this spec does not mention about roaming checking during or after handover procedure. Plz read it and give your opinion. This spec only contains less than 20 pages.

    Brgds

    #35835
    Atul
    Guest

    Nguyen, thanks for the specs reference for Inter PLMN Handover. Will go thru them and get back. But I think HPLMN1 MSC-A would anyway come to know of the handover request and can check the Inter PLMN roaming subscription of the MS. VPLMN2 MSC-B would just check whether handover request from MSC-A is to be entertained or not.
    Could you pl elaborate, what is the issue/concern you see here?
    Are you interested in knowing the exact sequence of operations or you find an issue coz of which you see it not happening.
    Regards.

    #35836
    Nguyen
    Guest

    Hi Atul,

    The spec 22.129 does not mention about roaming check at all. Plz be noted that the roaming checking procedure is similar to LU procedure, but it is more complicated. It is not just a roaming subscription checking.

    Brgds

    #35837
    Dimapl
    Guest

    Hi all,
    Shall we get back to inter-PLMN handover? Nguyen, thank you for the reference on inter-PLMN handover that you’ve given before. I went quickly throu it. (3GPP TS 22.129 version 5.2.0 Release 5) The spec leaves many issues open but it states (Annex A ) that if handover request is accepted by target PLMN and the call continues in adjacent PLMN, subscriber location information in HLR remains unchanged. After inter-PLMN handover, anchor MSC located in previous PLMN continues to control a call. When the call is over, LU takes place.

    #35838
    Kenneth Lima
    Guest

    Hi guys,
    Please help me out. During an inter-PLMN Handover when a MS moves from one MSC-A to MSC-B, who initiates the request actually? Is it A and if yes what happens when A losses control over the MS and the MS gets to the MSC of B. How is this scenario explained.
    Thank you

    #35839
    Nguyen
    Guest

    During inter-MSC handover, the serving BSC sends handover required message to the serving MSC (MSC-A), then MSC-A sends handover request message to the target MSC (MSC-B). MSC-A takes control over all connection of the MS. If A losses control, the call will drop immediately. The MS then register itself to the MSC-B by location updating procedure.

    #35840
    Kenneth Lima
    Guest

    Again if my MS moves from one country to the other and along the way my MSC losses control of me,what happens when i get to another country and want to roam with another GSM partner? How is this handover initiated.
    Thanks

    #35841
    Nguyen
    Guest

    When the MS moves from one country to another one in the idle mode, this is not a handover procedure. This is called roaming procedure.

    The MS will request location updating as usually. The visited network will check for roaming subscription of the MS, and if it is permitted, the location updating procedure will be processed as normally.

Viewing 15 posts - 16 through 30 (of 35 total)
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