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Subscriber unreachable

Viewing 15 posts - 1 through 15 (of 16 total)
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  • #61686 Reply
    Fresh Opt
    Guest

    Hi,
    What causes subscriber to be unreachable if I know that subscriber it is located to a cell. After second attempt the subscriber can be reachable. It happens very often. Is it related to paging? If yes, what’s the solution?
    Regards,
    Fresh Opt

    #61687 Reply
    AliAsgher
    Guest

    Please check whether paging discards are present on the cell.

    #61688 Reply
    ipx
    Guest

    fresh opt,

    the subscriber can only be reached after the 2nd attempt ?
    this particular MS only or all MS in the cell ?
    all the time, or just once in a while ?

    does the MS make a call setup or a location update before you attempt to reach it for the 2nd time ?

    what is the delay between the two call attempts ?

    can you increase this duration ?

    how did you detect this problem, could you please describe the method ?

    AliAsgher,
    If a Paging is discarded due to congestion, it is going to be repeated by the MSC. In other terms : if the MSC doesn’t get a Paging Response before a certain timer, it will repeat the Paging 1 or 2 times.

    The subscriber is said to be “unreachable”, and it can mean two things :
    1/ the first paging is always lost (incl. the repeatitions) and the 2nd paging is always successful. But I don’t think so. Too weird.

    2/ the IMSI is not present in the VLR, therefore the MSC doesn’t send the 1st paging : it directly respond to the calling party, saying ‘called party unreachable’. But why would this IMSI becomes attached at the second attempt ?

    Well, i must admit, i need more inputs from fresh opt…

    cheers
    pix

    #61689 Reply
    AliAsgher
    Guest

    Dear Pix,

    In case paging discards are high on the cell, there is probability that the page is not sent (1st time and repeatition both). I was just assuming this case. Whereas on following attempts may be the page was transmitted and call was through.

    Also I don’t think it is possible that the case described (1st time unsuccessful and second time successful) is happening all the time. It must be happening some of the time. Thatswhy I suspected paging getting lost due to high PCH congestion.

    I have observed two such cases where

    1) In a high rise building MS was reselecting many cells and was continuously doing Location updates. Overshooting of too distant cells was the cause and even sometimes the MS was going into emergency calls.

    2) In case MS sends a channel request, then in the time when the channel request is sent and the status of the MS is not registered as dedicated mode, if a page is sent for the MS it will be lost as MS will not respond and also the network does not know that MS is in dedicated mode.

    #61690 Reply
    Fresh Opt
    Guest

    Hi guys,
    we were both in the same Location Area. I don’t know were we in the same cell, but we were close to each other. The second MS did some calls, after a while I called him, couldn’t succeed (message: “Subscriber is unreachable..”). After the second try I could call him and it was OK. The place is urban area, very “busy” cells. It not happened only to me, we received many subscriber complaints, that was the reason I posted this issue. It’s strange! Most of cells in the area are not congested, paging load is around 59%. Is it related to paging or some other issues (in NSS for example)?
    Regards,
    Fresh Opt

    #61691 Reply
    SHELDON
    Guest

    Hi Fresh Opt,

    As Pix and AliAsgher pointed out, it MIGHT be a paging problem. You say your paging load is 59%, but what percentage of your pages are discarded?

    Also, are all the complaints/experienced coming from the same location? If yes, then it can also be caused by a faulty BCCH TRX (transmitting corrupted paging msgs).

    The problem can also be coming from somewhere else, eg the core network, IN, etc. Check the MSC-VLR/HLR signalling to make sure everything’s ok.

    REGARDS,
    SHELDON

    #61692 Reply
    Fresh Opt
    Guest

    Hi,
    Thanks to you all. I’ll be focusing on paging. And I was thinking to remove some cells from the LAC in order to reduce loading. It’s a city with 2 BSCs and 1 LAC, 190 cells. How can I check paging congestion and discarding? Any counter (vendor Alcatel rel. B9)?
    Thanks again.
    Regards,
    Fresh Opt

    #61693 Reply
    pix
    Guest

    fresh opt,

    do you have a RNO around ?
    there are few indicators to check the paging load.

    #61694 Reply
    Fresh Opt
    Guest

    Hi Pix,
    Yes, we have RNO. I can see paging load but not paging congestion.
    And loading is 59%.
    Regards,
    Fresh Opt

    #61695 Reply
    Guru
    Guest

    There is a chance of getting ” not reachable” if the MS is located in a LAC boundary.

    #61696 Reply
    Fresh Opt
    Guest

    Hi guys,
    I found that subscribers which are connected to GPRS can’t be paged. How is it possible that, it shouldn’t. Any suggestions?
    Regards,

    #61697 Reply
    Fresh Opt
    Guest

    Anyone? Could GPRS cause paging discards?

    #61698 Reply
    SHELDON
    Guest

    Hi Fresh Opt,

    I would say GPRS CAN lead to paging discards, but in my opinion, the effect of GPRS on paging discards will be minimal. I say CAN because if you’re using combined procedures for both CS and PS paging, then it’s possible some CS pages will be discarded when the paging queue is full (due to many PS pages). I hope we’re on the same page regarding ‘paging discards’.

    The ability or otherwise to page subscribers connected to GPRS depends on several factors.
    1. Your GPRS network operation mode( mode III is required to be able to have concurrent PS and CS connections)
    2. MS capabilities (CLASS A and B MSs can engage in both PS and CS connections at the same time)
    3. The MS’s GPRS MM state

    Let me elaborate a little on 3: For an ordinary MS which is GPRS ‘connected’, the ability or otherwise to page it depends on the current MM state. If the MS is engaging in packet transfer(READY state), then it can’t monitor the paging channel, thus it can’t respond to pages. However, if the MS is in standby or Idle state, it can respond to pages.

    Regards,

    SHELDON

    #61699 Reply
    Fresh Opt
    Guest

    Hi Sheldon,
    as I find out subscribers connected to GPRS they often use GPS navigation with Google map. So, for sure it’s the case under 3 you described. We use network operation mode II. Do you think is normal in these conditions we have?
    Thank you for your answers.
    Regards,
    Fresh Opt

    #61700 Reply
    Arif
    Guest

    Hi Fresh Opt,

    We have the identical problem in our network as well. We have Gs interface, i.e. MTC can be done during upload or download state.

    Is the problem of yours solved? Please share the info.

    BR.

    Arif

Viewing 15 posts - 1 through 15 (of 16 total)
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