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Data Services after cell re selection

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  • #58756 Reply
    RG
    Guest

    Dear All,

    In my network i facing the Issue that some of the time MS is not able to resume data services after cell re-selection.

    Kindly let me know on which interface and parameter i need to work upon.

    #58757 Reply
    Bijoy
    Guest

    please check if GPRS services are allowed for the cell which got re-selected.

    #58758 Reply
    RG
    Guest

    Yes, GPRS/EGPRS services are allowed in the cell. Also both the cells are in the same RA.

    #58759 Reply
    Bijoy
    Guest

    Hi RG
    Which system are you using?

    #58760 Reply
    RG
    Guest

    Vendor is ZTE

    The main issue is after reselection out of 100 time, 50 time MS is able to resume the service and other 50 time MS cant resume the service.

    In the signalling i have noticed as below:

    1.) MS is not responding to Packet Uplink Assignment and Packet Uplink Ack/Nack.

    2.) After this there are a series of Immediate Assignment in which the access cause is “Answer to Paging” but after that also services are not resumed.

    3.) Service got resumed after refreshing the page or after re openning the site or start starting the download aagin (i.e. when MS is sending the EGPRS packet channel request) again.

    Pls help me Pix/Bijoy to find the out the rot cause of the problem and kindly guide me on which parameters i need to work.

    #58761 Reply
    SUMIT MENARIA
    Guest

    Dear all,
    I am new to this forum ,but i have the same problem in my network…
    There have been TBF drops in my network due to errors in Cell reselection and RAU …We are using Nokia system
    Thanks in advance…
    Sumeit

    #58762 Reply
    Bijoy
    Guest

    Ok RG.
    1.There will be PS assignment reject or failure in this case.Have you checked the reasons.
    2.What is the Rx_lev_acccess min for GPRS.check that.
    3.Is there N3101 or N3103 overflow.
    4.If call setup indication rate is poor.In this case,check the PS paging success rate LAC and RAC wise.
    5.Are you using NACC or NCCR(Network controlled cell reslection)?
    6.What is the value of t3168?
    7.Are you using extended UL TBF function.

    #58763 Reply
    Pix
    Guest

    Hello RG,

    After the reselection, it is up to the MS to establish a new UL TBF in the target cell (it was in DL or UL TBF before).

    The sequence goes like this:
    UL : Channel Request
    DL : Immediate Assignment
    DL : USF is given to the MS
    UL : RLC data blocks
    etc…

    In the description of your problem, you say
    “1.) MS is not responding to Packet Uplink Assignment and Packet Uplink Ack/Nack.

    2.) After this there are a series of Immediate Assignment in which the access cause is “Answer to Paging” but after that also services are not resumed.

    3.) Service got resumed after refreshing the page or after re openning the site or start starting the download aagin (i.e. when MS is sending the EGPRS packet channel request) again.”

    Why do you expect a PUAS in the target cell ? There is no PUAS after a reselection.

    Best Regards,
    Pix

    #58764 Reply
    RG
    Guest

    Thanks Pix and Bijoy for the replies.

    1.There will be PS assignment reject or failure in this case.Have you checked the reasons.

    – There is no PS assignment reject or failure message.

    2.What is the Rx_lev_acccess min for GPRS.check that.

    – It is 98 dB

    3.Is there N3101 or N3103 overflow.

    – Yes inthe performance statistics, I had found overflow for N3101 in the Uplink and due to POLL & N3105 in the Downlink.

    4.If call setup indication rate is poor.In this case,check the PS paging success rate LAC and RAC wise.

    – No PBCCH, using the signalling of BCCH

    5.Are you using NACC or NCCR(Network controlled cell reslection)?

    – It is MS controlled cell reselection.

    6.What is the value of t3168?

    – It is 4s

    7.Are you using extended UL TBF function.

    – Yes

    #58765 Reply
    RG
    Guest

    In the “Packet Resource Request” i am getting Access Type as:

    1.) ACCESS_TYPE : (0) Two Phase Access Request

    2.) ACCESS_TYPE : (2) Cell Update

    during cell reselection. Pls help me to understand the difference between these two Access reasons.

    Regards

    RG

    #58766 Reply
    Bijoy
    Guest

    Hi RG
    1.) ACCESS_TYPE : (0) Two Phase Access Request

    In this case,one PDCH is initially reserved for the sending of one uplink RLC block.This is used to let the MS send a Packet Resource Request message, to further specify its capabilities and/or demands.
    2.) ACCESS_TYPE : (2) Cell Update

    Reselection of a new cell having the same RAC as the previous one

    #58767 Reply
    RG
    Guest

    Hi Bijoy,

    Thanks bijoy for ur timely repply. But still I am having the following confusions:

    1.) *** ACCESS_TYPE : (2) Cell Update

    Reselection of a new cell having the same RAC as the previous one.

    If this is the reason then why I dont get cell update all the time when cell is reselected having same RAC as previous one.

    2.) Also I am getting another cause as:
    ACCESS_TYPE : (1) Page Response

    Pls help me to understand these scenario’s.

    Regards
    RG

    #58768 Reply
    Bijoy
    Guest

    Hi RG
    cell update takes place when MS is in READY state,in STANDBY state ,no cell update takes place.

    The 2nd one is simple response to paging

    #58769 Reply
    RG
    Guest

    Hi Bijoy,

    After every cell reselection (within same RAC & LAC), I am not getting Access Type as “Cell Update”. Most of the time after re selection i recieve Access Type as “Two Phase Access Request”.

    Can u help me to know the reason if as mentioned by you as:

    “cell update takes place when MS is in READY state,in STANDBY state ,no cell update takes place”.

    #58770 Reply
    Bijoy
    Guest

    when a TBF transfer is ongoing then only you need to know the about the new cell,its capability.So cell update takes place during READY State only.

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