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D/L TBF establishment

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  • #58593 Reply
    CM
    Guest

    There are two situations described in 3GPP 44.060.

    1. After sending a Packet Uplink Ack / Nack with final bit set, and there is no other TBF active, the MS goes into packet idle mode and does not monitor PDCH.

    2. When the MS sends Packet Downlink Ack / Nack with final bit set it starts T3192. While T3192 is running the MS monitors PDCH. When T3192 expires the MS goes to packet idle mode.

    My question: does the MS still listen on PDCH, because T3192 is running, after the network sends PUAN?

    In other words, we have this situation:

    1. D/L TBF and U/L TBF are both active
    2. D/L TBF ends, T3192 is running, but no more D/L data to send.
    3. U/L TBF ends, T3192 is still running
    4. New D/L data arrives, T3192 is still running…. How should the D/L TBF be assigned? PACCH or CCCH? (I don’t have PCCCH) Logs show that, in this situation, sometimes PACCH works, sometimes it doesn’t.

    Is this what the delayed D/L TBF release mechanism is intended for?

    #58594 Reply
    Bijoy
    Guest

    Hi CM
    You are Right.
    Hope this explanation clears your doubt
    The purpose of this function is to be able to set up a Downlink TBF using PACCH shortly after the release of a DL TBF. When a downlink TBF is released, the MS starts timer T3192 and stays on the PACCH until T3192 expires. In the BSS there is a corresponding timer T3193 that is started when the TBF has been released. The PDCHs that were assigned to the TBF are still reserved for the MS for the duration of timer T3193.If more data arrives from SGSN before T3193 has expired, a new DL TBF is set up and PACKET DOWNLINK ASSIGNMENT message is sent to the MS on the PACCH. The poll bit is set in the message indicating that the MS shall answer with a PACKET CONTROL ACKNOWLEDGEMENT message.

    If this message is not received by the BSC new attempts (maximum 3) to set up a downlink TBF are done. New attempts to set up a downlink TBF can be done using PCCCH, CCCH, PACCH (normal) or PACCH (after release) depending on the traffic situation and the configuration of the BSS.

    If this message is received, the downlink scheduling is started and the downlink TBF is established.

    PDCHs and TBF is finally released if/when BSS timer T3193 expires after which normal set up of downlink using PCCCH, CCCH or PACCH will have to be used to set up a new downlink TBF

    #58595 Reply
    Mac
    Guest

    Hi all,

    I have following queries:

    1. Does the TBF drop increase as MCS increases? (assuming that radio conditions are good). If yes, why?

    2. What are the reasons for TBF drop?

    3. How to measure TBF establishment success rate in NOKIA system?

    Thanx in advance!!

    #58596 Reply
    Pix
    Guest

    Mac,

    1/ No, it shouldn’t.

    2/ Usually, it’s a radio problem : interference or coverage. Sometimes, it is the MS itself which bugs (stagnating window).

    3/ Nokia ? Don’t know about it, sorry 🙂

    #58597 Reply
    mike
    Guest

    hi all,

    i have the following questions which i will appreciate if someone can help me with some answers.

    what is the KPI/target for TBF Establishment success rate uplink/downlink and for TBF drop rate downlink/uplink

    please help
    thank you in advance

    #58598 Reply
    Bijoy
    Guest

    Hi mike
    TBF Establishment success rate uplink/downlink—-98%
    TBF drop rate downlink/uplink—2%

    #58599 Reply
    Fresh Opt
    Guest

    Hi,
    How to reduce tbf drop due to stagnating window?
    Thanks,

    #58600 Reply
    Fresh Opt
    Guest

    Anyone?

    #58601 Reply
    Pix
    Guest

    Hi,

    Stagnating window is due to MS failure, which keeps repeating the same data.
    How high is the rate in your situation ?

    Regards,
    pix

    #58602 Reply
    Fresh Opt
    Guest

    Hi Pix,
    the rate varies from 45% to 80% usualy at evening (18:00-23:00). There’s only one cell affected. If it’s the MS issue than I don’t know how to improve the drop. We have reinitialised and resynchronised GPRS in that cell and no better results seen.
    Thanks,

    #58603 Reply
    Pix
    Guest

    Hello,

    It is indeed possible that in this one cell, there is one faulty MS. You just have to wait that this customer complains about impossibility to finish a transfer (or hanging transfer).

    You can try to increase the detection threshold (how many times the window is stalled…)

    N_STAGNATING_WINDOW_DL_LIMIT
    if the problem is in DL,

    or…
    N_STAGNATING_WINDOW_UL_LIMIT
    if the problem is in UL.

    (there are 2 different indicators : (UL) GPRS_UL_TBF_drop_N_stagnatingWindow and (DL) GPRS_DL_TBF_drop_N_stagnatingWindow )

    Regards,

    #58604 Reply
    Fresh Opt
    Guest

    Thanks Pix, I appreciate that!

    #58605 Reply
    Mohan
    Guest

    Hi all,

    I have a following queries.

    1. DL and UL TBF drop rates are high. action items to resolve the same. Equipment used Huawei equipment

    #58606 Reply
    Bijoy
    Guest

    Hi Mohan
    Is it due to N3105 & n3103 overflow??

    Br\\
    Bijoy

    #58607 Reply
    andy
    Guest

    do you know why TBF Establishment success rate uplink is bad while TBF Establishment success rate downlink is good?

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Reply To: D/L TBF establishment
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