openbts-p2.8-gprs-exp and pcu issues

Vladimir Rolbin vrolbin at gmail.com
Sun Nov 4 09:59:57 UTC 2012


hi,

T3192 is 500 ms for my env set..

Regards,
Vladimir


On Sun, Nov 4, 2012 at 8:58 AM, jolly <andreas at eversberg.eu> wrote:

> Ivan Kluchnikov wrote:
> > In attachment you can find patch for osmo-pcu.
> >
>
> hi ivan,
>
> i looked at you patch. it primarily removes the ability to re-assign an
> existing downlink TBF on PACCH:
>
> -       if (old_tbf) {
> +       if (old_tbf&&(old_tbf->direction == GPRS_RLCMAC_UL_TBF)) {
>
> a downlink TBF will, after polling the final ack, start T3193 and exist
> until T3193 times out.  the value for that timer is set by BTS. on the
> phone T3192 is running, which is a little shorter. the phone will stay
> on PDCH and listens for re-assignment on PACCH until T3192 times out.
> T3192 is set by system information message. what settings do you have
> for these two timers?
>
> there are three cases where assignment on PACCH is performed:
>
> 1. at gprs_rlcmac_downlink_ack() the
> gprs_rlcmac_trigger_downlink_assignment() is called, if the dowlink TBF
> has just finished, but more frames already arrived from SGSN. (T3193 not
> started yet, but MS will have T3192 running.)
> 2. at gprs_bssgp_pcu_rx_dl_ud() the
> gprs_rlcmac_trigger_downlink_assignment() is called, if the dowlink TBF
> still exists because a frame has arrived from SGSN. (T3193 running, and
> so T3192 on the MS.)
> 3. at gprs_bssgp_pcu_rx_dl_ud() the
> gprs_rlcmac_trigger_downlink_assignment() is called, if an uplink TBF
> exists because a frame has arrived from SGSN.
>
> in your patch you changed the condition for triggering downlink
> assignment on PACCH to uplink TBF only. This would break the case where
> T3193 is still pending and the re-use of downlink TBF.
>
> the case where a downlink TBF still exists would result in a PCH/AGCH
> assignment, which causes problems, especially when multislot allocation
> is used. this is because the selected (multiple) slots at
> gprs_bssgp_pcu_rx_dl_ud() cannot be assigned on PCH/AGCH, just only one.
>
> i cannot see what your decision for your patch was. i guess that SI 13
> uses a low or no T3192 timer value.
>
> regards,
>
> andreas
>
>
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