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sched: Modify DL scheduling to use different priorities 

Currently the DL blocks are scheduled round robin to each TBF that is
either in state FLOW or FINISHED and not waiting for an IMM.ASS
confirmation. This way, if single blocks has been NACK'ed by the MS
and the PCU has already resent the missing packets, the PCU starts
retransmitting them until it has received an ACK/NACK even if other
TBF have RLC blocks that need to be transmitted.

This commit changes sched_select_downlink to select the next TBF with
the highest priority, where blocks that are going to be resent again
have a lower priority unless the window is stalling. If there is only
one TBF the old behaviour is kept, since there is no other TBF that
can have a higher priority.

If there is much packet loss on a single phone, this modification can
lead to a higher latency for that MS.

Sponsored-by: On-Waves ehf
This commit is contained in:
Jacob Erlbeck 2015-03-02 14:28:12 +01:00
parent 1842c921b3
commit 0eabffdc35
1 changed files with 23 additions and 6 deletions
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29
src/gprs_rlcmac_sched.cpp
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@ -167,8 +167,9 @@ static struct msgb *sched_select_downlink(struct gprs_rlcmac_bts *bts,
uint8_t block_nr, struct gprs_rlcmac_pdch *pdch)
{
struct msgb *msg = NULL;
struct gprs_rlcmac_dl_tbf *tbf = NULL;
uint8_t i, tfi;
struct gprs_rlcmac_dl_tbf *tbf, *prio_tbf = NULL;
int prio, max_prio = -1;
uint8_t i, tfi, prio_tfi;
/* select downlink resource */
for (i = 0, tfi = pdch->next_dl_tfi; i < 32;
@ -189,13 +190,29 @@ static struct msgb *sched_select_downlink(struct gprs_rlcmac_bts *bts,
if (tbf->m_wait_confirm)
continue;
/* compute priority */
if (tbf->state_is(GPRS_RLCMAC_FINISHED) &&
tbf->m_window.resend_needed() < 0)
/* would re-retransmit blocks */
prio = 1;
else
prio = 2;
/* get the TBF with the highest priority */
if (prio > max_prio) {
prio_tfi = tfi;
prio_tbf = tbf;
max_prio = prio;
}
}
if (prio_tbf) {
LOGP(DRLCMACSCHED, LOGL_DEBUG, "Scheduling data message at "
"RTS for DL TFI=%d (TRX=%d, TS=%d)\n", tfi, trx, ts);
"RTS for DL TFI=%d (TRX=%d, TS=%d)\n", prio_tfi, trx, ts);
/* next TBF to handle resource is the next one */
pdch->next_dl_tfi = (tfi + 1) & 31;
pdch->next_dl_tfi = (prio_tfi + 1) & 31;
/* generate DL data block */
msg = tbf->create_dl_acked_block(fn, ts);
break;
msg = prio_tbf->create_dl_acked_block(fn, ts);
}
return msg;