Attention is currently required from: pespin. fixeria has posted comments on this change. ( https://gerrit.osmocom.org/c/osmo-bts/+/27836 )

Change subject: osmo-bts-trx: check if scheduling of [dummy] FACCH/H is allowed ......................................................................

Patch Set 1:

(1 comment)

File src/osmo-bts-trx/sched_lchan_tchh.c:

https://gerrit.osmocom.org/c/osmo-bts/+/27836/comment/6a31ff75_9b743ebe PS1, Line 414: if (!sched_tchh_dl_facch_map[br->fn % 26])

I'm a bit lost here. […]

"Why first try to send dummy stuff" - where? This is not the case. Currently (without this patch) if tch_dl_dequeue() yields nothing we're scheduling dummy FACCH *regardless* if it's permitted to start at the given TDMA FN or not. This may result in misaligned FACCH transmission, so the MS will not able to decode anything and will report BER>0.

With this patch applied we a) schedule FACCH if it's allowed to start at the current TDMA FN; b) send whatever was in the burst buffer (garbage) if FACCH is not permitted. This is the best we can do without introducing additional complexity. Ideally the upper layers should guarantee that the queue is never empty, but currently this is not the case.