fixeria has uploaded this change for review. ( https://gerrit.osmocom.org/c/osmo-bts/+/27550 )
Change subject: osmo-bts-trx: rx_tchh_fn(): use proper meas averaging mode ......................................................................
osmo-bts-trx: rx_tchh_fn(): use proper meas averaging mode
Compared to TCH/F, TCH/H is a bit special in a way that:
* speech frames are interleaved over 4 consecutive bursts, * while FACCH frames are interleaved over 6 consecutive bursts.
This is why in rx_tchh_fn() we allocate a buffer large enough to store up to 6 bursts. Let's say we have that buffer filled up completely with all 6 bursts (from 'a' to 'f'). Now attempting to decode them may yield either a speech frame or a FACCH frame:
+---+---+---+---+---+---+ | a | b | c | d | e | f | Burst 'a' received first, 'f' last +---+---+---+---+---+---+ ^^^^^^^^^^^^^^^ Speech frame (bursts 'a' .. 'd') ^^^^^^^^^^^^^^^^^^^^^^^ FACCH frame (bursts 'a' .. 'f')
For FACCH we use measurement averaging mode SCHED_MEAS_AVG_M_S6N6, so that 6 last samples are averaged - so far so good. For speech we use SCHED_MEAS_AVG_M_S4N4, so that 4 last samples corresponding to bursts 'c', 'd', 'e', 'f' are averaged - this is wrong.
We actually need to average the *first* 4 samples corresponding to bursts 'a', 'b', 'c', 'd' in the case of speech. Let's add and use a new averaging mode SCHED_MEAS_AVG_M_S6N4 for that.
Change-Id: Iea6f4e5471550f4c2b57aaebeac83c80e879489d --- M include/osmo-bts/scheduler.h M src/osmo-bts-trx/sched_lchan_tchh.c M src/osmo-bts-trx/scheduler_trx.c 3 files changed, 5 insertions(+), 2 deletions(-)
git pull ssh://gerrit.osmocom.org:29418/osmo-bts refs/changes/50/27550/1
diff --git a/include/osmo-bts/scheduler.h b/include/osmo-bts/scheduler.h index 8643edd..1e1a2d7 100644 --- a/include/osmo-bts/scheduler.h +++ b/include/osmo-bts/scheduler.h @@ -306,10 +306,12 @@
/* Averaging mode for trx_sched_meas_avg() */ enum sched_meas_avg_mode { - /* last 4 bursts (default for xCCH, TCH/H, PTCCH and PDTCH) */ + /* last 4 bursts (default for xCCH, PTCCH and PDTCH) */ SCHED_MEAS_AVG_M_S4N4, /* last 8 bursts (default for TCH/F and FACCH/F) */ SCHED_MEAS_AVG_M_S8N8, + /* first 4 of last 6 bursts (default for TCH/H) */ + SCHED_MEAS_AVG_M_S6N4, /* last 6 bursts (default for FACCH/H) */ SCHED_MEAS_AVG_M_S6N6, /* first 4 of last 8 bursts */ diff --git a/src/osmo-bts-trx/sched_lchan_tchh.c b/src/osmo-bts-trx/sched_lchan_tchh.c index 8264163..edbb566 100644 --- a/src/osmo-bts-trx/sched_lchan_tchh.c +++ b/src/osmo-bts-trx/sched_lchan_tchh.c @@ -64,7 +64,7 @@ * Even FN ending at: 10,11,19,20,2,3 */ int fn_is_odd = (((bi->fn + 26 - 10) % 26) >> 2) & 1; - enum sched_meas_avg_mode meas_avg_mode = SCHED_MEAS_AVG_M_S4N4; + enum sched_meas_avg_mode meas_avg_mode = SCHED_MEAS_AVG_M_S6N4; struct l1sched_meas_set meas_avg; unsigned int fn_begin; unsigned int fn_tch_end; diff --git a/src/osmo-bts-trx/scheduler_trx.c b/src/osmo-bts-trx/scheduler_trx.c index 78c7b4a..6ce5a9a 100644 --- a/src/osmo-bts-trx/scheduler_trx.c +++ b/src/osmo-bts-trx/scheduler_trx.c @@ -635,6 +635,7 @@ static const uint8_t trx_sched_meas_modeset[][2] = { [SCHED_MEAS_AVG_M_S4N4] = { 4, 4 }, [SCHED_MEAS_AVG_M_S8N8] = { 8, 8 }, + [SCHED_MEAS_AVG_M_S6N4] = { 6, 4 }, [SCHED_MEAS_AVG_M_S6N6] = { 6, 6 }, [SCHED_MEAS_AVG_M_S8N4] = { 8, 4 }, [SCHED_MEAS_AVG_M_S6N2] = { 6, 2 },
-
fixeria