Change in ...osmo-bts[master]: l1sap: Compute statistics on FN advance in PH-RTS.ind

Harald Welte gerrit-no-reply at lists.osmocom.org
Sun Jun 2 18:48:50 UTC 2019


Harald Welte has uploaded this change for review. ( https://gerrit.osmocom.org/c/osmo-bts/+/14336


Change subject: l1sap: Compute statistics on FN advance in PH-RTS.ind
......................................................................

l1sap: Compute statistics on FN advance in PH-RTS.ind

Let's keep some statistics about the min/max/average frame number
advance that we're observing above L1SAP when comparing the time in the
PH-RTS.ind and the frame number we observe in PH-DATA.ind of data
that was received on the uplink.

The statistics are currently only shown in the VTY, but this is a
precursor to using them to correctly advance the LAPDm timers in a
follow-up patch.

Change-Id: I8f739fdb808a614f080afbc4654641ec3df19eb2
Related: OS#2294
Related: OS#3906
---
M include/osmo-bts/bts.h
M include/osmo-bts/gsm_data_shared.h
M src/common/bts.c
M src/common/l1sap.c
M src/common/vty.c
5 files changed, 44 insertions(+), 0 deletions(-)



  git pull ssh://gerrit.osmocom.org:29418/osmo-bts refs/changes/36/14336/1

diff --git a/include/osmo-bts/bts.h b/include/osmo-bts/bts.h
index 970fb1b..4d13214 100644
--- a/include/osmo-bts/bts.h
+++ b/include/osmo-bts/bts.h
@@ -65,5 +65,7 @@
 int bts_supports_cm(struct gsm_bts *bts, enum gsm_phys_chan_config pchan,
 		    enum gsm48_chan_mode cm);
 
+int32_t bts_get_avg_fn_advance(struct gsm_bts *bts);
+
 #endif /* _BTS_H */
 
diff --git a/include/osmo-bts/gsm_data_shared.h b/include/osmo-bts/gsm_data_shared.h
index 90772e2..f972a67 100644
--- a/include/osmo-bts/gsm_data_shared.h
+++ b/include/osmo-bts/gsm_data_shared.h
@@ -738,6 +738,14 @@
 		uint8_t tc4_ctr;
 	} si;
 	struct gsm_time gsm_time;
+	/* frame number statistics (FN in PH-RTS.ind vs. PH-DATA.ind */
+	struct {
+		int32_t min;		/* minimum observed */
+		int32_t max;		/* maximum observed */
+		int32_t avg256;		/* accumulator */
+		uint32_t avg_count;	/* number of samples accumulated in avg256 */
+		uint32_t avg_window;	/* number of averages in avg_count */
+	} fn_stats;
 	/* Radio Link Timeout counter. -1 disables timeout for
 	 * lab/measurement purpose */
 	int radio_link_timeout;
diff --git a/src/common/bts.c b/src/common/bts.c
index 97e7a8b..3626b05 100644
--- a/src/common/bts.c
+++ b/src/common/bts.c
@@ -223,6 +223,11 @@
 	rc = osmo_fsm_register(&dtx_dl_amr_fsm);
 	OSMO_ASSERT(rc == 0);
 
+	bts->fn_stats.min = INT32_MAX;
+	bts->fn_stats.max = INT32_MIN;
+	bts->fn_stats.avg_count = 0;
+	bts->fn_stats.avg_window = 256;
+
 	return rc;
 }
 
diff --git a/src/common/l1sap.c b/src/common/l1sap.c
index 59d5b93..0e0b396 100644
--- a/src/common/l1sap.c
+++ b/src/common/l1sap.c
@@ -719,6 +719,31 @@
         return l1sap_fn2ccch_block(fn) < num_agch(trx, "PH-RTS-IND");
 }
 
+/* return the measured average of frame numbers that the RTS clock is running in advance */
+int32_t bts_get_avg_fn_advance(struct gsm_bts *bts)
+{
+	return bts->fn_stats.avg256 / bts->fn_stats.avg_count;
+}
+
+static void l1sap_update_fnstats(struct gsm_bts *bts, uint32_t rts_fn)
+{
+	int32_t delta = (rts_fn + GSM_HYPERFRAME - bts->gsm_time.fn) % GSM_HYPERFRAME;
+
+	if (delta < bts->fn_stats.min)
+		bts->fn_stats.min = delta;
+	if (delta > bts->fn_stats.max)
+		bts->fn_stats.max = delta;
+
+	if (bts->fn_stats.avg_count > bts->fn_stats.avg_window) {
+		/* reset and start old average and new sample */
+		bts->fn_stats.avg256 = (bts->fn_stats.avg256 / bts->fn_stats.avg_count) + delta;
+		bts->fn_stats.avg_count = 2;
+	} else {
+		bts->fn_stats.avg256 += delta;
+		bts->fn_stats.avg_count++;
+	}
+}
+
 /* PH-RTS-IND prim received from bts model */
 static int l1sap_ph_rts_ind(struct gsm_bts_trx *trx,
 	struct osmo_phsap_prim *l1sap, struct ph_data_param *rts_ind)
@@ -745,6 +770,8 @@
 
 	DEBUGPGT(DL1P, &g_time, "Rx PH-RTS.ind chan_nr=%s link_id=0x%02xd\n", rsl_chan_nr_str(chan_nr), link_id);
 
+	l1sap_update_fnstats(trx->bts, fn);
+
 	/* reuse PH-RTS.ind for PH-DATA.req */
 	if (!msg) {
 		LOGPGT(DL1P, LOGL_FATAL, &g_time, "RTS without msg to be reused. Please fix!\n");
diff --git a/src/common/vty.c b/src/common/vty.c
index 1d25bfb..f4fc181 100644
--- a/src/common/vty.c
+++ b/src/common/vty.c
@@ -895,6 +895,8 @@
 		VTY_NEWLINE);
 	vty_out(vty, "  OML Link state: %s.%s",
 		bts->oml_link ? "connected" : "disconnected", VTY_NEWLINE);
+	vty_out(vty, "  PH-RTS.ind FN advance average: %d, min: %d, max: %d%s",
+		bts_get_avg_fn_advance(bts), bts->fn_stats.min, bts->fn_stats.max, VTY_NEWLINE);
 
 	llist_for_each_entry(trx, &bts->trx_list, list) {
 		struct phy_instance *pinst = trx_phy_instance(trx);

-- 
To view, visit https://gerrit.osmocom.org/c/osmo-bts/+/14336
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Gerrit-Project: osmo-bts
Gerrit-Branch: master
Gerrit-Change-Id: I8f739fdb808a614f080afbc4654641ec3df19eb2
Gerrit-Change-Number: 14336
Gerrit-PatchSet: 1
Gerrit-Owner: Harald Welte <laforge at gnumonks.org>
Gerrit-MessageType: newchange
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