Change in osmo-bts[master]: osmo-bts-trx: report interference levels to the upper layers

fixeria gerrit-no-reply at lists.osmocom.org
Tue Jun 8 16:01:51 UTC 2021


fixeria has uploaded this change for review. ( https://gerrit.osmocom.org/c/osmo-bts/+/24613 )


Change subject: osmo-bts-trx: report interference levels to the upper layers
......................................................................

osmo-bts-trx: report interference levels to the upper layers

In trx_sched_ul_burst(), treat all BURST.ind and NOPE.ind mapped
to inactive logical channels as interference.  Average the RSSI
values on the fly using a sliding average with constant a=0.5.

Report averaged values for each logical channel every 104 TDMA
frames (SACCH period) by calling gsm_lchan_interf_meas_push().

Change-Id: I4686448e42a40df56c1d27a14fd0a4d43fd144a5
Related: I78b6d8beffa5228a28231b75728e7aebdd3cb23c
Related: SYS#5313, OS#1569
---
M include/osmo-bts/scheduler.h
M src/common/scheduler.c
M src/osmo-bts-trx/scheduler_trx.c
3 files changed, 100 insertions(+), 10 deletions(-)



  git pull ssh://gerrit.osmocom.org:29418/osmo-bts refs/changes/13/24613/1

diff --git a/include/osmo-bts/scheduler.h b/include/osmo-bts/scheduler.h
index 86bfdf9..7b3daa3 100644
--- a/include/osmo-bts/scheduler.h
+++ b/include/osmo-bts/scheduler.h
@@ -132,10 +132,14 @@
 	uint8_t			ul_encr_key[MAX_A5_KEY_LEN];
 	uint8_t			dl_encr_key[MAX_A5_KEY_LEN];
 
-	/* Simple ring buffer (up to 8 unique measurements) */
+	/* Uplink measurements */
 	struct {
-		struct l1sched_meas_set buf[8];
+		/* Active channel measurements (simple ring buffer) */
+		struct l1sched_meas_set buf[8]; /* up to 8 entries */
 		unsigned int current; /* current position */
+
+		/* Interference measurements */
+		int interf_avg; /* sliding average */
 	} meas;
 
 	/* handover */
diff --git a/src/common/scheduler.c b/src/common/scheduler.c
index 3ab94a2..f74688c 100644
--- a/src/common/scheduler.c
+++ b/src/common/scheduler.c
@@ -1438,6 +1438,31 @@
 	return 0;
 }
 
+/* Process a single noise measurement for an inactive timeslot. */
+static void trx_sched_noise_meas(struct l1sched_chan_state *l1cs,
+				 const struct trx_ul_burst_ind *bi)
+{
+	int *Avg = &l1cs->meas.interf_avg;
+
+	/* EWMA (Exponentially Weighted Moving Average):
+	*
+	*   Avg[n] = a * Val[n] + (1 - a) * Avg[n - 1]
+	*
+	* Implemented using the '+=' operator:
+	*
+	*   Avg += a * Val - a * Avg
+	*   Avg += a * (Val - Avg)
+	*
+	* We use constant 'a' = 0.5, what is equal to:
+	*
+	*   Avg += (Val - Avg) / 2
+	*
+	* We don't really need precisity here, so no scaling.
+	*/
+
+	*Avg += (bi->rssi - *Avg) / 2;
+}
+
 /* Process an Uplink burst indication */
 int trx_sched_ul_burst(struct l1sched_ts *l1ts, struct trx_ul_burst_ind *bi)
 {
@@ -1463,15 +1488,13 @@
 	l1cs = &l1ts->chan_state[bi->chan];
 	func = trx_chan_desc[bi->chan].ul_fn;
 
-	/* TODO: handle noise measurements */
-	if (bi->chan == TRXC_IDLE && bi->flags & TRX_BI_F_NOPE_IND) {
-		LOGL1SB(DL1P, LOGL_DEBUG, l1ts, bi, "Rx noise measurement (%d)\n", bi->rssi);
-		return -ENOTSUP;
-	}
-
 	/* check if channel is active */
-	if (!TRX_CHAN_IS_ACTIVE(l1cs, bi->chan))
-		return -EINVAL;
+	if (!TRX_CHAN_IS_ACTIVE(l1cs, bi->chan)) {
+		/* handle noise measurements */
+		if (bi->chan >= TRXC_TCHF)
+			trx_sched_noise_meas(l1cs, bi);
+		return 0;
+	}
 
 	/* omit bursts which have no handler, like IDLE bursts */
 	if (!func)
diff --git a/src/osmo-bts-trx/scheduler_trx.c b/src/osmo-bts-trx/scheduler_trx.c
index 1a4f03f..0a2052c 100644
--- a/src/osmo-bts-trx/scheduler_trx.c
+++ b/src/osmo-bts-trx/scheduler_trx.c
@@ -60,6 +60,65 @@
 	return 0;
 }
 
+static void ts_report_interf_meas(const struct gsm_bts_trx_ts *ts)
+{
+	const struct l1sched_ts *l1ts = ts->priv;
+	unsigned int ln;
+
+	for (ln = 0; ln < ARRAY_SIZE(ts->lchan); ln++) {
+		const struct gsm_lchan *lchan = &ts->lchan[ln];
+		enum trx_chan_type dcch, acch;
+		int interf_avg;
+
+		/* We're not interested in active channels */
+		if (lchan->state == LCHAN_S_ACTIVE)
+			continue;
+
+		switch (lchan->type) {
+		case GSM_LCHAN_SDCCH:
+			if (ts->pchan == GSM_PCHAN_CCCH_SDCCH4 ||
+			    ts->pchan == GSM_PCHAN_CCCH_SDCCH4_CBCH) {
+				dcch = TRXC_SDCCH4_0 + ln;
+				acch = TRXC_SACCH4_0 + ln;
+			} else { /* SDCCH/8 otherwise */
+				dcch = TRXC_SDCCH8_0 + ln;
+				acch = TRXC_SACCH8_0 + ln;
+			}
+			break;
+		case GSM_LCHAN_TCH_F:
+			dcch = TRXC_TCHF;
+			acch = TRXC_SACCHTF;
+			break;
+		case GSM_LCHAN_TCH_H:
+			dcch = TRXC_TCHH_0 + ln;
+			acch = TRXC_SACCHTH_0 + ln;
+			break;
+		default:
+			/* Skip other lchan types */
+			continue;
+		}
+
+		OSMO_ASSERT(dcch < ARRAY_SIZE(l1ts->chan_state));
+		OSMO_ASSERT(acch < ARRAY_SIZE(l1ts->chan_state));
+
+		interf_avg = (l1ts->chan_state[dcch].meas.interf_avg +
+			      l1ts->chan_state[acch].meas.interf_avg) / 2;
+
+		gsm_lchan_interf_meas_push((struct gsm_lchan *) lchan, interf_avg);
+	}
+}
+
+static void bts_report_interf_meas(const struct gsm_bts *bts)
+{
+	const struct gsm_bts_trx *trx;
+	unsigned int tn;
+
+	llist_for_each_entry(trx, &bts->trx_list, list) {
+		for (tn = 0; tn < ARRAY_SIZE(trx->ts); tn++)
+			ts_report_interf_meas(&trx->ts[tn]);
+	}
+}
+
 /* Find a route (PHY instance) for a given Downlink burst request */
 static struct phy_instance *dlfh_route_br(const struct trx_dl_burst_req *br,
 					  struct gsm_bts_trx_ts *ts)
@@ -189,6 +248,10 @@
 	struct gsm_bts_trx *trx;
 	unsigned int tn;
 
+	/* Report interference measurements */
+	if (fn % 104 == 0) /* SACCH period */
+		bts_report_interf_meas(bts);
+
 	/* send time indication */
 	l1if_mph_time_ind(bts, fn);
 

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Gerrit-Project: osmo-bts
Gerrit-Branch: master
Gerrit-Change-Id: I4686448e42a40df56c1d27a14fd0a4d43fd144a5
Gerrit-Change-Number: 24613
Gerrit-PatchSet: 1
Gerrit-Owner: fixeria <vyanitskiy at sysmocom.de>
Gerrit-MessageType: newchange
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