Report interference levels in RSL RF RESource INDication

This change implements general interference averaging logic for
the higher layers.  In l1sap_info_time_ind(), where we receive
TDMA time updates from BTS model, call rsl_tx_rf_res() for each
transceiver according to the interval defined by the Intave
parameter received from the BSC.  In rsl_tx_rf_res() perform
the actual averaging for each inactive logical channel, and
then send everything to the BSC over the A-bis/RSL.

The BTS model specific code needs to report the measurements
for each logical channel every 104 TDMA frames (SACCH period)
by calling gsm_lchan_interf_meas_push().

Change-Id: Id80fdbef087de625149755165c025c0a9563dc85
Related: SYS#5313, OS#1569

README.md

@@ -96,7 +96,6 @@ Common Core
  * System Information limited to 1,2,2bis,2ter,2quater,3,4,5,6,9,13
  * No RATSCCH in AMR
  * Will reject TS 12.21 STARTING TIME in SET BTS ATTR / SET CHAN ATTR
- * No reporting of interference levels as part of TS 08.58 RF RES IND
  * No support of TS 08.58 MultiRate Control
  * No support of TS 08.58 Supported Codec Types
  * No support of Bter frame / ENHANCED MEASUREMENT REPORT

doc/manuals/abis/oml.adoc

@@ -394,8 +394,8 @@ stored items are currently not used in the OsmoBTS code base.
 | 0x13 | 9.4.19 | File Version  |  | _ignored_
 | 0x14 | 9.4.20 | GSM Time  |  | _ignored_
 | 0x16 | 9.4.22 | HW Configuration  |  | _ignored_
-| 0x18 | 9.4.24 | Intave Parameter  | <- | _ignored_
-| 0x19 | 9.4.25 | Interference level Boundaries  | <- | _ignored_
+| 0x18 | 9.4.24 | Intave Parameter  | <- |
+| 0x19 | 9.4.25 | Interference level Boundaries  | <- |
 | 0x1a | 9.4.26 | List of Required Attributes  |  | _ignored_
 | 0x1c | 9.4.28 | Manufacturer Dependent State  |  | _ignored_
 | 0x1d | 9.4.29 | Manufacturer Dependent Thresholds  |  | _ignored_

include/osmo-bts/gsm_data.h

@@ -337,6 +337,9 @@ struct gsm_lchan {
 			/* standard deviation of toa256 value during measurement period */
 			uint16_t toa256_std_dev;
 		} ext;
+		/* Interference levels reported by PHY (in dBm) */
+		int16_t interf_meas_dbm[31]; /* Intave max is 31 */
+		uint8_t interf_meas_num;
 	} meas;
 	struct {
 		struct amr_multirate_conf amr_mr;
@@ -537,6 +540,9 @@ uint8_t gsm_lchan2chan_nr(const struct gsm_lchan *lchan);
 uint8_t gsm_lchan_as_pchan2chan_nr(const struct gsm_lchan *lchan,
 				   enum gsm_phys_chan_config as_pchan);
 
+void gsm_lchan_interf_meas_push(struct gsm_lchan *lchan, int dbm);
+int gsm_lchan_interf_meas_calc_band(struct gsm_lchan *lchan);
+
 #define BSIC2BCC(bsic) ((bsic) & 0x07)
 #define BTS_TSC(bts) BSIC2BCC((bts)->bsic)
 
@@ -558,4 +564,16 @@ int conf_lchans_as_pchan(struct gsm_bts_trx_ts *ts,
 
 bool ts_is_pdch(const struct gsm_bts_trx_ts *ts);
 
+static inline bool lchan_is_dcch(const struct gsm_lchan *lchan)
+{
+	switch (lchan->type) {
+	case GSM_LCHAN_SDCCH:
+	case GSM_LCHAN_TCH_F:
+	case GSM_LCHAN_TCH_H:
+		return true;
+	default:
+		return false;
+	}
+}
+
 #endif /* _GSM_DATA_H */

src/common/gsm_data.c

@@ -280,6 +280,54 @@ uint8_t gsm_lchan_as_pchan2chan_nr(const struct gsm_lchan *lchan,
 	return gsm_pchan2chan_nr(as_pchan, lchan->ts->nr, lchan->nr);
 }
 
+/* Called by the model specific code every 104 TDMA frames (SACCH period) */
+void gsm_lchan_interf_meas_push(struct gsm_lchan *lchan, int dbm)
+{
+	const uint8_t meas_num = lchan->meas.interf_meas_num;
+
+	if (meas_num >= ARRAY_SIZE(lchan->meas.interf_meas_dbm)) {
+		LOGPLCHAN(lchan, DL1C, LOGL_ERROR, "Not enough room "
+			  "to store interference report (%ddBm)\n", dbm);
+		return;
+	}
+
+	lchan->meas.interf_meas_dbm[meas_num] = dbm;
+	lchan->meas.interf_meas_num++;
+}
+
+/* Called by the higher layers every Intave * 104 TDMA frames */
+int gsm_lchan_interf_meas_calc_band(struct gsm_lchan *lchan)
+{
+	const uint8_t meas_num = lchan->meas.interf_meas_num;
+	const struct gsm_bts *bts = lchan->ts->trx->bts;
+	int b, meas_avg, meas_sum = 0;
+
+	/* There must be at least one sample */
+	if (meas_num == 0)
+		return -EAGAIN;
+
+	/* Calculate the sum of all collected samples (in -x dBm) */
+	while (lchan->meas.interf_meas_num) {
+		uint8_t i = --lchan->meas.interf_meas_num;
+		meas_sum += lchan->meas.interf_meas_dbm[i];
+	}
+
+	/* Calculate the average of all collected samples */
+	meas_avg = meas_sum / (int) meas_num;
+
+	/* Determine the band using interference boundaries from BSC */
+	for (b = 0; b < ARRAY_SIZE(bts->interference.boundary); b++) {
+		if (meas_avg >= bts->interference.boundary[b])
+			break; /* Current 'b' is the band value */
+	}
+
+	LOGPLCHAN(lchan, DL1C, LOGL_DEBUG,
+		  "Interference AVG: %ddBm (band %d)\n",
+		  meas_avg, b);
+
+	return b;
+}
+
 /* determine logical channel based on TRX and channel number IE */
 struct gsm_lchan *rsl_lchan_lookup(struct gsm_bts_trx *trx, uint8_t chan_nr,
 				   int *rc)

src/common/l1sap.c

@@ -588,6 +588,20 @@ static unsigned int calc_exprd_rach_frames(struct gsm_bts *bts, uint32_t fn)
 	return rach_frames_expired;
 }
 
+static void l1sap_interf_meas_report(struct gsm_bts *bts)
+{
+	const uint32_t period = bts->interference.intave * 104;
+	struct gsm_bts_trx *trx;
+
+	if (bts->interference.intave == 0)
+		return;
+	if (bts->gsm_time.fn % period != 0)
+		return;
+
+	llist_for_each_entry(trx, &bts->trx_list, list)
+		rsl_tx_rf_res(trx);
+}
+
 /* time information received from bts model */
 static int l1sap_info_time_ind(struct gsm_bts *bts,
 			       struct osmo_phsap_prim *l1sap,
@@ -620,6 +634,9 @@ static int l1sap_info_time_ind(struct gsm_bts *bts,
 		bts->load.rach.total += calc_exprd_rach_frames(bts, fn);
 	}
 
+	/* Report interference levels to the BSC */
+	l1sap_interf_meas_report(bts);
+
 	return 0;
 }
 

src/common/rsl.c

@@ -427,6 +427,7 @@ static int rsl_tx_error_report(struct gsm_bts_trx *trx, uint8_t cause, const uin
 /* 8.6.1 sending RF RESOURCE INDICATION */
 int rsl_tx_rf_res(struct gsm_bts_trx *trx)
 {
+	unsigned int tn, ln;
 	struct msgb *nmsg;
 
 	LOGP(DRSL, LOGL_INFO, "Tx RSL RF RESource INDication\n");
@@ -434,8 +435,40 @@ int rsl_tx_rf_res(struct gsm_bts_trx *trx)
 	nmsg = rsl_msgb_alloc(sizeof(struct abis_rsl_common_hdr));
 	if (!nmsg)
 		return -ENOMEM;
-	// FIXME: add interference levels of TRX
-	msgb_tlv_put(nmsg, RSL_IE_RESOURCE_INFO, 0, NULL);
+
+	/* Add interference levels for each logical channel */
+	uint8_t *len = msgb_tl_put(nmsg, RSL_IE_RESOURCE_INFO);
+
+	for (tn = 0; tn < ARRAY_SIZE(trx->ts); tn++) {
+		struct gsm_bts_trx_ts *ts = &trx->ts[tn];
+
+		for (ln = 0; ln < ARRAY_SIZE(ts->lchan); ln++) {
+			struct gsm_lchan *lchan = &ts->lchan[ln];
+
+			/* We're not interested in active lchans */
+			if (lchan->state == LCHAN_S_ACTIVE) {
+				/* Avoid potential buffer overflow */
+				lchan->meas.interf_meas_num = 0;
+				continue;
+			}
+
+			/* Only for GSM_LCHAN_{SDCCH,TCH_F,TCH_H} */
+			if (!lchan_is_dcch(lchan))
+				continue;
+
+			/* Average all collected samples */
+			int band = gsm_lchan_interf_meas_calc_band(lchan);
+			if (band < 0)
+				continue;
+
+			msgb_v_put(nmsg, gsm_lchan2chan_nr(lchan));
+			msgb_v_put(nmsg, (band & 0x07) << 5);
+		}
+	}
+
+	/* Calculate length of the V part */
+	*len = msgb_l3len(nmsg) - 2;
+
 	rsl_trx_push_hdr(nmsg, RSL_MT_RF_RES_IND);
 	nmsg->trx = trx;