Improved generation of SYSTEM INFORMATIONs 2* and 5* for neighbour bands

In addition to SI 2 and SI 5, the SI 2ter and 2bis is generated, if
neighbour cells in other bands exist. Also it is indicated in the rest
octets of SI3, that SI 2ter is used. If no neighbour cell in a different
band exists, the SI 2ter and SI 5ter is omitted.

A special case is P-GSM range (channels 1-124). To be compatible with
older phones, SI 2bis and SI 5bis is used. If the BCCH lays inside the
P-GSM band, only neighbour cells of the P-GSM range are included in
SI 2 and SI 5. If neighbour cells exist in the same band (900), but lay
outside the P-GSM range, the SI 2bis and SI 5bis is used to extend the
list of neighbour cells. The extension is also indicated in SI 2 and
SI 5. If the BCCH lays inside the P-GSM range, but no neighbour cell
exists in the same band outside the P-GSM range, the SI 2bis ans SI 5bis
are omitted.

2 files changed, 265 insertions, 41 deletions

diff --git a/openbsc/src/libbsc/bsc_init.c b/openbsc/src/libbsc/bsc_init.c
index 441c0a9f0..6d00374e0 100644
--- a/openbsc/src/libbsc/bsc_init.c
+++ b/openbsc/src/libbsc/bsc_init.c
@@ -95,18 +95,10 @@ int bsc_shutdown_net(struct gsm_network *net)
 	return 0;
 }
 
-static int generate_and_rsl_si(struct gsm_bts_trx *trx, enum osmo_sysinfo_type i)
+static int rsl_si(struct gsm_bts_trx *trx, enum osmo_sysinfo_type i, int si_len)
 {
 	struct gsm_bts *bts = trx->bts;
-	int si_len, rc, j;
-
-	/* Only generate SI if this SI is not in "static" (user-defined) mode */
-	if (!(bts->si_mode_static & (1 << i))) {
-		rc = gsm_generate_si(bts, i);
-		if (rc < 0)
-			return rc;
-		si_len = rc;
-	}
+	int rc, j;
 
 	DEBUGP(DRR, "SI%s: %s\n", get_value_string(osmo_sitype_strs, i),
 		osmo_hexdump(GSM_BTS_SI(bts, i), GSM_MACBLOCK_LEN));
@@ -134,11 +126,11 @@ static int generate_and_rsl_si(struct gsm_bts_trx *trx, enum osmo_sysinfo_type i
 			}
 		} else
 			rc = rsl_sacch_filling(trx, osmo_sitype2rsl(i),
-					       GSM_BTS_SI(bts, i), rc);
+					       GSM_BTS_SI(bts, i), si_len);
 		break;
 	default:
 		rc = rsl_bcch_info(trx, osmo_sitype2rsl(i),
-				   GSM_BTS_SI(bts, i), rc);
+				   GSM_BTS_SI(bts, i), si_len);
 		break;
 	}
 
@@ -150,6 +142,8 @@ static int set_system_infos(struct gsm_bts_trx *trx)
 {
 	int i, rc;
 	struct gsm_bts *bts = trx->bts;
+	uint8_t gen_si[_MAX_SYSINFO_TYPE], n_si = 0, n;
+	int si_len[_MAX_SYSINFO_TYPE];
 
 	bts->si_common.cell_sel_par.ms_txpwr_max_ccch =
 			ms_pwr_ctl_lvl(bts->band, bts->ms_max_power);
@@ -159,26 +153,55 @@ static int set_system_infos(struct gsm_bts_trx *trx)
 
 	if (trx == bts->c0) {
 		/* 1...4 are always present on a C0 TRX */
-		for (i = SYSINFO_TYPE_1; i <= SYSINFO_TYPE_4; i++)
-			bts->si_valid |= (1 << i);
+		gen_si[n_si++] = SYSINFO_TYPE_1;
+		gen_si[n_si++] = SYSINFO_TYPE_2;
+		gen_si[n_si++] = SYSINFO_TYPE_2bis;
+		gen_si[n_si++] = SYSINFO_TYPE_2ter;
+		gen_si[n_si++] = SYSINFO_TYPE_3;
+		gen_si[n_si++] = SYSINFO_TYPE_4;
 
 		/* 13 is always present on a C0 TRX of a GPRS BTS */
 		if (bts->gprs.mode != BTS_GPRS_NONE)
-			bts->si_valid |= (1 << SYSINFO_TYPE_13);
+			gen_si[n_si++] = SYSINFO_TYPE_13;
 	}
 
 	/* 5 and 6 are always present on every TRX */
-	bts->si_valid |= (1 << SYSINFO_TYPE_5);
-	bts->si_valid |= (1 << SYSINFO_TYPE_6);
+	gen_si[n_si++] = SYSINFO_TYPE_5;
+	gen_si[n_si++] = SYSINFO_TYPE_5bis;
+	gen_si[n_si++] = SYSINFO_TYPE_5ter;
+	gen_si[n_si++] = SYSINFO_TYPE_6;
+
+	/* Second, we generate the selected SI via RSL */
+
+	for (n = 0; n < n_si; n++) {
+		i = gen_si[n];
+		bts->si_valid |= (1 << i);
+		/* Only generate SI if this SI is not in "static" (user-defined) mode */
+		if (!(bts->si_mode_static & (1 << i))) {
+			rc = gsm_generate_si(bts, i);
+			if (rc < 0)
+				goto err_out;
+			si_len[i] = rc;
+		} else {
+			if (i == SYSINFO_TYPE_5 || i == SYSINFO_TYPE_5bis
+			 || i == SYSINFO_TYPE_5ter)
+				si_len[i] = 18;
+			else if (i == SYSINFO_TYPE_6)
+				si_len[i] = 11;
+			else
+				si_len[i] = 23;
+		}
+	}
+
+	/* Third, we send the selected SI via RSL */
 
-	/* Second, we generate and send the selected SI via RSL */
 	for (i = SYSINFO_TYPE_1; i < _MAX_SYSINFO_TYPE; i++) {
 		if (!(bts->si_valid & (1 << i)))
 			continue;
 
-		rc = generate_and_rsl_si(trx, i);
+		rc = rsl_si(trx, i, si_len[i]);
 		if (rc < 0)
-			goto err_out;
+			return rc;
 	}
 
 	return 0;
diff --git a/openbsc/src/libbsc/system_information.c b/openbsc/src/libbsc/system_information.c
index 9842a9dfd..360d229ad 100644
--- a/openbsc/src/libbsc/system_information.c
+++ b/openbsc/src/libbsc/system_information.c
@@ -74,16 +74,12 @@ static int freq_list_bmrel_set_arfcn(uint8_t *chan_list, unsigned int arfcn)
 	if (arfcn == min_arfcn)
 		return 0;
 
-	if (arfcn < min_arfcn) {
-		LOGP(DRR, LOGL_ERROR, "arfcn(%u) < min(%u)\n", arfcn, min_arfcn);
-		return -EINVAL;
-	}
-	if (arfcn > min_arfcn + 111) {
+	if (((arfcn - min_arfcn) & 1023) > 111) {
 		LOGP(DRR, LOGL_ERROR, "arfcn(%u) > min(%u) + 111\n", arfcn, min_arfcn);
 		return -EINVAL;
 	}
 
-	bitno = (arfcn - min_arfcn);
+	bitno = (arfcn - min_arfcn) & 1023;
 	byte = bitno / 8;
 	bit = bitno % 8;
 
@@ -94,19 +90,22 @@ static int freq_list_bmrel_set_arfcn(uint8_t *chan_list, unsigned int arfcn)
 
 /* generate a cell channel list as per Section 10.5.2.1b of 04.08 */
 static int bitvec2freq_list(uint8_t *chan_list, struct bitvec *bv,
-			    const struct gsm_bts *bts)
+			    const struct gsm_bts *bts, int bis, int ter)
 {
-	int i, rc, min = 1024, max = -1;
+	int i, rc, min = -1, max = -1, pgsm = 0;
 
 	memset(chan_list, 0, 16);
 
-	/* P-GSM-only handsets only support 'bit map 0 format' */
 	if (bts->band == GSM_BAND_900
-	 && bts->c0->arfcn >= 1 && bts->c0->arfcn <= 124) {
+	 && bts->c0->arfcn >= 1 && bts->c0->arfcn <= 124)
+		pgsm = 1;
+	/* P-GSM-only handsets only support 'bit map 0 format' */
+	if (!bis && !ter && pgsm) {
 		chan_list[0] = 0;
 
 		for (i = 0; i < bv->data_len*8; i++) {
-			if (bitvec_get_bit_pos(bv, i)) {
+			if (i >= 1 && i <= 124
+			 && bitvec_get_bit_pos(bv, i)) {
 				rc = freq_list_bm0_set_arfcn(chan_list, i);
 				if (rc < 0)
 					return rc;
@@ -119,10 +118,30 @@ static int bitvec2freq_list(uint8_t *chan_list, struct bitvec *bv,
 	chan_list[0] = 0x8e;
 
 	for (i = 0; i < bv->data_len*8; i++) {
-		if (bitvec_get_bit_pos(bv, i)) {
-			if (i < min)
+		/* in case of SI2 or SI5 allow all neighbours in same band
+		 * in case of SI*bis, allow neighbours in same band ouside pgsm
+		 * in case of SI*ter, allow neighbours in different bands
+		 */
+		if (bitvec_get_bit_pos(bv, i)
+		 && ((!bis && !ter && gsm_arfcn2band(i) == bts->band)
+		  || (bis && pgsm && gsm_arfcn2band(i) == bts->band && (i < 1 || i > 124))
+		  || (ter && gsm_arfcn2band(i) != bts->band))) {
+			/* 955..1023 < 0..885 */
+			if (min < 0)
+				min = i;
+			if (i >= 955 && min < 955)
+				min = i;
+			if (i >= 955 && min >= 955 && i < min)
 				min = i;
-			if (i > max)
+			if (i < 955 && min < 955 && i < min)
+				min = i;
+			if (max < 0)
+				max = i;
+			if (i < 955 && max >= 955)
+				max = i;
+			if (i >= 955 && max >= 955 && i > max)
+				max = i;
+			if (i < 955 && max < 955 && i > max)
 				max = i;
 		}
 	}
@@ -133,7 +152,7 @@ static int bitvec2freq_list(uint8_t *chan_list, struct bitvec *bv,
 		return 0;
 	}
 
-	if ((max - min) > 111) {
+	if (((max - min) & 1023) > 111) {
 		LOGP(DRR, LOGL_ERROR, "min_arfcn=%u, max_arfcn=%u, "
 			"distance > 111\n", min, max);
 		return -EINVAL;
@@ -144,7 +163,11 @@ static int bitvec2freq_list(uint8_t *chan_list, struct bitvec *bv,
 	chan_list[2] = (min & 1) << 7;
 
 	for (i = 0; i < bv->data_len*8; i++) {
-		if (bitvec_get_bit_pos(bv, i)) {
+		/* see notes above */
+		if (bitvec_get_bit_pos(bv, i)
+		 && ((!bis && !ter && gsm_arfcn2band(i) == bts->band)
+		  || (bis && pgsm && gsm_arfcn2band(i) == bts->band && (i < 1 || i > 124))
+		  || (ter && gsm_arfcn2band(i) != bts->band))) {
 			rc = freq_list_bmrel_set_arfcn(chan_list, i);
 			if (rc < 0)
 				return rc;
@@ -179,11 +202,12 @@ static int bitvec2freq_list(uint8_t *chan_list, struct bitvec *bv,
 	}
 
 	/* then we generate a GSM 04.08 frequency list from the bitvec */
-	return bitvec2freq_list(chan_list, bv, bts);
+	return bitvec2freq_list(chan_list, bv, bts, 0, 0);
 }
 
 /* generate a cell channel list as per Section 10.5.2.1b of 04.08 */
-static int generate_bcch_chan_list(uint8_t *chan_list, struct gsm_bts *bts, int si5)
+static int generate_bcch_chan_list(uint8_t *chan_list, struct gsm_bts *bts,
+	int si5, int bis, int ter)
 {
 	struct gsm_bts *cur_bts;
 	struct bitvec *bv;
@@ -207,7 +231,28 @@ static int generate_bcch_chan_list(uint8_t *chan_list, struct gsm_bts *bts, int
 	}
 
 	/* then we generate a GSM 04.08 frequency list from the bitvec */
-	return bitvec2freq_list(chan_list, bv, bts);
+	return bitvec2freq_list(chan_list, bv, bts, bis, ter);
+}
+
+static int list_arfcn(uint8_t *chan_list, uint8_t mask, char *text)
+{
+	int n = 0, i;
+	struct gsm_sysinfo_freq freq[1024];
+
+	memset(freq, 0, sizeof(freq));
+	gsm48_decode_freq_list(freq, chan_list, 16, 0xce, 1);
+	for (i = 0; i < 1024; i++) {
+		if (freq[i].mask) {
+			if (!n)
+				LOGP(DRR, LOGL_INFO, "%s", text);
+			LOGPC(DRR, LOGL_INFO, " %d", i);
+			n++;
+		}
+	}
+	if (n)
+		LOGPC(DRR, LOGL_INFO, "\n");
+
+	return n;
 }
 
 static int generate_si1(uint8_t *output, struct gsm_bts *bts)
@@ -226,6 +271,7 @@ static int generate_si1(uint8_t *output, struct gsm_bts *bts)
 	rc = generate_cell_chan_list(si1->cell_channel_description, bts);
 	if (rc < 0)
 		return rc;
+	list_arfcn(si1->cell_channel_description, 0xce, "Serving cell:");
 
 	si1->rach_control = bts->si_common.rach_control;
 
@@ -248,9 +294,11 @@ static int generate_si2(uint8_t *output, struct gsm_bts *bts)
 	si2->header.skip_indicator = 0;
 	si2->header.system_information = GSM48_MT_RR_SYSINFO_2;
 
-	rc = generate_bcch_chan_list(si2->bcch_frequency_list, bts, 0);
+	rc = generate_bcch_chan_list(si2->bcch_frequency_list, bts, 0, 0, 0);
 	if (rc < 0)
 		return rc;
+	list_arfcn(si2->bcch_frequency_list, 0xce,
+		"Neighbour cells in same band:");
 
 	si2->ncc_permitted = bts->si_common.ncc_permitted;
 	si2->rach_control = bts->si_common.rach_control;
@@ -258,6 +306,65 @@ static int generate_si2(uint8_t *output, struct gsm_bts *bts)
 	return sizeof(*si2);
 }
 
+static int generate_si2bis(uint8_t *output, struct gsm_bts *bts)
+{
+	int rc;
+	struct gsm48_system_information_type_2bis *si2b =
+		(struct gsm48_system_information_type_2bis *) output;
+	int n;
+
+	memset(si2b, GSM_MACBLOCK_PADDING, GSM_MACBLOCK_LEN);
+
+	si2b->header.l2_plen = (22 << 2) | 1;
+	si2b->header.rr_protocol_discriminator = GSM48_PDISC_RR;
+	si2b->header.skip_indicator = 0;
+	si2b->header.system_information = GSM48_MT_RR_SYSINFO_2bis;
+
+	rc = generate_bcch_chan_list(si2b->bcch_frequency_list, bts, 0, 1, 0);
+	if (rc < 0)
+		return rc;
+	n = list_arfcn(si2b->bcch_frequency_list, 0xce,
+		"Neighbour cells in same band, but outside P-GSM:");
+	if (n) {
+		/* indicate in SI2 and SI2bis: there is an extension */
+		struct gsm48_system_information_type_2 *si2 =
+			(struct gsm48_system_information_type_2 *)
+				bts->si_buf[SYSINFO_TYPE_2];
+		si2->bcch_frequency_list[0] |= 0x20;
+		si2b->bcch_frequency_list[0] |= 0x20;
+	} else
+		bts->si_valid &= ~(1 << SYSINFO_TYPE_2bis);
+
+	si2b->rach_control = bts->si_common.rach_control;
+
+	return sizeof(*si2b);
+}
+
+static int generate_si2ter(uint8_t *output, struct gsm_bts *bts)
+{
+	int rc;
+	struct gsm48_system_information_type_2ter *si2t =
+		(struct gsm48_system_information_type_2ter *) output;
+	int n;
+
+	memset(si2t, GSM_MACBLOCK_PADDING, GSM_MACBLOCK_LEN);
+
+	si2t->header.l2_plen = (22 << 2) | 1;
+	si2t->header.rr_protocol_discriminator = GSM48_PDISC_RR;
+	si2t->header.skip_indicator = 0;
+	si2t->header.system_information = GSM48_MT_RR_SYSINFO_2ter;
+
+	rc = generate_bcch_chan_list(si2t->ext_bcch_frequency_list, bts, 0, 0, 1);
+	if (rc < 0)
+		return rc;
+	n = list_arfcn(si2t->ext_bcch_frequency_list, 0x8e,
+		"Neighbour cells in different band:");
+	if (!n)
+		bts->si_valid &= ~(1 << SYSINFO_TYPE_2ter);
+
+	return sizeof(*si2t);
+}
+
 static struct gsm48_si_ro_info si_info = {
 	.selection_params = {
 		.present = 0,
@@ -304,6 +411,13 @@ static int generate_si3(uint8_t *output, struct gsm_bts *bts)
 	si3->cell_sel_par = bts->si_common.cell_sel_par;
 	si3->rach_control = bts->si_common.rach_control;
 
+	if ((bts->si_valid & (1 << SYSINFO_TYPE_2ter))) {
+		LOGP(DRR, LOGL_INFO, "SI 2ter is included.\n");
+		si_info.si2ter_indicator = 1;
+	} else {
+		si_info.si2ter_indicator = 0;
+	}
+
 	/* SI3 Rest Octets (10.5.2.34), containing
 		CBQ, CELL_RESELECT_OFFSET, TEMPORARY_OFFSET, PENALTY_TIME
 		Power Offset, 2ter Indicator, Early Classmark Sending,
@@ -370,9 +484,92 @@ static int generate_si5(uint8_t *output, struct gsm_bts *bts)
 	si5->rr_protocol_discriminator = GSM48_PDISC_RR;
 	si5->skip_indicator = 0;
 	si5->system_information = GSM48_MT_RR_SYSINFO_5;
-	rc = generate_bcch_chan_list(si5->bcch_frequency_list, bts, 1);
+	rc = generate_bcch_chan_list(si5->bcch_frequency_list, bts, 1, 0, 0);
+	if (rc < 0)
+		return rc;
+	list_arfcn(si5->bcch_frequency_list, 0xce,
+		"Neighbour cells in same band:");
+
+	/* 04.08 9.1.37: L2 Pseudo Length of 18 */
+	return l2_plen;
+}
+
+static int generate_si5bis(uint8_t *output, struct gsm_bts *bts)
+{
+	struct gsm48_system_information_type_5bis *si5b;
+	int rc, l2_plen = 18;
+	int n;
+
+	memset(output, GSM_MACBLOCK_PADDING, GSM_MACBLOCK_LEN);
+
+	/* ip.access nanoBTS needs l2_plen!! */
+	switch (bts->type) {
+	case GSM_BTS_TYPE_NANOBTS:
+	case GSM_BTS_TYPE_HSL_FEMTO:
+		*output++ = (l2_plen << 2) | 1;
+		l2_plen++;
+		break;
+	default:
+		break;
+	}
+
+	si5b = (struct gsm48_system_information_type_5bis *) output;
+
+	/* l2 pseudo length, not part of msg: 18 */
+	si5b->rr_protocol_discriminator = GSM48_PDISC_RR;
+	si5b->skip_indicator = 0;
+	si5b->system_information = GSM48_MT_RR_SYSINFO_5bis;
+	rc = generate_bcch_chan_list(si5b->bcch_frequency_list, bts, 1, 1, 0);
+	if (rc < 0)
+		return rc;
+	n = list_arfcn(si5b->bcch_frequency_list, 0xce,
+		"Neighbour cells in same band, but outside P-GSM:");
+	if (n) {
+		/* indicate in SI5 and SI5bis: there is an extension */
+		struct gsm48_system_information_type_5 *si5 =
+			(struct gsm48_system_information_type_5 *)
+				bts->si_buf[SYSINFO_TYPE_5];
+		si5->bcch_frequency_list[0] |= 0x20;
+		si5b->bcch_frequency_list[0] |= 0x20;
+	} else
+		bts->si_valid &= ~(1 << SYSINFO_TYPE_5bis);
+
+	/* 04.08 9.1.37: L2 Pseudo Length of 18 */
+	return l2_plen;
+}
+
+static int generate_si5ter(uint8_t *output, struct gsm_bts *bts)
+{
+	struct gsm48_system_information_type_5ter *si5t;
+	int rc, l2_plen = 18;
+	int n;
+
+	memset(output, GSM_MACBLOCK_PADDING, GSM_MACBLOCK_LEN);
+
+	/* ip.access nanoBTS needs l2_plen!! */
+	switch (bts->type) {
+	case GSM_BTS_TYPE_NANOBTS:
+	case GSM_BTS_TYPE_HSL_FEMTO:
+		*output++ = (l2_plen << 2) | 1;
+		l2_plen++;
+		break;
+	default:
+		break;
+	}
+
+	si5t = (struct gsm48_system_information_type_5ter *) output;
+
+	/* l2 pseudo length, not part of msg: 18 */
+	si5t->rr_protocol_discriminator = GSM48_PDISC_RR;
+	si5t->skip_indicator = 0;
+	si5t->system_information = GSM48_MT_RR_SYSINFO_5ter;
+	rc = generate_bcch_chan_list(si5t->bcch_frequency_list, bts, 1, 0, 1);
 	if (rc < 0)
 		return rc;
+	n = list_arfcn(si5t->bcch_frequency_list, 0x8e,
+		"Neighbour cells in different band:");
+	if (!n)
+		bts->si_valid &= ~(1 << SYSINFO_TYPE_5ter);
 
 	/* 04.08 9.1.37: L2 Pseudo Length of 18 */
 	return l2_plen;
@@ -481,9 +678,13 @@ typedef int (*gen_si_fn_t)(uint8_t *output, struct gsm_bts *bts);
 static const gen_si_fn_t gen_si_fn[_MAX_SYSINFO_TYPE] = {
 	[SYSINFO_TYPE_1] = &generate_si1,
 	[SYSINFO_TYPE_2] = &generate_si2,
+	[SYSINFO_TYPE_2bis] = &generate_si2bis,
+	[SYSINFO_TYPE_2ter] = &generate_si2ter,
 	[SYSINFO_TYPE_3] = &generate_si3,
 	[SYSINFO_TYPE_4] = &generate_si4,
 	[SYSINFO_TYPE_5] = &generate_si5,
+	[SYSINFO_TYPE_5bis] = &generate_si5bis,
+	[SYSINFO_TYPE_5ter] = &generate_si5ter,
 	[SYSINFO_TYPE_6] = &generate_si6,
 	[SYSINFO_TYPE_13] = &generate_si13,
 };