Change in osmo-bts[master]: l1sap: add repeated downlink SACCH

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dexter gerrit-no-reply at lists.osmocom.org
Wed Nov 11 17:34:53 UTC 2020


dexter has uploaded this change for review. ( https://gerrit.osmocom.org/c/osmo-bts/+/21105 )


Change subject: l1sap: add repeated downlink SACCH
......................................................................

l1sap: add repeated downlink SACCH

3GPP TS 44.006, section 11 describes a method how the downlink
SACCH transmission can be repeated to increase transmission
reliability.

Depends: libosmocore I61ea6bf54ea90bd69b73ea0f0f3dc19a4214207b
Change-Id: I00806f936b15fbaf6a4e7bbd61f3bec262cdbb28
Related: OS#4794, SYS#5114
---
M include/osmo-bts/bts.h
M include/osmo-bts/gsm_data.h
M src/common/l1sap.c
M src/common/rsl.c
M src/common/vty.c
5 files changed, 77 insertions(+), 3 deletions(-)



  git pull ssh://gerrit.osmocom.org:29418/osmo-bts refs/changes/05/21105/1

diff --git a/include/osmo-bts/bts.h b/include/osmo-bts/bts.h
index fdcc67b..950551c 100644
--- a/include/osmo-bts/bts.h
+++ b/include/osmo-bts/bts.h
@@ -341,6 +341,9 @@
 	/* 3GPP TS 44.006, section 10, Repeated Downlink FACCH */
 	bool facch_repetition_enabled;
 
+	/* 3GPP TS 44.006, section 11.2, Procedure for Repeated SACCH on the downlink */
+	bool dl_sacch_repetition_enabled;
+
 	void *model_priv; /* Allocated by bts_model, contains model specific data pointer */
 };
 
diff --git a/include/osmo-bts/gsm_data.h b/include/osmo-bts/gsm_data.h
index 59fd809..2441286 100644
--- a/include/osmo-bts/gsm_data.h
+++ b/include/osmo-bts/gsm_data.h
@@ -264,6 +264,7 @@
 
 		/* SLOT #0 and #1 to store FACCH for repetition */
 		struct gsm_rep_facch rep_facch[2];
+		struct msgb *rep_sacch;
 
 	} tch;
 
diff --git a/src/common/l1sap.c b/src/common/l1sap.c
index 6001b9f..30f226a 100644
--- a/src/common/l1sap.c
+++ b/src/common/l1sap.c
@@ -964,6 +964,44 @@
 	return msg;
 }
 
+/* Special dequeueing function with SACCH repetition (3GPP TS 44.006, section 11) */
+static inline struct msgb *lapdm_phsap_dequeue_msg_sacch(struct gsm_lchan *lchan, struct lapdm_entity *le)
+{
+	struct osmo_phsap_prim pp;
+	struct msgb *msg;
+	uint8_t sapi;
+
+	/* SACCH repetition disabled by the MS */
+	if (((lchan->meas.l1_info[0] >> 1) & 1) == 0) {
+		/* Toss pending repetition candidate */
+		if (lchan->tch.rep_sacch)
+			msgb_free(lchan->tch.rep_sacch);
+		lchan->tch.rep_sacch = NULL;
+
+		/* Fetch new FACCH from queue normally */
+		return lapdm_phsap_dequeue_msg(le);
+	}
+
+	/* Repeat pending candidate */
+	if (lchan->tch.rep_sacch) {
+		msg = lchan->tch.rep_sacch;
+		lchan->tch.rep_sacch = NULL;
+		return msg;
+	}
+
+	/* Fetch new SACCH from queue ... */
+	if (lapdm_phsap_dequeue_prim(le, &pp) < 0)
+		return NULL;
+	msg = pp.oph.msg;
+
+	/* Only SAPI 0 SACCH frames are repetition candidates, see also 3GPP TS 44.006, section 11.2 */
+	sapi = (msg->data[0] >> 2) & 0x07;
+	if (sapi == 0)
+		lchan->tch.rep_sacch = msg;
+
+	return msg;
+}
+
 /* 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)
@@ -1044,7 +1082,10 @@
 			p[0] = lchan->ms_power_ctrl.current;
 			p[1] = lchan->rqd_ta;
 			le = &lchan->lapdm_ch.lapdm_acch;
-			pp_msg = lapdm_phsap_dequeue_msg(le);
+			if (lchan->ts->trx->bts->dl_sacch_repetition_enabled)
+				pp_msg = lapdm_phsap_dequeue_msg_sacch(lchan, le);
+			else
+				pp_msg = lapdm_phsap_dequeue_msg(le);
 		} else {
 			if (lchan->ts->trx->bts->dtxd)
 				dtxd_facch = true;
diff --git a/src/common/rsl.c b/src/common/rsl.c
index 16109b2..26560b9 100644
--- a/src/common/rsl.c
+++ b/src/common/rsl.c
@@ -823,13 +823,16 @@
 	 */
 	lapdm_channel_exit(&lchan->lapdm_ch);
 
-	/* Also ensure that there are no leftovers from repeated FACCH
-	 * that might cause memory leakage. */
+	/* Also ensure that there are no leftovers from repeated FACCH or
+	 * repeated SACCH that might cause memory leakage. */
 	if (lchan->tch.rep_facch[0].msg)
 		msgb_free(lchan->tch.rep_facch[0].msg);
 	if (lchan->tch.rep_facch[1].msg)
 		msgb_free(lchan->tch.rep_facch[1].msg);
 	memset(lchan->tch.rep_facch, 0, sizeof(lchan->tch.rep_facch));
+	if(lchan->tch.rep_sacch)
+		msgb_free(lchan->tch.rep_sacch);
+	lchan->tch.rep_sacch = NULL;
 
 	return tx_rf_rel_ack(lchan, chan_nr);
 }
diff --git a/src/common/vty.c b/src/common/vty.c
index 59a6dee..f8033df 100644
--- a/src/common/vty.c
+++ b/src/common/vty.c
@@ -307,6 +307,8 @@
 	vty_out(vty, " smscb queue-hysteresis %d%s", bts->smscb_queue_hyst, VTY_NEWLINE);
 	if (bts->facch_repetition_enabled)
 		vty_out(vty, " facch-repetition%s", VTY_NEWLINE);
+	if (bts->dl_sacch_repetition_enabled)
+		vty_out(vty, " sacch-repetition%s", VTY_NEWLINE);
 
 	bts_model_config_write_bts(vty, bts);
 
@@ -823,6 +825,28 @@
 	return CMD_SUCCESS;
 }
 
+DEFUN_ATTR(cfg_bts_dl_sacch_repetition, cfg_bts_dl_sacch_repetition_cmd,
+	   "dl-sacch-repetition",
+	   "enable downlink SACCH repetition\n",
+	   CMD_ATTR_IMMEDIATE)
+{
+	struct gsm_bts *bts = vty->index;
+
+	bts->dl_sacch_repetition_enabled = true;
+	return CMD_SUCCESS;
+}
+
+DEFUN_ATTR(cfg_bts_no_dl_sacch_repetition, cfg_bts_no_dl_sacch_repetition_cmd,
+	   "no dl-sacch-repetition",
+	   NO_STR "disable downlink SACCH repetition\n",
+	   CMD_ATTR_IMMEDIATE)
+{
+	struct gsm_bts *bts = vty->index;
+
+	bts->dl_sacch_repetition_enabled = false;
+	return CMD_SUCCESS;
+}
+
 #define DB_MDB_STR 							\
 	"Unit is dB (decibels)\n"					\
 	"Unit is mdB (milli-decibels, or rather 1/10000 bel)\n"
@@ -1917,6 +1941,8 @@
 	install_element(BTS_NODE, &cfg_bts_smscb_qhyst_cmd);
 	install_element(BTS_NODE, &cfg_bts_facch_repetition_cmd);
 	install_element(BTS_NODE, &cfg_bts_no_facch_repetition_cmd);
+	install_element(BTS_NODE, &cfg_bts_dl_sacch_repetition_cmd);
+	install_element(BTS_NODE, &cfg_bts_no_dl_sacch_repetition_cmd);
 
 	install_element(BTS_NODE, &cfg_trx_gsmtap_sapi_all_cmd);
 	install_element(BTS_NODE, &cfg_trx_gsmtap_sapi_cmd);

-- 
To view, visit https://gerrit.osmocom.org/c/osmo-bts/+/21105
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Gerrit-Project: osmo-bts
Gerrit-Branch: master
Gerrit-Change-Id: I00806f936b15fbaf6a4e7bbd61f3bec262cdbb28
Gerrit-Change-Number: 21105
Gerrit-PatchSet: 1
Gerrit-Owner: dexter <pmaier at sysmocom.de>
Gerrit-MessageType: newchange
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