[PATCH] osmo-pcu[master]: LC15: Fix TA adjustment

[Minh-Quang Nguyen]

Review at  https://gerrit.osmocom.org/4678

LC15: Fix TA adjustment

Change-Id: I65212f8203f1a35278890f51db038d689b2493d5
---
M src/bts.cpp
M src/bts.h
M src/osmo-bts-litecell15/lc15_l1_if.c
M src/pcu_l1_if.h
4 files changed, 57 insertions(+), 11 deletions(-)


  git pull ssh://gerrit.osmocom.org:29418/osmo-pcu refs/changes/78/4678/1

diff --git a/src/bts.cpp b/src/bts.cpp
index e41b1fa..7ffb132 100644
--- a/src/bts.cpp
+++ b/src/bts.cpp
@@ -1619,20 +1619,48 @@
 	return rc;
 }
 
-void bts_update_tbf_ta(const char *p, uint32_t fn, uint8_t trx_no, uint8_t ts,
-		       uint8_t ta)
+void bts_update_tbf_ta(const char *p, uint32_t fn, uint8_t trx_no, uint8_t ts, int8_t ta)
 {
+	int ta_final;
+	bool need_update = false;
+
 	struct gprs_rlcmac_ul_tbf *tbf =
 		bts_main_data()->bts->ul_tbf_by_poll_fn(fn, trx_no, ts);
 	if (!tbf)
 		LOGP(DL1IF, LOGL_DEBUG, "[%s] update TA = %u ignored due to "
 		     "unknown UL TBF on TRX = %d, TS = %d, FN = %d\n",
 		     p, ta, trx_no, ts, fn);
-	else if (tbf->ta() != ta) {
-		LOGP(DL1IF, LOGL_INFO, "[%s] Updating TA %u -> %u on "
-		     "TRX = %d, TS = %d, FN = %d\n",
-		     p, tbf->ta(), ta, trx_no, ts, fn);
-		tbf->set_ta(ta);
+	else {
+		/* we need to distinguish TA information provided by L1
+		 * from PH-DATA-IND and PHY-RA-IND so that we can properly
+		 * update TA for given TBF
+		 */
+		if (!strcmp(p, "PH-DATA")) {
+			if (ta) {
+				/* adjust TA based on TA provided by PH-DATA-IND */
+				ta_final = tbf->ta() + ta;
+				need_update = true;
+			}
+		} else if ((!strcmp(p, "PH-RA"))) {
+			if (tbf->ta() != ta) {
+				/* adjust TA based on TA provided by PH-RA-IND */
+				ta_final = ta;
+				need_update = true;
+			}
+		}
+
+		if (need_update) {
+			/* limit TA range is between 0 and 63 bits */
+			if (ta_final < 0)
+				ta_final = 0;
+			else if (ta_final > 63)
+				ta_final = 63;
+
+			LOGP(DL1IF, LOGL_INFO, "[%s] Updating TLLI=0x%08x: TA %u -> %u on "
+				 "TRX = %d, TS = %d, FN = %d\n",
+				 p, tbf->tlli(), tbf->ta(), ta_final, trx_no, ts, fn);
+			tbf->set_ta((uint8_t)ta_final);
+		}
 	}
 }
 
diff --git a/src/bts.h b/src/bts.h
index d65cd2f..139aeae 100644
--- a/src/bts.h
+++ b/src/bts.h
@@ -162,8 +162,7 @@
 #ifdef __cplusplus
 extern "C" {
 #endif
-void bts_update_tbf_ta(const char *p, uint32_t fn, uint8_t trx_no, uint8_t ts,
-		       uint8_t ta);
+void bts_update_tbf_ta(const char *p, uint32_t fn, uint8_t trx_no, uint8_t ts, int8_t ta);
 #ifdef __cplusplus
 }
 #endif
diff --git a/src/osmo-bts-litecell15/lc15_l1_if.c b/src/osmo-bts-litecell15/lc15_l1_if.c
index 37b7f78..628bd3d 100644
--- a/src/osmo-bts-litecell15/lc15_l1_if.c
+++ b/src/osmo-bts-litecell15/lc15_l1_if.c
@@ -203,7 +203,7 @@
 
 	get_meas(&meas, &data_ind->measParam);
 	bts_update_tbf_ta("PH-DATA", data_ind->u32Fn, fl1h->trx_no,
-			  data_ind->u8Tn, qta2ta(meas.bto));
+			  data_ind->u8Tn, sign_qta2ta(meas.bto));
 
 	switch (data_ind->sapi) {
 	case GsmL1_Sapi_Pdtch:
@@ -248,7 +248,7 @@
 
 	DEBUGP(DL1IF, "Rx PH-RA.ind");
 	bts_update_tbf_ta("PH-RA", ra_ind->u32Fn, fl1h->trx_no, ra_ind->u8Tn,
-			  qta2ta(ra_ind->measParam.i16BurstTiming));
+			sign_qta2ta(ra_ind->measParam.i16BurstTiming));
 
 	return 0;
 }
diff --git a/src/pcu_l1_if.h b/src/pcu_l1_if.h
index 1618260..af51693 100644
--- a/src/pcu_l1_if.h
+++ b/src/pcu_l1_if.h
@@ -43,6 +43,25 @@
 	return qta >> 2;
 }
 
+static inline int8_t sign_qta2ta(int16_t qta)
+{
+	int8_t ta_adj = 0;
+
+	if (qta < -252)
+		qta = -252;
+
+	if (qta > 252)
+		qta = 252;
+
+	/* 1-bit TA adjustment  if TA error reported by L1 is higher outside +/- 2 qbits */
+	if (qta > 2)
+		ta_adj = 1;
+	if (qta < -2)
+		ta_adj = -1;
+
+	return (qta >> 2) + ta_adj;
+}
+
 /*
  * L1 Measurement values
  */

-- 
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Gerrit-MessageType: newchange
Gerrit-Change-Id: I65212f8203f1a35278890f51db038d689b2493d5
Gerrit-PatchSet: 1
Gerrit-Project: osmo-pcu
Gerrit-Branch: master
Gerrit-Owner: Minh-Quang Nguyen <minh-quang.nguyen at nutaq.com>