PCU: Fix TA adjustment
Promblem:
TA provided from L1 PH-DATA-IND is a relative amount of TA adjustment to actual TA
being used for given TBF. The current TA update algorithm in PCU simply applies the relative
amount of TA to given TBF but does not take into account of current TA.
As a result, the PCU will request wrong TA jump for given TBF if the MS is moving away from
BTS more than 2 km.
Related issue: http://osmocom.org/issues/2611
Fixes:
- The PCU needs increase or decrease current TA of given TBF on receiving of relative
amount of TA adjustment provided by PH-DATA-IND from L1
- The PCU needs to set absolute TA of given TBF on receiving absolute TA provided by
PH-RA-IND from L1.
Change-Id: I65212f8203f1a35278890f51db038d689b2493d5
diff --git a/src/bts.cpp b/src/bts.cpp
index e41b1fa..6bdbb85 100644
--- a/src/bts.cpp
+++ b/src/bts.cpp
@@ -1619,8 +1619,45 @@
return rc;
}
-void bts_update_tbf_ta(const char *p, uint32_t fn, uint8_t trx_no, uint8_t ts,
- uint8_t ta)
+/* update TA based on TA provided by PH-DATA-IND */
+void update_tbf_ta(struct gprs_rlcmac_ul_tbf *tbf, int8_t ta_delta)
+{
+ int16_t ta_adj;
+ uint8_t ta_target;
+
+ if (ta_delta) {
+ /* adjust TA based on TA provided by PH-DATA-IND */
+ ta_adj = tbf->ta() + ta_delta;
+
+ /* limit target TA in range 0..63 bits */
+ ta_target = ta_limit(ta_adj);
+
+ LOGP(DL1IF, LOGL_INFO, "PH-DATA-IND is updating TLLI=0x%08x: TA %u -> %u on "
+ "TRX = %d, TS = %d, FN = %d\n",
+ tbf->tlli(), tbf->ta(), ta_target,
+ tbf->trx->trx_no , tbf->poll_ts, tbf->poll_fn);
+ tbf->set_ta(ta_target);
+ }
+}
+
+/* set TA based on TA provided by PH-RA-IND */
+void set_tbf_ta(struct gprs_rlcmac_ul_tbf *tbf, uint8_t ta)
+{
+ uint8_t ta_target;
+
+ if (tbf->ta() != ta) {
+ /* limit target TA in range 0..63 bits */
+ ta_target = ta_limit(ta);
+
+ LOGP(DL1IF, LOGL_INFO, "PH-RA-IND is updating TLLI=0x%08x: TA %u -> %u on "
+ "TRX = %d, TS = %d, FN = %d\n",
+ tbf->tlli(), tbf->ta(), ta_target,
+ tbf->trx->trx_no , tbf->poll_ts, tbf->poll_fn);
+ tbf->set_ta(ta_target);
+ }
+}
+
+void bts_update_tbf_ta(const char *p, uint32_t fn, uint8_t trx_no, uint8_t ts, int8_t ta, bool is_rach)
{
struct gprs_rlcmac_ul_tbf *tbf =
bts_main_data()->bts->ul_tbf_by_poll_fn(fn, trx_no, ts);
@@ -1628,11 +1665,16 @@
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 (is_rach)
+ set_tbf_ta(tbf, (uint8_t)ta);
+ else
+ update_tbf_ta(tbf, ta);
+
}
}