Review at https://gerrit.osmocom.org/7079
common/l1sap.c: limit the minimal ToA for RACH bursts
In general, RACH bursts should not arrive with negative offset.
Let's limit early signal arrival up to 2 symbols, otherwise
it is most likely noise, interference or a ghost.
Change-Id: Id3983b1a3ced148ced101584cbc0267f059fe7f6
---
M src/common/l1sap.c
1 file changed, 10 insertions(+), 4 deletions(-)
git pull ssh://gerrit.osmocom.org:29418/osmo-bts refs/changes/79/7079/1
diff --git a/src/common/l1sap.c b/src/common/l1sap.c
index ecd6805..85f8830 100644
--- a/src/common/l1sap.c
+++ b/src/common/l1sap.c
@@ -1173,6 +1173,8 @@
return 0;
}
+#define RACH_MIN_TOA256 -2 * 256
+
/* RACH received from bts model */
static int l1sap_ph_rach_ind(struct gsm_bts_trx *trx,
struct osmo_phsap_prim *l1sap, struct ph_rach_ind_param *rach_ind)
@@ -1208,11 +1210,15 @@
lc = &trx->ts[0].lchan[CCCH_LCHAN].lapdm_ch;
- /* Make sure that ToA (Timing of Arrival) is acceptable */
- if (toa256 > btsb->max_ta * 256) {
+ /**
+ * Make sure that ToA (Timing of Arrival) is acceptable.
+ * We allow early arrival up to 2 symbols, and delay
+ * according to maximal allowed Timing Advance value.
+ */
+ if (toa256 < RACH_MIN_TOA256 || toa256 > btsb->max_ta * 256) {
LOGPFN(DL1C, LOGL_INFO, rach_ind->fn, "Ignoring RACH request: "
- "ToA(%d) exceeds the maximal allowed TA(%u) * 256
value\n",
- toa256, btsb->max_ta);
+ "ToA(%d) exceeds the allowed range (%d..%d)\n",
+ toa256, RACH_MIN_TOA256, btsb->max_ta * 256);
rate_ctr_inc2(trx->bts->ctrs, BTS_CTR_RACH_DROP);
return 0;
}
--
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Gerrit-MessageType: newchange
Gerrit-Change-Id: Id3983b1a3ced148ced101584cbc0267f059fe7f6
Gerrit-PatchSet: 1
Gerrit-Project: osmo-bts
Gerrit-Branch: master
Gerrit-Owner: Vadim Yanitskiy <[email protected]>
