laforge has submitted this change. (
https://gerrit.osmocom.org/c/osmo-bts/+/22509 )
Change subject: chan activ: activate DL SACCH only when TA is known
......................................................................
chan activ: activate DL SACCH only when TA is known
A channel activation for handover to another cell does not know the
Timing Advance until the handover RACH is received. It does not make
much sense to enable downlink SACCH without an accurate TA.
If the BSC omits the Access Delay IE (a.k.a. the Timing Advance), do not
enable downlink SACCH. This is expected to happen only for inter-cell
handover. In all other situations, the TA should be known either from a
Channel Request RACH for Immediate Assignment, or from the previous
lchan on the same cell upon Assignment / intra-cell handover.
Related: OS#4008 OS#4009 SYS#5192
Change-Id: I170b63c9856230d5f1a10654a9d950ada8e730d7
---
M src/common/rsl.c
1 file changed, 14 insertions(+), 2 deletions(-)
Approvals:
Jenkins Builder: Verified
pespin: Looks good to me, but someone else must approve
laforge: Looks good to me, approved
diff --git a/src/common/rsl.c b/src/common/rsl.c
index b4df22c..01a0ab4 100644
--- a/src/common/rsl.c
+++ b/src/common/rsl.c
@@ -1545,11 +1545,23 @@
}
/* Indicate which SAPIs should be enabled before the first RACH is
received, for handover. See 3GPP TS 48.058
- * 4.1.3 and 4.1.4. */
+ * 4.1.3 and 4.1.4.
+ *
+ * | | Access || transmit | activate
| This implementation
+ * | MS Power | Delay || on main channel | dl SACCH
| activates DL SACCH
+ *
-----------------------------------------------------------------------------------------
+ * async ho no * --> yes no
no
+ * async ho yes * --> yes may be started
no
+ * async ho yes yes --> yes may be started
yes
+ * sync ho no no --> yes no
no
+ * sync ho yes no --> yes may be started
no
+ * sync ho yes yes --> yes shall be
started yes
+ */
switch (type) {
case RSL_ACT_INTER_ASYNC:
case RSL_ACT_INTER_SYNC:
- lchan->want_dl_sacch_active = TLVP_PRES_LEN(&tp,
RSL_IE_MS_POWER, 1);
+ lchan->want_dl_sacch_active = (TLVP_PRES_LEN(&tp,
RSL_IE_MS_POWER, 1)
+ && TLVP_PRES_LEN(&tp,
RSL_IE_ACCESS_DELAY, 1));
break;
default:
lchan->want_dl_sacch_active = true;
--
To view, visit https://gerrit.osmocom.org/c/osmo-bts/+/22509
To unsubscribe, or for help writing mail filters, visit
https://gerrit.osmocom.org/settings
Gerrit-Project: osmo-bts
Gerrit-Branch: master
Gerrit-Change-Id: I170b63c9856230d5f1a10654a9d950ada8e730d7
Gerrit-Change-Number: 22509
Gerrit-PatchSet: 2
Gerrit-Owner: neels <nhofm...@sysmocom.de>
Gerrit-Reviewer: Jenkins Builder
Gerrit-Reviewer: laforge <lafo...@osmocom.org>
Gerrit-Reviewer: pespin <pes...@sysmocom.de>
Gerrit-MessageType: merged
