Change in osmo-bsc[master]: hodec2: fix low rxlev tch/h<->tch/f oscillation

neels gerrit-no-reply at lists.osmocom.org
Tue Jun 29 13:35:58 UTC 2021


neels has uploaded this change for review. ( https://gerrit.osmocom.org/c/osmo-bsc/+/24795 )


Change subject: hodec2: fix low rxlev tch/h<->tch/f oscillation
......................................................................

hodec2: fix low rxlev tch/h<->tch/f oscillation

Related: SYS#5365
Change-Id: Ibc3ac7ce6190b4e854fa42d5376a7038ddfbd6e5
---
M src/osmo-bsc/handover_decision_2.c
M tests/handover/test_amr_tch_h_to_f_rxlev_oscillation.ho_vty
2 files changed, 9 insertions(+), 11 deletions(-)



  git pull ssh://gerrit.osmocom.org:29418/osmo-bsc refs/changes/95/24795/1

diff --git a/src/osmo-bsc/handover_decision_2.c b/src/osmo-bsc/handover_decision_2.c
index d4ebc41..4fa41fb 100644
--- a/src/osmo-bsc/handover_decision_2.c
+++ b/src/osmo-bsc/handover_decision_2.c
@@ -1169,6 +1169,7 @@
 	bool assignment;
 	bool handover;
 	int neighbors_count = 0;
+	bool tch_f_with_low_rxlev;
 
 	OSMO_ASSERT(candidates);
 
@@ -1186,8 +1187,14 @@
 
 	assignment = ho_get_hodec2_as_active(bts->ho);
 	handover = ho_get_ho_active(bts->ho);
+	tch_f_with_low_rxlev = (lchan->type == GSM_LCHAN_TCH_F
+				&& rxlev_current >= 0
+				&& rxlev2dbm(rxlev_current) < ho_get_hodec2_min_rxlev(bts->ho));
 
-	if (assignment)
+	/* See if re-assignment within the same cell can resolve congestion.
+	 * But: when TCH/F has low rxlev, do not re-assign. If a low rxlev TCH/F were re-assigned to TCH/H, we would
+	 * subsequently oscillate back to TCH/F due to low rxlev. So skip TCH/F with low rxlev. */
+	if (assignment && !tch_f_with_low_rxlev)
 		collect_assignment_candidate(lchan, clist, candidates, rxlev_current);
 
 	if (handover) {
diff --git a/tests/handover/test_amr_tch_h_to_f_rxlev_oscillation.ho_vty b/tests/handover/test_amr_tch_h_to_f_rxlev_oscillation.ho_vty
index 076076b..2ef927d 100644
--- a/tests/handover/test_amr_tch_h_to_f_rxlev_oscillation.ho_vty
+++ b/tests/handover/test_amr_tch_h_to_f_rxlev_oscillation.ho_vty
@@ -17,13 +17,4 @@
 
 meas-rep lchan 0 0 1 0 rxlev 23 rxqual 1 ta 0
 congestion-check
-# FAIL: should stay on TCH/F because rxlev is low, do not oscillate between TCH/F and /H.
-expect-as from lchan 0 0 1 0 to lchan 0 0 4 0
-expect-ts-use trx 0 0 states * - - - TCH/H- - - *
-meas-rep lchan 0 0 4 0 rxlev 23 rxqual 1 ta 0
-expect-as from lchan 0 0 4 0 to lchan 0 0 1 0
-expect-ts-use trx 0 0 states * TCH/F - - - - - *
-meas-rep lchan 0 0 1 0 rxlev 23 rxqual 1 ta 0
-congestion-check
-expect-as from lchan 0 0 1 0 to lchan 0 0 4 0
-expect-ts-use trx 0 0 states * - - - TCH/H- - - *
+expect-no-chan

-- 
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Gerrit-Project: osmo-bsc
Gerrit-Branch: master
Gerrit-Change-Id: Ibc3ac7ce6190b4e854fa42d5376a7038ddfbd6e5
Gerrit-Change-Number: 24795
Gerrit-PatchSet: 1
Gerrit-Owner: neels <nhofmeyr at sysmocom.de>
Gerrit-MessageType: newchange
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