Change in osmo-bsc[master]: hodec2: fix intra-cell congestion balancing with source lchan on dyn TS

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laforge gerrit-no-reply at lists.osmocom.org
Wed Feb 3 08:31:32 UTC 2021


laforge has submitted this change. ( https://gerrit.osmocom.org/c/osmo-bsc/+/22527 )

Change subject: hodec2: fix intra-cell congestion balancing with source lchan on dyn TS
......................................................................

hodec2: fix intra-cell congestion balancing with source lchan on dyn TS

Related: SYS#5301
Change-Id: I332477cbddf32cf6f057007b45cda8477227f0b1
---
M src/osmo-bsc/handover_decision_2.c
M tests/handover/test_dyn_ts_amr_tch_f_to_h_congestion_assignment_2.ho_vty
M tests/handover/test_dyn_ts_amr_tch_h_to_f_congestion_assignment_2.ho_vty
3 files changed, 34 insertions(+), 15 deletions(-)

Approvals:
  Jenkins Builder: Verified
  laforge: Looks good to me, approved



diff --git a/src/osmo-bsc/handover_decision_2.c b/src/osmo-bsc/handover_decision_2.c
index 0bfae9b..2cb7a54 100644
--- a/src/osmo-bsc/handover_decision_2.c
+++ b/src/osmo-bsc/handover_decision_2.c
@@ -682,7 +682,18 @@
 	current_overbooked = load_above_congestion(c->current.free_tch, c->current.min_free_tch);
 	if (requirement & REQUIREMENT_A_TCHF) {
 		bool ok;
-		int32_t target_overbooked = load_above_congestion(c->target.free_tchf - 1, c->target.min_free_tchf);
+		int32_t target_overbooked;
+		int target_free_tchf_after_ho;
+
+		/* To evaluate whether a handover improves or worsens congestion on TCH/F, first figure out how many
+		 * TCH/F lchans will be occupied on the target after the handover. If the target is a different cell,
+		 * then we obviously reduce by one TCH/F. If source and target cell are the same (re-assignment), then
+		 * the source lchan may also free a TCH/F at the same time. Add up all of these effects to figure out
+		 * the congestion percentages before and after handover. */
+		target_free_tchf_after_ho = c->target.free_tchf - 1;
+		if (c->current.bts == c->target.bts)
+			target_free_tchf_after_ho += c->current.lchan_frees_tchf;
+		target_overbooked = load_above_congestion(target_free_tchf_after_ho, c->target.min_free_tchf);
 		LOGPHOLCHANTOBTS(c->current.lchan, c->target.bts, LOGL_DEBUG,
 				 "current overbooked = %s%%, TCH/F target overbooked after HO = %s%%\n",
 				 osmo_int_to_float_str_c(OTC_SELECT, current_overbooked, LOAD_PRECISION - 2),
@@ -718,7 +729,18 @@
 	}
 	if (requirement & REQUIREMENT_A_TCHH) {
 		bool ok;
-		int32_t target_overbooked = load_above_congestion(c->target.free_tchh - 1, c->target.min_free_tchh);
+		int32_t target_overbooked;
+		int target_free_tchh_after_ho;
+
+		/* To evaluate whether a handover improves or worsens congestion on TCH/H, first figure out how many
+		 * TCH/H lchans will be occupied on the target after the handover. If the target is a different cell,
+		 * then we obviously reduce by one TCH/H. If source and target cell are the same (re-assignment), then
+		 * the source lchan may also free one or two TCH/H at the same time. Add up all of these effects to
+		 * figure out the congestion percentages before and after handover. */
+		target_free_tchh_after_ho = c->target.free_tchh - 1;
+		if (c->current.bts == c->target.bts)
+			target_free_tchh_after_ho += c->current.lchan_frees_tchh;
+		target_overbooked = load_above_congestion(target_free_tchh_after_ho, c->target.min_free_tchh);
 		LOGPHOLCHANTOBTS(c->current.lchan, c->target.bts, LOGL_DEBUG,
 				 "current overbooked = %s%%, TCH/H target overbooked after HO = %s%%\n",
 				 osmo_int_to_float_str_c(OTC_SELECT, current_overbooked, LOAD_PRECISION - 2),
diff --git a/tests/handover/test_dyn_ts_amr_tch_f_to_h_congestion_assignment_2.ho_vty b/tests/handover/test_dyn_ts_amr_tch_f_to_h_congestion_assignment_2.ho_vty
index 6194596..a798457 100644
--- a/tests/handover/test_dyn_ts_amr_tch_f_to_h_congestion_assignment_2.ho_vty
+++ b/tests/handover/test_dyn_ts_amr_tch_f_to_h_congestion_assignment_2.ho_vty
@@ -14,16 +14,15 @@
 # (there must be at least one measurement report on each lchan for congestion check to work)
 meas-rep lchan * * * * rxlev 40 rxqual 0 ta 0 neighbors 30
 congestion-check
-# FAIL: after the handover from the dyn TS to TCH/H, the dyn TS has freed two TCH/H, while the static TCH/H has reduced
-# the TCH/H count by one. So the resulting free slots are 3 TCH/H, which means no congestion. A handover should occur.
-expect-no-chan
+expect-ho from lchan 0 0 1 0 to lchan 0 0 4 0
+expect-ts-use trx 0 0 states * pdch - - TCH/H- * * *
 
 # Again with one more TCH/H occupied, there will still be two free TCH/H after HO on the dyn TS
 set-ts-use trx 0 0 states * TCH/F - - TCH/H- * * *
 meas-rep lchan * * * * rxlev 40 rxqual 0 ta 0 neighbors 30
 congestion-check
-# FAIL: resulting free slots are 2 TCH/H, which means no congestion. A handover should occur.
-expect-no-chan
+expect-ho from lchan 0 0 1 0 to lchan 0 0 4 1
+expect-ts-use trx 0 0 states * pdch - - TCH/HH * * *
 
 # Again, with the target being a dyn TS
 create-bts trx-count 1 timeslots c+s4 dyn TCH/F TCH/F dyn PDCH PDCH PDCH
@@ -37,13 +36,12 @@
 set-ts-use trx 1 0 states * TCH/F TCH/F - pdch * * *
 meas-rep lchan 1 * * * rxlev 40 rxqual 0 ta 0 neighbors 30
 congestion-check
-# FAIL: after the handover from the dyn TS to TCH/H, the dyn TS has freed two TCH/H, while the static TCH/H has reduced
-# the TCH/H count by one. So the resulting free slots are 3 TCH/H, which means no congestion. A handover should occur.
-expect-no-chan
+expect-ho from lchan 1 0 1 0 to lchan 1 0 4 0
+expect-ts-use trx 1 0 states * pdch TCH/F - TCH/H- * * *
 
 # Again with one more TCH/H occupied, there will still be two free TCH/H after HO on the dyn TS
 set-ts-use trx 1 0 states * TCH/F TCH/F - TCH/H- * * *
 meas-rep lchan 1 * * * rxlev 40 rxqual 0 ta 0 neighbors 30
 congestion-check
-# FAIL: resulting free slots are 2 TCH/H, which means no congestion. A handover should occur.
-expect-no-chan
+expect-ho from lchan 1 0 1 0 to lchan 1 0 4 1
+expect-ts-use trx 1 0 states * pdch TCH/F - TCH/HH * * *
diff --git a/tests/handover/test_dyn_ts_amr_tch_h_to_f_congestion_assignment_2.ho_vty b/tests/handover/test_dyn_ts_amr_tch_h_to_f_congestion_assignment_2.ho_vty
index 36a9817..de9595b 100644
--- a/tests/handover/test_dyn_ts_amr_tch_h_to_f_congestion_assignment_2.ho_vty
+++ b/tests/handover/test_dyn_ts_amr_tch_h_to_f_congestion_assignment_2.ho_vty
@@ -21,8 +21,7 @@
 set-ts-use trx 0 0 states * TCH/H- - - TCH/F * * *
 meas-rep lchan * * * * rxlev 40 rxqual 0 ta 0 neighbors 30
 congestion-check
-# FAIL: after the handover from the dyn TS to TCH/F, the dyn TS has freed a TCH/F, while the static TCH/F has reduced
-# the TCH/F count by one. So the resulting free slots are 2 TCH/F, which means no congestion. A handover should occur.
-expect-no-chan
+expect-ho from lchan 0 0 1 0 to lchan 0 0 2 0
+expect-ts-use trx 0 0 states * pdch TCH/F - TCH/F * * *
 
 # (TCH/H -> TCH/F onto a dyn TS will always make TCH/H congestion worse, so there is no useful test case left here)

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Gerrit-Project: osmo-bsc
Gerrit-Branch: master
Gerrit-Change-Id: I332477cbddf32cf6f057007b45cda8477227f0b1
Gerrit-Change-Number: 22527
Gerrit-PatchSet: 2
Gerrit-Owner: neels <nhofmeyr at sysmocom.de>
Gerrit-Reviewer: Jenkins Builder
Gerrit-Reviewer: laforge <laforge at osmocom.org>
Gerrit-Reviewer: pespin <pespin at sysmocom.de>
Gerrit-MessageType: merged
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