Change in osmo-bts[master]: power_control: tolerate small deviations from 'rx-target'

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fixeria gerrit-no-reply at lists.osmocom.org
Sun Oct 18 15:22:26 UTC 2020


fixeria has uploaded this change for review. ( https://gerrit.osmocom.org/c/osmo-bts/+/20730 )


Change subject: power_control: tolerate small deviations from 'rx-target'
......................................................................

power_control: tolerate small deviations from 'rx-target'

Recently we've introduced EWMA based uplink power filtering, that
should reduce Uplink power oscillations.  However, the power loop
is still quite sensitive to small deviations from the target power
level: even such an insignificant deviation like 2-5 dBm triggers
the loop to increase or decrease the MS power level.  Even if the
EWMA based filtering is enabled with 80% smoothing (alpha = 0.2).

This change introduces a new configuration parameter - 'delta':

  uplink-power-target <-110-0> delta <1-25>

that together with the 'uplink-power-target' defines a range:

  [target - delta .. target + delta]

in which the MS power loop would not trigger any power changes.

This feature is now *enabled* by default, so given that:

  - default 'uplink-power-target' is -75 dBm, and
  - default 'delta' is 5 dBm,

the default Uplink power range is: -80 dBm ... -70 dBm.

Change-Id: Iacedbd4d69d3d74e2499af5622a07a8af0423da0
Related: SYS#4916
---
M include/osmo-bts/bts.h
M src/common/bts.c
M src/common/power_control.c
M src/common/vty.c
M tests/power/power_test.c
M tests/power/power_test.err
M tests/power/power_test.ok
7 files changed, 97 insertions(+), 11 deletions(-)



  git pull ssh://gerrit.osmocom.org:29418/osmo-bts refs/changes/30/20730/1

diff --git a/include/osmo-bts/bts.h b/include/osmo-bts/bts.h
index db8f741..a5637a2 100644
--- a/include/osmo-bts/bts.h
+++ b/include/osmo-bts/bts.h
@@ -298,6 +298,7 @@
 
 	/* TODO: move it to bts->ul_power_ctrl struct */
 	int ul_power_target;		/* Uplink Rx power target */
+	int ul_power_delta;		/* Tolerable Uplink Rx power deviation */
 
 	/* Uplink power control */
 	struct {
diff --git a/src/common/bts.c b/src/common/bts.c
index bb0795a..0bbd5cd 100644
--- a/src/common/bts.c
+++ b/src/common/bts.c
@@ -303,6 +303,7 @@
 	/* configurable via VTY */
 	bts->paging_state = paging_init(bts, 200, 0);
 	bts->ul_power_target = -75;	/* dBm default */
+	bts->ul_power_delta = 5;	/* -80 .. -70 dBm */
 	bts->ul_power_ctrl.pf_algo = MS_UL_PF_ALGO_EWMA;
 	bts->ul_power_ctrl.pf.ewma.alpha = 20; /* 80% smoothing */
 	bts->rtp_jitter_adaptive = false;
diff --git a/src/common/power_control.c b/src/common/power_control.c
index cf5ecf7..55755da 100644
--- a/src/common/power_control.c
+++ b/src/common/power_control.c
@@ -147,12 +147,12 @@
 		  "Diff between 'rx-target' %d dBm and 'rx-current' %d dBm is %d dBm\n",
 		  bts->ul_power_target, avg_ul_rssi_dbm, diff);
 
-	/* TODO: introduce 'delta' defining a range of tolerable deviation */
-	if (diff == 0) {
+	/* Tolerate small deviations from 'rx-target' */
+	if (abs(diff) <= bts->ul_power_delta) {
 		LOGPLCHAN(lchan, DLOOP, LOGL_INFO,
 			  "Keeping MS power at control level %d (%d dBm) because diff %d dBm "
-			  "from 'rx-target' %d dBm is not significant\n",
-			  ms_power_lvl, ms_dbm, diff, bts->ul_power_target);
+			  "from 'rx-target' %d dBm is not significant (delta is %d dBm)\n",
+			  ms_power_lvl, ms_dbm, diff, bts->ul_power_target, bts->ul_power_delta);
 		lchan->ms_power_ctrl.current = ms_power_lvl;
 		return 0;
 	}
diff --git a/src/common/vty.c b/src/common/vty.c
index 16ffe72..4d2c037 100644
--- a/src/common/vty.c
+++ b/src/common/vty.c
@@ -255,7 +255,10 @@
 		VTY_NEWLINE);
 	vty_out(vty, " paging lifetime %u%s", paging_get_lifetime(bts->paging_state),
 		VTY_NEWLINE);
-	vty_out(vty, " uplink-power-target %d%s", bts->ul_power_target, VTY_NEWLINE);
+	vty_out(vty, " uplink-power-target %d", bts->ul_power_target);
+	if (bts->ul_power_delta > 0)
+		vty_out(vty, " delta %d", bts->ul_power_delta);
+	vty_out(vty, "%s", VTY_NEWLINE);
 
 	/* MS Tx power filtering algorithm and parameters */
 	switch (bts->ul_power_ctrl.pf_algo) {
@@ -615,15 +618,37 @@
 	return CMD_SUCCESS;
 }
 
+#define UL_POWER_TARGET_CMD \
+	"uplink-power-target <-110-0>"
+#define UL_POWER_TARGET_CMD_DESC \
+	"Set the nominal target Rx Level for uplink power control loop\n" \
+	"Target uplink Rx level in dBm\n"
+
 DEFUN_ATTR(cfg_bts_ul_power_target, cfg_bts_ul_power_target_cmd,
-	   "uplink-power-target <-110-0>",
-	   "Set the nominal target Rx Level for uplink power control loop\n"
-	   "Target uplink Rx level in dBm\n",
+	   UL_POWER_TARGET_CMD, UL_POWER_TARGET_CMD_DESC,
 	   CMD_ATTR_IMMEDIATE)
 {
 	struct gsm_bts *bts = vty->index;
 
 	bts->ul_power_target = atoi(argv[0]);
+	bts->ul_power_delta  = 0;
+
+	return CMD_SUCCESS;
+}
+
+/* FIXME: libosmovty is unable to handle 'uplink-power-target <-110-0> [delta <1-25>]' */
+DEFUN_ATTR(cfg_bts_ul_power_target_delta,
+	   cfg_bts_ul_power_target_delta_cmd,
+	   UL_POWER_TARGET_CMD " delta <1-25>",
+	   UL_POWER_TARGET_CMD_DESC
+	   "Tolerable deviation from the target Rx Level\n"
+	   "Delta value in dBm\n",
+	   CMD_ATTR_IMMEDIATE)
+{
+	struct gsm_bts *bts = vty->index;
+
+	bts->ul_power_target = atoi(argv[0]);
+	bts->ul_power_delta  = atoi(argv[1]);
 
 	return CMD_SUCCESS;
 }
@@ -1849,6 +1874,7 @@
 	install_element(BTS_NODE, &cfg_bts_agch_queue_mgmt_default_cmd);
 	install_element(BTS_NODE, &cfg_bts_agch_queue_mgmt_params_cmd);
 	install_element(BTS_NODE, &cfg_bts_ul_power_target_cmd);
+	install_element(BTS_NODE, &cfg_bts_ul_power_target_delta_cmd);
 	install_element(BTS_NODE, &cfg_bts_no_ul_power_filter_cmd);
 	install_element(BTS_NODE, &cfg_bts_ul_power_filter_ewma_cmd);
 	install_element(BTS_NODE, &cfg_bts_min_qual_rach_cmd);
diff --git a/tests/power/power_test.c b/tests/power/power_test.c
index bf474ac..4daeec3 100644
--- a/tests/power/power_test.c
+++ b/tests/power/power_test.c
@@ -1,5 +1,6 @@
 /*
  * (C) 2013,2014 by Holger Hans Peter Freyther
+ * Contributions by sysmocom - s.m.f.c. GmbH <info at sysmocom.de>
  *
  * All Rights Reserved
  *
@@ -205,6 +206,32 @@
 	CHECK_UL_RSSI_AVG100(-92.0);
 }
 
+static void test_power_delta(void)
+{
+	struct gsm_lchan *lchan;
+
+	init_test(__func__);
+	lchan = &g_trx->ts[0].lchan[0];
+
+	/* Tolerate power deviations in range -80 .. -70 */
+	g_bts->ul_power_delta = 5;
+
+	lchan->ms_power_ctrl.current = ms_pwr_ctl_lvl(GSM_BAND_1800, 0);
+	OSMO_ASSERT(lchan->ms_power_ctrl.current == 15);
+	lchan->ms_power_ctrl.max = ms_pwr_ctl_lvl(GSM_BAND_1800, 26);
+	OSMO_ASSERT(lchan->ms_power_ctrl.max == 2);
+
+	apply_power_test(lchan, g_bts->ul_power_target, 0, 15);
+	apply_power_test(lchan, g_bts->ul_power_target + 3, 0, 15);
+	apply_power_test(lchan, g_bts->ul_power_target - 3, 0, 15);
+
+	apply_power_test(lchan, g_bts->ul_power_target, 0, 15);
+	apply_power_test(lchan, g_bts->ul_power_target + 5, 0, 15);
+	apply_power_test(lchan, g_bts->ul_power_target - 5, 0, 15);
+
+	apply_power_test(lchan, g_bts->ul_power_target - 10, 1, 13);
+}
+
 int main(int argc, char **argv)
 {
 	printf("Testing power loop...\n");
@@ -220,6 +247,7 @@
 
 	test_power_loop();
 	test_pf_algo_ewma();
+	test_power_delta();
 
 	printf("Power loop test OK\n");
 
diff --git a/tests/power/power_test.err b/tests/power/power_test.err
index 8368f57..3270c47 100644
--- a/tests/power/power_test.err
+++ b/tests/power/power_test.err
@@ -11,7 +11,7 @@
 (bts=0,trx=0,ts=0,ss=0) Diff between 'rx-target' -75 dBm and 'rx-current' -90 dBm is 15 dBm
 (bts=0,trx=0,ts=0,ss=0) Raising MS power from control level 7 (16 dBm) to 5, 20 dBm (rx-ms-pwr-lvl 7, max-ms-pwr-lvl 2, rx-current -90 dBm, rx-target -75 dBm)
 (bts=0,trx=0,ts=0,ss=0) Diff between 'rx-target' -75 dBm and 'rx-current' -75 dBm is 0 dBm
-(bts=0,trx=0,ts=0,ss=0) Keeping MS power at control level 5 (20 dBm) because diff 0 dBm from 'rx-current' -75 dBm is not significant
+(bts=0,trx=0,ts=0,ss=0) Keeping MS power at control level 5 (20 dBm) because diff 0 dBm from 'rx-target' -75 dBm is not significant (delta is 0 dBm)
 (bts=0,trx=0,ts=0,ss=0) Diff between 'rx-target' -75 dBm and 'rx-current' -90 dBm is 15 dBm
 (bts=0,trx=0,ts=0,ss=0) Raising MS power from control level 5 (20 dBm) to 3, 24 dBm (rx-ms-pwr-lvl 5, max-ms-pwr-lvl 2, rx-current -90 dBm, rx-target -75 dBm)
 (bts=0,trx=0,ts=0,ss=0) Diff between 'rx-target' -75 dBm and 'rx-current' -90 dBm is 15 dBm
@@ -29,7 +29,7 @@
 (bts=0,trx=0,ts=0,ss=0) Diff between 'rx-target' -75 dBm and 'rx-current' -90 dBm is 15 dBm
 (bts=0,trx=0,ts=0,ss=0) Keeping MS power at control level 29, 36 dBm (rx-ms-pwr-lvl 29, max-ms-pwr-lvl 29, rx-current -90 dBm, rx-target -75 dBm)
 (bts=0,trx=0,ts=0,ss=0) Diff between 'rx-target' -75 dBm and 'rx-current' -75 dBm is 0 dBm
-(bts=0,trx=0,ts=0,ss=0) Keeping MS power at control level 29 (36 dBm) because diff 0 dBm from 'rx-current' -75 dBm is not significant
+(bts=0,trx=0,ts=0,ss=0) Keeping MS power at control level 29 (36 dBm) because diff 0 dBm from 'rx-target' -75 dBm is not significant (delta is 0 dBm)
 (bts=0,trx=0,ts=0,ss=0) Diff between 'rx-target' -75 dBm and 'rx-current' -45 dBm is -30 dBm
 (bts=0,trx=0,ts=0,ss=0) Lowering MS power from control level 29 (36 dBm) to 1, 28 dBm (rx-ms-pwr-lvl 29, max-ms-pwr-lvl 29, rx-current -45 dBm, rx-target -75 dBm)
 (bts=0,trx=0,ts=0,ss=0) Diff between 'rx-target' -75 dBm and 'rx-current' -45 dBm is -30 dBm
@@ -45,7 +45,7 @@
 (bts=0,trx=0,ts=0,ss=0) Diff between 'rx-target' -75 dBm and 'rx-current' -40 dBm is -35 dBm
 (bts=0,trx=0,ts=0,ss=0) Lowering MS power from control level 14 (2 dBm) to 15, 0 dBm (rx-ms-pwr-lvl 14, max-ms-pwr-lvl 0, rx-current -40 dBm, rx-target -75 dBm)
 (bts=0,trx=0,ts=0,ss=0) Diff between 'rx-target' -75 dBm and 'rx-current' -75 dBm is 0 dBm
-(bts=0,trx=0,ts=0,ss=0) Keeping MS power at control level 15 (0 dBm) because diff 0 dBm from 'rx-current' -75 dBm is not significant
+(bts=0,trx=0,ts=0,ss=0) Keeping MS power at control level 15 (0 dBm) because diff 0 dBm from 'rx-target' -75 dBm is not significant (delta is 0 dBm)
 (bts=0,trx=0,ts=0,ss=0) Diff between 'rx-target' -75 dBm and 'rx-current' -78 dBm is 3 dBm
 (bts=0,trx=0,ts=0,ss=0) Raising MS power from control level 15 (0 dBm) to 13, 3 dBm (rx-ms-pwr-lvl 15, max-ms-pwr-lvl 2, rx-current -78 dBm, rx-target -75 dBm)
 (bts=0,trx=0,ts=0,ss=0) Diff between 'rx-target' -75 dBm and 'rx-current' -80 dBm is 5 dBm
@@ -58,3 +58,17 @@
 (bts=0,trx=0,ts=0,ss=0) Keeping MS power at control level 15, 0 dBm (rx-ms-pwr-lvl 15, max-ms-pwr-lvl 2, rx-current -50 dBm, rx-target -75 dBm)
 (bts=0,trx=0,ts=0,ss=0) Diff between 'rx-target' -75 dBm and 'rx-current' -92 dBm is 17 dBm
 (bts=0,trx=0,ts=0,ss=0) Raising MS power from control level 15 (0 dBm) to 13, 4 dBm (rx-ms-pwr-lvl 15, max-ms-pwr-lvl 2, rx-current -92 dBm, rx-target -75 dBm)
+(bts=0,trx=0,ts=0,ss=0) Diff between 'rx-target' -75 dBm and 'rx-current' -75 dBm is 0 dBm
+(bts=0,trx=0,ts=0,ss=0) Keeping MS power at control level 15 (0 dBm) because diff 0 dBm from 'rx-target' -75 dBm is not significant (delta is 5 dBm)
+(bts=0,trx=0,ts=0,ss=0) Diff between 'rx-target' -75 dBm and 'rx-current' -72 dBm is -3 dBm
+(bts=0,trx=0,ts=0,ss=0) Keeping MS power at control level 15 (0 dBm) because diff -3 dBm from 'rx-target' -75 dBm is not significant (delta is 5 dBm)
+(bts=0,trx=0,ts=0,ss=0) Diff between 'rx-target' -75 dBm and 'rx-current' -78 dBm is 3 dBm
+(bts=0,trx=0,ts=0,ss=0) Keeping MS power at control level 15 (0 dBm) because diff 3 dBm from 'rx-target' -75 dBm is not significant (delta is 5 dBm)
+(bts=0,trx=0,ts=0,ss=0) Diff between 'rx-target' -75 dBm and 'rx-current' -75 dBm is 0 dBm
+(bts=0,trx=0,ts=0,ss=0) Keeping MS power at control level 15 (0 dBm) because diff 0 dBm from 'rx-target' -75 dBm is not significant (delta is 5 dBm)
+(bts=0,trx=0,ts=0,ss=0) Diff between 'rx-target' -75 dBm and 'rx-current' -70 dBm is -5 dBm
+(bts=0,trx=0,ts=0,ss=0) Keeping MS power at control level 15 (0 dBm) because diff -5 dBm from 'rx-target' -75 dBm is not significant (delta is 5 dBm)
+(bts=0,trx=0,ts=0,ss=0) Diff between 'rx-target' -75 dBm and 'rx-current' -80 dBm is 5 dBm
+(bts=0,trx=0,ts=0,ss=0) Keeping MS power at control level 15 (0 dBm) because diff 5 dBm from 'rx-target' -75 dBm is not significant (delta is 5 dBm)
+(bts=0,trx=0,ts=0,ss=0) Diff between 'rx-target' -75 dBm and 'rx-current' -85 dBm is 10 dBm
+(bts=0,trx=0,ts=0,ss=0) Raising MS power from control level 15 (0 dBm) to 13, 4 dBm (rx-ms-pwr-lvl 15, max-ms-pwr-lvl 2, rx-current -85 dBm, rx-target -75 dBm)
diff --git a/tests/power/power_test.ok b/tests/power/power_test.ok
index 25551d8..a766c3b 100644
--- a/tests/power/power_test.ok
+++ b/tests/power/power_test.ok
@@ -72,4 +72,20 @@
 lchan_ms_pwr_ctrl(RxLvl=-110 dBm) returns 1 (expected 1)
 	MS current power 15 -> 13 (expected 13)
 	Avg[t] is -92.00 dBm (expected -92.00 dBm)
+
+Starting test case 'test_power_delta'
+lchan_ms_pwr_ctrl(RxLvl=-75 dBm) returns 0 (expected 0)
+	MS current power 15 -> 15 (expected 15)
+lchan_ms_pwr_ctrl(RxLvl=-72 dBm) returns 0 (expected 0)
+	MS current power 15 -> 15 (expected 15)
+lchan_ms_pwr_ctrl(RxLvl=-78 dBm) returns 0 (expected 0)
+	MS current power 15 -> 15 (expected 15)
+lchan_ms_pwr_ctrl(RxLvl=-75 dBm) returns 0 (expected 0)
+	MS current power 15 -> 15 (expected 15)
+lchan_ms_pwr_ctrl(RxLvl=-70 dBm) returns 0 (expected 0)
+	MS current power 15 -> 15 (expected 15)
+lchan_ms_pwr_ctrl(RxLvl=-80 dBm) returns 0 (expected 0)
+	MS current power 15 -> 15 (expected 15)
+lchan_ms_pwr_ctrl(RxLvl=-85 dBm) returns 1 (expected 1)
+	MS current power 15 -> 13 (expected 13)
 Power loop test OK

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Gerrit-Project: osmo-bts
Gerrit-Branch: master
Gerrit-Change-Id: Iacedbd4d69d3d74e2499af5622a07a8af0423da0
Gerrit-Change-Number: 20730
Gerrit-PatchSet: 1
Gerrit-Owner: fixeria <vyanitskiy at sysmocom.de>
Gerrit-MessageType: newchange
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