Change in osmo-bts[master]: l1sap: acch_repetition fix hysthereis threshold table

[dexter]

dexter has uploaded this change for review. ( https://gerrit.osmocom.org/c/osmo-bts/+/22119 )


Change subject: l1sap: acch_repetition fix hysthereis threshold table
......................................................................

l1sap: acch_repetition fix hysthereis threshold table

The table in repeated_ul_sacch_active_decision() is derived from the
second table in GSM 05.08 8.2.4 but the first table would be correct.
Also the lower threshold is not properly choosen. A lower threshold,
that derives from upper threshold shifted by 2 makes sense (BER must
improved by 2 RXQUAL steps before repetition is turned off.)

Change-Id: I1d9b5c8abb79938cdecdafed84ed2e5d47e0bd3a
Related: SYS#5114
---
M src/common/l1sap.c
1 file changed, 8 insertions(+), 4 deletions(-)



  git pull ssh://gerrit.osmocom.org:29418/osmo-bts refs/changes/19/22119/1

diff --git a/src/common/l1sap.c b/src/common/l1sap.c
index 48773f1..2757d70 100644
--- a/src/common/l1sap.c
+++ b/src/common/l1sap.c
@@ -1414,12 +1414,16 @@
 		return;
 	}
 
-	/* convert from RXQUAL value to ber10k vale,
-	 * see also GSM 05.08, section 8.2.4 */
+	/* convert from RXQUAL value to ber10k value.
+	 * see also GSM 05.08, section 8.2.4 (first table, without frame */
 	static const uint16_t ber10k_by_rxqual_upper[] =
-	    { 0, 26, 51, 100, 190, 380, 760, 1500 };
+	    { 0, 20, 40, 80, 160, 320, 640, 1280 };
 	static const uint16_t ber10k_by_rxqual_lower[] =
-	    { 0, 10, 10, 30, 64, 130, 270, 540 };
+	    { 0, 0, 0, 20, 40, 80, 160, 320 };
+	/* Note: The values in the upper vector are taken from the left side
+	 * of the table in GSM 05.08, section 8.2.4. The lower vector is just
+	 * the upper vector shifted by 2. */
+
 	upper = ber10k_by_rxqual_upper[lchan->repeated_acch_capability.rxqual];
 	lower = ber10k_by_rxqual_lower[lchan->repeated_acch_capability.rxqual];
 

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Gerrit-Project: osmo-bts
Gerrit-Branch: master
Gerrit-Change-Id: I1d9b5c8abb79938cdecdafed84ed2e5d47e0bd3a
Gerrit-Change-Number: 22119
Gerrit-PatchSet: 1
Gerrit-Owner: dexter <pmaier at sysmocom.de>
Gerrit-MessageType: newchange
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