Change in osmo-bts[master]: l1sap: Correctly count RACH slots in calc_exprd_rach_frames()

Harald Welte gerrit-no-reply at lists.osmocom.org
Sun May 26 09:09:21 UTC 2019


Harald Welte has submitted this change and it was merged. ( https://gerrit.osmocom.org/14159 )

Change subject: l1sap: Correctly count RACH slots in calc_exprd_rach_frames()
......................................................................

l1sap: Correctly count RACH slots in calc_exprd_rach_frames()

We used a bogus multiplication factor of four when computing the number
of expired RACH slots.  While there are four RACH slots per block (i.e.
4 times more RACH received than normal MAC blocks), that multiplier
doesn't apply here:  We are calling this function per *frame* and not
per *block*.  So the maximum number of RACH slots per *frame* is (in
most suual cases with a single CCCH) at maximum 1. Only some obscure
configurations with multiple CCCHs in a single cell would render higher
values.  In any case, *blocks* never even enter this equation.

This wrong multiplier resulted in rather weird RACH load reports to the
BSC.

Related: OS#3750
Change-Id: I6b14fd6e7819f9164fb4a09b432a9f419e3b6e5c
---
M src/common/l1sap.c
1 file changed, 1 insertion(+), 4 deletions(-)

Approvals:
  Jenkins Builder: Verified
  Vadim Yanitskiy: Looks good to me, but someone else must approve
  Harald Welte: Looks good to me, approved



diff --git a/src/common/l1sap.c b/src/common/l1sap.c
index f31d822..d9ffdb8 100644
--- a/src/common/l1sap.c
+++ b/src/common/l1sap.c
@@ -484,10 +484,7 @@
 			rach_frames_expired = 1;
 	}
 
-	/* Each Frame has room for 4 RACH slots, since RACH
-	 * slots are short enough to fit into a single radio
-	 * burst, so we need to multiply the final result by 4 */
-	return rach_frames_expired * 4;
+	return rach_frames_expired;
 }
 
 /* time information received from bts model */

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Gerrit-Project: osmo-bts
Gerrit-Branch: master
Gerrit-MessageType: merged
Gerrit-Change-Id: I6b14fd6e7819f9164fb4a09b432a9f419e3b6e5c
Gerrit-Change-Number: 14159
Gerrit-PatchSet: 2
Gerrit-Owner: Harald Welte <laforge at gnumonks.org>
Gerrit-Reviewer: Harald Welte <laforge at gnumonks.org>
Gerrit-Reviewer: Jenkins Builder (1000002)
Gerrit-Reviewer: Vadim Yanitskiy <axilirator at gmail.com>
Gerrit-CC: Pau Espin Pedrol <pespin at sysmocom.de>
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