Change in osmocom-bb[master]: trxcon/scheduler: FACCH: ensure fake measurements for BFI

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laforge gerrit-no-reply at lists.osmocom.org
Sun Mar 8 22:50:55 UTC 2020


laforge has submitted this change. ( https://gerrit.osmocom.org/c/osmocom-bb/+/17348 )

Change subject: trxcon/scheduler: FACCH: ensure fake measurements for BFI
......................................................................

trxcon/scheduler: FACCH: ensure fake measurements for BFI

According to 3GPP TS 45.003, clauses 4.2.5 and 4.3.5:

 - one FACCH/F frame steals a single speech frame,
 - one FACCH/H frame steals two speech frames.

A BFI (Bad Frame Indication) needs to be sent for each stolen
speech frame. This does not apply to CSD (data) channels though.

The BFI frames must have measurement data attached to them, and
due to their virtual nature (they do not actually come from the
air interface), the measurements must be crafted by trxcon.

Assigning a negative value to n_errors makes the code below the
'bfi' label craft fake measurement data. Otherwise, the actual
measurements belonging to the FACCH frame will be used.

Change-Id: Ia2f7c3cf7b1ef3737da6b1818cae2f001ee8768f
---
M src/host/trxcon/sched_lchan_tchf.c
M src/host/trxcon/sched_lchan_tchh.c
2 files changed, 4 insertions(+), 2 deletions(-)

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



diff --git a/src/host/trxcon/sched_lchan_tchf.c b/src/host/trxcon/sched_lchan_tchf.c
index d2cf030..788d153 100644
--- a/src/host/trxcon/sched_lchan_tchf.c
+++ b/src/host/trxcon/sched_lchan_tchf.c
@@ -136,7 +136,8 @@
 		sched_send_dt_ind(trx, ts, lchan, l2, GSM_MACBLOCK_LEN,
 			n_errors, false, false);
 
-		/* Send BFI instead of stolen TCH frame */
+		/* Send BFI substituting a stolen TCH frame */
+		n_errors = -1; /* ensure fake measurements */
 		goto bfi;
 	} else {
 		/* A good TCH frame received */
diff --git a/src/host/trxcon/sched_lchan_tchh.c b/src/host/trxcon/sched_lchan_tchh.c
index 599dd20..013dba9 100644
--- a/src/host/trxcon/sched_lchan_tchh.c
+++ b/src/host/trxcon/sched_lchan_tchh.c
@@ -315,7 +315,8 @@
 		sched_send_dt_ind(trx, ts, lchan, l2, GSM_MACBLOCK_LEN,
 			n_errors, false, false);
 
-		/* 1/2 BFI */
+		/* Send BFI substituting 1/2 stolen TCH frames */
+		n_errors = -1; /* ensure fake measurements */
 		goto bfi;
 	} else {
 		/* A good TCH frame received */

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Gerrit-Project: osmocom-bb
Gerrit-Branch: master
Gerrit-Change-Id: Ia2f7c3cf7b1ef3737da6b1818cae2f001ee8768f
Gerrit-Change-Number: 17348
Gerrit-PatchSet: 3
Gerrit-Owner: fixeria <axilirator at gmail.com>
Gerrit-Reviewer: Jenkins Builder
Gerrit-Reviewer: fixeria <axilirator at gmail.com>
Gerrit-Reviewer: laforge <laforge at osmocom.org>
Gerrit-MessageType: merged
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