[PATCH] osmo-pcu[master]: BTS: accept also relative frame numbers with rach requst

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dexter gerrit-no-reply at lists.osmocom.org
Mon Nov 7 12:15:15 UTC 2016


Review at  https://gerrit.osmocom.org/1205

BTS: accept also relative frame numbers with rach requst

The rach request contains a relative frame number (Fn % 42432),
while BTS::rcv_rach() accepts the full frame number only.

Since the BTS is always aware of the full frame number this is
not a problem. But for BSC co-located PCU schemes it is a problem
since the rach request only contains the relative frame number
as mentioned above.

The pcu continusly receives frame number updates with the GSM time
indication message. It is simple to re-calculate the full frame
number from that information.

This patch makes BTS::rcv_rach() compatible with relative frame
numbers, while not breaking the compatibility for full frame
numbers

Change-Id: Iaa182d8d29c6a0f5fa06064c2eb48b21b1ba2775
---
M src/bts.cpp
1 file changed, 7 insertions(+), 0 deletions(-)


  git pull ssh://gerrit.osmocom.org:29418/osmo-pcu refs/changes/05/1205/1

diff --git a/src/bts.cpp b/src/bts.cpp
index 4aa5c2c..8808537 100644
--- a/src/bts.cpp
+++ b/src/bts.cpp
@@ -484,6 +484,13 @@
 
 	rach_frame();
 
+	/* Santizize frame number */
+	Fn = Fn % 42432;
+
+	/* Restore the full frame number
+	 * (See also 3GPP TS 44.018, section 10.5.2.38) */
+	Fn = Fn + m_cur_fn - m_cur_fn % 42432;
+
 	LOGP(DRLCMAC, LOGL_DEBUG, "MS requests UL TBF on RACH, so we provide "
 		"one:\n");
 

-- 
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Gerrit-MessageType: newchange
Gerrit-Change-Id: Iaa182d8d29c6a0f5fa06064c2eb48b21b1ba2775
Gerrit-PatchSet: 1
Gerrit-Project: osmo-pcu
Gerrit-Branch: master
Gerrit-Owner: dexter <pmaier at sysmocom.de>



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