PCU scheduling and PACCH timeout question

Saurabh Sharan Saurabh.Sharan at radisys.com
Fri Feb 26 15:13:46 UTC 2016

Hello Max,
Though I have not analyzed the missing UL poll response, few of my observations from the pcap file attached is mentioned below
1.      There seems to be difference in FN UL versus DL being processed at any given time by the order of approx. 10 FNs, example given below
a.      Packet 7174 , FN 1137361 in DL @ 15:33:22.511809393
b.      Packet 7190,  FN 1137361 in UL @ 15:33:22.559427972
c.      From above example difference in time is 48milliseconds or approx.. 10FN duration
2.      For processing DL timeslots 2 to 6 at any given DL FN time taken seems to be approx. 3milliseconds, example given below
a.      Packet 7174 , FN 1137361 in DL @ 15:33:22.511809393 for TS 2
b.      Packet 7178, FN 1137361 in DL @ 15:33:22.514310379 for TS 6

Please let me know if these are known behavior in your integration environment ?
These time variations may have an impact on the poll response behavior from MS as well.


-----Original Message-----
From: Max [mailto:msuraev at sysmocom.de]
Sent: Thursday, February 25, 2016 3:58 PM
To: osmocom-net-gprs at lists.osmocom.org; Saurabh Sharan <Saurabh.Sharan at radisys.com>
Subject: PCU scheduling and PACCH timeout question


I'm trying to debug issue with current OsmoPCU master when some basebands ignore polling requests.

The debug output from RLCMAC layer and corresponding .pcap files are attached.
The issue appears somewhere after line 112 in debug.log The corresponding packet in pcu.pcapng is 6866

After receiving PACKET_CONTROL_ACK from phone we're trying to schedule polling at FN 1137123 (see packet 6869 in pcap) and than at FN 1137127 (packet 6874) which subsequently fails.
This seems suspiciously close but I have not found in the spec yet if this is legitimate thing to do.

There are several other occurrences like that in both log and pcap.

Have you experienced something like this? Do you have an idea why only some basebands are affected while others work fine?

Max Suraev <msuraev at sysmocom.de<mailto:msuraev at sysmocom.de>> http://www.sysmocom.de/ =======================================================================
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