PCU scheduling and PACCH timeout question

Max msuraev at sysmocom.de
Fri Feb 26 17:07:07 UTC 2016


I'm not sure what to make of this timing difference. I'm using sysmoBTS 
hw to test different osmoPCU versions (including ssharan/egprs) and I 
can see pacch timeouts on all of those I've tried. For some phones it 
really breaks connectivity, others seems to be able to ignore it 
somehow. I do not see a pattern yet.

Do you have some test setup where you try it and see if it's the same 
for you?

On 02/26/2016 04:13 PM, Saurabh Sharan wrote:
> 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
>
>  1. Packet 7174 , FN 1137361 in DL @ 15:33:22.511809393
>  2. Packet 7190,  FN 1137361 in UL @ 15:33:22.559427972
>  3. 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
>
>  4. Packet 7174 , FN 1137361 in DL @ 15:33:22.511809393 for TS 2
>  5. 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.
> Regards
> Saurabh
> -----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
> Hello.
> 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/ 
> =======================================================================
> * sysmocom - systems for mobile communications GmbH
> * Alt-Moabit 93
> * 10559 Berlin, Germany
> * Sitz / Registered office: Berlin, HRB 134158 B
> * Geschaeftsfuehrer / Managing Directors: Holger Freyther, Harald Welte

-- 
Max Suraev <msuraev at sysmocom.de> http://www.sysmocom.de/
=======================================================================
* sysmocom - systems for mobile communications GmbH
* Alt-Moabit 93
* 10559 Berlin, Germany
* Sitz / Registered office: Berlin, HRB 134158 B
* Geschaeftsfuehrer / Managing Directors: Holger Freyther, Harald Welte

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