[Tinyos-help] 802.15.4

Jan Hauer hauer at tkn.tu-berlin.de
Mon Nov 22 06:43:53 PST 2010

I've checked in a fix that makes the time-stamping more reliable (but
also more "conservative" -> in case there are problems the entire
queue is flushed). Please update from svn
(http://code.google.com/p/tinyos-main/source/checkout) and retry.


On Thu, Nov 18, 2010 at 10:46 AM, Jan Hauer <hauer at tkn.tu-berlin.de> wrote:
> yes - I can reproduce the problem and also believe that it is due to
> wrong (beacon) timestamps. will look into it and try to fix it asap.
> thanks,
> jan
> On Thu, Nov 18, 2010 at 10:02 AM, Aitor Hernandez <aitorhh at kth.se> wrote:
>> Hi guys,
>> I've seen this problem with TKN15.4. It is possible to synchronize N nodes
>> with TKN15.4 the problem is that they need to start the app at the same
>> time. From my experience I've realized that the problem comes from the
>> cc2420_tkn154 (maybe it happens with the default cc2420 implementation as
>> well).
>> If we have a network with N nodes running and transmitting data between
>> them, when we try to add another node we could have this problem. As far as
>> we have the radio enabled for reception for a long period (Scan period), the
>> cc2420 receives the beacons but data packets as well. Once it detects that
>> the received packet is a beacon, it sets the timestamp, but sometimes the
>> timestamp is wrong, due to the data packets, and then we lost the next
>> beacons.
>> Possible solutions:
>> Check the CC2420ReceiveP.nc and the m_timestamp_queue. I guess that the
>> problem should be there. I did some modifications on
>> the CC2420ReceiveP.nc to solve this problem, but I haven't test it properly.
>> If we lost the synchronization, scan again with MLME_SCAN.request(). It is a
>> "fake" solution, because the problem is still there, but for some app it
>> will work.
>> Start the nodes at the same time. It is not possible in a real deployment.
>> --
>> Aitor Hernandez
>> KTH | Automatic Control
>> Research engineer
>> Stockholm
>> Phone:  +46 (0)704 26 87 99
>> _______________________________________________
>> Tinyos-help mailing list
>> Tinyos-help at millennium.berkeley.edu
>> https://www.millennium.berkeley.edu/cgi-bin/mailman/listinfo/tinyos-help

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