Re: [Discuss-gnuradio] IEEE 802.15.4 on USRP N210

[Markus Becker]

> Hello everyone,
> 
> I am very fresh in the field of SDRs and encounter some problems in
> the implementation. But some basic information first.
> 
> I am trying to communicate between gnuradio (USRP) and 802.15.4 sensor
> nodes, as it has been done before (see Thomas Schmid @ UCLA). Because
> the hardware has evolved since then, I am using USRP N210s as the
> interface to the computer. The N210s are equipped with XCVR2450
> daugtherboards. I am using basically the ucla_zigbee_phy
> implementation and found an existing adaptation to the UHD driver
> online (Master Thesis by Kresimir Dabcevic).

Based on that 802.15.4 code, which we ported to the USRP2 (before UHD, 
though), we implemented a system which runs TinyOS based on the SDR.

Some information can be found in 
http://www.google.com/url?sa=t&source=web&cd=1&ved=0CBQQFjAA&url=http%3A%2F%2Fwww.sfb637.uni-
bremen.de%2Fpubdb%2Frepository%2FSFB637-T4-10-003-IC.pdf&ei=4CcxTpSKFceG-
wai-4yNDQ&usg=AFQjCNERfc8DNbtjLhJDg7I3P1SMS5ZdcA&sig2=5O_BjZgR6lbD5F6AjP7kdA

and

http://www.google.com/url?sa=t&source=web&cd=4&ved=0CCQQFjAD&url=http%3A%2F%2Fmail.millennium.berkeley.edu%2Fpipermail%2Ftinyos-
devel%2F2009-May%2F003851.html&ei=4CcxTpSKFceG-
wai-4yNDQ&usg=AFQjCNE0nUyB6KBcAJK1-UXrpZyLZu5fVQ&sig2=1guCm0r6UCCtCn1VYCxTBA

With that, we could make a 'simulated'/'emulated' TinyOS on USRP2 talk to 
TelosB nodes.

The code hasn't been updated to recent GNUradio, though.

Markus

> Now to the problem. After some minor changes in the test codes (see
> attachments), I can communicate between two N210s at 2.475 GHz.
> Problem 1: When changing the center frequency on both Tx and Rx,
> communication does not work any longer. Even a 5 MHz shift does the
> deal.
> Problem 2: Packets send from a sensor node are not received. The
> packets are sent from TinyOS. At the N210 receiver I check whether I
> find a SFD in the stream, but this does not happen (sending 1/sec).
> When increasing the transmission rate to 1/10msec, I occasionally
> detect a SFD. I have tried both with CC2420 and RF230 transceivers
> communicating at channel 25 (2.475 GHz).
> 
> I checked the received spectrum for both USRP tx and node tx with a
> simple FFT application. The result is attached as well. For this test
> I let the transmitter send every 10msec. Also here I have the feeling
> that
> the node signal is only processed occasionally.
> 
> I played a bit around with sample rates. When increasing the sample
> rate (before 1M) to 10M I seem to find the SFD more often, though it
> is hard to tell, as the SFD then is also found relatively often in the
> noise. I tried to filter the noise with the power squelch in the code,
> but the threshold has to be very low to get something from the node,
> which in itself is quite weird.
> 
> I hope someone might have an idea or a tip what else I could check out.
> 
> Thanks in advance, Sebastian
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| Dipl.-Ing. Markus Becker
| Communication Networks
| TZI - Center for Computing Technologies
| University Bremen
| Germany
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| web: http://www.comnets.uni-bremen.de/~mab/
| mailto: address@hidden
| telephone: +49 421 218 62379
| building: NW1 room: N2260
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