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Re: [Discuss-gnuradio] IEEE 802.15.4 on USRP N210
From: |
Marius |
Subject: |
Re: [Discuss-gnuradio] IEEE 802.15.4 on USRP N210 |
Date: |
Wed, 27 Jul 2011 22:27:29 +0200 |
Hi Sebastian!
I don't really understand what you're trying to archive, but here's a
stack for 802.15.4:
http://wiesel.ece.utah.edu/redmine/projects/gr-ieee802-15-4/wiki
> 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
Works fine here. The XCVR is a much better choice than the RFX,
because it has TX gain.
> 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.
How did you change the frequencies? If you change the center-frequency
on a FFT your USRP2 <-> PC communication breaks down? What is the
decimation?
> Problem 2: Packets send from a sensor node are not received.
Do you send a full 802.15.4 MAC sublayer? The stack you mentioned uses
a Packet Sink that drops packets on certain conditions. I changed that
recently for my efforts.
> I have the feeling
> that
> the node signal is only processed occasionally.
In that case try attaching the GDB and log (verbose define statement
at the C code). Actually if GNU Radio drops vectors it outputs an "S"
indicating an overflow.
> I played a bit around with sample rates.
To demodulate you need at least 2 * the frequency of the channel. So
in case of 802.15.4 something like 5 MS/s should be sufficient.
> I hope someone might have an idea or a tip what else I could check out.
I actually finished a project on 802.15.4 and used USRP2s with the
WIESEL stack to analyze a real-time sensor network. I'll commit some
stuff quite soon (this week). E. g. a complete demod and mod path in
GRC. Most stuff is in German though. :)
Best,
Marius