[Discuss-gnuradio] Reconfigurable OFDM using the USRP - it's possible, here's a video

[Keith Nolan]

Hi all,

I know that there will be another burst of OFDM development work in the
coming weeks so just wanted to add some input that might be of interest to
all. 

We [Centre for Telecommunications Value-Chain Research] are using USRPs for
our dynamic spectrum access and cognitive radio work. We're not using GNU
Radio, just the USRP and our own software. I've posted a video on
http://www.youtube.com/emergingnetworks showing the USRP in action with
reconfigurable OFDM operating at 2.35GHz. We have successfully demonstrated
a live OFDM txrx link between two USRPs so it is definitely possible over a
6-10 feet range even with only 50mW peak tx power (in fact, we have achieved
this with a lot less power). 

We are doing a lot of collaborative work with Tom Rondeau in VT. As part of
this, one of the demonstrations involves making a gap in the middle of the
OFDM spectrum for a narrowband signal (the dbpsk signal from the
benchmark_tx.py script for example). The idea is to demonstrate that
coexistence between multiple users on the same spectrum segment is possible.
The video shows how OFDM can be 'sculpted' to achieve this. I have a much
better resolution video of this if anyone wants to take a closer look as
youtube has compressed it a lot, please let me know if you want it.

This is a 1MHz total bandwidth OFDM signal using a 256 bin IFFT; the number
of carriers is varied from 255 right down to zero and back again in various
spectral configurations. I had a screen capture program running on the
laptop also, so anything greater was resulting in underruns (we've
demonstrated up to 4MHz bandwidth but don't have the processing horsepower
to do much with it)

On that webpage, there's also a very quick tour of what Tom and CTVR were
demonstrating during the recent IEEE DySPAN conference in Dublin. The
cameraman for that clip was sacked shortly afterwards but there is a proper
video of all the demos in production.

Videos: http://www.youtube.com/emergingnetworks

Emerging networks webpage with more information:
http://www.emergingnetworks.info

Best wishes,
Keith

-------------
Keith Nolan Ph.D.
Emerging Network Architectures
Centre for Telecommunications Value-Chain Research (CTVR)
Rm. 1.17, Lloyd Building
University of Dublin,Trinity College 
Dublin 2
Rep. of Ireland.
e: address@hidden
p: (+353) 1-896-8443
w: http://www.emergingnetworks.info
skype: cognitive_radio