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: [EMAIL PROTECTED] p: (+353) 1-896-8443 w: http://www.emergingnetworks.info skype: cognitive_radio _______________________________________________ Discuss-gnuradio mailing list [email protected] http://lists.gnu.org/mailman/listinfo/discuss-gnuradio
