RE: [Discuss-gnuradio] OFDM modulation/demodulation over USRP2

[Patrik Eliardsson]

Hi,

I've tried the OFDM example on the USRP2 with minor changes and I didn't 
encounter any problems. Be sure that you have the same FFT-length, number of 
occupied tones, interpolation/decimation on both the receiver and transmitter. 
Have you tried to increase the distance between the transmitter and the 
receiver? Depending on your surrounding environment you may have to tweak the 
length of the CP. 

I have the same configuration as you, but I have the RFX2400 instead of the 
XCVR2450.

Regards,
Patrik Eliardsson

> -----Original Message-----
> From: 
> address@hidden 
> [mailto:address@hidden
> org] On Behalf Of Veljko Pejovic
> Sent: Wednesday, January 13, 2010 10:22 PM
> To: address@hidden
> Subject: [Discuss-gnuradio] OFDM modulation/demodulation over USRP2
> 
> Hi,
> 
> I'm using Ubuntu 9.10, gnuradio version 3.2.2 and two USRP2 
> boards with XCVR2450 daughter boards. The boards are about a 
> meter apart from each other.
> 
> I'm trying to get OFDM working over USRP2 boards and for that 
> I'm using GRC. I created a simple local loop (without USRPs):
> signal_source->modulation->channel_model->demodulation->scope_
> sink. In this case OFDM modulation/demodulation works fine. 
> However, when I split the loop into a sender 
> signal_source->modulation->usrp2_sink and a receiver: 
> usrp2_src->demodulation->scope_sink the decoding does not 
> work, i.e. I don't get any output on the scope_sink. 
> Although, FFT of the usrp2_src output looks exactly like what 
> OFDM should look like.
> I'm pretty sure that the error is connected to OFDM as I got 
> this transmitter/receiver pair working with GMSK, for example.
> 
> I also tried the examples in
> gnuradio-3.2.2/gnuradio-examples/python/ofdm which I had to 
> tweak a bit in order to get them using USRP2, but I got the 
> same results:
> there is an OFDM-like signal in the air, but it's not getting decoded.
> 
> Did anyone got OFDM demodulation working on USRP2? If so, any 
> hints are highly appreciated.
> 
> Thanks,
> 
> 
> Veljko
> 
> 
> _______________________________________________
> Discuss-gnuradio mailing list
> address@hidden
> http://lists.gnu.org/mailman/listinfo/discuss-gnuradio
>