Re: [Discuss-gnuradio] OFMD TX and RX

2010-06-21 Thread Mike Jameson
Hi Rahman, Just like you, my USRPs have suddenly started failing the CRC for every packet. By changing the frequency to 1MHZ I'm back to 99% correctly received :) From searching the mailing list it looks like it's related to the increased frequency offset due to aliasing at the higher frequencies

Re: [Discuss-gnuradio] OFMD TX and RX

2010-06-19 Thread Rahman Doost
Thanks Mike for the comment. I did change the bandwidth, but some error poped up at runtime for 1.5. Lower values like 0.1 or 0.2 did not change the behavior of the receiver. Still no correct packet. I receive the packets though but they fail the CRC check I guess, since I get this "ok:false" statu

Re: [Discuss-gnuradio] OFMD TX and RX

2010-06-17 Thread Mike Jameson
missed off the filename: ofdm_receiver.py :) On 17 June 2010 10:27, Mike Jameson wrote: > Hi Rahman, > > Try broadening the bandwidth of the receiver to allow for the frequency > offset between your USRP2s: > > In /usr/lib/python2.6/dist-packages/gnuradio/blks2impl > > on line 67 look for "tb

Re: [Discuss-gnuradio] OFMD TX and RX

2010-06-17 Thread Mike Jameson
Hi Rahman, Try broadening the bandwidth of the receiver to allow for the frequency offset between your USRP2s: In /usr/lib/python2.6/dist-packages/gnuradio/blks2impl on line 67 look for "tb = bw*0.08" change this to a higher value such as "tb = bw*1.5" This works for me using usrps. Mike On

Re: [Discuss-gnuradio] OFMD TX and RX

2010-06-16 Thread Rahman Doost
Guys, I'm working on the same thing, I'm trying to receive something with OFDM example, USRP2 and XCVR boards. But it doesn't work. The transmitter is sending and the rx signal is crystal clear with spectrum analyzer but no packet is caught. Could anyone of you send me the command you're using at

Re: [Discuss-gnuradio] OFMD TX and RX

2010-06-15 Thread Mike Jameson
Hi Chris, The default settings do drop alot of packets as you are seeing. These are some of the things I've adjusted which happen to have brought my packet reception rate up to 99% using 1 USRP with a Basic RX and TX joined with a 10db attenuator: - For benchmark_tx.py and benchmark_rx.py add '-

Re: [Discuss-gnuradio] OFMD TX and RX

2010-06-15 Thread Chris_Spain
Thank you Fisheep, you confirmed what I was thinking but, I don't Know why, the packets are been received with no errors, I lost packets but the packets that I receive are good. I don't Know how GNU Radio implementation maps 1024 bytes over 200 carriers with a bpsk modulation, and then the transm

Re: [Discuss-gnuradio] OFMD TX and RX

2010-06-15 Thread Fisheep
Hi, I'm not sure why you can't receive all the packet correctly, but I can briefly tell you how ofdm implement in GNU Radio. First, fft_length=512 means it will take 512 subcarriers to do ifft/fft, and occupied_tones=200 means it only take 200 subcarriers to put your modulation symbol. Besides,

[Discuss-gnuradio] OFMD TX and RX

2010-06-13 Thread Chris_Spain
Hello everybody, I' am trying to test and understand the OFDM Modulation implemented in GNU Radio. I'm using the deafult values, fft_lenth=512, occupied_tones =200, cp_length= 128 and bpsk modulation, besides, I'm using a RFX900 Daughterboards on USPR and I'm connecting the TX and RX with a coax