Hi Tom, Thanks for your suggestion. I will take your advice and try it out.
But recently I connect two USRP1 with the cable not through the antennas, hoping to remove the channel effect in this experiment. At the receiver, using the usrp_fft.py to observe the spectrum of received signal which is discontinuously transmitted from transmitter. The result shows that sometimes the spectrum doesn't get rise when transmitter send a packet.Is it possible that the transmitted packet doesn't transmit from USRP1? If possible, how do I examine this problem? Sorry, I'm not very expert in hardware implementation, but I will do my best to get familiar with USRP. Fisheep Tom Rondeau wrote: > > On Tue, Sep 14, 2010 at 12:52 AM, Fisheep <fisheep0...@gmail.com> wrote: >> >> Hi, >> >> My problem is that I try to discontinuously send "a" OFDM packet by using >> time.sleep() on USRP1, but fail to successfully receive this OFDM packet >> at >> the receiver sometimes. >> >> Brief Setting Description: >> Code : gnuradio-example/python/ofdm/benchmark_ofdm_tx{rx}.py >> Daughterboard : FLEX900 >> OS : Ubuntu 8.10 >> Tx : >> send_pkt(data) -> time.sleep(1) -> send_pkt(data) -> time.sleep(1) -> >> ... >> Rx : >> ok = False , pktno = 65537, .... >> ok = True , pktno = 1 , .... >> ... >> >> I have surveyed about this discussion on the forum. Using discontinuous >> transmission is to ensure the transmitter successly sending a packet and >> receiver will receive this packet. And I try this scheme on single >> carrier >> case like benchmark_tx{rx}.py on digital file, every packet is successful >> receive at receiver. But when changing to OFDM, not every packet is >> successful receive. >> >> Is it that fft consumes lots of time and causes the transmitter doesn't >> send >> this packet? >> I think this is the main different between single carrier and OFDM. >> >> If anyone have any idea about this problem, please let me know. >> I am deeply appreciative. >> >> >> Fisheep > > > Fisheep, > > I don't think anyone has actually tried doing this. I know when Matt > and I put the system together, we were concerned only with the > continuous case. We have some improvements to the OFDM pieces that are > on my todo list, though, and once the continuous case is finished, > we'll work on the discontinuous. Until then, though, I'm afraid the > only advice I could give would be completely speculative. > > My first thought would be to see how the synchronization is behaving; > that's almost certainly where the problem is. We have the > "gr_plot_ofdm.py" script that helps to visualize what's happening with > the received symbols (you'll need to turn logging on and have scipy > and matplotlib installed). Play with that in loopback mode to > understand what you're seeing, then see what happens with your > over-the-air tests. > > If you figure out ways to make it better, I'd love to hear it! > > Tom > > _______________________________________________ > Discuss-gnuradio mailing list > Discuss-gnuradio@gnu.org > http://lists.gnu.org/mailman/listinfo/discuss-gnuradio > > -- View this message in context: http://old.nabble.com/USRP1-cannot-transmit-receive-a-OFDM-packet-discontinuously-sometimes-tp29705204p29715560.html Sent from the GnuRadio mailing list archive at Nabble.com. _______________________________________________ Discuss-gnuradio mailing list Discuss-gnuradio@gnu.org http://lists.gnu.org/mailman/listinfo/discuss-gnuradio