On Thu, Jul 26, 2012 at 04:09:31PM -0700, Frederick Lee wrote: > The channel model block contains a timing offset, and noise adder > which I didn't use in my simulations. The only things I changed were > the frequency offsets and the multipath variable (from what I found > online, it's used to change amplitude and phase shift of the signal). > The only difference that I can see between the channel model and using > actual USRPs is that USRPs up converts the signal into IF ( I believe > ), converts it to analog, and the daughter board converts it to RF. > Then the reverse happens in the other USRP. When the two USRPs are > transmitting, any of the four things that the channel model does can > happen, but the main ones I'm concerned about is the frequency shift., > and the DPSK block seemed to have taken care of that ( at least in the > simulation ). > I was using the */gr-uhd/examples/grc/uhd_dpsk_mod.grc and other > similar examples as somewhat of a guide, and I don't see anything that > looks very different from what I used. What kind of other adjustments > must I make?
Frederick, all kinds of stuff can go wrong. When you say you see 'nothing' on the FFT sink, do you mean you see only noise, or literally nothing? Here's a typical ist of things I do when debugging such a link: 1) Use a spectral analyzer to see if the transmitter is actually transmitting (where you want it to) 2) Connect an FFT sink directly to the UHD source to see if the signal looks as expected You've got a couple of things that surprise me in your FG: - the packet decoder (I'm not 100% what that does) searches for a bit string? If so, you have no way to guarantee you're actually receiving that specific sequence. If you're literally rx'ing nothing, perhaps that doesn't trigger. - Why do you LPF bits? MB -- Karlsruhe Institute of Technology (KIT) Communications Engineering Lab (CEL) Dipl.-Ing. Martin Braun Research Associate Kaiserstraße 12 Building 05.01 76131 Karlsruhe Phone: +49 721 608-43790 Fax: +49 721 608-46071 www.cel.kit.edu KIT -- University of the State of Baden-Württemberg and National Laboratory of the Helmholtz Association
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