On Mon, Jan 30, 2012 at 11:12 AM, Martin Braun <martin.br...@kit.edu> wrote:
> On Mon, Jan 30, 2012 at 04:11:05PM +0100, Florian Schlembach wrote: > > We have now extended our tests to the tests with two USRP2s with > > daughterboards: Neither the benchmark_tx.py example nor the tunnel.py is > > receiving any packets. We checked the spectrum and tuned the gains as > well. > > (OFDM) > > > > Now, we played with the benchmark files and tunnel.py located in the > narrowband > > folder and therefore changed the modulation scheme from BPSK to GMSK and > > ultimately receiving all the packets!! That's strange. > > > > Does anybody knows what code be the problem that we can't establish any > > connection using higher order modulation schemes? Could it possibly be > our > > slightly outdated UHD version? > > > > We are totally clueless, so we appreciate any idea/help! > > This won't really help, but I remember we had exactly the same troubles > here. > This was before UHD was even released, so I doubt that's the reason. > Unfortunately, I can't remember how (or: if) we fixed it :( but I'll > keep you updated if my memory comes up with something. > > But fiddling with gain values is often useful; even if you've already > done that I recommend trying again, by reducing tx-amplitude and the > actual gain values, shifting the terminals around (perhaps they're too > close?). > > MB > The benchmark OFDM scripts were made as simple examples of OFDM and were not made very robust. I can get them working within an office space fairly easily, but I seem to be the only one. When I moved everything over the using the UHD interface, I tested everything OTA successfully, so they do still work. One thing that I noticed was that the --tx-amp=0.8. That's very high for OFDM with it's large PAPR. Try backing off on that (to around 0.2 - 0.3) and try again. You won't get much range from this signal, though. Tom
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