Re: [Discuss-gnuradio] a report on dqpsk modulation in gnuradio

[Johnathan Corgan]

On Sat, Dec 6, 2008 at 12:29 PM, Bill Stevenson
<address@hidden> wrote:

> Johnathan, could you tell me the detailed configurations of your setup, for
> example, which demo files were you using, what were the arguments you used
> for your transmission? I also hope the data I got is useful for your
> development. Thank you!!!

The likely culprit here is the default values of the frequency/phase
tracking loop and bit timing recovery gain parameters.  There really
isn't a one size fits all value for these.

These are configured on the command line of benchmark_rx.py:

--costas-alpha=xxx
--gain-mu=xxx

Try setting the first to 0.05 and the second to 0.001 as a starting
point; these are what I use successfully with otherwise default
parameters.  Unfortunately, tweaking these is a trial and error
process; the correct values depend on your USRP crystal stability,
receiver signal to noise ratio, and samples per symbol value.

-Johnathan