[Discuss-gnuradio] Rayleigh Fading

[Bastian Bloessl]

Hi,

I’m currently looking into the Rayleigh fading implementation, but, 
unfortunately, don’t get some implementation details.

For example, the generation of the sinusoids [1]

float s_i = scale_sin*cos(2*M_PI*d_fDTs*d_m*cos(alpha_n)+d_psi[n]);

AFAIS, alpha_n is uniformly distributed between [-pi; pi], so FDTs * 
cos(alpha_n) is a random walk through the doppler spectrum.
However, multiplying that with d_m (the absolute sample number) will amplify 
the effect over time and change autocorrelation properties.

I did some simulations that seem to confirm that.

Since one comment in the code mentions a table, I wondered whether there is a 
reference to a description of the algorithm. (I hope I didn’t miss it in the 
docs)

Best,
Bastian


[1] 
https://github.com/gnuradio/gnuradio/blob/next/gr-channels/lib/flat_fader_impl.cc#L76