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[Discuss-gnuradio] Rayleigh Fading
From: |
Bastian Bloessl |
Subject: |
[Discuss-gnuradio] Rayleigh Fading |
Date: |
Thu, 18 Feb 2016 15:01:46 -0800 |
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
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