How to change path gains in rayleighchan MatLab?

Question

I am trying to simulate a channel with multipath and fading in MatLab using the function rayleighchan and I want to change the path gains, because the function put them randomly. I have spent a lot of hours trying to do it and reading documentation, but I haven't been able to do it. Could Someone help me?

Thank you very much.

Answer 1

This is because what you are really looking for is changing the AvgPathGainsdB, and not PathGains.

Explanation

Understand that multi-path fading is a complex process, more so when Doppler spread is involved. The Rayleigh channel class (rayleighchan) generates non-LOS multi-path channels that are characterized by Rayleigh fading.

The variables PathDelays are the excess delays due to each multi-path component, where each path has an amplitude that is Rayleigh distributed, and phase that is uniformly distributed.

The mean amplitude for the Rayleigh distribution of each path is decided by the average path gains property (AvgPathGainsdB), while the exact amplitudes are statistically generated in PathGains.

Example

If you want a three path channel, where the delays of the paths are [0, 10, 50] us, with average path gains of [0, -3, -5] dB, do the following:

rchan = rayleighchan([0, 10e-6, 50e-6], [0, -3, -5]);

If there is Doppler spread, the PathGains change over time, as you filter your signal through this object.