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Why the spectrum I get from 'Visualiza​tion'-'Fre​quency response' in 'comm.RayleighChannel' is sometimes different from the spectrum I culculate from 'PathGainsOutputPort'?

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zihao du
zihao du on 3 Jun 2020
Answered: Chaitanya Mallela on 30 Sep 2020
Here is my codes, if I change 'Seed' number from '1' to '73', the spectrums will be different, why this happens?Thanks for help.
clear; clc; close all;
rchan = comm.RayleighChannel('SampleRate',1000, ...
'PathDelays',[0 1e-3 2e-3],...
'AveragePathGains',[0 -3 -6], ...
'MaximumDopplerShift',0, ...
'PathGainsOutputPort',true,...
'RandomStream','mt19937ar with seed','Seed',1,...
'Visualization','Frequency response');
[chanOut,pathGain] = rchan(1);
h = pathGain(1,:);
Nfft = 1000;
H = fft(h,Nfft);
H_power_dB = 10*log10(abs(H.*conj(H)));
figure;
plot((-Nfft/2+1:Nfft/2),H_power_dB,'k-');
hold on; xlabel('Frequency[Hz]'), ylabel('Channel power[dBw]');

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Answers (1)

Chaitanya Mallela
Chaitanya Mallela on 30 Sep 2020
Seed property corresponds to the generation of random stream.Seed serves as a unique identifier of a pseudo-random sequence i.e., for each particular seed there is a unique pseudo-random sequence.Once the seed is specified the same random stream is generated for each time when simulated.

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