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rayleighchan & frequency channel response function

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h_ebrahimi

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Hi
I am currently writing matlab code for simulation of ofdm in frequency delective fading channel. I use rayleighchan function in matlab. i want to equalize signal in reciever, i cant obtain the channel response function? i realy confused?! rayleighchan is a class, but i need an equation....
please help me
 

You can obtain CIR (Channel Impulse Response) by accessing rayleighchan output class member.

This code extracts CIR from rayleighchan output:
Code: 
    % Call rayleigh channel
    constFading  = rayleighchan(1/Fs,fd,tau,P);

    if (fd>0)
        constFading.StoreHistory = 1;
    end

    outFading    = filter(constFading,inFading);

    % Extract CIR
    n_path = length(P);

    a = zeros(length(outFading),n_path);
    for i_path=1:n_path
        a(:,i_path) = constFading.PathGains(:,i_path);
    end

    alphaMatrix = constFading.channelFilter.alphaMatrix;
    h = a * alphaMatrix;
 
Last edited:

having found the impulse response of the channel, how to calculate the delay spread of the channel...?
 

sombdy plz rspond to the above query..!!
 

the above code shows an error..??? Undefined function or variable 'inFading'.

Error in ==> rayleighcir at 13
outFading = filter(constFading,inFading);
 

what does it mean by alphaMatrix
 

Re: rayleighchan & frequency channel response function

i m trying to get CIR,h, as 128 by 1 matrix..but this program generates 128 by 4689 matrix..plz explain alphaMatrix and its use..?
infading can be any random matrix?
 
Last edited:

Sorry I had not seen this forum for years. Hopefully it's not too late for me to answer this :smile:

The inFading is the input for the rayleigh channel. It is your transmitted signal.

I am not the one who created rayleighchan class and alpha matrix, so I can only make a guess. My best guess is that the alpha matrix simulates time-variance behavior of the fading channel.

If fd/Fs is very small (almost zero), I noticed that every column of the h matrix are identical, indicating that the impulse response doesn't change over time (time-invariant). As for channel with large normalized doppler frequency, the impulse response between each time sample varies over time (time-variant channel).
 

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