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A Single-tap 'flat Raleigh fading channel' is implemented as.

N=length(X);    % X is any signal
ray = sqrt(0.5*((randn(1,N)).^2+(randn(1,N)).^2));
Data_sent = X.*ray; 
  1. Is it a single path? What I have to do if I want to model MULTIPATH single-tap and multipath multi-tap channel ? I am confused in number of paths and taps.
  2. How to simulate 'i.i.d Raleigh distributed T tap frequency selective channel'? Thanks
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  • $\begingroup$ Do you understand what multipath means? Do you understand how frequency selectiveness due to multipath happens? $\endgroup$ – Marcus Müller Dec 13 '16 at 11:27
  • $\begingroup$ Yeah, I know the multipath concept theory. I know the number of paths through which the signal reach the receiver and there is delay among the different paths. If the delay spread is greater than the symbol duration then we get inter symbol interference . But I can not relate with the simulation. I am confused in where in the matlab code I include the 'number of paths', the 'number of taps' and then how to include the frequency selectivity. $\endgroup$ – Digi1 Dec 13 '16 at 11:38
  • $\begingroup$ So is this a questio to explain your matlab code? I must admit that I find it so trivial that I wonder what you want us to explain? Also, this is not really the "explain matlab code" stackexchange site – it's the signal processing site, so you might want to specify why your question is a signal processing and not a pure "I can't read matlab" question! $\endgroup$ – Marcus Müller Dec 13 '16 at 11:41
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each tap can corresponds to each path.if two different paths followed by signal gives same delay to recieve these two paths corresponds to single tap.if transmitted signal bandwidth is greater than channel coherence bandwidth(inverse of two times delay spread) channel acts as frequency selective channel.so the frequency selectivity of the channel depends on the transmitted signal that is not mentioned above.

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  • $\begingroup$ Thank you very much. So number taps is the number of delays. For the frequency selective channel I know the general theory but I don't know how to implement. More specifically if you could explain by giving the generic equations. For example i have a random signal X= randi([0 1],1,25); .. As in flat fading I have to multiply the signal with the impulse response of the channel i.e 'ray' in this case. Now if I want this signal to pass through a frequency selective channel. I need to know the bandwidth and delay spread . what equations should represent the model? $\endgroup$ – Digi1 Dec 13 '16 at 12:31
  • $\begingroup$ when we model the channel as multipath,thus model is done under the assumption that signal bandwidth is greater than channel bandwidth.even though you have given random signal it doesn't give any time sense.the final conclusion is if you have taken channel model number of taps its already implies that you are simulating your multipath multitap frequency selective channel.If you want to know further deep analysis you have to go through power delay profile analysis of channel where you will get the idea of delay spread and coherence bandwidth of the channel $\endgroup$ – sathish Dec 13 '16 at 13:00

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