%frequency-selective rayleigh fading channel
%Power-delay spectrum is modeled by an exponential pdf
%Arrival time is modeled by an uniform distribution
clear all;
Mumean=70;%(ns)
pds=[];
Ptotal=0;
for Tk=1:1:100
    pdsTk=(1./Mumean).*exp(-Tk./Mumean);
    pds=[pds,pdsTk];
    Ptotal=Ptotal+pdsTk;
end
pds=pds./Ptotal;
figure
subplot(1,2,1);
Tk=1:1:100;
plot(Tk,pds);
xlabel('Delay steps');
ylabel('Power');
N_path=4;
tao=round(rand(1,4).*99)+1
for k=1:100
      pds0(1,k)=~all(k-tao);  
end
     pds1=pds0.*pds;
     pds2=pds1./sum(pds1);    
subplot(1,2,2);
stem(Tk,pds2);
xlabel('Delay steps');
ylabel('Power of 4 paths');