how to get SNR in Cogntive radio

currently my code is:

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%monte carlo simulation

function [y1,y2,y3,y4]= ed(SNRL,SNRS,SNRH,n) %ed is the energy detection

g1= SNRL:SNRS:SNRH;

g=10.^(g1/10);

beta=0.8; % is the probability pfa, it cannot be more than 1

pf1=zeros(1,length(g));

pd1=zeros(1,length(g));

pf2=zeros(1,length(g));

pd2=zeros(1,length(g));

for i=1 : length(g)

y0 = randn(n,1000000);

   y1= randn(n,1000000)*sqrt(g(i))+y0; 

       %Tgam is the threshold of gamma distribution 
       Tgam = gaminv((1-beta),n/2,(2/n)*(1+g(i))); %probab of flase detection
       pf1(i)= gamcdf(Tgam,n/2,(2/n)*(1+g(i))); %ho
       pd1 (i) = gamcdf(Tgam,n/2,2/n); %h1 % prob of detection

       pf2(i)= length (find(sum(y1.^2)/n<Tgam))/1000000;
       pd2 (i) = length (find(sum(y0.^2)/n<Tgam))/1000000; 

     y1=pf1; y2=pd1; y3=pf2; y4=pd2;
  end

   % print graphs
   figure (1)
   plot(g1,y4,'--c','LineWidth',4);
   grid on;

              xlabel('sample cycles');
              ylabel(' probability of detection (Pd) ');
    hold on;

    figure(1)
     plot(g1,y2,'-k','LineWidth',2);
   grid on;
   hleg1 = legend('beta = 0.2 for pd2','beta = 0.2 for pd1');
   hold on;

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to run the above simulation input" [y1,y2,y3,y4]= ed(0,1,25,2); " in command window.

the "g" in the code above represents the normalisation i.e it represents variance(signal)/variance (noise)

as SNR= power(signal)/power(noise) as the variance of the data is the power.

so i essentially want to "split" the g up. so substitute g= for SNR= power(signal)/power(noise)

this is so that i can add the signal power back into y1 ect.. i.e y1= randn(n,1000000)*sqrt(var(signal))+y0;

thank you for any suggestions.

Answer 1

[walid ghanem]

thanks ali and keep going