Code covered by the BSD License

# Contemporary Communications Systems Matlab Files

### Omar Ruiz (view profile)

Matlab Files in this book

[p]=cm_sm34(snr_in_dB)
```function [p]=cm_sm34(snr_in_dB)
% [p]=cm_sm34(snr_in_dB)
%		CM_SM34  finds the probability of error for the given
%   		value of snr_in_dB, signal-to-noise ratio in dB.
N=10000;
E=1;				  	% energy per symbol
snr=10^(snr_in_dB/10);	 	  	% signal-to-noise ratio
sgma=sqrt(E/(4*snr));	  	  	% noise variance
% Generation of the data source follows.
for i=1:2*N,
temp=rand;			  	% a uniform random variable between 0 and 1
if (temp<0.5),
dsource(i)=0;		  	% With probability 1/2, source output is "0."
else
dsource(i)=1;		  	% With probability 1/2, source output is "1"
end;
end;
% Differential encoding of the data source follows
mapping=[0 1 3 2];
M=4;
[diff_enc_output] = cm_dpske(E,M,mapping,dsource);
for i=1:N,
[n(1) n(2)]=gngauss(sgma);
r(i,:)=diff_enc_output(i,:)+n;
end;
% detection and the probability of error calculation
numoferr=0;
prev_theta=0;
for i=1:N,
theta=angle(r(i,1)+j*r(i,2));
delta_theta=mod(theta-prev_theta,2*pi);
if ((delta_theta<pi/4) | (delta_theta>7*pi/4)),
decis=[0 0];
elseif (delta_theta<3*pi/4),
decis=[0 1];
elseif (delta_theta<5*pi/4)
decis=[1 1];
else
decis=[1 0];
end;
prev_theta=theta;
% Increase the error counter, if the decision is not correct.
if ((decis(1)~=dsource(2*i-1)) | (decis(2)~=dsource(2*i))),
numoferr=numoferr+1;
end;
end;
p=numoferr/N;```