Code covered by the BSD License

# Contemporary Communications Systems Matlab Files

### Omar Ruiz (view profile)

Matlab Files in this book

[p]=ss_Pe97(rho_in_dB)
```function [p]=ss_Pe97(rho_in_dB)
% [p]=ss_Pe97(rho_in_dB)
%		SS_PE97  finds the measured error rate. The value of
%   		signal per interference ratio in dB is given as an input
%   		to the function.
rho=10^(rho_in_dB/10);
Eb=rho;					% energy per information bit
E=Eb/2;					% energy per symbol transmitted
% the optimal value of alpha
if (rho>2),
alpha=2/rho;
else
alpha=1;
end;
% the variance of the additive noise
if (E>1),
sgma=sqrt(E/2);
else
sgma=sqrt(1/2);
end;
N=10000;	      	      		% number of bits transmitted
% generation of the data sequence
for i=1:N,
temp=rand;
if (temp<0.5)
data(i)=1;
else
data(i)=0;
end;
end;
% Find the transmitted signals.
for i=1:N,
if (data(i)==0),
tr11c(i)=sqrt(E);  tr12c(i)=sqrt(E);
tr11s(i)=0;	 tr12s(i)=0;
tr21c(i)=0;	 tr22c(i)=0;
tr21s(i)=0;	 tr22s(i)=0;
else
tr11c(i)=0;	 tr12c(i)=0;
tr11s(i)=0;	 tr12s(i)=0;
tr21c(i)=sqrt(E);	 tr22c(i)=sqrt(E);
tr21s(i)=0;	 tr22s(i)=0;
end;
end;

% Find the received signals, make the decisions, and count the number of errors made.
num_of_err=0;
for i=1:N,
% determine if there is jamming
if (rand<alpha),
jamming1=1;	       			% jamming present on the second transmission
else
jamming1=0;	       			% jamming not present on the first transmission
end;
if (rand<alpha),
jamming2=1;	       			% jamming present on the second transmission
else
jamming2=0;	       			% jamming not present on the second transmission
end;
if (jamming1==1)
r11c=tr11c(i)+gngauss(sgma);    r11s=tr11s(i)+gngauss(sgma);
r21c=tr21c(i)+gngauss(sgma);    r21s=tr21s(i)+gngauss(sgma);
else
r11c=tr11c(i);    r11s=tr11s(i);
r21c=tr21c(i);    r21s=tr21s(i);
end;
if (jamming2==1)
r12c=tr12c(i)+gngauss(sgma);    r12s=tr12s(i)+gngauss(sgma);
r22c=tr22c(i)+gngauss(sgma);    r22s=tr22s(i)+gngauss(sgma);
else
r12c=tr12c(i);    r12s=tr12s(i);
r22c=tr22c(i);    r22s=tr22s(i);
end;
% Compute the decision variables, first the weights.
if (jamming1==1),
w1=1/sgma^2;
else
w1=10;
end;
if (jamming2==1),
w2=1/sgma^2;
else
w2=10;
end;
% The intermediate decision variables are computed as follows.
r11=r11c^2+r11s^2;
r12=r12c^2+r12s^2;
r21=r21c^2+r21s^2;
r22=r22c^2+r22s^2;
% Finally, the resulting decision variables x and y are computed.
x=w1*r11+w2*r12;
y=w1*r21+w2*r22;
% Make the decision.
if (x>y),
decis=0;
else
decis=1;
end;
% Increment the counter if this is an error.
if (decis~=data(i)),
num_of_err=num_of_err+1;
end;
end;
% The measured bit error rate is then
p=num_of_err/N;```