Code covered by the BSD License

# Contemporary Communications Systems Matlab Files

### Omar Ruiz (view profile)

Matlab Files in this book

[p]=ss_Pe94(snr_in_dB, Lc, A, w0)
```function [p]=ss_Pe94(snr_in_dB, Lc, A, w0)
% [p]=ss_Pe94(snr_in_dB, Lc, A, w0)
%		SS_PE94  finds the measured error rate. The function
%   		that returns the measured probability of error for the given value of
%   		the snr_in_dB, Lc, A and w0.
snr=10^(snr_in_dB/10);
sgma=1;		      			% Noise standard deviation is fixed.
Eb=2*sgma^2*snr;      			% signal level required to achieve the given
% signal-to-noise ratio
E_chip=Eb/Lc;	      			% energy per chip
N=10000;	      			% number of bits transmitted
% The generation of the data, noise, interference, decoding process and error
% counting is performed all together in order to decrease the run time of the
% program. This is accomplished by avoiding very large sized vectors.
num_of_err=0;
for i=1:N,
% Generate the next data bit.
temp=rand;
if (temp<0.5),
data=-1;
else
data=1;
end;
% Repeat it Lc times, i.e. divide it into chips.
for j=1:Lc,
repeated_data(j)=data;
end;
% pn sequence for the duration of the bit is generated next
for j=1:Lc,
temp=rand;
if (temp<0.5),
pn_seq(j)=-1;
else
pn_seq(j)=1;
end;
end;
% the transmitted signal is
trans_sig=sqrt(E_chip)*repeated_data.*pn_seq;
% AWGN with variance sgma^2
noise=sgma*randn(1,Lc);
% interference
n=(i-1)*Lc+1:i*Lc;
interference=A*sin(w0*n);
rec_sig=trans_sig+noise+interference;
% Determine the decision variable from the received signal.
temp=rec_sig.*pn_seq;
decision_variable=sum(temp);
% making decision
if (decision_variable<0),
decision=-1;
else
decision=1;
end;
% If it is an error, increment the error counter.
if (decision~=data),
num_of_err=num_of_err+1;
end;
end;
% then the measured error probability is
p=num_of_err/N;```