B. P. Lathi, Zhi Ding - Modern Digital and Analog Communication Systems-Oxford University Press (2009)

598 PERFORMANCE ANALYSIS OF DIGITAL COMMUNICATION SYSTEMS
% which is f_ovsamp /T (T=l is the symbol duration )
s_up=upsample ( s_data, f_ovsamp) ;
% Identify the decision delays due to pulse shaping
% and matched filters
delayrc=2*delay_rc * f_ovsamp ;
% Generate QAM- 16 signaling with pulse-shaping
xrcos=conv ( s_up,prcos) ;
% Find the signal length
Lrcos=length (xrcos) ;
SER= [] ;
noiseq=randn (Lrcos ,l)+j *randn (Lrcos,1) ;
Es=lO;
% symbol energy
% Generating the channel noise (AWGN )
for i=l:9,
Eb2N(i)=i*2;
Eb2N_num=l0 (Eb2N(i) /10) ;
Var_n=Es/ (2*Eb2N_num) ;
signois=sqrt (Var_n/2) ;
awgnois=signois*noiseq;
% AWGN
% Add noise to signals at the channel output
yrcos=xrcos+awgnois;
% Apply matched filters first
zl=conv (yrcos, pcmatch) ;clear awgnois, yrcos;
% Sampling the received signal and acquire samples
zl=zl (delayrc+l : f_ovsamp :end) ;
%(Eb/N in dB )
% Eb/N in numeral
%1/SNR is the noise variance
% standard deviation
% Decision based on the sign of the samples
decl=sign (real (zl (l:L) ) )+sign ( real (zl (l:L) )-2)+ ...
sign (real (zl(l :L) )+2)+ ...
j*( sign ( imag (zl (l:L) ) )+sign (imag (zl (l:L) )-2)+ . ..
sign ( imag (zl (l:L) )+2) );
% Now compare against the original data to compute BER for
% the three pulses
%BER= [BER; sum(abs ( s_data-decl ))/(2*L) ]
SER= [SER; sum ( s_data~=decl) /L] ;
Q(i)=3*0. 5*erfc ( sqrt ((2*Eb2N_num/5)/2) );
%Compute the Analytical BER
end
figure (l)
subplot (lll)
figber=semilogy (Eb2N, Q, 'k-' ,Eb2N,SER , 'b- *');
axis ( (2 18 . 99e-5 l] );
legend ('Analytical ', 'Root-raised cosine');
xlabel ('E_b/N (dB) ') ;ylabel ('Symbol error probability');
set ( figber, 'Linewidth ' , 2) ;
% Constellation plot
figure (2)
subplot (lll)
plot (real (zl (l:min (L, 4000) )) ,imag (zl (l:min (L,4000) )) , '.');