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

716 DIGITAL COMMUNICATIONS UNDER LINEARLY DISTORTIVE CHANNELS
% Correct carrier and synchronization is assumed .
% Root-raised cosine pulse of rolloff factor = 0.5 is used
% Matched filter is applied at the receiver front end .
% The program estimates the symbol error rate (SER) at different Eb/N
clear;clf;
L=l000000;
% Total data symbols in experiment is 1 million
% To display the pulse shape , we oversample the signal
% by factor of f_ovsamp=S
f_ovsamp=8 ;
% Oversampling factor vs data rate
delay_rc=4 ;
% Generating root-raised cosine pulseshape (rolloff factor = 0.5)
prcos=rcosflt([ 1 ] , 1, f_ovsamp , 'sqrt ' , 0.5, delay_rc ); % RRC pulse
prcos=prcos (l:end-f_ovsamp+ l) ;
% remove O's
prcos=prcos/norm (prcos );
% normalize
pcmatch=prcos (end : -1:1) ;
% MF
% Generating random signal data for polar signaling
s_data=4*round ( rand (L, 1) )+2*round (rand (L, l) )-3+...
+j *(4 *round (rand (L, 1) )+2 *round (rand (L ,l))- 3) ;
% upsample to match the 'oversampling rate ' (normalize by 1/T) .
% It 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 polar signaling of different pulse-shaping
xrcos=conv ( s_up,prcos) ;
[c_num ,c_den] = cheby2 (12,20, (1+ 0.5) /8) ;
% The next commented line finds frequency response
%[H, fnlz ]=freqz (c_num ,c_den, 512,8) ;
% The lowpass filter is the Tx filter before signal is sent to channel
xchout=filter ( c_num ,c_den,xrcos) ;
% We can now plot the power spectral densities of the two signals
% xrcos and xchout
% This shows the filtering effect of the Tx filter before
% transmission in terms of the signal power spectral densities
% It shows how little lowpass Tx filter may have distorted the signal
plotPSD_comparison
% Apply a 2-ray multipath channel
mpath= [l 0 0 -0 .65] ;
% multipath delta(t)- 0.65 delta (t-3T/8)
% time-domain multipath channel
h=conv (conv (prcos , pcmatch ) ,mpath) ;
hscale=norm (h) ;
xchout=conv (mpath,xchout ); % apply 2-ray multipath
xrxout=conv (xchout, pcmatch) ; % send the signal through matched filter
% separately from the noise
delaychb=delayrc+3 ;
out_mf=xrxout ( delaychb+l:f_ovsamp :delaychb+L* f_ovsamp) ;
clear xrxout;