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

10.12 MATLAB Exercises 597
Figure 1 0.48
Eye diagram of
the real
(in-phase)
component of the
16-QAM
transmission at
the receiver
matched filter
output.
5---------------
4
3
2
-2
-3
-4
-5 ----------------
-1 -0.5 0
Time. T,
0.5
COMPUTER EXERCISE 10.3: 16-QAM MODULATION
In this exercise, we will consider a more complex QAM constellation for transmission. The M-ary QAM
was analyzed in Sec. 10.6.6. In MATLAB program Exl 0 _3 . m, we control the transmission bandwidth
by applying the root-raised cosine pulse with roll-off factor of 0.5 as the baseband pulse shape. For each
symbol period T, eight uniform samples are used to approximate and emulate the continuous time signals.
Figure 10.48 illustrates the open eye diagram of the in-phase (real) part of the matched filter output prior
to being sampled. Very little ISi is observed at the point of sampling, validating the use of the root-raised
cosine pulse shape in conjunction with the matched filter detector for ISi-free transmission.
% Matlab Program <Ex10_3 .m>
% This Matlab exercise <Ex10_3 .m> performs simulation of
% QAM-16 baseband polar transmission in AWGN channel .
% Root-raised cosine pulse of rolloff factor = 0.5 is used
% Matched filter receiver is designed to detect the symbols
% The program estimates the symbol error rate (BER) 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=8
f_ovsamp=B;
% Oversampling factor vs data rate
delay_rc=4 ;
% Generating root-raised cosine pulseshape (rolloff factor 0.5)
prcos=rcosflt([ 1 J, 1, f_ovsamp , 'sqrt ', 0.5, delay_rc );
prcos=prcos (l: end- f_ovsamp+ l} ;
prcos=prcos/ norm (prcos);
pcmatch=prcos (end:- 1:1) ;
% Generating random signal data for polar signal ing
s_data=4* round (rand (L, 1) ) +2*round ( rand (L, 1) ) -3+ ...
+j*(4 *round (rand(L ,1))+2*round (rand(L ,1))- 3) ;
% upsample to match the
% 'oversampling rate '