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

12.12 MATLAB Exercises 725
Fi g ure 1 2.24
Symbol error rate
(SER) comparison
of DFE,
linear equalization,
and
under ideal
channel.
10-3 _;::.
ISi-free (analysis) •::
-e-- Without equalizer
-- DFE
- - - - Linear equalizer
10 -4 '----'-------'--------1-V-----'------'-- - --.....J
10 15 20 25 30
E/A./, dB
COMPUTER EXERCISE 12.3: OFDM TRANSMISSION OF QAM SIGNALS
In the example, we will utilize OFDM for QAM transmission. We choose the number of subcarriers (and
the FFT size) as N = 32. We let the finite impulse response (FIR) channel to be
channel= [0. 3 -0. 5 0 1 .2 -0.3]
The channel length is 6 (L = 5 in Section 12.7). For this reason, we can select the cyclic prefix length to
be the minimum length of L = 5.
% Matlab Program <Exl2_3 .m>
% This Matlab exerc ise <Ex12_3 .m> performs simulation of
% an OFDM system that emp loys QAM-16 baseband signaling
% a mul tipath channel with AWGN .
% Correct carrier and synchronization is assumed .
% 32 subcarriers are used wi th channel length of 6
% and cycli c pre fix length of 5.
clear;clf;
L=16 00000;
Lfr=L/32 ;
% Total data symbol s in experiment is 1 million
% number of data frames
% Generating random signal data for polar signaling
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);
channel= [ 0.3 -0.5 0 1 .2 -0.3] ;
hf= fft( channel , 32);
p_data=reshape (s_data , 32,Lfr) ;
p_td= ifft (p_data );
p_cyc= [ p_td ( end- 4:end, :) ;p_td] ;
% channel in t -domain
% find the channel in f -domain
% SIP conversion
% IFFT to convert to t -domain
% add cycli c pre fix