% ofdm.m
% Simulation program to realize OFDM transmission system
%
clear all
clc
%
%********************** preparation part ***************************
para=128; % Number of parallel channel to transmit (points)
fftlen=128; % FFT length
noc=128; % Number of carrier
nd=6; % Number of information OFDM symbol for one loop
ml=2; % Modulation level : QPSK
sr=250000; % Symbol rate
br=sr.*ml; % Bit rate per carrier
gilen=32; % Length of guard interval (points)
ebn0=3; % Eb/N0
%************************** main loop part **************************
nloop=100; % Number of simulation loops
noe = 0; % Number of error data
nod = 0; % Number of transmitted data
eop=0; % Number of error packet
nop=0; % Number of transmitted packet
for iii=1:nloop
%************************** transmitter *********************************
%************************** Data generation ****************************
seldata=rand(1,para*nd*ml)>0.5; % rand : built in function
%****************** Serial to parallel conversion ***********************
paradata=reshape(seldata,para,nd*ml); % reshape : built in function
%************************** QPSK modulation *****************************
[ich,qch]=qpskmod(paradata,para,nd,ml);
kmod=1/sqrt(2); % sqrt : built in function
ich1=ich.*kmod;
qch1=qch.*kmod;
%******************* IFFT ************************
x=ich1+qch1.*i;
y=ifft(x); % ifft : built in function
ich2=real(y); % real : built in function
qch2=imag(y); % imag : built in function
%********* Gurad interval insertion **********
[ich3,qch3]= giins(ich2,qch2,fftlen,gilen,nd);
fftlen2=fftlen+gilen;
%********* Attenuation Calculation *********
spow=sum(ich3.^2+qch3.^2)/nd./para; % sum : built in function
attn=0.5*spow*sr/br*10.^(-ebn0/10);
attn=sqrt(attn);
%*************************** Receiver *****************************
%***************** AWGN addition *********
[ich4,qch4]=comb(ich3,qch3,attn);
%****************** Guard interval removal *********
[ich5,qch5]= girem(ich4,qch4,fftlen2,gilen,nd);
%****************** FFT ******************
rx=ich5+qch5.*i;
ry=fft(rx); % fft : built in function
ich6=real(ry); % real : built in function
qch6=imag(ry); % imag : built in function
%***************** demoduration *******************
ich7=ich6./kmod;
qch7=qch6./kmod;
[demodata]=qpskdemod(ich7,qch7,para,nd,ml);
%************** Parallel to serial conversion *****************
demodata1=reshape(demodata,1,para*nd*ml);
%************************** Bit Error Rate (BER) ****************************
% instantaneous number of error and data
noe2=sum(abs(demodata1-seldata)); % sum : built in function
nod2=length(seldata); % length : built in function
% cumulative the number of error and data in noe and nod
noe=noe+noe2;
nod=nod+nod2;
% calculating PER
if noe2~=0
eop=eop+1;
else
eop=eop;
end
eop;
nop=nop+1;
fprintf('%d\t%e\t%d\n',iii,noe2/nod2,eop); % fprintf : built in function
plot(ebn0,noe2/nod2);
end
%********************** Output result ***************************
per=eop/nop;
ber=noe/nod;
fprintf('%f\t%e\t%e\t%d\t\n',ebn0,ber,per,nloop);
fid = fopen('BERofdm.dat','a');
fprintf(fid,'%f\t%e\t%e\t%d\t\n',ebn0,ber,per,nloop);
fclose(fid);
%******************** end of file ***************************
