% ofdmce.m
%
% Simulation program to realize OFDM transmission system
%
% GI CE GI data GI data...(data 6symbols)
% (CE: Chanel estimation symbol, GI Guard interval)
%
%********************** preparation part ***************************
clear all;
para=52; % Number of parallel channel to transmit (points)
fftlen=64; % FFT length
noc=53; % Number of carriers
nd=6; % Number of information OFDM symbol for one loop
knd=1; % Number of known channel estimation (CE) OFDM symbol
ml=2; % Modulation level : QPSK
sr=250000; % OFDM symbol rate (250 ksyombol/s)
br=sr.*ml; % Bit rate per carrier
gilen=16; % Length of guard interval (points)
ebn0=15; % Eb/N0
%%%%%%%%%%%%% fading initialization %%%%%%%%%%%
tstp=1/sr/(fftlen+gilen); % Time resolution
itau=[0]; % Arrival time for each multipath normalized by tstp
dlvl1=[0]; % Mean power for each multipath normalized by direct wave.
n0=[6]; % Number of waves to generate fading n0(1),n0(2)
th1=[0.0]; % Initial Phase of delayed wave
itnd1=[1000]; % set fading counter
now1=1; % Number of directwave + Number of delayed wave
fd=150; % Maximum Doppler frequency
flat=1; % Flat or not (see ofdm_fading.m)
itnd0=nd*(fftlen+gilen)*20; % Number of fading counter to skip
%************************** main loop part **************************
nloop=1000; % 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
%************************** transmitter *****************************
for iii=1:nloop
seridata=rand(1,para*nd*ml)>0.5; % DC=0
paradata=reshape(seridata,para,nd*ml); %size(51 * nd*ml)
%-------------- ml modulation ----------------
[ich,qch]=qpskmod(paradata,para,nd,ml);
kmod=1/sqrt(2);
ich=ich.*kmod;
qch=qch.*kmod;
% CE data generation
kndata=zeros(1,fftlen);
kndata0=2.*(rand(1,52)>0.5)-1;
kndata(2:27)=kndata0(1:26);
kndata(39:64)=kndata0(27:52);
ceich=kndata; % CE:BPSK
ceqch=zeros(1,64);
%------------- data mapping (DC=0) -----------
[ich1,qch1]=crmapping(ich,qch,fftlen,nd);
ich2=[ceich.' ich1]; % I-channel transmission data
qch2=[ceqch.' qch1]; % Q-channel transmission data
%------------------- IFFT -------------------
x=ich2+qch2.*i;
y=ifft(x);
ich3=real(y);
qch3=imag(y);
%---------- Gurad interval insertion ---------
fftlen2=fftlen+gilen;
[ich4,qch4]= giins(ich3,qch3,fftlen,gilen,nd+1);
%---------- Attenuation Calculation ----------
spow=sum(ich4.^2+qch4.^2)/nd./para;
attn=0.5*spow*sr/br*10.^(-ebn0/10);
attn=sqrt(attn);
%********************** fading channel ******************************
%If you would like to simulate performance under fading, please remove "*"
%from the following four sentenses
[ifade,qfade,ramp,rcos,rsin]=sefade(ich4,qch4,itau,dlvl1,th1,n0,itnd1,now1,length(ich4),tstp,fd,flat);
itnd1 = itnd1+itnd0; % Updata fading counter
ich4=ifade;
qch4=qfade;
%*************************** Receiver *****************************
%--------------- AWGN addition ---------------
[ich5,qch5]=comb(ich4,qch4,attn);
%----Perfect fading compensation for one path fading ----
%If you would like to simulate performance under perfect compensation, please remove "*"
%from the following four sentenses
%ifade2=1./ramp.*(rcos(1,:).*ich5+rsin(1,:).*qch5);
%qfade2=1./ramp.*(-rsin(1,:).*ich5+rcos(1,:).*qch5);
%ich5=ifade2;
%qch5=qfade2;
%----------- Guard interval removal ----------
[ich6,qch6]= girem(ich5,qch5,fftlen2,gilen,nd+1);
%------------------ FFT --------------------
rx=ich6+qch6.*i;
ry=fft(rx);
ich7=real(ry);
qch7=imag(ry);
%-------------- Fading compensation by CE symbol --------------
%
%If you would like to simulate performance under CE-based compensation, please remove "*"
%in this area
%
% preparation known CE data
ce=1;
ice0=ich2(:,ce);
qce0=qch2(:,ce);
% taking CE data out of received data
ice1=ich7(:,ce);
qce1=qch7(:,ce);
% calculating reverse rotation
iv=real((1./(ice1.^2+qce1.^2)).*(ice0+i.*qce0).*(ice1-i.*qce1));
qv=imag((1./(ice1.^2+qce1.^2)).*(ice0+i.*qce0).*(ice1-i.*qce1));
% matrix for reverse rotation
ieqv1=[iv iv iv iv iv iv iv];
qeqv1=[qv qv qv qv qv qv qv];
% reverse rotation
icompen=real((ich7+i.*qch7).*(ieqv1+i.*qeqv1));
qcompen=imag((ich7+i.*qch7).*(ieqv1+i.*qeqv1));
ich7=icompen;
qch7=qcompen;
%---------- CE symbol removal ----------------
ich8=ich7(:,knd+1:nd+1);
qch8=qch7(:,knd+1:nd+1);
% DC and pilot data removal
[ich9,qch9]=crdemapping(ich8,qch8,fftlen,nd);
%----------------- demoduration --------------
ich10=ich9./kmod;
qch10=qch9./kmod;
[demodata]=qpskdemod(ich10,qch10,para,nd,ml);
%-------------- error calculation ----------
demodata1=reshape(demodata,1,para*nd*ml);
noe2=sum(abs(demodata1-seridata));
nod2=length(seridata);
% calculating PER
if noe2~=0
eop=eop+1;
else
eop=eop;
end
eop;
nop=nop+1;
% calculating BER
noe=noe+noe2;
nod=nod+nod2;
%fprintf('%d\t%e\t%d\n',iii,noe2/nod2,eop);
end
per=eop/nop;
ber=noe/nod;
%********************** Output result ***************************
fprintf('%f\t%e\t%e\t%d\t%d\n',ebn0,ber,per,nloop,fd);
fid = fopen('BERofdmce.dat','a');
fprintf(fid,'%f\t%e\t%e\t%d\t\n',ebn0,ber,per,nloop);
fclose(fid);
%******************** end of file ***************************
