ofdm.m

考虑频率偏移的OFDM仿真程序,直接根据经典参考文献编写

para=256; % Number of parallel channel to transmit (points)
fftlen=256; % FFT length
noc=256; % Number of carrier
nd=1; % 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=15; % Length of guard interval (points)
fullen=gilen+para; %ofdm符号总长
% ebn0=7; %Eb/N0
snr=10^(ebn0/10);

deltad=0; %时延
deltaf=0; %频偏

%************************** main loop part **************************

%************************** 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 *****************************

%*************************加频率偏移和时延***************************

[ich3,qch3]=delay(ich3,qch3,length(ich3),deltad);
y=ich3+qch3.*i;
for k=1:length(ich3);
y(k)=y(k)*exp(i*2*pi*deltaf*k/para);
end
ich3=real(y);
qch3=imag(y);
%for k=1:length(ich3);
%y(k)=y(k)*exp(i*2*pi*deltaf*k/para);
%end


%***************** AWGN addition ********* 

% [ich4,qch4]=comb(ich3,qch3,attn);

ich4 = ich3;
qch4 = qch3;
y=ich4+qch4.*i;

%****************** 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;
figure(1);
plot(ich7(:,1),qch7(:,1),'*');grid on;
[demodata]=qpskdemod(ich7,qch7,para,nd,ml);