% OFDM_basic.m
clear all
NgType=1; % NgType=1/2 for cyclic prefix/zero padding
if NgType==1
nt='CP';
elseif NgType==2
nt='ZP';
end
Ch=0; % Ch=0/1 for AWGN/multipath channel
if Ch==0
chType='AWGN';
Target_neb=100;
else
chType='CH';
Target_neb=500;
end
figure(Ch+1), clf
PowerdB=[0 -8 -17 -21 -25]; % Channel tap power profile 'dB'
Delay=[0 3 5 6 8]; % Channel delay 'sample'
Power=10.^(PowerdB/10); % Channel tap power profile 'linear scale'
Ntap=length(PowerdB); % Chanel tap number
Lch=Delay(end)+1; % Channel length
Nbps=4;
M=2^Nbps; % Modulation order=2/4/6 for QPSK/16QAM/64QAM
Nfft=64; % FFT size
Ng=Nfft/4; % Guard interval length
Nsym=Nfft+Ng; % Symbol duration
Nvc=Nfft/4; % Nvc=0: no virtual carrier
Nused=Nfft-Nvc;
EbN0=[0:5:20]; % EbN0
N_iter=1e5; % Number of iterations for each EbN0
Nframe=3; % Number of symbols per frame
sigPow=0; % Signal power initialization
file_name=['OFDM_BER_' chType '_' nt '_' 'GL' num2str(Ng) '.dat'];
fid=fopen(file_name, 'w+');
norms=[1 sqrt(2) 0 sqrt(10) 0 sqrt(42)]; % BPSK 4-QAM 16-QAM
for i=0:length(EbN0)
randn('state',0);
rand('state',0);
%Ber2=ber(); % BER initialization
Neb=0;
Ntb=0; % Initialize the number of error/total bits
for m=1:N_iter
% Tx______________________________________________________________
X= randint(1,Nused*Nframe,M); % bit: integer vector
Xmod= qammod(X,M,0,'gray')/norms(Nbps);
if NgType~=2
x_GI=zeros(1,Nframe*Nsym);
elseif NgType==2
x_GI= zeros(1,Nframe*Nsym+Ng);
% Extend an OFDM symbol by Ng zeros
end
kk1=[1:Nused/2];
kk2=[Nused/2+1:Nused];
kk3=1:Nfft;
kk4=1:Nsym;
for k=1:Nframe
if Nvc~=0
X_shift= [0 Xmod(kk2) zeros(1,Nvc-1) Xmod(kk1)];
else
X_shift= [Xmod(kk2) Xmod(kk1)];
end
x= ifft(X_shift);
x_GI(kk4)= guard_interval(Ng,Nfft,NgType,x);
kk1=kk1+Nused;
kk2=kk2+Nused;
kk3=kk3+Nfft;
kk4=kk4+Nsym;
end
if Ch==0
y= x_GI; % No channel
else % Multipath fading channel
channel=(randn(1,Ntap)+j*randn(1,Ntap)).*sqrt(Power/2);
h=zeros(1,Lch);
h(Delay+1)=channel; % cir: channel impulse response
y = conv(x_GI,h);
end
if i==0 % Only to measure the signal power for adding AWGN noise
y1=y(1:Nframe*Nsym);
sigPow = sigPow + y1*y1';
continue;
end
% Add AWGN noise________________________________________________
snr = EbN0(i)+10*log10(Nbps*(Nused/Nfft)); % SNR vs. Eb/N0
noise_mag = sqrt((10.^(-snr/10))*sigPow/2);
y_GI = y + noise_mag*(randn(size(y))+j*randn(size(y)));
% Rx_____________________________________________________________
kk1=(NgType==2)*Ng+[1:Nsym];
kk2=1:Nfft;
kk3=1:Nused;
kk4=Nused/2+Nvc+1:Nfft;
kk5=(Nvc~=0)+[1:Nused/2];
if Ch==1
H= fft([h zeros(1,Nfft-Lch)]); % Channel frequency response
H_shift(kk3)= [H(kk4) H(kk5)];
end
for k=1:Nframe
Y(kk2)= fft(remove_GI(Ng,Nsym,NgType,y_GI(kk1)));
Y_shift=[Y(kk4) Y(kk5)];
if Ch==0
Xmod_r(kk3) = Y_shift;
else
Xmod_r(kk3)= Y_shift./H_shift; % Equalizer - channel compensation
end
kk1=kk1+Nsym;
kk2=kk2+Nfft;
kk3=kk3+Nused;
kk4=kk4+Nfft;
kk5=kk5+Nfft;
end
X_r=qamdemod(Xmod_r*norms(Nbps),M,0,'gray');
Neb=Neb+sum(sum(de2bi(X_r,Nbps)~=de2bi(X,Nbps)));
Ntb=Ntb+Nused*Nframe*Nbps; %[Ber,Neb,Ntb]=ber(bit_Rx,bit,Nbps);
if Neb>Target_neb
break;
end
end
if i==0
sigPow= sigPow/Nsym/Nframe/N_iter;
fprintf('Signal power= %11.3e\n', sigPow);
fprintf(fid,'%%Signal power= %11.3e\n%%EbN0[dB] BER\n', sigPow);
else
Ber = Neb/Ntb;
fprintf('EbN0=%3d[dB], BER=%4d/%8d =%11.3e\n', EbN0(i), Neb,Ntb,Ber)
fprintf(fid, '%d\t%11.3e\n', EbN0(i), Ber);
if Ber<1e-6
break;
end
end
end
if (fid~=0)
fclose(fid);
end
disp('Simulation is finished');
plot_ber(file_name,Nbps);
OFDM传输系统的仿真实现_通信
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2022-07-14
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