ofdm.m

simulation signal ofdm

% Modulation OFDM

clear all;

Fd=1; % symbol rate (1Hz)

Fs=1*Fd; % so luong mau moi symbol

M=4; % So muc duoc dieu che tren moi song mang

Ndata=1024; % so symbol duoc truyen

Sdata=64; % 64 du lieu symbol moi khung den ifft

Slen=128; % 128 symbol cho IFFT

Nsym=16; % so luong khung -> Nsym khung

GIlen=144; % symbol voi khoang bao ve them vao

GI=16; % do dai khoang bao ve

% Tao vector

X=zeros(Ndata,1);

Y1=zeros(Ndata,1);

Y2=zeros(Ndata,1);

Y3=zeros(Slen,1);

z0=zeros(Slen,1);

z1=zeros(Ndata/Sdata*Slen,1);

g=zeros(GIlen,1);

z2=zeros(GIlen*Nsym,1);

% Tao ma tran cac so nguyen ngau nhien

X = randint(Ndata, 1, M);

% symbol so duoc map nhu mot symbol tuong tu

Y1 = modmap(X, Fd, Fs, 'qask', M);

% chuyen qua so phuc

Y2=amodce(Y1,1,'qam');

for j=1:Nsym;

for i=1:Sdata;

Y3(i+Slen/2-Sdata/2,1)=Y2(i+(j-1)*Sdata,1);

end

z0=ifft(Y3);

for i=1:Slen;

z1(((j-1)*Slen)+i)=z0(i,1);

end

for i=1:Slen;

g(i+16)=z0(i,1);

end

for i=1:GI;

g(i)=z0(i+Slen-GI,1);

end

for i=1:GIlen;

z2(((j-1)*GIlen)+i)=g(i,1);

end

end

f = linspace(-Sdata,Sdata,length(z1));

Y4 = fft(z1);

% Neu Y4 nho hon 0.01 Y4=0.001

for j=1:Ndata/Sdata*Slen;

if abs(Y4(j)) < 0.01

Y4(j)=0.01;

end

end

Y4 = 10*log10(abs(Y4));

figure( );

subplot(2,1,1);plot(f,abs(z1),'b');grid on;

Title('Signal in Time Domain','Color','b');

xlabel('Time, s','Color','b');

ylabel('Amplitude','Color','b')

f = linspace(-Sdata,Sdata,length(Y4));

subplot(2,1,2); plot(f,Y4,'r');grid on;

Title('Signal in Frequency Domain','Color','r');

xlabel('Frequency, Hz','Color','r');

ylabel('Magnitude square, dB','Color','r')


axis([-64 64 -20 20]);

% The end!