%DVB-T 2K signal generation Eq. (2.1.4) vs. 2N-IFFT
clear all;
close all;
Tu=224e-6; %useful OFDM symbol period
T=Tu/2048; %baseband elementary period
G=0; %choice of 1/4, 1/8, 1/16, and 1/32
delta=G*Tu; %guard band duration
Ts=delta+Tu; %total OFDM symbol period
Kmax=1705; %number of subcarriers
Kmin=0;
FS=4096; %IFFT/FFT length
q=10; %carrier period to elementary period ratio
fc=q*1/T; %carrier frequency
Rs=4*fc; %simulation period
M=Kmax+1;

a=-1+2*round(rand(M,1)).'+i*(-1+2*round(rand(M,1))).';
A=length(a);
info = [ a.'];
tt=0:1/Rs:Ts;
TT=length(tt);
k=Kmin:Kmax;
for t=0:(TT-1); % Eq. (2.1.4)
phi=a(k+1).*exp((1j*2*(((t*(1/Rs))-delta))*pi/Tu).*((k-(Kmax-Kmin)/2)));
s(t+1)=real(exp(1j*2*pi*fc*(t*(1/Rs))).*sum(phi));
end
infof=zeros(FS,1);
infof(1:(A/2)) = [ a(1:(A/2)).'];
infof((FS-((A/2)-1)):FS) = [ a(((A/2)+1):A).'];
carriers=FS.*ifft(infof,FS); % IFFT
%Upconverter
L = length(carriers);
chips = [ carriers.';zeros((2*q)-1,L)];
p=1/Rs:1/Rs:T/2;
g=ones(length(p),1);
dummy=conv(g,chips(:));
u=[dummy(1:TT)];
[b,a] = butter(13,1/20);
uoft = filter(b,a,u);
s_tilde=(uoft.').*exp(1i*2*pi*fc*tt);
sf=real(s_tilde);
figure(1);
plot(tt,s,'b',tt,sf,'g');
figure(2);
pwelch(s,[],[],[],Rs);
hold on;
pwelch(sf,[],[],[],Rs);
hold off;