OFDM_signal.m

% OFDM_signal.m

%MIMO-OFDM Wireless Communications with MATLAB¢ç   Yong Soo Cho, Jaekwon Kim, Won Young Yang and Chung G. Kang
%2010 John Wiley & Sons (Asia) Pte Ltd

clear
N=8; b=2; M=2^b; Nos=16; NNos=N*Nos; T=1/NNos; time = [0:T:1-T];
%if b==1, Mod='BPSK'; mod_object = modem.pskmod('M',M); A=1;
% elseif b==2, Mod='QPSK';  mod_object = modem.pskmod('M',M); A=1;
% else Mod=[num2str(2^b) 'QAM']; mod_object = modem.qammod('M',M); 
%      Es=1; A=sqrt(3/2/(M-1)*Es); 
%end
%[inI,inQ,Mod,Nsym] = mapper(b,N,'Y');
%msgint=randint(1,N,M); X=A*modulate(mod_object,msgint);
[X,Mod] = mapper(b,N); X(1)=0+j*0; % A block of 16 QPSK symbols with no DC-subcarrier 
for i = 1:N
   if i<=N/2,  x = ifft([zeros(1,i-1) X(i) zeros(1,NNos-i+1)],NNos);
   else  x = ifft([zeros(1,NNos-N+i-1) X(i) zeros(1,N-i)],NNos);
   end
   xI(i,:) = real(x); xQ(i,:) = imag(x);
end
sum_xI = sum(xI); sum_xQ = sum(xQ);
figure(1), clf, subplot(311)
plot(time,xI,'k:','linewidth',1), hold on, plot(time,sum_xI,'b','linewidth',2)
title([Mod ', N=' num2str(N)]); ylabel('x_{I}(t)'); axis([0 1 min(sum_xI) max(sum_xI)]);
subplot(312)
plot(time,xQ,'k:','linewidth',1); hold on, plot(time,sum_xQ,'b','linewidth',2)
ylabel('x_{Q}(t)'); axis([0 1 min(sum_xQ) max(sum_xQ)]);
subplot(313), plot(time,abs(sum_xI+j*sum_xQ),'b','linewidth',2); hold on;
ylabel('|x(t)|'); xlabel('t');
clear('xI'), clear('xQ')
N=2^4;  NNos=N*Nos; T=1/NNos; time=[0:T:1-T]; Nhist=1e3;
for k = 1:Nhist
   [X,Mod] = mapper(b,N); X(1)=0+j*0; % A block of 16 QPSK symbols with no DC-subcarrier 
   for i = 1:N
      if (i<= N/2)  x = ifft([zeros(1,i-1) X(i) zeros(1,NNos-i+1)],NNos);
       else  x = ifft([zeros(1,NNos-N/2+i-N/2-1) X(i) zeros(1,N-i)],NNos);
      end
      xI(i,:) = real(x); xQ(i,:) = imag(x);
   end
   HistI(NNos*(k-1)+1:NNos*k) = sum(xI); HistQ(NNos*(k-1)+1:NNos*k) = sum(xQ);
end
N_bin = 30;
figure(2), clf, subplot(311)
[xI_dist,bins] = hist(HistI,N_bin);   bar(bins,xI_dist/sum(xI_dist),'k');
title([Mod ', N=' num2str(N)]);  ylabel('pdf of x_{I}(t)');
subplot(312)
[xQ_dist,bins] = hist(HistQ,N_bin);  bar(bins,xQ_dist/sum(xQ_dist),'k');
ylabel('pdf of x_{Q}(t)');
subplot(313)
[xabs_dist,bins] = hist(abs(HistI+j*HistI),N_bin);  bar(bins,xabs_dist/sum(xabs_dist),'k');
ylabel('pdf of |x(t)|');  xlabel('x_{0}');