ip_07_09.rar_ifft matlab_ip_07_09_ofdm matlab _信道建模_信道模型

% MATLAB script for Illustrative Problem 9, Chapter 7. % echo on clear; K=10; N=2*K; Ts=25; T=N*Ts; a=rand(1,(K-1)*4); % k-1符号，1个保护间隔0 a=sign(a-0.5); b=reshape(a,K-1,4); % Generate the 16QAM points XXX=2*b(:,1)+b(:,2)+j*(2*b(:,3)+b(:,4)); % 随机声称9个16点QAM星座点 XX=XXX'; X=[0 XX 0 conj(XX(K-1:-1:1))]; % X长度为20，等于N xt=zeros(1,T+1); % IDFT t for t=0:T % 载波分辨力 for k=0:N-1 % 载波数量 xt(t+1)=xt(t+1)+1/sqrt(N)*X(k+1)*exp(j*2*pi*k*t/T); end end % IDFT n xn=zeros(1,N); for n=0:N-1 for k=0:N-1 xn(n+1)=xn(n+1)+1/sqrt(N)*X(k+1)*exp(j*2*pi*n*k/N); end end % IFFT xn1=ifft(X,N)*sqrt(N); % pause % press any key to see a plot of x(t) plot([0:T],real(xt),'r',[0:T/N:T-T/N],xn,'.b',[0:T/N:T-T/N],xn1,'og'),grid legend('连续信号','采样信号','IFFT信号*4.5') hold on % 画出每个子载波波形 for ii=[10,12] plot([0:T],1/sqrt(N)*X(ii)*exp(j*2*pi*(ii-1)*[0:T]/T),':') end hold off % Check the difference between xn and samples of x(t) for n=0:N-1 d(n+1)=xt(T/N*n+1)-xn(1+n); % echo off end % echo on e=norm(d); Y=zeros(1,K); % DFT for k=0:K-1 for n=0:N-1 Y(k+1)=Y(k+1)+1/sqrt(N)*xn(n+1)*exp(-j*2*pi*k*n/N); end end Y1=fft(xn1,N)/sqrt(N); % echo on dd=Y(1:K)-X(1:K); dd1=Y1(1:K)-X(1:K); ee=norm(dd) ee2=norm(dd1)