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  • CCS

    Generation of an OFDM signal

    The modulator and demodulator in an OFDM system are usually implemented by use
    of a parallel bank of tuned filters based on the discrete Fourier Transform (DFT). To
    demonstrate this implementation, let us consider an OFDM modulator that generates
    K independent subcarriers, where each subcarrier is modulated by symbols selected
    from a QAM signal constellation.

     

    Matlab Coding

     

     1 % MATLAB script for Illustrative Problem 8.2.
     2 echo on
     3 clear;
     4 K=10;N=2*K;T=100;
     5 a=rand(1,36); 
     6 a=sign(a-0.5);
     7 b=reshape(a,9,4);
    8 % Generate the 16QAM points 9 XXX=2*b(:,1)+b(:,2)+j*(2*b(:,3)+b(:,4)); 10 XX=XXX'; 11 X=[0 XX 0 conj(XX(9:-1:1))]; 12 xt=zeros(1,101); 13 for t=0:100 14 for k=0:N-1 15 xt(1,t+1)=xt(1,t+1)+1/sqrt(N)*X(k+1)*exp(j*2*pi*k*t/T); 16 echo off 17 end 18 end 19 echo on 20 xn=zeros(1,N); 21 for n=0:N-1 22 for k=0:N-1 23 xn(n+1)=xn(n+1)+1/sqrt(N)*X(k+1)*exp(j*2*pi*n*k/N); 24 echo off 25 end 26 end 27 echo on 28 pause % press any key to see a plot of x(t) 29 plot([0:100],abs(xt))

    30 % Check the difference between xn and samples of x(t)
    31 for n=0:N-1
    32     d(n+1)=xt(T/N*n+1)-xn(1+n);
    33     echo off
    34 end
    35 echo on
    36 e=norm(d);
    37 Y=zeros(1,10);
    38 for k=1:9
    39     for n=0:N-1
    40         Y(1,k+1)=Y(1,k+1)+1/sqrt(N)*xn(n+1)*exp(-j*2*pi*k*n/N);
    41         echo off
    42     end
    43 end
    44 echo on
    45 dd=Y(1:10)-X(1:10);
    46 ee=norm(dd);

    >> ee

    ee =

    1.7359e-14

    >> e

    e =

    4.1301e-14

    Reference,

      1. <<Contemporary Communication System using MATLAB>> - John G. Proakis

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  • 原文地址:https://www.cnblogs.com/zzyzz/p/13702307.html
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