word 第23,24,3,4课
z变换求响应,离散时间系统分析

不知道能不能高亮显示，频偏仿真。

痴心男http://im.cx/n posted @ 2010年5月16日 04:44 in 未分类 , 1560 阅读

 

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%**************************************************************************
 
%The simulation adopted the model in paper "ML estimation of time and
 
%frequency offset" written by J.J van de Beek e.t.Programmed by binyue-Liu
 
%**************************************************************************
 
close all; clear all;
 
N=1024;                                     %length of one symbol
 
L=128;                                      %length of CP
 
SNR=15;
 
Symbol_num=6;
 
Bit_sym=4;                                  %16_QAM
 
s=randint(1,N*Symbol_num*Bit_sym);
 
s_map=qammod(2.^(Bit_sym-1:-1:0)*reshape(s,Bit_sym,N*Symbol_num),16);
 
%Reflecting to the 16_QAM constallation
 
t=ifft(reshape(s_map,N,Symbol_num))*N;        %OFDM modulation
 
t_add_CP=[t(N-L+1:N,:);t];                  %Addition with CP
 
SNR_line=10^(SNR/10);                   
 
transmit=reshape(t_add_CP,1,(N+L)*Symbol_num);
 
sigmma=(1^2+3^2)/2/SNR_line;
 
Noise=(randn(1,(N+L)*Symbol_num)+j*randn(1,(N+L)*Symbol_num))*sqrt(sigmma/2);
 
recieve=zeros(1,Symbol_num*(N+L));
 
erro_rate=zeros(1,10);
 
index=1;
 
for e=0.02:0.01:0.12;                     %The offset of norminal carrier frequency
 
    for i=1:Symbol_num;   
 
        k=1:N+L;
 
        recieve((i-1)*(N+L)+1:(N+L)*i)=transmit((i-1)*(N+L)+1:(N+L)*i).*exp(j*2*pi*e*k/N);
 
    end
 
    r=reshape(recieve+Noise,N+L,Symbol_num);
 
    r1=reshape(fft(r(L+1:end,:))/N,1,N*Symbol_num);
 
    Out_symbol=qamdemod(r1,16);
 
     
 
    Out_bit=zeros(4,N*Symbol_num);
 
    for i=1:N*Symbol_num;
 
      for k=1:Bit_sym
 
        Out_bit(k,i)=floor(Out_symbol(i)/(2^(Bit_sym-k)));
 
        if Out_bit(k,i)==1
 
           Out_symbol(i)=Out_symbol(i)-2^(Bit_sym-k);
 
        else
 
        end
 
      end
 
    end
 
    Out_bit=reshape(Out_bit,1,Bit_sym*N*Symbol_num);
 
erro_rate(index)=length(find(Out_bit~=s))/length(s);
 
index=index+1;
 
end
 
semilogy(0.02:0.01:0.12,erro_rate,'-*')
 
axis([0.01 0.12 10^(-5) 1])
 
 
 
 
 
 
 
     
 
     
 
     
 
     
 
     
 
     
 
     
 
     
 
     
 
    

 

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