qpsk_zuoye.m

matlab的调制解调

% 发送比特速率100kbit/s;mutipath number is 22;

 clc; clear all; close all;
 N=2*10^4;
 sig_send=rand(1,N); sig_send=sign(sig_send-0.5);
 n=4;
 sig_refer=[1  1; 1  -1; -1  1; -1  -1];
 sig_temp=zeros(4,2*n);
 sig_temp(1,:)=symbol_sample(sig_refer(1,:),n);
 sig_temp(2,:)=symbol_sample(sig_refer(2,:),n);
 sig_temp(3,:)=symbol_sample(sig_refer(3,:),n);
 sig_temp(4,:)=symbol_sample(sig_refer(4,:),n);
 
 sig_qpsk=zeros(size(sig_send,2)/2,2);
 
 for ii=1:2:size(sig_send,2)-1
     sig_qpsk((ii+1)/2,1)=sig_send(ii);
 end;
 for ii=2:2:size(sig_send,2)
     sig_qpsk((ii)/2,2)=sig_send(ii);
 end;
 
% ---  awgn channel----------------------------
snr_plot=-10:10;
    bit_error=[];
for snr=-10:10
    num_error=0;
 for ii=1:size(sig_send,2)/2
     sig_chan=symbol_sample(sig_qpsk(ii,:),n);
     sig_rec=awgn(sig_chan,snr,'measured');
     rec_temp=sig_rec*sig_temp';
     if max(rec_temp)==rec_temp(1)
        deci=[1 1];
     elseif max(rec_temp)==rec_temp(2)
         deci=[1 -1];
     elseif max(rec_temp)==rec_temp(3)
         deci=[-1 1];
     elseif max(rec_temp)==rec_temp(4)
         deci=[-1 -1];
     end;
     
     if deci(1)~=sig_qpsk(ii,1)
        num_error=num_error+1;
     elseif deci(2)~=sig_qpsk(ii,2)
        num_error=num_error+1;
     end;
 end;
 bit_error_temp=num_error/N;
 bit_error=[bit_error,bit_error_temp];
end;
figure; 
semilogy(snr_plot,bit_error,'r*-.'); grid on; 
title('AWGN信道情况的误码率'); 
ylabel('BER'); xlabel('信噪比(dB)');
%----------------------awgn channel--------------------
%----------------------rayleigh channel----------------
 sig_refer=[1  i; 1  -i; -1  i; -1  -i];
 sig_temp=zeros(4,2*n);
 sig_temp(1,:)=symbol_sample(sig_refer(1,:),n);
 sig_temp(2,:)=symbol_sample(sig_refer(2,:),n);
 sig_temp(3,:)=symbol_sample(sig_refer(3,:),n);
 sig_temp(4,:)=symbol_sample(sig_refer(4,:),n);
snr_plot=-10:10;
bit_error_ray=[];
for snr=-10:10
    num_error=0;
    x1=symbol_sample(sig_qpsk(:,1)',n);
    x2=symbol_sample(sig_qpsk(:,2)',n);
    sigma=1/sqrt(10^(snr/10));
    num_path=2;   ray_factor=0.5;  
    time_delay=[0,2];  p_path=[1,3/7];
    y1=Rayleigh_DuoJing...
    (x1,sigma,num_path,ray_factor,time_delay,p_path);
    y2=i*Rayleigh_DuoJing...
    (x2,sigma,num_path,ray_factor,time_delay,p_path);
   for ii=1:N/2
       cor_temp=...
  real([y1(n*(ii-1)+1:n*ii),y2(n*(ii-1)+1:n*ii)]*sig_temp');
       if max(cor_temp)==cor_temp(1)
        deci=[1 1];
     elseif max(cor_temp)==cor_temp(2)
         deci=[1 -1];
     elseif max(cor_temp)==cor_temp(3)
         deci=[-1 1];
     elseif max(cor_temp)==cor_temp(4)
         deci=[-1 -1];
     end;
     
     if deci(1)~=sig_qpsk(ii,1)
        num_error=num_error+1;
     elseif deci(2)~=sig_qpsk(ii,2)
        num_error=num_error+1;
     end;
   end;
    bit_error_temp=num_error/N;
    bit_error_ray=[bit_error_ray,bit_error_temp];
end;
figure; 
semilogy(snr_plot,bit_error_ray,'r^-.');  grid on;
title('Rayleigh信道误码率');  ylabel('BER'); xlabel('信噪比');