www.pudn.com > DPSK.zip > DPSK_2_plot.m

tic 
clear; 
SNRindB1=0:1:15;                       %  ready for plotting practical error bit/symbol rario 
SNRindB2=0:0.1:15;                     %  ready for plotting theoretical error bit/symbol rario 
M=2;                                   %  8 DPSK 
k=log2(M);                           
N=10000;                               %  N is the number of octal random integer 
N_bit=N*k;                             %  N_bit is the the total numbers binary bit 
for SNRindB=1:length(SNRindB1) 
    data_bin=rand(k,N)>0.5;            %  generating 3*N 0-1 array 
    sym_oct=data_bin(1,:)*1;        %  N octal random integers 
    %  Gray mapping 
    idx=find(sym_oct==0); 
    rad_init(idx)=0/M*2*pi; 
    idx=find(sym_oct==1); 
    rad_init(idx)=1/M*2*pi; 
 
    dif_rad(1)=rad_init(1);                                    %  initiating the first differential angle 
    for j=2:N 
        dif_rad(j)=mod((rad_init(j)+dif_rad(j-1)),2*pi); 
    end 
    %  I and Q 
    data_I=cos(dif_rad); 
    data_Q=sin(dif_rad); 
    data=data_I+i*data_Q; 
    %  generating noise 
    snr_in_dec=10.^((SNRindB-1)/10); 
    sigma=sqrt(1/(2*k*snr_in_dec));                            %  culculation fomula of sigma 
%     [noise_I noise_Q]=gngauss(N,sigma); 
%     noise_I_Q=[noise_I;noise_Q];                               %  noise is 2*N gauss random number array by sigma 
%     noise=noise_I+i*noise_Q; 
%     data_add_noise=data+noise; 
    data_add_noise=gngauss(N,data,sigma); 
    %  data_differential + noise_gauss 
 
    %  Next, we begin decision 
    decs_data=zeros(1,N);                                      %  decs_data is for containing octal data 
    decs_bin=zeros(1,N);                                       %  decs_bin is for containing binary data 
    decs_rad=angle(data_add_noise);                            %  culculating the differential phase 
    culcu_rad(1)=decs_rad(1); 
    for j=2:N 
        culcu_abs_rad(j)=mod((decs_rad(j)-decs_rad(j-1)),2*pi); 
    end                                                        %  in this time, the cul_rad is the absolute phase angle added noise 
     
    index1=find(culcu_abs_rad3*pi/2); 
    decs_bin(:,index1)=repmat([0]',1,length(index1)); 
    decs_bin(:,index2)=repmat([0]',1,length(index2)); 
    index1=find(culcu_abs_rad>pi/2);                                 %  1 decision 
    index2=find(culcu_abs_rad(index1)<3*pi/2); 
    decs_bin(:,index1(index2))=repmat([1]',1,length(index2)); 
 
     
    % END binary decision above 
    decs_data=decs_bin(1,:)*1;       %  N octal random integers which had been decided 
    num_of_err_bit=length(find(xor(data_bin,decs_bin)));             %  culculating the total number of error bit 
    num_of_err_symbol=length(find(sym_oct-decs_data));               %  culculating the total number of error symnol 
    pb(SNRindB)=num_of_err_bit/N_bit 
    ps(SNRindB)=num_of_err_symbol/N; 
end 
semilogy(SNRindB1,pb,'k*'); 
hold on; 
semilogy(SNRindB1,ps,'b'); 
pb_from_ps=ps/1; 
semilogy(SNRindB1,pb_from_ps,'r');                                   %  pb_from_ps is probability of error bit by directly culculating pb 
grid on; 
toc