clc;
clear;
close all;
warning off;
addpath(genpath(pwd));
r=5;
N=2^r-1;%周期31
a=ones(1,r);
m=zeros(1,N);
for i=1:(2^r-1)
temp= mod((a(5)+a(2)),2);
for j=r:-1:2
a(j)=a(j-1);
end
a(1)=temp;
m(i)=a(r);
end
m=m*2-1;%双极性码
%产生随机发送信息，并进行BPSK/QPSK调制
n=1000;
Y_BIT_sum=zeros(1,36);
for jj=1:100%跑100次，得到平滑曲线
source=randi([0 1],1,n);
% s_imag=randi(1,n);
s_BPSK=2*source-1;
%产生扩频信号：
for z=1:1000
y_BPSK(31*(z-1)+(1:31))=m*s_BPSK(z);
end
%加入高斯白噪声
SNR=-30:5;
for i=1:length(SNR)
y(i,:)=awgn(y_BPSK,SNR(i));
end
%解扩
for z=1:1000
for i=1:length(SNR)
o_BPSK(i,z)=y(i,31*(z-1)+(1:31))/m;
end
end
Y_RE=o_BPSK;
%判决
Y_RE(o_BPSK>0)=1;
Y_RE(o_BPSK<0)=0;
Y_ERRO=zeros(length(SNR),1000);
Y_BIT=zeros(1,length(SNR));
for i=1:length(SNR)
Y_ERRO(i,:)=abs(Y_RE(i,:)-source);
Y_BIT(i)=sum(Y_ERRO(i,:))/n;
end
Y_BIT_sum=Y_BIT_sum+Y_BIT;
end
Y_BIT_av=Y_BIT_sum/100;
figure;
semilogy(SNR,Y_BIT_av,'b-o');
xlabel('SNR');ylabel('误码率');
grid on;
