clear all; close all; Tc = 1;
N = 128; %扩频增益
gx= '1000010111000101'; %g(x) = x^15+x^13+x^9+x^8+x^7+x^5+1 g = bin2dec(gx); state = 1; L = 2^13;
EcN0dB = -21:-14;
for k=1:length(EcN0dB)
error(k)=0; %计数错误比特数 total(k)=0; %计数总的传输比特数 sigma(k) = sqrt( 10.^(-EcN0dB(k)/10) /2 ); while( error(k)<100 ) %多径结构
p1 = sqrt(0.5/2)*( randn(1,L)+j*randn(1,L) ); p2 = sqrt(0.3/2)*( randn(1,L)+j*randn(1,L) ); p3 = sqrt(0.2/2)*( randn(1,L)+j*randn(1,L) ); t1 = 0; t2 = 1; t3 = 2;
[pt state]= mgen(g,state,L+t3); pt = 2*pt-1;
%数据产生
d = sign( randn(1,L/N) ); %一次64个 %扩频，先将数据扩展，然后与pt点积 dd = sigexpand(d,N); s = conv( dd,ones(1,N) );
st = s(1:L+t3).*pt(1:L+t3); %扩频
%经过多径信道，加入噪声
z = sigma(k)* ( randn(1,L)+j*randn(1,L) );
rt = st(1:L).*p1 + st(t2+1:L+t2).*p2 + st(t3+1:L+t3).*p3 + z;
%rake接收
r1 = rt.*conj(p1).*pt(1:L);
r2 = rt.*conj(p2).*pt(t2+1:L+t2); r3 = rt.*conj(p3).*pt(t3+1:L+t3);
%积分
r1 = reshape(r1,N,L/N); y1 = sum(r1); r2 = reshape(r2,N,L/N); y2 = sum(r2); r3 = reshape(r3,N,L/N); y3 = sum(r3); %合并
y = y1+y2+y3; %最大比合并 %判决
dc = sign(real(y));
error(k) = error(k) + sum( abs( (d-dc) )/2 ) total(k) = total(k) + L/N; end end
ber = error./total;
semilogy(EcN0dB,ber);
xlabel('Ec/N0/dB');ylabel('误比特率');