clear all;
%%
L=32;                  
%Tw=2*10^(-9);                   %脈沖寬度
%tp=0.4395*10^(-9);              %PPM時延
Tf=2*10^(-6);                   
fc=1.1*10^9;                
t0=2.2*10^(-9);                 
tt=zeros(1,L);
ttp=zeros(1,L);
for l=1:L
    tt(l)=l*2.2*10^(-9)+0.5e-9;           %定義抽頭時延值
end
for s1=1:100
a=random('rayl',0.9,1,L);             %信道幅度選擇瑞利分布的隨機數
a1=a.*exp(i*2*pi*fc*tt);                 %定義多徑衰落a(tl)
a2=abs(sum(a1.^2)); 
a3=abs(sum(a1).^2);
SNR=0:0.25:15;
for i2=1:length(SNR)
    snr=10^(SNR(i2)/10);
    PPM_Pe1(s1,i2)=0.5.*erfc(sqrt(snr)/sqrt(2));
    MRC_x=sqrt(snr.*a2);
    MRC_Pe1(s1,i2)=0.5.*erfc(MRC_x/sqrt(2));
    SLC_x=sqrt(a2.*snr./(2+L./(a2.*snr)));
    SLC_Pe1(s1,i2)=0.5.*erfc(SLC_x/sqrt(2));       %求誤碼率
    EGC_x=sqrt(a3.*snr/L);
    EGC_Pe1(s1,i2)=0.5.*erfc(EGC_x/sqrt(2)); 
end
end

%%


PPM_Pe=sum(PPM_Pe1)/100;
MRC_Pe=sum(MRC_Pe1)/100;


SLC_Pe=sum(SLC_Pe1)/100;
EGC_Pe=sum(EGC_Pe1)/100;
figure(1);                 %畫圖
semilogy(SNR,MRC_Pe,'r:',SNR,SLC_Pe,'b',SNR,EGC_Pe,'g*');      %overlapped PPM 
grid on;
hold on;
axis([0,15,10^(-5),1]);
xlabel('SNR(dB)');
ylabel('BER');
legend('MRC－Rake','SLC－Rake','EGC－Rake');