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Numusers=1; 
Nc=16;  %扩频因子 
ISI_Length=1; %每径延时为ISI_Length/2 
EbN0db = [0:2:10]; 
Tlen=5000;%数据长度 
Bit_Error_Number1=0;%误比特率的初始值 
Bit_Error_Number2=0; 
Bit_Error_Number3=0; 
power_unitary_factor1=sqrt(5/9);%每径功率因子 
power_unitary_factor2=sqrt(3/9); 
power_unitary_factor3=sqrt(1/9); 
s_initial=randsrc(1,Tlen);%数据源 
%产生Walsh 矩阵                      
Wal2=[1 1;1 -1]; 
Wal4=[Wal2 Wal2;Wal2 Wal2*(-1)]; 
Wal8=[Wal4 Wal4;Wal4 Wal4*(-1)]; 
Wal16=[Wal8 Wal8;Wal8 Wal8*(-1)]; 
%扩频 
s_spread=zeros(Numusers,Tlen*Nc); 
ray1=zeros(Numusers,2*Tlen*Nc); 
ray2=zeros(Numusers,2*Tlen*Nc); 
ray3=zeros(Numusers,2*Tlen*Nc); 
for i=1:Numusers 
    x0=s_initial(i,:).'*Wal16(8,:); 
    x1=x0.'; 
    s_Spread(i,:)=(x1(:)).'; 
end 
%将每个扩频后输出重复为两次，有利于下面的延迟（延迟了半个码元） 
ray1(1:2:2*Tlen*Nc-1)=s_Spread(1:Tlen*Nc);  
ray1(2:2:2*Tlen*Nc)=ray1(1:2:2*Tlen*Nc-1); 
 
%产生第二径和第三径信号 
ray2(ISI_Length+1:2*Tlen*Nc)=ray1(1:2*Tlen*Nc-ISI_Length); 
ray3(2*ISI_Length+1:2*Tlen*Nc)=ray1(1:2*Tlen*Nc-2*ISI_Length); 
 
for nEN = 1:length(EbN0db) 
    en = 10^(EbN0db(nEN)/10);      % convert Eb/N0 from unit db to normal numbers 
    sigma = sqrt((32/(2*en))); 
    %接收到的信号demp 
    demp=power_unitary_factor1*ray1+power_unitary_factor2*ray2+power_unitary_factor3*ray3+(randn(1,2*Tlen*Nc)+randn(1,2*Tlen*Nc)*i)*sigma; 
    dt=reshape(demp,32,Tlen)'; 
    %将Walsh码重复为两次 
    Wal16_d(1:2:31)=Wal16(8,1:16); 
    Wal16_d(2:2:32)=Wal16(8,1:16); 
    %解扩后rdata1为第一径输出 
    rdata1=dt*Wal16_d(1,:).'; 
    %将Walsh码延迟半个码片 
    Wal16_delay1(1,2:32)=Wal16_d(1,1:31); 
    %解扩后rdata2为第二径输出 
    rdata2=dt*Wal16_delay1(1,:).'; 
    %将Walsh码延迟一个码片 
    Wal16_delay2(1,3:32)=Wal16_d(1,1:30); 
    Wal16_delay2(1,1:2)=Wal16_d(1,31:32); 
    %解扩后rdata3为第三径输出 
    rdata3=dt*Wal16_delay2(1,:).'; 
    p1=rdata1'*rdata1; 
    p2=rdata2'*rdata2; 
    p3=rdata3'*rdata3; 
    p=p1+p2+p3; 
    u1=p1/p; 
    u2=p2/p; 
    u3=p3/p; 
    %最大值合并 
    rd_m1=real(rdata1*u1+rdata2*u2+rdata3*u3); 
    %等增益合并 
    rd_m2=(real(rdata1+rdata2+rdata3))/3; 
    %选择式合并 
    u=[u1,u2,u3]; 
    maxu=max(u); 
    if(maxu==u1) 
        rd_m3=real(rdata1); 
    else if(maxu==u2) 
            rd_m3=real(rdata2); 
        else rd_m3=real(rdata3); 
        end 
    end 
    %三种方法判决输出 
    r_Data1=sign(rd_m1)'; 
    r_Data2=sign(rd_m2)'; 
    r_Data3=sign(rd_m3)'; 
    %计算误比特率 
    Bit_Error_Number1=length(find(r_Data1(1:Tlen)~=s_initial(1:Tlen))); 
    Bit_Error_Rate1(nEN)=Bit_Error_Number1/(Tlen); 
    Bit_Error_Number2=length(find(r_Data2(1:Tlen)~=s_initial(1:Tlen))); 
    Bit_Error_Rate2(nEN)=Bit_Error_Number2/(Tlen); 
    Bit_Error_Number3=length(find(r_Data3(1:Tlen)~=s_initial(1:Tlen))); 
    Bit_Error_Rate3(nEN)=Bit_Error_Number3/(Tlen);      
end 
semilogy(EbN0db,Bit_Error_Rate1,'*-');hold on; 
semilogy(EbN0db,Bit_Error_Rate2,'o-'); hold on; 
semilogy(EbN0db,Bit_Error_Rate3,'+-'); 
legend('最大比合并','等增益合并','选择式合并'); 
xlabel('信噪比'); 
ylabel('误比特率'); 
title('3种主要分集合并方式性能比较');