%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
 %10/6/2008     zhangsong
 %一個具有差錯檢測的DF仿真程序
 %新CRC
 %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
echo off;clear all;close all;clc;
tic
N=1000;
L=65;    %一幀長度
BerSnrTable=zeros(20,5);
for snr=0:25
    BerSnrTable(snr+1,1) = snr;
    sig=1/sqrt(10^(snr/10));
    temp=0;
    temp1=0;
    for i=1:N
        BitsTx = floor(rand(1,L)*2);
        BitsTxcrc=CrcEncode(BitsTx);
        BitsTxcnv=cnv(BitsTxcrc);
        Mod8Tx=mod_8psk(BitsTxcnv);
        M=length(Mod8Tx);
        %以下為假設信道模型和噪聲模型，由于本次仿真重點不在于此，所以做以下簡化
        H1d=randn(1,M)+j*randn(1,M);
        H12=randn(1,M)+j*randn(1,M);
        H2d=randn(1,M)+j*randn(1,M);
        Z1d=randn(1,M)+j*randn(1,M);
        Z12=randn(1,M)+j*randn(1,M);
        Z2d=randn(1,M)+j*randn(1,M);
        % d接收
        Y1d=H1d.*Mod8Tx+sig*Z1d;
        %user2接收并解碼
        Y12=H12.*Mod8Tx+sig*Z12;
        R12=conj(H12).*Y12;
        BitR12=demod_8psk(R12);
        BitR12viterbi=viterbi(BitR12);
        BitR12viterbi=BitR12viterbi(1:length(BitR12viterbi)-1);
        [BitR12decrc,error]=CrcDecode(BitR12viterbi);
         %error=0,正確解碼   error=1，錯誤解碼
         %非協作情況
        if(error==1)
            R1d=conj(H1d).*Y1d; 
            BitR1d=demod_8psk(R1d);
            BitR1dviterbi=viterbi(BitR1d);
            BitR1dviterbi=BitR1dviterbi(1:length(BitR1dviterbi)-1);
            BitR1ddecrc=CrcDecode(BitR1dviterbi);
            [Num,Ber] = symerr(BitR1ddecrc,BitsTx);
            BerSnrTable(snr+1,2)=BerSnrTable(snr+1,2)+Num;
        end
         %協作情況
        if(error==0)
            Bits2d=BitR12decrc;
            Bits2dcrc=CrcEncode(Bits2d);
            Bits2dcnv=cnv(Bits2dcrc);
            Mod8_2d=mod_8psk(Bits2dcnv);
            Y2d=H2d.*Mod8_2d+sig*Z2d;
            %最大合并比在此處的簡化形式
            Rd=conj(H2d).*Y2d+conj(H1d).*Y1d;
            BitRd=demod_8psk(Rd);
            BitRdviterbi=viterbi(BitRd);
            BitRdviterbi=BitRdviterbi(1:length(BitRdviterbi)-1);
            BitRddecrc=CrcDecode(BitRdviterbi);
            [Num,Ber] = symerr(BitRddecrc,BitsTx);
            BerSnrTable(snr+1,2)=BerSnrTable(snr+1,2)+Num;
            temp=temp+1;
        end   
    end
    BerSnrTable(snr+1,3)=BerSnrTable(snr+1,2)/(L*N);  %此處將M改成N
    BerSnrTable(snr+1,4)=temp;
end   
semilogy(BerSnrTable(:,1),BerSnrTable(:,3),'r*-');
figure
semilogy(BerSnrTable(:,1),BerSnrTable(:,4),'g*-');
time_of_sim = toc
echo on;