%function pb=multi_awgn_vita(Eb_to_Nj_in_dB,Eb_to_No_in_dB,BPH,number_of_states,Q)
%VITERBI      This procedure simulates the Viterbi sequnce decoding of the
%             differential frequency hopping system
%
%             Eb_to_Nj_in_dB is the signal-to-jamming ratio given in dB
%
%             Eb_to_No_in_dB is the signal-to-noise ratio given in dB
%
%             BPH is the number of bits transmitted by one hop
%
%             number_of_states is the number of states in the DFH
%             trellis,corresponding to the right L stages of the DFH encoding 
%             shift register 
%
%             Q is the number of jamming tones in the DFH bandwidth
%             這個(gè)程序是正確的,帶(8,4)糾錯(cuò)碼,編碼后在后面只補(bǔ)上L個(gè)0,即符號(hào)流總長度是2N+L而不是2(N+L),
%             而multi_awgn_vita_encode.m是帶(8,4)糾錯(cuò)碼但符號(hào)流總長度是2(N+L),這兩個(gè)程序都對(duì)


%********系統(tǒng)參數(shù)********%
Eb_to_Nj_in_dB=12;
Eb_to_No_in_dB=13.35;
BPH=2;
number_of_states=16;
Q=1; % 干擾音的個(gè)數(shù)
%************************%




N=1000; % 每次符號(hào)流長度
times=10; % 重復(fù)做500次
fanout=2^BPH; % DFH的扇出系數(shù)
Eb_to_Nj=10^(Eb_to_Nj_in_dB/10); % 比值形式的Eb/Nj
Eb_to_No=10^(Eb_to_No_in_dB/10); % 比值形式的Eb/No
L=floor(log(number_of_states)/log(fanout)); % 編碼移位寄存器的長度為L+1,最右邊L級(jí)是其狀態(tài)位,與網(wǎng)格圖中的狀態(tài)一一對(duì)應(yīng)(注意并不是與跳頻頻點(diǎn)一一對(duì)應(yīng))

num_of_err=zeros(1,times);
% pb=zeros(1,times);
for rep=1:times

% source=[randint(1,N,fanout),zeros(1,L)]; % 信息源:(注意不是10進(jìn)制的,而是fanout進(jìn)制的)隨機(jī)符號(hào)流,最后補(bǔ)上L個(gè)0符號(hào),使移位寄存器的狀態(tài)清零
source=randint(1,N,fanout);
%***********************信源部分************************%

% 將信息符號(hào)流轉(zhuǎn)化成二進(jìn)制信息比特流
dsource=zeros(1,N*BPH); 
if(BPH~=1)
    for i=1:N
        dsource((i-1)*BPH+1:i*BPH)=deci2change(source(i),BPH,2);
    end
else
    dsource=source(1:N);%*****
end

%******************************************************%


% *******************差錯(cuò)控制編碼部分(8,4)碼**********************%
G=[1 0 0 0 1 0 1 1;0 1 0 0 1 1 0 1;0 0 1 0 0 1 1 1;0 0 0 1 1 1 1 0];
dsource_coded=encode(dsource,8,4,'linear',G)';
source_coded0=zeros(1,2*N);
if (BPH~=1)
    for i=1:2*N
        register=dsource_coded((i-1)*BPH+1:i*BPH);
        source_coded0(i)=change2deci(register,2);
    end
else
    source_coded0=dsource_coded(1:2*N);
end
% *****************************************************************%

source_coded=[source_coded0,zeros(1,L)];%在編碼序列后面加L個(gè)0符號(hào),使移位寄存器狀態(tài)清零
% ******************* G 函數(shù)實(shí)現(xiàn)部分 ************************ %

% 先定義三個(gè)關(guān)鍵矩陣"nextstates" "output" "input"
nextstate=zeros(number_of_states,fanout); % nextstate矩陣:行代表網(wǎng)格圖中的各狀態(tài)(一一對(duì)應(yīng)),列與輸入移位寄存器的信息符號(hào)一一對(duì)應(yīng),
                                          % 矩陣中存儲(chǔ)的內(nèi)容是與當(dāng)前狀態(tài)和輸入符號(hào)對(duì)應(yīng)的下一狀態(tài)號(hào)(即存儲(chǔ)網(wǎng)格圖的狀態(tài)轉(zhuǎn)移規(guī)則)  
output=zeros(number_of_states,fanout);    % output矩陣:行代表網(wǎng)格圖中的各狀態(tài)(一一對(duì)應(yīng)),列與輸入移位寄存器的信息符號(hào)一一對(duì)應(yīng),
                                          % 矩陣中存儲(chǔ)的內(nèi)容是與當(dāng)前狀態(tài)和輸入符號(hào)對(duì)應(yīng)的網(wǎng)格圖分支轉(zhuǎn)移輸出(分支轉(zhuǎn)移輸出是跳頻頻率號(hào))
input=zeros(number_of_states,number_of_states);
number_of_out=number_of_states*fanout;% 跳頻頻點(diǎn)數(shù)Nt
for i=0:number_of_states-1
    for j=0:fanout-1
        [next_state,out_put]=G_func1(i,j,L,fanout);
        nextstate(i+1,j+1)=next_state;
        output(i+1,j+1)=out_put;
        input(i+1,next_state+1)=j;
    end
end 
% ********************************************************* %


% ********************維特比譯碼部分**********************%

depth_of_trellis=length(source_coded);%******************* %depth_of_trellis=2N+L
Eb=1;
Es=Eb*BPH*(1/2);
% Ej0=(Eb*number_of_out*Q)/(Eb_to_Nj);% 每個(gè)多音干擾的能量Ej0
Ej0=(Es*number_of_out)/(BPH*Q*Eb_to_Nj); % 每跳時(shí)間內(nèi)每個(gè)多音干擾的能量Ej0
sgma=sqrt(Eb/(2*Eb_to_No));% AWGN的均方根
thyta=2*pi*rand;% 干擾音與跳頻信號(hào)的相對(duì)相位
demod_input=zeros(number_of_out,depth_of_trellis);
f=zeros(1,depth_of_trellis);
rc=zeros(1,number_of_out);
rs=zeros(1,number_of_out);
D=0; % D 記錄網(wǎng)格圖的當(dāng)前狀態(tài),這里初始狀態(tài)是0狀態(tài)

% *******************信道和非相干解調(diào)部分:加多音干擾和噪聲,然后非相干解調(diào)****************** %
for i=1:depth_of_trellis % i表示網(wǎng)格圖的時(shí)間走勢(shì)
    f(i)=output(D+1,source_coded(i)+1); % f(i)是i時(shí)刻的分支轉(zhuǎn)移輸出,即i時(shí)刻的跳頻頻率號(hào) %************************
%   J=randint(1,Q,number_of_out); % J 矩陣中存放Q個(gè)干擾音所在的頻率號(hào)
    J=gen_multijammer(Q,number_of_out);% J 矩陣中存放Q個(gè)干擾音所在的頻率號(hào),干擾音所在頻率號(hào)范圍也是[0,number_of_out-1]而不是[1,number_of_out]
    for j=0:number_of_out-1
        if (j==f(i))
            rc(j+1)=sqrt(Es)+sgma*randn;
            rs(j+1)=sgma*randn;
        else
            rc(j+1)=sgma*randn;
            rs(j+1)=sgma*randn;
        end
    end
    for k=1:Q
        for j=0:number_of_out-1
            if (j==J(k))
                rc(j+1)=rc(j+1)+sqrt(Ej0)*cos(thyta);
                rs(j+1)=rs(j+1)+sqrt(Ej0)*sin(thyta);
            end
        end
    end
    for j=0:number_of_out-1
        demod_input(j+1,i)=sqrt(rc(j+1)^2+rs(j+1)^2);
    end
    D=nextstate(D+1,source_coded(i)+1);   %*************************
end
            

% *******************信道和非相干解調(diào)部分:加多音干擾和噪聲,然后非相干解調(diào)****************** %

% for i=1:depth_of_trellis % i表示網(wǎng)格圖的時(shí)間走勢(shì)
%     f(i)=output(D+1,source(i)+1); % f(i)是i時(shí)刻的分支轉(zhuǎn)移輸出,即i時(shí)刻的跳頻頻率號(hào)
%     J=randint(1,Q,number_of_out); % J 矩陣中存放Q個(gè)干擾音所在的頻率號(hào)
%     for k=1:Q
%         for j=0:number_of_out-1
%             if (j==J(k)&j~=f(i)) % 頻點(diǎn)上有干擾而無信號(hào)
%                 rc=sqrt(Ej0)*cos(thyta)+sgma*randn;
%                 rs=sqrt(Ej0)*sin(thyta)+sgma*randn;
%                 demod_input(j+1,i)=sqrt(rc^2+rs^2);
%             end
%             if (j==J(k)&j==f(i)) % 頻點(diǎn)上既有干擾又有信號(hào)
%                 rc=sqrt(Es)+sqrt(Ej0)*cos(thyta)+sgma*randn;
%                 rs=sqrt(Ej0)*sin(thyta)+sgma*randn;
%                 demod_input(j+1,i)=sqrt(rc^2+rs^2);
%             end
%             if (j~=J(k)&j==f(i)) % 頻點(diǎn)上有信號(hào)而無干擾
%                 rc=sqrt(Es)+sgma*randn;
%                 rs=sgma*randn;
%                 demod_input(j+1,i)=sqrt(rc^2+rs^2);
%             end
%             if (j~=J(k)&j~=f(i)) % 頻點(diǎn)上既無信號(hào)又無干擾
%                 rc=sgma*randn;
%                 rs=sgma*randn;
%                 demod_input(j+1,i)=sqrt(rc^2+rs^2);
%             end
%         end
%     end
%     D=nextstate(D+1,source(i)+1);
% end
% ************************************************************************%



% sgma=sqrt(Es/(BPH*2*Eb_to_No));
% demod_input=zeros(number_of_out,depth_of_trellis);
% f=zeros(1,depth_of_trellis);
% D=0;
% for i=1:depth_of_trellis
%     f(i)=output(D+1,source(i)+1);
%     for j=0:number_of_out-1
%         if(j~=f(i))
%            rc=sgma*randn;
%            rs=sgma*randn;
%        else
%            rc=sqrt(E)+sgma*randn;
%            rs=sgma*randn;
%        end
%        demod_input(j+1,i)=sqrt(rc^2+rs^2);
%    end
%     D=nextstate(D+1,source(i)+1);
% end
% demod_input=demod_input/sgma^2;

state_metric=zeros(number_of_states,2);
survivor_state=zeros(number_of_states,depth_of_trellis+1);
for i=1:depth_of_trellis-L
    flag=zeros(1,number_of_states);
    if i<=L+1
        step=2^((L+1-i)*BPH);
    else
        step=1;
    end
    for j=0:step:number_of_states-1
        for m=0:fanout-1
            branch_metric=demod_input(output(j+1,m+1)+1,i);
            if((state_metric(nextstate(j+1,m+1)+1,2)<state_metric(j+1,1)...
                    +branch_metric)|flag(nextstate(j+1,m+1)+1)==0)
                state_metric(nextstate(j+1,m+1)+1,2)=state_metric(j+1,1)+branch_metric;
                survivor_state(nextstate(j+1,m+1)+1,i+1)=j;
                flag(nextstate(j+1,m+1)+1)=1;
            end
        end
    end
    state_metric=state_metric(:,2:-1:1);
end
for i=depth_of_trellis-L+1:depth_of_trellis
    flag=zeros(1,number_of_states);
    last_stop=number_of_states/(2^((i-depth_of_trellis+L-1)*BPH));
    for j=0:last_stop-1
        branch_metric=demod_input(output(j+1,m+1)+1,i);
        if((state_metric(nextstate(j+1,1)+1,2)<state_metric(j+1,1)...
            +branch_metric)|flag(nextstate(j+1,1)+1)==0)
            state_metric(nextstate(j+1,1)+1,2)=state_metric(j+1,1)+branch_metric;
            survivor_state(nextstate(j+1,1)+1,i+1)=j;
            flag(nextstate(j+1,1)+1)=1;
        end
    end
    state_metric=state_metric(:,2:-1:1);
end
state_sequence=zeros(1,depth_of_trellis+1);
for i=1:depth_of_trellis
    state_sequence(1,depth_of_trellis-i+1)=survivor_state((state_sequence(1,depth_of_trellis+2-i)...
        +1),depth_of_trellis-i+2);
end
decoder_output=zeros(1,BPH*(depth_of_trellis-L));% length(decoder_output)=BPH*2N
for i=1:depth_of_trellis-L
    dec_output_deci=input(state_sequence(1,i)+1,state_sequence(1,i+1)+1);
    if(BPH~=1)
        dec_output_bin=deci2change(dec_output_deci,BPH,2);
        decoder_output((i-1)*BPH+1:i*BPH)=dec_output_bin;
    else
        decoder_output(1,i)=dec_output_deci;
    end
end
% ************************************************************************%

% ***********(8,4)譯碼部分***********%

deco_input=zeros(1,BPH*2*N);
deco_input(1:BPH*2*N)=decoder_output(1:BPH*2*N);
deco_output=decode(deco_input,8,4,'linear',G)';% (8,4)譯碼器的譯碼輸出(長為BPH*(N+L)個(gè)比特,列矢量)

% ***********************************%


for i=1:N*BPH
    if(dsource(i)~=deco_output(i))
       num_of_err(rep)=num_of_err(rep)+1;
   end
end

end % 與最外層"多少遍" for循環(huán)對(duì)應(yīng)的end

Pb=sum(num_of_err)/(N*times*BPH) % N 是一遍的符號(hào)流長度,總共進(jìn)行times遍,共N*times個(gè)符號(hào)