%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


%********系統參數********%
Eb_to_Nj_in_dB=[15];
Eb_to_No_in_dB=15;
BPH=2;
number_of_states=16;
Q=1; % 干擾音的個數
N=10000; % 每次符號流長度
times=500; % 重復做500次
PB_all=zeros(length(Eb_to_Nj_in_dB),1);
vita_symbol_err=zeros(length(Eb_to_Nj_in_dB),times);% 維特比譯碼后符號錯誤計數器
num_of_err=zeros(length(Eb_to_Nj_in_dB),times);
WTbarpp=waitbar(0,'Outer SNRs Loop:Please wait...');
for pp=1:length(Eb_to_Nj_in_dB)
fanout=2^BPH; % DFH的扇出系數
Eb_to_Nj=10^(Eb_to_Nj_in_dB(pp)/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級是其狀態位,與網格圖中的狀態一一對應(注意并不是與跳頻頻點一一對應)

WTbar=waitbar(0,'SNR inside loop:Please wait...');
for rep=1:times

source=[randint(1,N,fanout),zeros(1,L)]; % 信息源:隨機符號流,最后補上L個0符號,使移位寄存器的狀態清零

%***********************信源部分************************%

% 將信息符號流轉化成二進制信息比特流,不包括最后補上的L個0符號(dsource只是在最后計算誤碼率的時候用)
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

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



% ******************* G 函數實現部分 ************************ %

% 先定義三個關鍵矩陣"nextstates" "output" "input"
nextstate=zeros(number_of_states,fanout); % nextstate矩陣:行代表網格圖中的各狀態(一一對應),列與輸入移位寄存器的信息符號一一對應,
                                          % 矩陣中存儲的內容是與當前狀態和輸入符號對應的下一狀態號(即存儲網格圖的狀態轉移規則)  
output=zeros(number_of_states,fanout);    % output矩陣:行代表網格圖中的各狀態(一一對應),列與輸入移位寄存器的信息符號一一對應,
                                          % 矩陣中存儲的內容是與當前狀態和輸入符號對應的網格圖分支轉移輸出(分支轉移輸出是跳頻頻率號)
input=zeros(number_of_states,number_of_states);
number_of_out=number_of_states*fanout;% 跳頻頻點數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 
% ********************************************************* %



depth_of_trellis=length(source);
% Es=1;
% Eb=Es/BPH;
Eb=1;
Es=BPH*Eb;
% Ej0=(Eb*number_of_out*Q)/(Eb_to_Nj);% 每個多音干擾的能量Ej0
Ej0=(Es*number_of_out)/(BPH*Q*Eb_to_Nj); % 每跳時間內每個多音干擾的能量Ej0
sgma=sqrt(Eb/(2*Eb_to_No));% AWGN的均方根
demod_input=zeros(number_of_out,depth_of_trellis);
f=zeros(1,depth_of_trellis);
D=0; % D 記錄網格圖的當前狀態,這里初始狀態是0狀態

% *******************信道和非相干解調部分:加多音干擾和噪聲,然后非相干解調****************** %
for i=1:depth_of_trellis % i表示網格圖的時間走勢
    rc=zeros(1,number_of_out);
    rs=zeros(1,number_of_out);
    f(i)=output(D+1,source(i)+1); % f(i)是i時刻的分支轉移輸出,即i時刻的跳頻頻率號
%     theta_s=2*pi*rand;
%     theta_j=2*pi*rand;% 干擾音與跳頻信號的相對相位
%   J=randint(1,Q,number_of_out); % J 矩陣中存放Q個干擾音所在的頻率號
    J=gen_multijammer(Q,number_of_out);% J 矩陣中存放Q個干擾音所在的頻率號,干擾音所在頻率號范圍也是[0,number_of_out-1]而不是[1,number_of_out]
    for j=0:number_of_out-1
        if (j==f(i))
            theta_s=2*pi*rand;% //random phase of the signal tone
            rc(j+1)=sqrt(Es)*cos(theta_s)+sgma*randn;
            rs(j+1)=sqrt(Es)*sin(theta_s)+sgma*randn;
        else
            rc(j+1)=sgma*randn;
            rs(j+1)=sgma*randn;
        end
    end
    for k=1:Q
        theta_j=2*pi*rand;% //random phase of each jamming tone
        for j=0:number_of_out-1
            if (j==J(k))
                rc(j+1)=rc(j+1)+sqrt(Ej0)*cos(theta_j);
                rs(j+1)=rs(j+1)+sqrt(Ej0)*sin(theta_j);
            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(i)+1);
end
% ************************************************************ %

% ****************** 維特比譯碼模塊 ************************** %
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_symbol=zeros(1,depth_of_trellis-L);% length(decoder_output_symbol)=N,維特比譯碼后的輸出符號流
decoder_output=zeros(1,BPH*(depth_of_trellis-L));
for i=1:depth_of_trellis-L
    dec_output_deci=input(state_sequence(1,i)+1,state_sequence(1,i+1)+1);
    decoder_output_symbol(i)=dec_output_deci;
    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

for i=1:N  %計算維特比譯碼之后的符號錯誤率
    if (decoder_output_symbol(i)~=source(i))
        vita_symbol_err(pp,rep)=vita_symbol_err(pp,rep)+1;
    end
end

for i=1:N*BPH
    if(dsource(i)~=decoder_output(i))
       num_of_err(pp,rep)=num_of_err(pp,rep)+1;
   end
end 
% ******************** End of Viterbi Decoding Modular ****************** %
waitbar(rep/times,WTbar)
end % 與rep times循環對應的 end
close(WTbar)
waitbar(pp/length(Eb_to_Nj_in_dB),WTbarpp)
end % 與最外層"多少遍"pp for循環對應的end
close(WTbarpp)

PB_all=sum(num_of_err,2)/(N*times*BPH) % N 是一遍的符號流長度,總共進行times遍,共N*times個符號

symerr_num_biterr=zeros(2*length(Eb_to_Nj_in_dB),times);
for i=1:length(Eb_to_Nj_in_dB)
    symerr_num_biterr(2*i-1,:)=vita_symbol_err(i,:);
    symerr_num_biterr(2*i,:)=num_of_err(i,:);
end