function [status, timer,comm,counter,flag,ack] = state_machine(pre_status_matrix, pre_next_status_timer,pre_comm_matrix,frame_size...
,back_off_counter,first_frame_flag,priority_matrix,max_DIFS,x_position,y_position,ack_matrix)
global plot_flag;
%Stacte table
% 0: idle(nothing to send)
% 1: waiting for the media available (have something to send)
% 2: Free media and wait for DIFS (have something to send)
% 3: Sending Data
% 4: waiting for SIFS
% 5: sending ACK
% 6: wait for ACK
% -1: Random back-off (Data collision)
back_off_base=4;
max_back_off=8;
len=size(pre_status_matrix,1);
status=zeros(len,1);
timer=zeros(len,1);
comm = zeros(len,1);
counter=back_off_counter;
flag=first_frame_flag;
ack=ack_matrix;
for i=1:len % go through each nodes;
count=0; % count the number of node sending data at the same time if >1 there is a collision
busy_flag=0;
switch pre_status_matrix(i,1)
case 0 %pre state is idle
for j=1:len %check if we receive message
if(pre_status_matrix(j,2)==3&&first_frame_flag(j)==1)
frame_size(i)=frame_size(j);
count=count+1;
tmp=pre_comm_matrix(j);
end
end
if (count==1&&tmp==i) % need to receive message
status(i)=7; % go to ceceive state
timer(i)=frame_size(i);
comm(i)=pre_comm_matrix(i);
elseif(pre_comm_matrix(i)==0) % don need ack message check comm matrix nothing to send stay idle
status(i)=0;
timer(i)=0;
comm(i)=pre_comm_matrix(i);
else %have something to send check if channel is busy
comm(i)=pre_comm_matrix(i);
for j=1:len
if(i~=j && pre_status_matrix(j,2)==3||pre_status_matrix(j,2)==5) %channel is busy
status(i)=1;
timer(i)=0;
busy_flag=1;
end
end
if(busy_flag==0) % channel is not busy
status(i)=2;
timer(i)=randi([max_DIFS-priority_matrix(i) max_DIFS]);
end
end
case 1 %pre state is waiting for media vailiable
comm(i)=pre_comm_matrix(i);
for j=1:len %check if we receive message
if(pre_status_matrix(j,2)==3&&first_frame_flag(j)==1)
frame_size(i)=frame_size(j);
count=count+1;
tmp=pre_comm_matrix(j);
end
end
if (count==1&&tmp==i) % need to receive message
status(i)=7; % go to ceceive state
timer(i)=frame_size(i);
comm(i)=pre_comm_matrix(i);
else %then keep sensing the channel
for j=1:len
if(pre_status_matrix(j,2)==3||pre_status_matrix(j,2)==5) %channel is busy
status(i)=1;
timer(i)=0;
end
end
if(status(i)~=1) % channel is not busy
status(i)=2;
timer(i)=randi([max_DIFS-priority_matrix(i) max_DIFS]);
end
end
case 2 %pre state is waiting DFS
comm(i)=pre_comm_matrix(i);
if(pre_status_matrix(i,2)==3) % already start sending data
status(i)=3;
timer(i)=frame_size(i);
% sx=x_position(i);
% sy=y_position(i);
% dx=x_position(comm(i));
% dy=y_position(comm(i));
% plot_line(sx,sy,dx,dy,'y')
plot_flag(i,1)=1;
plot_flag(i,2)=1;
plot_flag(i,3)=x_position(i);
plot_flag(i,4)=y_position(i);
plot_flag(i,5)=x_position(comm(i));
plot_flag(i,6)=y_position(comm(i));
else
for j=1:len
if(i~=j && pre_status_matrix(j,2)==3 || pre_status_matrix(j,2)==5) %channel is busy
status(i)=1;
timer(i)=0;
end
end
if(status(i)~=1) % channel is not busy
status(i)=2;
timer(i)=pre_next_status_timer(i)-1;
end
if(status(i)==2 && timer(i)==0) %finish DIFS start sending Data
status(i)=3;
timer(i)=frame_size(i);
flag(i)=1;
plot_flag(i,1)=1;
plot_flag(i,2)=1;
plot_flag(i,3)=x_position(i);
plot_flag(i,4)=y_position(i);
plot_flag(i,5)=x_position(comm(i));
plot_flag(i,6)=y_position(comm(i));
end
for k=1:len %check if we receive message
if(pre_status_matrix(k,2)==3&&first_frame_flag(k)==1)
frame_size(i)=frame_size(k);
count=count+1;
tmp=pre_comm_matrix(k);
end
end
if (count==1&&tmp==i) % need to receive message
status(i)=7; % go to ceceive state
timer(i)=frame_size(i);
comm(i)=pre_comm_matrix(i);
end
end
case 3 %pre state is sending data
comm(i)=pre_comm_matrix(i); %keep sending and timer -1
status(i)=3;
timer(i)=pre_next_status_timer(i)-1;
flag(i)=0;
if(timer(i)==0) %finished sending data, begin waite for ACK
status(i)=6;
timer(i)=4;
end
case 4 %pre state is waiting for SIFS
comm(i)=pre_comm_matrix(i);
status(i)=4;
timer(i)=pre_next_status_timer(i)-1;
if(timer(i)==0) %finished waiting SIFS
status(i)= 5;
timer(i)=2;
% sx=x_position(i);
% sy=y_position(i);
% dx=x_position(ack(i));
% dy=y_position(ack(i));
%
