selectiverepeat.asv

本程序是用java编写的一些关于arq协议实现的小程序

function [Umas,Pak,Ack]=selectiverepeat(amas,Nsimul,Ploss,SWS);
%function [Umas,Pak,Ack]=gobackn(amas,Nsimul,Ploss,SWS);

% function [Umas,Pak,Ack]=selectiverepeat(amas,Nsimul,Ploss,SWS);
%
% GoBackN algoritnm simulation 
% MaxSeqNum=SWS+1
% 
%
% Input:
%
% amas - t_prop/t_transm    -  can be an array, in which case
% simulation is repeated for each value of an array and 
% cirresponding utilization is recorded in corresponding element of Umas
%
% Nsimul - number of sent frames to simulate
% time required is proportional to Nsimul
% quality of utilization estimates improves with Nsimul
% recommended Nsimul=100;
%
% Ploss - probability of packet loss (or receiving with an error)
% this probability is assumed the same for data packets and acknowledgments
%
% SWS - sender window size
% note: receiver window size - 1 in this algorith
%
% Output:
%
% Umas - vector containing channel utilization estimates for values of a
% in amas parameter. Length(Umas)=Length(amas)
%
% In case of the length(amas)>1 the following 2 output parameters
% output the result for the simulation for the last entry of vector amas
%
% Pak - matrix, each raw contains a signature of the simulated data packet sent.
% structure of the raw: (Pak#   Time_sent  Time_received  sequence#)
% Time_received = Inf   if the packet is lost
%
% Ack - matrix, each raw contains a signature of the simulated acknowledgment 
% packet sent.
% structure of the raw: (Ack#   Time_sent  Time_received  sequence#)
% Time_received = Inf   if the ack is lost
%



if Ploss<0 | Ploss>1 
   error('Ploss not in limits [0,1]');
end

if SWS<1
   error('wrong SWS');
end


Umas=[];

for j=1:length(amas)
   
   a=amas(j);
   
	Tprop=1;
	Ttran=Tprop/a;

	Pak=[];
    % Pak - matrix, each raw contains a signature of the simulated data packet sent.
% structure of the raw: (Pak#   Time_sent  Time_received  sequence#)
% Time_received = Inf   if the packet is lost

	Ack=[];
    % Ack - matrix, each raw contains a signature of the simulated acknowledgment 
% packet sent.
% structure of the raw: (Ack#   Time_sent  Time_received  sequence#)
% Time_received = Inf   if the ack is lost

	time=0;
   
   framen=0;
   U=0;
   Maxfrn=floor(2*SWS-1);   %for SR SWS<(MaxSeqNum+1)/2 (definition)
   
   LFR=-1;  %last frame recv
   LFA=-1;  %last frame acked
   LFS=-1;  %last frame sent
   
   busysender=0;       
   stackarrive=[0 0];
   stackarrive(1,:)=[];   
   stackack=[0 0];
   stackack(1,:)=[];
   stacktimeout=[0 0]; %every packed goes in timeout array until it is received, then overwritten 
   stacktimeout(1,:)=[];
   timestep=min(Tprop,Ttran)/50;
   Timeout=Ttran+2*Tprop+3*timestep;    %make timeout be slightly greater than the normal time to send packet and receive ack
   
   paknum = 0;


%----------------------------------------------------------
time2=time;