功能描述：
%%---IEEE802.11 CSMA/CA AdHoc Network------%%


% close all;
% clear all;
for M = 2;
%M=5;   %無(wú)線節(jié)點(diǎn)數(shù)量
Counter=0;%數(shù)據(jù)包發(fā)送成功計(jì)算器
Delay=0;
PacketResendingRate=0;  %數(shù)據(jù)包重發(fā)率                  
TotalTimeInSeconds=200;%總仿真時(shí)間，單位：秒
Resend = zeros(1,M);
BER=10^(-6);%誤碼率
SendTime = zeros(1,M);%數(shù)據(jù)包發(fā)送時(shí)間向量
ChannelBusy = 0;
Start = 0;
Collition = 0;
DeferenceTime = 0;      %發(fā)送完成時(shí)間
Throughput = 0;
Throughput_Result = zeros(1,TotalTimeInSeconds);           
PacketResendingRate_Result = zeros(1,TotalTimeInSeconds);
Delay_Result = zeros(1,TotalTimeInSeconds);
ArrivalTime = 1:M;       %新數(shù)據(jù)包到無(wú)線節(jié)點(diǎn)發(fā)送緩沖區(qū)的時(shí)間
PacketLength = 1:M;     %到無(wú)線節(jié)點(diǎn)發(fā)送緩沖區(qū)的新數(shù)據(jù)包大小
HasPacket = zeros(1,M);
CW = 1:M;
BackoffTimer = 1:M;
PacketBuff = zeros(M,5001); %無(wú)線節(jié)點(diǎn)發(fā)送緩沖區(qū)各數(shù)據(jù)包大小矩陣
CollitionStations = zeros(1,M+1);  %沖突站點(diǎn)號(hào)向量
PhyRate = 2*10^6;           %物理層數(shù)據(jù)率=2Mbit/s
SlotTime = 20*10^(-6);      %時(shí)隙間隔=20us
TotalTime = TotalTimeInSeconds/SlotTime;  %總仿真時(shí)間，單位：slot
SIFS = 0.5;      %SIFS=0.5*slot,10us
DIFS = 2.5;      %DIFS=2.5*slot,50us 
ACK = 14*8/(PhyRate*SlotTime); %ACK大小，單位：slot
AverageArrivalTime = 110;    %slots
AveragePacketLength = 50;    %slots
CurBufferSize = zeros(1,M); %當(dāng)前發(fā)送幀長(zhǎng)
Buffer_Threshold = 8*10^6/(PhyRate*SlotTime);%AP最大緩沖區(qū)大小

%初始化
for i = 1:M
    ArrivalTime(i) = ExpDis(AverageArrivalTime);  %初始化到達(dá)時(shí)間  
    PacketLength(i) = 50;%初始化分組長(zhǎng)度
    CW(i) = 32; %競(jìng)爭(zhēng)窗口，CW = 32 slots
    BackoffTimer(i) = 1200; %退避時(shí)間用 1200 slots來(lái)代表無(wú)窮大
end


for t = 1:TotalTime
    for i = 1:M
    %更新發(fā)送緩沖區(qū)
        if t == ArrivalTime(i)
            %目前不能發(fā)送，push分組進(jìn)PackeBuff，修改退避計(jì)數(shù)器
            if CurBufferSize(i) < Buffer_Threshold - PacketLength(i)
                PacketBuff = Push(PacketBuff,i,PacketLength(i));
            %Push新數(shù)據(jù)包
                CurBufferSize(i) = CurBufferSize(i) + PacketLength(i);
                HasPacket(i) = 1;

                if BackoffTimer(i) == 1200
                    BackoffTimer(i) = RandSel(CW(i));%退避計(jì)數(shù)器達(dá)到最大1200時(shí)，重置退避計(jì)數(shù)器
                end
            end
            ArrivalTime(i) = ExpDis(AverageArrivalTime) + PacketLength(i) + t;
            %下一個(gè)數(shù)據(jù)包的到達(dá)時(shí)間
            PacketLength(i) = 50;
            %下一個(gè)數(shù)據(jù)包的大小
        end
    end

    for i = 1:M
        if HasPacket(i) == 1 & ChannelBusy == 0 %PackeBuff中有數(shù)據(jù)包發(fā)送并且信道空閑
            if BackoffTimer(i) == 0 %退避時(shí)間=0則發(fā)送
                CollitionStations = Add(CollitionStations,i);%加入沖突站點(diǎn)序列中
                if Resend(i)==0 ; %第一次發(fā)送
                    SendTime(i)=t+DIFS;
                 end
                Start = 1;
            else
                BackoffTimer(i) = BackoffTimer(i) - 1;%退避時(shí)間=0則 退避時(shí)間-1
            end
        end
    end


  
    if Start == 1%信道改為忙碌
        ChannelBusy = 1;
        n = CollitionStations(1);
        
        if n == 1%信道中只有一個(gè)站點(diǎn)發(fā)送數(shù)據(jù)則為正常發(fā)送情況
            DeferenceTime = floor(t + SIFS + DIFS + ACK + PacketBuff(CollitionStations(2),2));
            %PacketBuff(CollitionStations(2),2)數(shù)據(jù)長(zhǎng)度
            %成功發(fā)送時(shí)間
            Collition=0;%沒(méi)有碰撞
        else
            DeferenceTime = floor(t + DIFS + MaxLength(PacketBuff,CollitionStations));
            %發(fā)生碰撞要加上最大的沖突數(shù)據(jù)時(shí)間段
            Collition=1;%發(fā)生碰撞
        end
        Start=0;%信道恢復(fù)空閑        
    end

    if t == DeferenceTime & ChannelBusy == 1%信道忙的時(shí)候達(dá)到站點(diǎn)的等待時(shí)間
        if Collition == 0
            n = CollitionStations(2);
            PER=1-(1-BER)^(PacketBuff(n,2)*PhyRate*SlotTime);
            AckER=1-(1-BER)^(ACK*PhyRate*SlotTime);
            if rand>=PER & rand>=AckER;
               PacketLost=0;%無(wú)錯(cuò)誤
            else
               PacketLost=1;
            end
           
        end
        if Collition == 0 & PacketLost==0%發(fā)送成功
            n = CollitionStations(2);
            CurBufferSize(n) = CurBufferSize(n) - PacketBuff(n,2);
            Throughput = Throughput + PacketBuff(n,2) * SlotTime * PhyRate;
            PacketBuff = Pop(PacketBuff,n);
            Resend(n)=0;
            Delay = Delay+t-SendTime(n);
            Counter=Counter+1;
            CW(n) = 32;
            k = PacketBuff(n,1);
            if k ==0%如果沒(méi)有數(shù)據(jù)等待發(fā)送，將HasPacke置0，BackoffTimer置Max
                HasPacket(n) = 0;
                BackoffTimer(n) = 1200;
            else%還有數(shù)據(jù)分發(fā)送，修改碰撞計(jì)數(shù)器
                BackoffTimer(n) = RandSel(CW(n));
            end    
        else%發(fā)送失敗
           PacketResendingRate=PacketResendingRate+1;
            n = CollitionStations(1);
            for i = 1:n
                j = CollitionStations(i+1);
                CW(j) = Increase(CW,j);
                BackoffTimer(j) = RandSel(CW(j));
                Resend(j)=1;
            end    
        end
        CollitionStations = zeros(1,M+1);
        DeferenceTime = 0;
        ChannelBusy = 0;
        Collition = 0;
    end
    
    if mod(t,1/SlotTime) == 0%時(shí)間為整數(shù)
        s = t * SlotTime;
        s = round(s);
        Throughput_Result(s) = Throughput;
        if Counter~=0
        Delay_Result(s)=Delay*SlotTime/Counter;%平均時(shí)延
        else
        Delay_Result(s)=0;
        end
        PacketResendingRate_Result(s) = PacketResendingRate;
        Throughput = 0;
        PacketResendingRate=0;
        Delay = 0;
        Counter=0;
    end
end




savefile = sprintf('Packet Resending Rate M=(%d).txt',M);
fid = fopen(savefile,'a+');
fprintf(fid,'%1.6f     ',PacketResendingRate_Result);
fclose(fid);

savefile = sprintf('Throughput M=(%d).txt',M);
fid = fopen(savefile,'a+');
fprintf(fid,'%1.6f     ',Throughput_Result);
fclose(fid);

savefile = sprintf('Average Delay M=(%d).txt',M);
fid = fopen(savefile,'a+');
fprintf(fid,'%1.6f     ',Delay_Result);
fclose(fid);
end

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