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📋📋📋本文目录如下：🎁🎁🎁
目录
💥1 概述
📚2 运行结果
🎉3 参考文献
🌈4 Matlab代码实现
💥1 概述
本文基于ALOHA MAC方法的蒙特卡罗模拟。
📚2 运行结果
部分代码：
N=60;
Ts=0.0002; %Ts= 1200/6000000= 0.2msec
lamda= 250:200:2050; %[packet/sec]
lamda2= lamda.*Ts; % lamda2=arrival rate=0.05:0.03:0.32 [packet/slot]
s = zeros(1, length(lamda));
g = zeros(1, length(lamda));
d = zeros(1, length(lamda));
for l=1:1:length(lamda)
%TIMING PARAMETERS (PART 1)
num_arrival_per_station = 1000000;
interarrival_time= exprnd(1/(lamda2(l)), N, num_arrival_per_station); %[slot]
arrival_schedule= cumsum(interarrival_time,2); %cumsum:Cumulative sumcollapse. B = cumsum(A,dim)
%this double loop method works but very inefficient
% arrival_schedule= zeros(N,num_arrival_per_station);
% for n =1:N
% for i = 1:num_arrival_per_station
% arrival_schedule(n, i) = sum(interarrival_time(n, 1:i));
% end
% end
retransmission_schedule= zeros(1,N);
simulation_time=1000000;
current_time_slot=1;
%DIFFERENT TRANSMIT INDICATORS (PART 2)
transmit_status_indicator = zeros(1,N) ; % 0 for not transmitting, 1 for transmitting
retransmit_status = zeros(1,N) ; % 0 for no retransmission, 1 for pending retransmission
retransmission_attempt = zeros(1,N) ; %if pkt tx fail once becomes 1 , fail twice becomes 2, and so on ...useful for updating window for retransmission scheduling
max_retransmission_attempt = 11;
%%STATS PARAMETERS (PART 3)
total_transmissions = 0;
total_successful_transmissions = 0 ; %use for throughput computation
total_delay_time = 0 ; %use for average delay computation
packet_index=ones(1, N);
while (current_time_slot < simulation_time)
%%FUNCTION: check_whether_each_station_transmits_in_this_slot (PART 4)
for j= 1:1:N
%retransmission_schedule(1,j)
if (retransmit_status(1,j)==1) %check if status is retransmit
if (retransmission_schedule(1,j)==current_time_slot) %check if retransmission count down timer arrived
transmit_status_indicator(1,j)=1;
j_tx=j;
end
elseif (all(retransmit_status==0)==1) %no pendiong retranmission
if (current_time_slot >= arrival_schedule(j,packet_index(1,j))) % there's a new packet
transmit_status_indicator(1,j)=1;
j_tx=j;
end
end
end
% Number of stations which transmit in this slot
num_transmitting_stations = sum(transmit_status_indicator);
total_transmissions = total_transmissions + num_transmitting_stations;
%%FUNCTION: CHECK_SUCCESSFUL_OR_FAILED_TRANSMISSION (PART 5)
if (num_transmitting_stations==1) %if transmission succeed
total_successful_transmissions = total_successful_transmissions+1;
% get packet arrival time. Based on difference between transmitted time and original arrival time, we can get this_unique_packet_delay_time
this_unique_packet_delay_time_after_successful_tx= current_time_slot - arrival_schedule(j_tx, packet_index(1,j_tx));
total_delay_time = total_delay_time + this_unique_packet_delay_time_after_successful_tx;
transmit_status_indicator(1,j_tx) = 0; %update tx status
retransmit_status(1,j_tx) = 0; %update re-tx status
%update which next packet to be served, do something with arrival_schedule?
packet_index(1,j_tx)= packet_index(1,j_tx) + 1; %increase packet index at the station has packet successfully transmitted
retransmission_attempt(1,j_tx)=0;
retransmission_schedule(1,j_tx)=0;
else %if transmission fails
for j=1:1:N
retransmit_status(1,j) = transmit_status_indicator(1,j);
if ((retransmit_status(1,j)==1)&&(retransmission_schedule(1,j)<=current_time_slot))
%if (retransmit_status(1,j)==1)
retransmission_schedule(1,j) = current_time_slot + randi([1, 2^(retransmission_attempt(1,j))+1],1);
retransmission_attempt(1,j) = retransmission_attempt(1,j)+1;
if (retransmission_attempt(1,j) > max_retransmission_attempt)
%discard the packet and serving next packet
packet_index(1,j)= packet_index(1,j) + 1;
retransmission_attempt(1,j)=0;
retransmission_schedule(1,j)=0;
retransmit_status(1,j)=0;
end
transmit_status_indicator(1,j)=0;
end
end
end
current_time_slot = current_time_slot + 1 ;
end %belongs to while loop of incrementing simulation time
🎉3 参考文献
部分理论来源于网络，如有侵权请联系删除。
