Probabilistic analysis of IEEE 802.11 (802.11e)
11 May 2010
16 Sep 2013)
Evaluating probabilities that a specified station gains the access to the wireless medium.
function [p_coll] = edca_probability_collision(matrix)
% Returns the probability of collision for a general number of stations with general parameters
% matrix.............input matrix containing all the required parameters:
% matrix = [N10 N1
% N20 N2
% NK0 NK];
% for K stations. The first column specifies the corresponding
% penalties (i.e. AIFS) and the second the range of random numbers
% (i.e. the contention window CW).
% p_coll............probability that a collision occurs
% Example of use:
% M = [ 3 10; 5 8; 0 11; 1 2; 1 7; 0 6; 5 2];
% [p_coll] = edca_probability_collision(M)
K = size(matrix,1); %number of stations
total = 0;
% Calculates the complementary probability (such a way is not very efficient),
% i.e. "1-(probability that any of the stations wins)".
% It means that the winning probability is calculated K-times,
% once for each of the K stations.
for cnt = 0:(K-1) %loop over the stations
% The probability that wins the first, second,..., K-th station:
p_win = edca_probability_win(shift_nth_station_to_first(matrix,cnt+1));
% Their sum
total = total + p_win;
% Complementary probability
p_coll = 1 - total;