Research work at the EDCA mechanism adjusts several parameters to prioritize the traffic and differentiate the service classes, such as Arbitrary Inter-frame Spacing (AIFS), minimum contention windows (CWmin), maximum contention window (CWmax), and persistence factor (PF).
Each AC is configured with four contention parameters: arbitrary interframe spacing (AIFS), minimum and maximum contention windows (CWmin and CWmax), and the TXOP limit.
The value of the transmitting probability can be adjusted by tuning contention parameters, such as the minimum contention window ), the maximum contention window, retry limit, the maximum backoff stage, arbitrary interface spaces (AIFS), and so forth.
For traffic category, let denote contention window size at retransmission stage and let denote the maximum contention window size.
(i) We study the particular case in which the minimum contention window is equal to the maximum contention window.
If the contention window reaches the maximum contention window ({CW}_{max }=2^{m_{w}}text {CW}_{min }), it remains unchanged until the transmission succeeds.
E[b i ] for stage i is W i 2, where W i is the maximum contention window size in contention stage i.
In the remainder of the paper, unless otherwise stated, we will not use BEB (e.g., we will set the maximum contention window to the same value of the minimum contention window).
In the first one, we use different values for the minimum and maximum contention window ( and ), while in the second one, the same value is used for both contention windows.
Notations and variables Meaning and explanation Number of estimated active connections Probability of a contention failure Transmission probability Utilization factor of contention period Optimal value of parameter p Initial backoff window size Maximum backoff window size Maximum number of backoff stages Average contention window size Optimal contention window size.
The figure further verifies that there exists an optimum contention window size that maximizes throughput.
