  IEEE 802.11 networks have a great role to play in supporting and deploying of
the Internet of Things (IoT). The realization of IoT depends on the ability of
the network to handle a massive number of stations and transmissions, and to
support Quality of Service (QoS). IEEE 802.11 networks enable the QoS by
applying the Enhanced Distributed Channel Access (EDCA) with static parameters
regardless of existing network capacity or which Access Category (AC) of QoS is
already active. Our objective in this paper is to improve the efficiency of the
uplink access in 802.11 networks; therefore we proposed an algorithm called QoS
Categories Activeness-Aware Adaptive EDCA Algorithm (QCAAAE) which adapts
Contention Window (CW) size, and Arbitration Inter-Frame Space Number (AIFSN)
values depending on the number of associated Stations (STAs) and considering
the presence of each AC. For different traffic scenarios, the simulation
results confirm the outperformance of the proposed algorithm in terms of
throughput (increased on average 23%) and retransmission attempts rate
(decreased on average 47%) considering acceptable delay for sensitive delay
services.
