I. Introduction
Due to the inherent capacity limitations of wireless technologies based on the IEEE 802.11 standard [1], the WLAN easily becomes a bottleneck for communication. In these cases, the Enhanced Distributed Channel Access (EDCA) of the IEEE 802.11e standard [2] will be beneficial to prioritize for example voice and video traffic over more elastic data traffic. EDCA allows for differentiation between four different access categories (ACs) at each station and a transmission queue associated with each AC. Each AC at a station has a conceptual “backoff instance” responsible for channel access for each AC, often referred to as the Enhanced Distributed Channel Access Function (EDCAF).