Limitations of the IEEE 802.11e EDCA protocol when supporting real-time communication

In this paper, we analyze the timing behavior of the EDCA communication mechanism defined in the IEEE 802.11e standard, when it is used to support real-time (RT) traffic. In the context of this paper, RT traffic means small sized packets generated in periodic intervals, which must be delivered before the end of the message stream period. Otherwise, the message is considered to be delayed and a deadline loss occurs. The target of this paper is to understand the limitations of the highest priority level of the EDCA mechanism (voice category) when supporting RT communication. We have assessed this mechanism considering an open communication environment, where there are RT and non-RT stations operating in the same frequency band. Furthermore, a realistic error-prone model channel was used to measure the impact of interferences against an error-free channel. We show that in the most cases evaluated, both the number of packet losses and the average packet delays forecast an unacceptable number of deadline losses for the RT message streams, even for intermediate load cases. As a conclusion of this paper, we present some potential future directions toward improved QoS in wireless networks.