An enhanced HCF for IEEE 802.11e wireless networks

In this paper the behavior of the upcoming MAC protocol for wireless LANs IEEE 802.11e is investigated. Based on the results, we propose an enhancement for Hybrid Coordination Function (HCF) to improve its Admission Control Unit (ACU). The analysis of Enhanced Distributed Channel Access (EDCA) and HCF schemes is performed for different network sizes. Three types of traffic - voice, video and bursty data - are considered in this analysis. Four metrics - transfer delay, jitter, throughput and packet loss - are considered in studying the behavior of these schemes. It is shown that EDCA does well for small to moderate network, whereas HCF performs better for larger networks. However, bursty traffic received very poor service from both schemes, and likely to starve in a heavily loaded system. The performance of the proposed scheme is evaluated through ns-2 simulator and then compared against the standard schemes in 802.11e. Our enhanced HCF (eHCF) shows fairness in allocating bandwidth to different priority classes by employing the Class-Based Queuing - like mechanism in its ACU.