Real-Time Applications In 803.11 WLAN Using Feedback-Based Bandwidth Allocation

The Hybrid Coordination Function (HCF) has been recently proposed by the 802.11e working group in order to provide real-time services in Wireless Local Area Networks (WLANs). HCF is made of a contention-based channel access, known as Enhanced Distributed Coordination Access (EDCA), and of a HCF Controlled Channel Access (HCCA), which requires a centralized controller, called Hybrid Coordinator (HC). This paper proposes two feedback-based bandwidth allocation algorithms exploiting HCCA for dynamically assigning the WLAN channel bandwidth to mobile stations hosting real-time traffic streams. Proposed algorithms, which have been referred to as Feedback Based Dynamic Scheduler (FBDS) and Proportional Integral (PI)-FBDS, have been designed using classic discrete-time feedback control theory. Simulation results, obtained using the ns-2 simulator, have shown that, unlike the simple scheduler proposed by the 802.11e working group, both FBDS and PI-FBDS provide a real-time service regardless of the network load. Moreover, when the PI-FBDS is used, the best trade-off between one-way packet delays and network utilization is achieved.