A New Scheduler to Guarantee Delay Bound with Bandwidth Optimization for HCCA in IEEE 802.11 e WLANs

摘要

IEEE 802.11 e Medium Access Control (MAC) is a supplement to the IEEE 802.11 Wireless Network (WLAN) standard to support Quality of Service (QoS). The 802.1 le MAC defines a new coordination Junction, namely Hybrid Coordination Function (HCF), which takes the QoS requirements of flows into account and allocates transmission opportunity (TXOP) to stations. On the basis of mean sending rate, delay of variable bit rate (VBR) traffic cannot be bounded with the reference HCF scheduling algorithm proposed in this supplement. In this paper, we propose a new scheduling algorithm that utilizes the token bucket and a modified Latency-Rate (LR) scheduling algorithm to guarantee a bounded delay for HCF controlled channel access (HCCA). The new TXOP is calculated to optimize the number of stations accommodated and takes into account delay bound and token bucket parameters. We show that is possible to obtain the worst-case performance guarantees on delay. Properties of the proposal are investigated both theoretically and using ns-2 simulations. We present a set of simulations with both constant bit rate (CBR) and VBR flows and performance comparisons with HCF scheduling algorithm. The results show that the upper bounds can be achieved for a large range of networks load.