Improving QOS in WLAN using dynamic weighted fair scheduling

Abstract

The demand for end-to-end Quality of Service (QoS) in Wireless Local Area Networks (WLANs) is becoming ever more important due to the trend towards converged communication networks. However, providing QoS in WLANs is more challenging than wired networks due to the mobility of Stations (STA), interference, and channel fading. The recently accepted QoS mechanism in WLAN; the IEEE 802.11e has limitations in providing fairness to different types of traffic. In a shared medium like WLAN, fair bandwidth allocation is important to provide an acceptable level of QoS and prevent starvation of traffic. This research proposes Dynamic Weighted Fair Scheduling Scheme (DWFSS) to improve fairness in WLANs by enhancing the IEEE 802.11e Hybrid Coordination Function (HCF). The DWFSS allocates bandwidth to four different classes of traffic. Every class is assigned a weight which represents a percentage of the total bandwidth. The weights are dynamically changed to optimize the utilization of bandwidth. The service interval in IEEE 802.11e is divided into two polling intervals i.e., High Priority Polling Interval (HPPI) and Low Priority Polling Interval (LPPI). The Quality of Service Stations (QSTAs) with high priority traffic are polled during HPPI and QSTAs with low priority traffic are polled during LPPI. The DWFSS is evaluated in a simulation environment using multiple types of traffic and compared with the standard scheduler. The performance of DWFSS is evaluated on NCTUns simulator. The simulation results show that DWFSS improved fairness when compared to IEEE 802.11e standard scheduler. This improves Quality of Experience (QoE) of users as well. When compared with IEEE 802.11e, the DWFSS increased average throughput by 13.48% and reduced average jitter by 16.21% while maintaining an acceptable level of end-to-end delay.