Enhanced PCF Protocols for Real-time Multimedia Services over 802.11 Wireless Networks

In wireless network environment, different traffic classes exhibit a variety of characteristics and service requirements [4,5,7], such as data rate, maximum tolerable packet error rate and delay bounds. Although IEEE 802.11e [9,10] addresses the QoS issues and classifies the traffic into four prioritized access categories, there is still no guarantee of real-time transmission service due to the lack of an effective coordinating mechanism [11] among contending clients and a satisfactory scheduling method for various delay-sensitive packets from multiple traffic flows. In this work, we propose a nearly complete polling list solution to IEEE 802.11 WLAN by enhancing the original PCF protocol with better demand assignment features. A flexible and fair polling list method among the various time bounds is investigated in the proposed scheme. The performance evaluation based on NS-2 network simulator [12,13] shows that our schemes are well suited for variable bit rate service in real-time multimedia applications.