Special Issue: Emerging WLAN Applications and Technologies

Today, we are witnessing that the wireless local area networks (WLANs) are being rapidly and widely accepted as a complementary technology of the high-speed wired LAN technologies such as ethernet for portable and mobile devices. The state-of-the-art WLAN can support up to 54 Mbps transmission rate. While today’s WLANs are considered wireless ethernet by virtue of supporting best-effort services, the needs for quality-of-service (QoS) provisioning across the wireless link are arising, for example in order to support audio/video (AV) traffic within home wirelessly. It is widely known that the current WLAN technologies are vulnerable to the security attacks, and in order to make the WLAN more accepted, making it more secure is a key requirement. The WLANs are also considered a complementary technology for the 3G wireless—thanks to its high speed along with the low cost. For a wider acceptance in the market, the WLAN technologies should be evolved such that they support QoS provisioning, secure communications, interworking with other wireless networks, extended operation times of battery-powered devices, seamless mobility supports, fair bandwidth sharing with other wireless devices. We are honored and pleased to report that we have received a total of 25 high quality paper submissions out of which we were able to accept only eight. The submissions covered the various aspects of WLAN applications and technologies. We now briefly introduce the eight papers, which appear in this issue. The first article of this issue by Arunesh Mishra, Nick L. Petroni, Jr. and William A. Arbaugh is a survey paper dealing with WLAN security issues. In the past few years, IEEE 802.11 standard-based WLANs have experienced tremendous growth. However, numerous security problems have dampened this growth. The IEEE and vendors sensitive to these issues began a wholesale redesign of the security architecture, while simultaneously producing measures for mitigating existing problems. In this paper, the authors describe the past and future security architectures as well as the problems and concerns with them. The second article by Liqiang Zhang and Sherali Zeadally proposes a framework for efficient resource management in IEEE 802.11 WLANs. The upcoming IEEE standard 802.11e achieves service differentiation by assigning different channel access parameters (CAPs) to different traffic classes at the MAC layer. However, such relative differentiation does not yield QoS guarantee. In practice, appropriately selecting CAPs a priori is difficult. Time-varying traffic loads also make the use of fixed CAPs inefficient for both QoS support and channel utilization. In this paper, the authors propose a novel architecture called HARMONICA, in which the access point dynamically selects the best CAPs for each traffic class to optimally match their QoS requirements. They then present and discuss a simple admission control mechanism used by HARMONICA to avoid congestion. The simulation results demonstrate that under an interference-free environment, HARMONICA can guarantee the QoS for all traffic classes while simultaneously achieving quasioptimal channel utilization. The third article by Yuan Xue, Kai Chen and Klara Nahrstedt considers how to provide proportional delay differentiation in WLAN via cross-layer scheduling. Providing service differentiation in wireless networks has attracted much attention in recent research. However, existing studies so far have focused on the design of differentiated media access algorithms. Some QoS metrics, such as queueing delay, cannot be completely addressed by these approaches. This paper addresses this problem by introducing the concept of proportional service differentiation, to the domain of wireless network and focuses on providing proportional delay differentiation in WLANs. The authors argue that delay differentiation in WLAN