The conceptual shift in the expectations of the wireless users from voice towards multimedia, from availability towards acceptable quality, and from stand-alone towards group-oriented computing has a significant impact on today's networks in terms of the need for mobility, quality of service (QoS) and multicasting. Ad hoc networks, being independent of any fixed infrastructure, can provide mobile users with these features, if necessary QoS multicasting strategies are developed. The aim of this article is to define the building blocks of such an ad hoc QoS multicasting (AQM) protocol. AQM achieves multicasting efficiency by tracking the availability of resources for each node within its neighbourhood. Computation of free bandwidth is based on reservations made for ongoing sessions and similar information reported by neighbours. Current QoS status is announced at the initiation of a new session and updated periodically in the network to the extent of QoS provision. Thus, nodes are prevented from applying for membership if there is no QoS path for the session. When nodes join a session with certain service requirements, a request-reply-reserve process ensures that the QoS information is refreshed and used to select the most appropriate routes. To evaluate the efficiency of AQM in providing multicast users with QoS and satisfying application requirements, two new performance metrics, member and session satisfaction grades are introduced. AQM is compared to a non-QoS scheme with particular emphasis on these criteria. Simulation results show that, by applying QoS restrictions, AQM significantly improves multicasting efficiency. Thus, QoS is both essential for and applicable to multicasting in order to support mobile multimedia applications in ad hoc networks. q

Infrastructure communications for traffic safety applications. In [Host publication title missing] (pp. 448-453).

The ever-increasing volume of air transport necessitates new technologies to be adopted by the flight industry to fulfil the requirements of safety, security, affordability and environment friendliness while still meeting the growing demand. What we need to achieve this goal is a new type of aircraft cruise control, interconnecting all the onboard active control systems and making more accurate control decisions than is currently possible, thus improving the overall flight efficiency. "Active Aircraft" envisions such a nervous system of distributed wireless sensor and actuator network (WSAN) components, enabling the early detection of potential problems, and quick, accurate reactions to these. As part of this vision, WSAN deployed on aircraft wings help the reduction of aerodynamic drag and significantly reduce fuel consumption.In this article, we first describe this conceptual change in aircraft control technology. We then introduce a WSAN application to reduce skin friction drag, and a network topology to enable it. In our application, WSAN form virtual flap arrays on the wings to measure the skin friction in real time, and to react using synthetic jet actuators, which suck and expel air on the wing to reduce the friction. The Active Aircraft vision imposes stringent performance requirements on the underlying WSAN communication algorithms. The medium access control and routing protocols, in particular, must meet the quality of service criteria set by active control applications. Thus, we also present the application characteristics of Active Aircraft and raise the issue of design considerations with regard to the communication protocols.

Emerging wireless sensor and actuator network (WSAN) technology has the potential to enable semi-autonomous air-flow control to improve the aerodynamic performance of aircraft. In this paper, a WSAN topology comprising of multiple linear sensor clusters terminated by actuators is proposed for active flow control. Two interference aware convergecast scheduling strategies are presented and analyzed, with the objective of jointly minimizing latency and energy consumption. The proposed schemes are required to coordinate local convergecast communications in each cluster, on the one hand, and to arbitrate between mutually interfering nodes of different clusters contending for the wireless channel, on the other. Initial results show that a 19s and 11s convergecast delay moderate to high energy consumption can be achieved.