Wireless networks and mobile computing research has until recently concentrated on single-hop networks (network nodes communicating directly to a fixed infrastructure), such as cellular or satellite systems. Wireless ad hoc networking covers multi-hop scenarios (network nodes communicating via other network nodes) such as conference, hospital, battlefield, rescue, and monitoring scenarios. Wireless ad hoc networks are formed by a set of hosts that communicate with each other over a wireless channel. Each node has the ability to communicate directly with another node in its physical neighborhood. They operate in a self-organized and decentralized manner and message communication takes place via multi-hop spreading. A packet is sent to its target node through a set of intermediate nodes that act as routers. Particular ad hoc network systems include packet radio networks, sensor networks, personal communication systems, rooftop networks, and wireless local area networks.
These were the foci of the Fourth Workshop on Wireless Ad hoc and Sensor Networks, held in conjunction with the International Conference on Distributed Computing Systems (ICDCS 2007), on June 25, 2007, in Toronto, ON, Canada. The workshop attracted no less than 33 papers in all areas of wireless ad hoc and sensor networks, out of which a total of 12 papers were selected for presentation in four separate sessions. The authors of three of the best papers presented at the workshop were then invited to submit expanded versions of their papers for inclusion in this special issue. Those submissions underwent the review process, and the result is in your hands now.
The paper by Li and Kotz concerns the dissemination of high volume data streams to many concurrent applications over a low bandwidth mesh network. The authors exploit the fact that many applications can tolerate a certain degree of quality loss, and that the source data can often be partitioned into a number of (possibly overlapping) subsets which satisfy the quality requirements of the applications. With these observations in mind, the network can then choose the data subset that can offer best efficiency in a multicasting scenario. The authors show that this approach, termed ‘group-aware stream filtering,’ offers distinct benefits over similar approaches, and analyze key factors that affect its performance.
The paper by Huang, Bhatti, and Sørensen examines OLSR, a proactive routing protocol in a mobile ad hoc network (MANET), and analyzes the impact of topology updates on its performance. This analysis provides crucial insights into the manner in which topology updates affect the routing algorithm, with particular emphasis on the interplay between the proactive routing protocol and reactive topology update mechanism. Furthermore, it examines the range of parameter values in which topology update period can be maximized without degrading the performance of the routing algorithm.
The paper by Djukic and Valaee discusses an approach to use the ubiquitous 802.11 technology to emulate an 802.16-compliant mesh network. To this end, 802.16 packets are embedded into 802.11a broadcast packets, with adjustments made to align the packets to 802.15 TDMA frame boundaries. In this manner, mesh network functionality can be emulated with commercially available hardware, offering substantially improved performance compared to the case where that same hardware is used in a CSMA-CA 802.11 scenario. The price to pay for this improvement is the need for a small software patch that takes care of QoS-related constraints of 802.16 networks.
We wish to thank the authors as well as the reviewers for their hard work and the effort they have invested in producing this special issue. We would also like to express our sincere gratitude to the Editor-In-Chief, Professor Ivan Stojmenovic, for providing this opportunity, and to the Editorial Staff at Taylor & Francis for their support and professionalism.