Guest Editorial Special Issue: Medium Access Control Protocols for Wireless Ad Hoc Networks

Wireless ad hoc networks enable over-the-air information exchange among (mobile) entities without a fixed infrastructure, and are very attractive for many commercial and military applications where pre-existing infrastructures are either infeasible or too expensive. However, this new form of communications poses new challenges to traditional networking architectures and protocols designed for wired or infrastructure-based wireless networks, and has stimulated considerable research interests in recent years. Medium access control (MAC) is one of the major research interests in wireless ad hoc networks, where neighboring entities may have to share the same radio channel and information flows may be relayed in a hop-by-hop manner. Many new MAC protocols have been proposed and evaluated and, at the same time, existing MAC protocols are tailored and improved for wireless ad hoc networks. These MAC protocols have considerable implications on the performance of upper layer protocols such as packet routing and end-to-end flow and congestion control. In addition, new technologies for the physical layer keep emerging and enable more sophisticated MAC protocols. Other driving factors for this active research area include the desire for high-speed, low-latency, and quality-of-service (QoS)-provisioned communications among mobile entities. This special issue consists of nine papers addressing recent cutting edge research and state-ofthe-art technology of MAC for ad hoc networks. It is timely and valuable for future analysis, implementation, and experiments. In the first paper ‘Understanding the key performance issues with MAC protocols for multi-hop wireless networks,’ Iyer and Rosenberg demonstrate that the performance of multi-hop networks depends critically on the design of the underlying MAC protocol. A list of problems that affect MAC protocols in multi-hop wireless networks are identified, such as the hidden node, the deaf node, the exposed node problems, and the link layer congestion problem. The performance of three existing MAC protocols is evaluated. Then a simple but robust two-channel MAC protocol (termed 2CM) is proposed, which is based on the IEEE 802.11 protocol augmented with a busy-tone channel. It is shown that the proposed protocol makes effective use of the busy-tone signal to mitigate the hidden node problem considerably. A logical control channel is not required, and a reliable link layer acknowledgement mechanism can be provided as well. In the second paper ‘Access control in ad hoc networks with selfish nodes,’ Zhao proposes a game theory-based access control scheme for ad hoc networks where nodes selfishly compete for channel access in order to maximize their own payoffs. An equilibrium transmission probability is derived, and saturation throughput and packet transmission delay performance are analyzed. It is shown that a relatively high transmission throughput is possible using this scheme which allows simultaneous transmissions under low co-channel interference conditions. The third and fourth papers focus on clustered ad hoc networks. In the paper ‘MAPLE: a framework for mobility-aware pro-active low energy clustering in ad hoc mobile wireless networks,’ Palit, Hossain, and Thulasiraman present a framework for mobility-aware pro-active low energy clustering in ad hoc mobile wireless networks. The proposed framework uses radio link level information for predicting node mobility and a reservation-based technique for channel access by the mobile nodes. An approximate analytical bound on the maximum number of nodes in the network for bounded clustering delay has been also obtained. Simulation results show that the proposed framework results in superior clustering performance in terms of stability, load distribution, and control