A cross-layer approach to increase spatial reuse and throughput for ad hoc networks

Ad hoc networks employing adaptive-transmission protocols can alter transmission parameters over a particular link to suit the perceived channel environment. Such capabilities can lead to significant performance improvements over statically configured protocols. Ad hoc networks rely on channel-access mechanisms to govern temporal use of the transmission medium amongst the individual network nodes. Effective operation of a channel-access mechanism can improve the ability of a physical-layer adaptivetransmission protocol to accommodate changing channel conditions. Joint consideration of the interoperability of these two mechanisms motivates cross-layer design of adaptivetransmission protocols for ad hoc networks. In this thesis we examine the integration of a new channel-access mechanism with a physical-layer adaptive-transmission protocol to create a cross-layer protocol with enhanced capabilities. We derive specific physical-layer measurements which are used by each node in the network to control channel-access behavior in a distributed manner. We examine the design tradeoffs associated with various protocol strategies and compare the performance of several protocols. Effective ways to integrate spatial reuse capabilities without introducing excessive interference into the network are investigated. We propose a distributed heuristic using cross-layer information to drive a channelaccess protocol which works in conjunction with an adaptive-transmission protocol. We show that the new protocol outperforms statically configured transmission protocols as well as protocols which act independently of cross-layer enhancements.