Abstract

Recent years have witnessed a remarkable interest in wireless multihop ad hoc networks that need little or no infrastructure support. Such networks have enabled the existence of various applications ranging from the monitoring of herds of animals to supporting communication in military battle-fields and civilian disaster recovery scenarios as well as providing an emergency warning system for vehicles on the road. Currently, the distributed coordination function (DCF) of the IEEE is the industry dominant MAC protocol for wireless multihop ad hoc environment due to its simple implementation and distributed nature. Nevertheless, the DCF access method does not make efficient use of the shared channel due to its inherent conservative approach in assessing the level of interference. Moreover, the implementation of DCF in multihop ad hoc networks suffers from the exposed and hidden terminal problems; both of these problems highly affect the spectrum spatial reuse and accordingly causes serious throughput deterioration. To date, various methods have been proposed to enhance the throughput of the DCF; namely, tuning the carrier sensing threshold, the transmission attempt probability through changing the binary exponential backoff, controlling the frame transmit power, adapting the physical transmission rate of data frame, and the use of directional antennas. In this thesis, we develop mathematical tools to study the effectiveness of the interplay among the various tunable parameters and propose suitable protocols for achieving better utilization of the wireless spectrum.