Hybrid MAC protocols for mobile and ad hoc networks

Future tactical and commercial communication systems will consist of large populations of wireless networked devices that are capable of communicating “on the move.” A mobile ad hoc network (MANET) consists of a group of mobile nodes that collectively form a wireless network without the aid of any infrastructure. The nodes directly exchange information using a shared wireless channel, and network connectivity is determined by a combination of node proximity and radio signal propagation characteristics. This forms a instantaneous multi-hop network architecture that remains dynamically reconfigureable in the presence of node mobility. These charactersitics make a MANET an ideal choice for the rapid deployment of tactical communication systems.; The performance of a MANET ultimately relies on the effective access to the shared wireless channel. Channel access is determined by a medium access control (MAC) protocol that controls when a node is permitted to transmit a packet. Thus the performance of the MAC protocol has an immediate and fundamental impact on the overall efficiency of the MANET. However, many of the proposed MAC protocols employ designs that are not well-suited to cope with the dynamically changing network conditions within the MANET architecture. Moreover, the proposed designs are unable to effectively support the diverse transmission services required by higher layer MANET services and applications.; In this thesis, the author proposes a new class of MAC protocols that offers scalable and efficient performance across the full range of MANET operating conditions. The proposed design features a hybrid channel access strategy that dynamically adapts its operation according to the local network conditions, i.e., the current traffic load and network topology. The proposed hybrid protocol is shown to remain scalable in the presence of increasing traffic load and network connectivity, while efficiently managing the available channel resources. Furthermore, the hybrid protocol design is extended to realize a unified set of transmission services that effectively support unicast, multicast and broadcast packet transmission within a single protocol framework. Quality of service (QoS) provisioning is also facilitated by the inclusion of an effective bandwidth management service that permits nodes to reserve critical channel resources. These results contribute towards the realization of MAC layer services that are dynamically adaptive to changes in the underlying network architecture and better facilitate the demands of higher layer MANET services and applications.