Performance of a hybrid routing protocol for mobile ad hoc networks

Mobile ad hoc networks are characterized by multi-hop wireless links, absence of any fixed networking infrastructure, and a dynamic network topology. Routing protocols for such networks typically use exchanges of control packets, either at fixed intervals of time or in response to a requirement, to adapt to the changing network topology. Balancing the optimality of the routes used in an ad hoc network as well as the overhead incurred from transmissions of routing packets is a challenging task. In this paper, we propose a hybrid routing scheme that combines proactive route optimization to a reactive routing protocol, for reducing the average end-to-end delay in packet transmissions without exceeding the routing overhead. The proposed scheme uses a pre-emptive route discovery to replace an existing route by a shorter route when the route has been used for a given interval of time. The optimum time for making the pre-emptive search is obtained by studying the statistical distributions of the link and route lifetimes. The preemptive search is restricted within a limited distance from the old route by using a query-localization method. Performance evaluations of the proposed hybrid scheme in comparison with a purely on-demand routing protocol are presented.