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. We propose a hybrid routing scheme that combines proactive route optimization with 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.