Ad-Hoc, Mobile, and Wireless Networks

We introduce Space-Time Routing (STR), a new approach to routing in mobile ad hoc networks. In STR, the age of routing state is considered jointly with the distance to the destination. We give a general description of STR, which can accommodate various temporal (age) and spatial (distance) metrics. Our formulation of STR describes a family of routing algorithms, parameterized by a choice of node clock scheme, a neighbor-distance function and a binding spatio-temporal metric which allows the algorithm to compare potential routes taking into account both their age and their distance to the destination. We discuss possible instantiations of a Space-Time Routing protocol. In particular, we review FRESH (FResher Encounter SearcH), a routing algorithm using temporal information only, and GREP (Generalized Route Establishment Protocol), a routing protocol which uses jointly spatial and temporal information about routes. We discuss a third STR algorithm using only physical notions of space and time, and finally show that STR provides loop-free routes.