Page 2 Lecture Notes in Computer Science 2865 Edited by G. Goos ...

Space-Time Routing in Ad Hoc Networks ⋆Henri Dubois-Ferrière 1 , Matthias Grossglauser 1 , and Martin Vetterli 1,21 School of Computer and Communication Sciences, EPFL, Lausanne, Switzerland{Henri.Dubois-Ferriere,Matthias.Grossglauser,Martin.Vetterli}@epfl.ch2 Department of EECS, University of California Berkeley, USAAbstract. We introduce Space-Time Routing (STR), a new approachto routing in mobile ad hoc networks. In STR, the age of routing state isconsidered jointly with the distance to the destination. We give a generaldescription of STR, which can accommodate various temporal (age) andspatial (distance) metrics. Our formulation of STR describes a family ofrouting algorithms, parameterized by a choice of node clock scheme, aneighbor-distance function and a binding spatio-temporal metric whichallows the algorithm to compare potential routes taking into accountboth their age and their distance to the destination. We discuss possibleinstantiations of a Space-Time Routing protocol. In particular, we reviewFRESH (FResher Encounter SearcH), a routing algorithm using temporalinformation only, and GREP (Generalized Route EstablishmentProtocol), a routing protocol which uses jointly spatial and temporal informationabout routes. We discuss a third STR algorithm using onlyphysical notions of space and time, and finally show that STR providesloop-free routes.1 IntroductionAn ad hoc network is a communication medium where users or nodes also providethe infrastructure for communication. That is, nodes play both the role ofterminals (i.e. source and destination of messages) and of relays. Thus, a messagetraverses an ad hoc network by being relayed from node to node, until itreaches its destination. When, in addition, nodes are moving, this becomes achallenging task, since the topology of the network is in constant flux. How tofind a destination, how to route to that destination, and how to insure robustcommunication in the face of constant topology change are major challenges inmobile ad hoc networks.Routing in ad hoc networks is a well studied topic, with a number of proposedprotocols like AODV [1] and DSR [2], as well as simulation studies. A commonpoint of existing algorithms is that their computations involve almost exclusivelydistance (or spatial) types of information. This approach can be traced all theway back to the classic Dijkstra, Bellman-Ford, and Floyd-Warshall algorithms,which are driven by quantities measuring distances 1 between nodes.⋆ The work presented in this paper was supported (in part) by the National CompetenceCenter in Research on Mobile Information and Communication Systems(NCCR-MICS), a center supported by the Swiss National Science Foundation undergrant number 5005-673221 equivalently, transmission costs.S. Pierre, M. Barbeau, and E. Kranakis (Eds.): ADHOC-NOW 2003, LNCS 2865, pp. 1–11, 2003.c○ Springer-Verlag Berlin Heidelberg 2003