MOBILITY AWARE ROUTING WITH PARTIAL ROUTE PRESERVATION IN WIRELESS SENSOR NETWORKS Sanat Sarangi, Subrat Kar Bharti School of Telecommunication Technology And Management, IIT Delhi New Delhi 110016 India sanat.sarangi@gmail.com, subrat@ee.iitd.ac.in ABSTRACT We propose a novel reactive routing algorithm called PARTROUTE which achieves energy efficient routing in sensor networks with stationary and mobile nodes. PARTROUTE uses coarse mobility awareness in each node to reduce the overheads of reactive routing by intelligently re-using parts of the created on-demand routes beyond their standard lifetime. We show that the responsiveness of the network improves while the overall network traffic is reduced. The effectiveness of PARTROUTE with a large percentage of mobile nodes is also shown. Keywords: wireless sensor network, routing protocol, PARTROUTE, mobility aware, AODV, AODVjr 1 INTRODUCTION A typical sensor network has a single gateway and a set of connected nodes that participate in sensing and forwarding application defined events to the gateway. Some of the key driving factors in designing routing algorithms for sensor networks are (a) size of the network (the number of nodes), (b) limited node energy, (c) deployment topology and (d) provision for node mobility. Traditionally, there have been two approaches to routing– proactive and reactive. In proactive routing, routes can be computed and updated beforehand so that data is sent through the best possible route. In reactive routing, routes are created on-demand. The diversity of sensor network applications have driven the evolution of classes of application appropriate routing algorithms which can be cluster-based [1], hierarchical [2], robust [3], energy-aware [4], geographic [5], query based [6] or swarm-behaviour- based [7]. When some nodes in the network are mobile, reactive routing becomes necessary. Dynamic Source Routing (DSR) [8] and Ad-hoc On-demand Distance Vector Routing (AODV) [9] are popular reactive algorithms developed for mobile ad-hoc networks (MANETs). 2 MOTIVATION Most reactive algorithms assume that the nodes in the network are mobile. However, mobile nodes are not explicitly aware of their own mobility. Recently, in [10], PH-MA-AODV and Agg-AODV have been proposed that use mobility awareness to improve the performance of reactive algorithms with high-speed MANETs. In PH-MA-AODV a highly mobile node discards a route-request to prevent itself from participating in route formation. In Agg-AODV the route-request accumulates the degree of mobility of each intermediate node and the destination chooses the route with minimum mobility. However, both the algorithms assume that the intermediate nodes can precisely measure their speed of movement. In [11], prediction of broken links is used to trigger routing updates before links break. Mobility requirements in most sensor networks are different from those of MANETs. The emphasis in sensor networks is on minimizing energy consumption with provision for (often low) mobility within a stationary mesh of nodes where all nodes talk to a central gateway. We propose a routing algorithm PARTROUTE for memory-constrained and energy-sensitive sensor networks with stationary and mobile nodes where each node is explicitly aware of its mobility status at any point of time and this knowledge is used to intelligently preserve part(s) of the route(s) formed during reactive routing beyond the standard route lifetime. PARTROUTE dynamically adapts itself to changing network conditions and helps improve event delivery while reducing both (a) the overall network traffic and (b) latency of route formation (which is critical) for mobile nodes. With rapid strides in Micro Electro-Mechanical Systems (MEMS), coarse mobility (moving or stationary) awareness can now be easily added to UbiCC Journal, Volume 6: Issue 2 848 Ubiquitous Computing and Communication Journal (ISSN 1992-8424)