An Energy Efficient Routing Scheme for Mobile Wireless Sensor Networks Lan Tien Nguyen †1 , Xavier Defago †2 , Razvan Beuran *†3 , Yoichi Shinoda †*4 † Japan Advanced Institute of Science and technology 1-1 Asahidai, Nomi, Ishikawa 923-1292 1 lannt@jaist.ac.jp 2 defago@jaist.ac.jp 4 shinoda@jaist.ac.jp * National Institute of Science and Technology, Hokuriku Research Center 2-12 Asahidai, Nomi, Ishikawa, 923-1211 3 razvan@nict.go.jp Abstract— Research on wireless sensor networks has recently received much attention as they offer an advantage of monitoring various kinds of environment by sensing physical phenomenon. Among various issues, energy consumption is one of the most important criteria for routing protocol in wireless sensor networks (WSNs). This paper introduces an energy efficient clustering algorithm for mobile sensor network based on the LEACH protocol. The proposed protocol adds feature to LEACH to support for mobile nodes and also reduces the consumption of the network resource in each round. The proposed protocol is simulated and the results show a significant reduction in network energy consumption compared to LEACH. I. INTRODUCTION Recent technological advantages allow the manufacturing of small and low cost sensing devices to be technically and economically possible. The sensing devices are used to monitor various kinds of ambient conditions like temperature, humidity, etc and then transform them into electric signal. A wireless sensor network contains hundreds or thousands of these sensor devices that have the ability to communicate either directly to the Base Station (BS) or among each other. Usually, sensor nodes are scattered in the sensing field, being the area where we want to monitor some ambient conditions. Sensor nodes have to coordinate among themselves to get information about the physical environment. The information collected by sensor nodes is routed to the Base Station either directly or through other sensor nodes. The Base Station is a fixed node or mobile node, which is capable to connect the sensor network to an infrastructure networks or to the Internet where users can access and process data. Routing in WSNs is very challenging due to the specific characteristics that distinguish WSNs from other wireless networks such as wireless ad hoc networks or cellular networks. Many new algorithms have been proposed, taking into consideration the inherent features of WSNs along with the application and architecture requirements. Based on the network structure adopted, routing protocols for WSNs can be classified into flat network routing, hierarchical network routing, location-based network routing [2]. In flat network routing, all nodes have the same functionality and they work together to perform sensing and routing tasks. The Sensor Protocols for Information via Negotiation (SPIN) [3] and Directed Diffusion [4] fall into this category. Hierarchical network routing divides the network into clusters to achieve energy-efficient, scalability and one of the famous hierarchical network routing protocol is low-energy adaptive clustering hierarchy (LEACH) [5]. In location-based network routing, location information of nodes is used to compute the routing path. This information can be obtained from global positioning system (GPS) devices attached to each sensor node. Examples of location-based network routing protocols include geography adaptive routing (GAF) [6] and Geographic and Energy-Aware Routing (GEAR) [7]. During the creation of network topology, the process of setting up routes in WSNs is usually influenced by energy considerations. Because the power attenuation of a wireless link is proportional to square or even higher order of the distance between the sender and the receiver, multi-hop routing is assumed to use less energy than direct communication. However, multi-hop routing introduces significant overhead to maintain the network topology and medium access control. In the case that all the sensor nodes are close enough to the BS, direct communication could be the best choice for routing since it reduces network overhead and have a very simple nature. But in most cases, sensor nodes are randomly scattered so multi-hop routing is unquestionably de- facto. Many research projects and papers have shown that the hierarchical network routing and specially the clustering mechanisms make significant improvement in WSNs in reducing energy consumption and overhead [8-9]. We also have to note that most of clustering protocols proposed for WSNs assume that nodes are stationary. The reason for sensor nodes to be taken as stationary is the assumption of simple network topology. Clustering protocols can reduces signalling overhead since they do not have to manage the mobility pattern or location information of sensor nodes. As a result, it allows nodes saving more energy leading to a longer network life time. However, with some applications such as animal tracking, search and rescue activities this assumption is not very realistic; hence there are raising demands for clustering protocols to support mobile nodes. 978-1-4244-2489-4/08/$20.00 © 2008 IEEE IEEE ISWCS 2008 568