%0 Journal Article
%T Prolonging the Lifetime of Two-Tiered Wireless Sensor Networks with Mobile Relays
%A Theodore C. Kotsilieris
%A George T. Karetsos
%J ISRN Sensor Networks
%D 2013
%R 10.1155/2013/610796
%X We propose a clustering scheme for wireless sensor nodes in hierarchical wireless sensor networking architectures that employs mobile relay nodes in order to achieve energy conservation and network lifetime prolongation. The key aspects of our scheme are relay node relocation and reclustering when failures are detected. The performance of the proposed approach is evaluated via simulations for various topology layouts based on the sensor node population and number of mobile relay nodes employed. The results show significant energy savings in particular for topologies with large numbers of sensors. 1. Introduction Wireless sensor networks are becoming more and more popular nowadays due to the significant advantages they present in carrying out specialized monitoring tasks in certain application areas. These areas vary from military [1] and target tracking [2] to healthcare [3每5] and environmental monitoring [6每8]. However, there exist certain aspects that need to be addressed during deployment in order to achieve the best possible functionality and eliminate as much as possible problems that are inherent in wireless sensors technology and networking [9]. One of the most important design issues of a wireless sensor network that should be carefully treated is energy consumption and management that directly affects the network＊s lifetime. Many research approaches have been proposed already as potential solutions to this problem. The suggested methods span from MAC layer algorithms [10每15] and topology control actions [16, 17] to hierarchical architectures that adopt the introduction of special purpose nodes, called relay nodes [18每20]. Research efforts on hierarchical architectures, also called two-tiered architectures, apart from introducing the role of a relay node (RN) or cluster head (CH), go further by applying clustering techniques that aim at minimizing the sensor communication cost [18, 21]. Several techniques have been proposed in the literature that aim to avoid rapid battery drainage that consequently may cause network connectivity failures or sensing area holes [22每25]. In single-hop operation of wireless sensor nodes (WSNs), data propagation towards the destination (i.e., the base station (BS)) that will further process the sensed data is accomplished by the relay nodes. Thus, in hierarchical deployments the critical factor is the lifetime achieved by the relay nodes which has to be enhanced as much as possible. Towards this, a measurable objective is the number of data gathering rounds that can be carried out by an RN. A data gathering round of
%U http://www.hindawi.com/journals/isrn.sensor.networks/2013/610796/