International Journal of Computer Applications (0975 – 8887) Volume 57– No.9, November 2012 41 Distance based Cluster Head Selection Algorithm for Wireless Sensor Network Bhawnesh Kumar Department of Computer Science & Engineering Mewar University Rajasthan, India Vinit Kumar Sharma Department of Computer Science & Engineering Shamli Institute of Engineering & Technology, Shamli, U.P., India ABSTRACT In this paper, a distance based Cluster head selection algorithm is proposed for improving the sensor network life time. This protocol achieves a good performance in terms of lifetime by balancing the energy load among all the nodes. This clustering technique help to prolong the life of wireless sensor network, especially in hostile environment where battery replacement of individual sensor nodes is not possible after their deployment in the given target area. Therefore, the proposed technique to distribute the role of the cluster head (CH) among the wireless sensor nodes in the same cluster is vital to increase the lifetime of the network. This algorithm uses a distance based method for providing the cluster head selection. Clustering techniques also provide good load balancing, and in-network data aggregation. Keywords Sensor Networks, Clustering, Network life Time, Energy Efficiency, Data Aggregation 1. INTRODUCTION The continuous enhancement in communication, computation and hardware technologies enable new devices known as sensor nodes [1]. Wireless Sensor Networks (WSNs) are formed by hundreds or thousands of nodes that gather information and forward it to a sink node. These large numbers of nodes, which have the ability to communicate wirelessly, to perform limited computation, and to sense their surroundings, form the WSN [2]. Specific functions can be obtained through cooperation between these nodes; functions such as sensing, tracking, and alerting [3]. These functions make these wireless sensors very useful for monitoring natural phenomena, environmental changes, controlling security, estimating traffic flows, monitoring military application, and tracking friendly forces in the battlefields [2]. We consider a network of energy-constrained sensors that are deployed over a geographic area for monitoring the environment. Among the sources of energy consumption in a sensor node, wireless data transmission is the most critical. Obviously, WSNs need to be stable in design and structure to transfer data among the wireless sensors safely and without any problems, because of their use in critical areas and real time systems. Moreover, consuming less energy and increasing the lifetime of the wireless sensor nodes are the main objectives in designing the WSN, because of the limitation of the power resources and the difficulties of replacing the batteries of the wireless sensors. Wireless Sensor Networks present vast challenges in terms of implementation. There are several key attributes that designers must carefully consider, which are of particular importance in wireless sensor networks.  Cost of nested clustering  Selection of Cluster heads and sub cluster heads  Synchronization  Data Aggregation  Repair Mechanisms  Quality of Service (QoS) 2. CLUSTERING Cluster may be defined as follows: Definition: Dividing the sensor networks into small manageable units is called as clustering & process known as clustering process. Though the main reason behind the implementation of the clustering approach is to improve the scalability of the network (prolong), it is an important factor in achieving energy efficient routing of data within the network [12]. Study on energy efficient routing in WSN brings this two broad classification of approaches. They are,  Clustering approach  Tree based approach In a wireless sensor network, cluster is a group of sensor nodes in which one node will act as a cluster head (CH) [9, 10], and remaining nodes will act as member nodes. Clustering helps in reducing the number of exchanged communications in wireless sensor network resulting in low consumption of battery power of individual sensor nodes. This increases the life span of the wireless sensor network. A cluster head is selected for each cluster based on the energy level of that node or distance based also. The main objective is to make only the cluster head communicate with the base station so that the remaining node can be put to a sleep state. Fig. 1 Cluster head model in WSNs Base Station Cluster Head Member Node