International Journal of Wireless & Mobile Networks (IJWMN) Vol. 4, No. 4, August 2012 DOI : 10.5121/ijwmn.2012.4411 155            Dipak Wajgi 1 and Dr. Nileshsingh V. Thakur 2 1 Department of Computer Science and Engineering, Shri. Ramdeobaba College of Engineering and Management, Nagpur, India wajgi@rediffmail.com 2 Department of Computer Science and Engineering, Shri. Ramdeobaba College of Engineering and Management, Nagpur, India thakurnisvis@rediffmail.com ABSTRACT In wireless sensor network, clustering is used as an effective technique to achieve scalability, self- organization, power saving, channel access, routing etc.[3]. Lifetime of sensor nodes determines the lifetime of the network and is crucial for the sensing capability.[2]. Clustering is the key technique used to extend the lifetime of a sensor network. Clustering can be used for load balancing to extend the lifetime of a sensor network by reducing energy consumption. Load balancing using clustering can also increase network scalability. Wireless sensor network with the nodes with different energy levels can prolong the network lifetime of the network and also its reliability. In this paper we propose a clustering technique which will balance the load among the cluster by using some backup nodes. The backup high energy and high processing power nodes replace the cluster head after the cluster reaches to its threshold limit. This approach will increase the network lifetime and will provide high throughput. KEYWORDS wireless sensor network, clustering , reliability, scalability 1. INTRODUCTION Information gathering is a fast growing and challenging field in today’s world of computing. Sensors provide a cheap and easy solution to these applications especially in the inhospitable and low-maintenance areas where conventional approaches prove to be very costly. Sensors are tiny devices that are capable of gathering physical information like heat, light or motion of an object or environment. Sensors are deployed in an ad-hoc manner in the area of interest to monitor events and gather data about the environment. Networking of these unattended sensors is expected to have significant impact on the efficiency of many military and civil applications, such as combat field surveillance, security and disaster management. Sensors in such systems are typically disposable and expected to last until their energy drains. Therefore, energy is a very scarce resource for such sensor systems and has to be managed wisely in order to extend the life of the sensors for the duration of a particular mission. Typically sensor networks follow the model of a base station or command node, where sensors relay streams of data to the command node either periodically or based on events. The command node can be statically located in the vicinity of the sensors or it can be mobile so that it can move around the sensors and collect data. In either case, the command node cannot be reached efficiently by all the sensors in the system. The nodes that are located far away from the command node will consume more energy to transmit data then other nodes and therefore will die sooner[6].