IJCSNS International Journal of Computer Science and Network Security, VOL.9 No.2, February 2009 386 Manuscript received February 5, 2009 Manuscript revised February 20, 2009 Energy Efficient Communication Protocol for a Mobile Wireless Sensor Network System Hiren Kumar Deva Sarma 1 Avijit Kar 2 Rajib Mall 3 1. Department of IT, Sikkim Manipal Institute of Technology, Sikkim, INDIA 2. Department of CSE, Jadavpur University, Jadavpur, Kolkata, INDIA 3. Department of CSE, IIT Kharagpur, Kharagpur, INDIA Abstract Wireless Sensor Network Systems can be applied to monitor different environments ranging from military to civil applications. It has been observed that different protocols required for smooth functioning of the network system are highly application specific. Another important fact is that the communication protocols have significant role in achieving right performance of the network system. In this paper we consider a highly dynamic wireless sensor network system in which the sensor nodes are mobile as well as the base station is also mobile. We propose a hierarchical energy efficient communication protocol for such type of a wireless sensor network namely wireless Sensor system for Hierarchical Information gathering through Virtual triangular Areas (SHIVA). Our approach considers a cluster head set in place of a single cluster head for a cluster. We also follow a novel approach for clustering process. Simulation results show the energy analysis in the system. Key Words: Energy Efficient Routing, Wireless Sensor Networks, Base Station Mobility, Sensor Node Mobility 1. Introduction Wireless Sensor Network (WSN) is becoming very popular area for research & development and has been a hot stuff for researchers and engineers in the current time. The wide varieties of the possible applications of wireless sensor networks have made researchers and engineers attracted towards it. Internetworking of unattended sensors wirelessly and making it possible to process the data sensed by the sensors in the sensor network system and finally communicating the data sensed by individual sensors in their locality to a powerful computer which is located far away from the sensor field make it possible to monitor events in an area of interest from a remote place. The sensors are equipped with sensing, data processing and communication capabilities. Also these sensors are powered by battery. The sensing circuitry in the sensor node makes measurements of different parameters from the surrounding environment and transforms these into an electric signal. By processing of such a signal, some properties of the source objects located in the environment or some information about different events happening in the environment may be revealed. Sensors can process the sensed data locally though each sensor is equipped with limited processing capability. And this local processing is important as this process may reduce the volume of data to be sent or communicated to the Base Station. The data sensed by the sensors are sent to the command center popularly known as Base Station / Sink usually via a radio transmitter. This communication may be direct i.e. directly from the sensor to the base station or indirect i.e. through some intermediate sensor nodes. This absolutely depends on the logical organization of the wireless sensor network (e.g. whether hierarchical or flat). Since these types of network are battery driven, the sensors are always energy constrained. Also these systems are typically disposable and expected to last as long as they have energy or battery power. Therefore, wise management of energy is extremely important in such systems in order to get an extended life of the network for the duration of a particular mission. Scalability is another important issue in the design of such networks. Any protocol designed for such networks should be scalable so that it can handle a larger network of thousand of thousands sensor nodes. Most importantly any protocol designed for WSN is application specific. Different types of applications demand either the modification of the existing protocol or an entirely new protocol. It has already been accepted that WSN may be deployed for military and civil applications e.g. combat field surveillance, security, environment monitoring, traffic monitoring on highways/roads, disaster management etc. Every application demands a particular model regarding