ENERGY EFFICIENT HYBRID SCHEME FOR DATA AGGREGATION IN GRID BASED WIRELESS SENSOR NETWORKS AMANDEEP KAUR AND DR.RAJNEESH GUJRAL M.M.Engineering College/ Department of Computer Science andEngineering, Maharishi Markandeshwar University, Ambala, Haryana, India Email: amanya3110@gmail.com, drrajneeshgujral@mmumullana.org ABSTRACT: Large scale Wireless Sensor Networks (WSNs) will be enormously deployed in different kinds of applications. It is likely that redundant data will be detected by nodes when sensing an event. As energy efficiency is the critical issue in WSNs. Several aggregation, clustering and routing protocols have been developed in order to reduce the network traffic toward the sink and therefore prolong the network lifetime. An alternative of clustering is to build chains instead of clusters. Grid based WSNs have the advantages of dynamic topology management and flexible selection of routing path. In this paper we propose a hybrid grid and chain based data aggregation method based on sleep/awake mode to improve the lifetime of WSNs. Aggregated data moves from node to node along the chain, and finally reach to the BS. Further simulation results show that the proposed solution has better performance in terms of energy efficiency and number of dead nodes which increase network lifetime. KEYWORDS: Data Aggregation, Network lifetime, Wireless Sensor networks. INTRODUCTION Recent advances in miniaturization and low-power design have led to the development of small- sized battery-operated sensors that are capable of detecting ambient conditions such as temperature and sound. Sensors are generally equipped with data processing and communication capabilities. The sensing circuitry measures parameters from the environment surrounding the sensor and transforms them into an electric signal. Processing such a signal reveals some properties about objects located and/or events happening in the vicinity of the sensor. Each sensor has an onboard radio that can be used to send the collected data to interested parties. Such technological development has encouraged practitioners to envision aggregating the limited capabilities of the individual sensors in a large scale network that can operate unattended [1–3].Data aggregation [4] is a key task performed within WSNs to fuse information from multiple sensors and deliver it to a sink node in a manner that eliminates redundancy and enables energy saving. As a popular approach for data aggregation such as LEACH [5], HEED [6] uses cluster head for communicating data to sink. If sink is far away, high energy will be required to successfully deliver the packet. Another approach PEGASIS [7] has a drawback that energy expenditure will be high in case the neighbours along the chain are too distant. This paper presents an Energy Efficient Hybrid Scheme for Data Aggregation (E 2 HSDA) protocol which is based on sleep/awake mode pattern [20-22]. It focuses on eliminating these limitations by using multihop communication instead of single hop for improving the network lifetime. With this method, the nodes in the sensor network can be in one of the two states: sleep state and waking state. In the sleep state, the node turns off its transmitter so that it is unable to transmit packets thereby saving energy whereas in the waking state, the sensor can be in one of the other three operating modes, i.e., either make measurements, perform some computation or communicate information to the fusion centre. In the present