International Journal of Computer Applications (0975 – 8887) Volume 90 – No 4, March 2014 1 Data Aggregation based Cooperative MIMO System for Wireless Sensor Networks: Performance Analysis Syed Akhtar Imam Department of Electronics & Communication Engineering Jamia Millia Islamia, New Delhi, India Vibhav Kumar Sachan Department of Electronics & Communication Engineering KIET Group of Institutions, Ghaziabad, U.P, India Shivani Singh Department of Electronics & Communication Engineering KIET Group of Institutions, Ghaziabad, U.P, India ABSTRACT To increase the life span of wireless sensor network, energy consumption must be minimized while satisfying given throughput and delay requirement. In this paper, we described an energy model based on cooperative MIMO scheme considering of both transmission and data aggregation energy is proposed for wireless sensor network. Based on this consequence, jointly considering both cooperative MIMO and data aggregation techniques which shows performance enhancement over conventional SISO system for same signal- to-noise ratio. Moreover, at critical distance value MIMO system outperforms SISO system is compared. The results show that MQAM is the best modulation technique is proved by simulations and suitable diversity technique for energy miniaturization to send a given number of bits are analyzed. Keywords Alamouti diversity schemes, Data aggregation, Energy Efficiency, Wireless sensor network. 1. INTRODUCTION World-wide communication is possible with anyone or anywhere using multi-media ranges evolving wireless communication. Wireless sensor networks are made up of various sensor devices that are spread over the geographical area to be monitored and communicate as well as gather information from environment using wireless links. Battery is the main power source in a sensor node, in this consequence energy is a very critical resource in wireless technology. To save energy efficient transmission technique is required so that energy consumption must be minimized while satisfying given throughput and delay requirements [1]. In order to minimize total energy consumption includes both transmission energy and circuit energy consumption for both MIMO and SISO systems have been proposed. Recent investigation on multi-input-multi-output (MIMO) illustrates a huge improvement of energy –efficiency in WSNs [3]- [9].However, direct application of MIMO techniques to sensor networks is not practical due to the limited physical size of sensor node which typically can only support a single antenna. Therefore, by allowing individual single antenna nodes to cooperate on information transmission and reception, a cooperative MIMO system can be constructed such that Energy efficient MIMO schemes can be developed. While data aggregation has been considered an essential tool for integrating such data to reduce redundancy and to reduce energy consumption by minimizing number of transmission. In this context, an energy model for WSNs based on the energy consumption is formulated mathematically to calculate overall energy consumption of cooperative MIMO systems with data aggregation consideration. Following energy- efficient communication techniques for maximizing lifetime and for delay reduction of wireless sensor networks are discussed in this paper .A comparison study is done between MIMO approach and SISO approach at critical distance values. The results shows in this paper promises that joint consideration of the energy consumption of cooperative MIMO and data aggregation techniques will further reduce energy consumption and thus improves network lifetime. The rest of the paper is organized as follows: In section 2, System model for MIMO system including energy consumption is described. In section 3, Energy analysis of point-to-point communication systems for jointly considering data aggregation into a cooperative MIMO communication system is investigated .Comparisons of the critical distances at which cooperative MIMO outperforms the SISO system for different parameters discussed in section 4. Finally, summarizes our conclusions in section 5. 2. SYSTEM MODEL A better and practical approach to exploit diversity schemes in WSNs .Space-time coding (STC) technique in wireless systems are most widely used with the aim of joint channel encoding of multiple transmit antennas to achieve coding gain and diversity gain . As shown in figure 1, Alamouti space- time block code (STBC) employing two transmit antennas and a single receiver antenna [2]. s1 and s2 are two different symbols that are transmitted simultaneously in first time slot from antenna 1 and 2. Consecutively, two coded symbols such as * 2 s  and * 1 s are transmitted during next time slot. The main concept of the Alamouti’s STBC scheme for any number of transmit antenna based on orthogonal designs using both real and complex constellations to achieve diversity. Where (*) denotes complex conjugate. The transmission code matrix for the Alamouti codes, multiplies the code matrix S by its Hermitian transpose S T satisfies as