Multiple MIMO scenarios for Power Management in Wireless Sensor Networks E. D. Vagenas * , G. S. Paschos, S. A. Kotsopoulos and V. Stylianakis † 1. Introduction One of the most promising application of the well known Ad Hoc Networks are the Wireless Sensor Networks. The sensor nodes are miniature devices equipped with a sensor, a transceiver and the necessary electronic circuits and able to collect and forward information. These nodes are designed to be deployed randomly or strategically in area and left operating until their battery is totally used up. Therefore, a major domain of interest in their design is the power management. Many ways of reserving energy have been proposed in the literature, including energy-aware protocols (e.g. MAC protocols), energy-aware routing, QoS scheduling, data gathering schemes, power-aware electronics and many other. This paper investigates the use of Multiple-Input Multiple-Output (MIMO) systems for energy conservation. The application of MIMO systems in Wireless Sensor Networks is very little explored. In [1], Cui and Goldsmith proposed both the use of a flat MIMO system and the use of nodes transmitting in a cooperative mode. The showed that in some cases power consumption in the electronic circuit of a MIMO system can be deficient. In [2], Jayaweera investigated even deeper the consumed energy of a sensor node employing a MIMO transceiver. Dai and Xiao in [3] and [4], proposed cooperative MIMO systems and the use of V-BLAST techniques as a more power efficient scheme. In this paper, an investigation of power efficiency of several MIMO scenarios is made. We take into consideration the room constraint of a sensor node and its impact on array characteristics. Taken fixed bit rate and antenna space into account, the optimum MIMO scheme is elected. A QoS operating mode is proposed, according to which, the transceiver is able to choose between the scenarios in real-time functioning. 2. Antenna deployment Many promising applications of Wireless Sensor Networks demand a very small sensor size. Even though the progress in electronics has provided with very small and fully integrated transceivers, the sensor size remains a design constraint for the antenna of the sensor, and even more for the case of a multi-antenna as in a MIMO system. For this reason, we deploy three different scenarios with 1, 2 and 4 element antenna respectively, all to fit in a * Aircraft Engineer Efstathios D. Vagenas; Electrical Engineer Georgios S. Paschos; Prof. Stavros A. Kotsopoulos, Wireless Telecommunication Laboratory. † Lect. Vasileios Stylianakis, Wired Telecommunication Laboratory, Department of Telecommunications, Faculty of Electrical Engineering and Computer Science, University of Patras, Kato Kastritsi, Patra, tel. 00302610997301, e-mail: kotsop@ee.upatras.gr