Positioning Research, Based On The Goal Of Wireless Sensor Networks

Recent advances in wireless communications and electronics have enabled the development of small-size sensor nodes with capabilities to sense the environment, process the information, and communicate with each other. These tiny sensor nodes stimulate great interests in wireless sensor networks (WSNs) which have been considered as one of the ten most important technologies for 21th century. WNSs have a variety of applications such as environmental monitoring, infrastructure management, public safety, medical, home and office security, transportation, and military. In the area of defense applications, distributed wireless sensor networks can be used for target localization, tracking, and identification in the battlefield environment. In this thesis, we focus on the acoustic source localization in WSNs.The existing acoustic source localization techniques are typically based on three types of sensor measurement from physical variables: time delay of arrival, direction of arrival and received sensor signal strength or energy. As the energy-based source location methodsIt is found that the energy-based methods derived from the received signal energy are much appropriate for the application to sensor networks. Therefore, this paper focuses on the energy-based localization methods. First we discuss some kinds of existing energy-based methods, such as the maximum likelihood (ML) method, and least squares (LS) method. Specifically, the LS methods include nonlinear LS (NLS), constrained LS (CLS) and linear LS method. For NLS and linear LS method, this paper presents weighting matrices for them. Then two weighted solutions, weighted nonlinear LS and weighted linear LS, are given. Besides, we also propose a new LS method which can solve both the source energy and location. Similarly, we propose a weighting matrix for it. Compared with existing LS methods, the weighted LS solutions deliver more accurate results and offer flexible implementation to reduce computational load. Extensive simulations are conducted to confirm the performance advantages.