Design and Implementation of a Decentralized

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Design and Implementation of a Decentralized Positioning System for Wireless Sensor Networks Chin-Liang Wang Department of Electrical Engineering and Institute of Communications Engineering National Tsing Hua University Hsinchu, Taiwan 30013, R.O.C. [email protected] Dong-Shing Wu and Fu-Fu Shu Institute of Communications Engineering National Tsing Hua University Hsinchu, Taiwan 30013, R.O.C. Abstract —In terms of the location-aware applications for wire- less sensor networks, it is crucial to improve the measurement reliability of the received physical signal as well as the target po- sitioning and tracking performance in a real environment. In the localization process, reflection, scattering, and other physical phenomena have a negative impact on the measurement reliabili- ty and the estimation accuracy at local sensor nodes. In this pa- per, we describe using a particle filter to increase the received signal strength (RSS) measurement reliability of each local sensor node and then use the least mean squares (LMS) algorithm to estimate the path loss exponent of the distance-dependent path loss model in our laboratory environment. Using the Industrial Technology Research Institute (ITRI) sensor platform, the expe- rimental results show that the proposed LMS-based method can reduce the average noise variance by approximately 1 dB. Then the filtered RSS samples and the estimated path loss exponent are applied in the proposed weighted sign algorithm (WSA), which are implemented in the ITRI sensor platform for target position- ing and tracking in our laboratory surroundings. The location estimation of a target is formulated as a weighted least squares (WLS) problem, and then is solved based on the WSA in an itera- tive and decentralized manner. Experimental results demonstrate that the proposed WSA-based positioning and tracking scheme achieves a maximum error distance of approximately 1.7 meters, average error distances of approximately 0.96 meters (positioning case) and 1.38 meters (tracking case), which are not far from those obtained from computer simulations (0.67 meters and 0.91 meters, respectively). Keywords - decentralized approach; particle filter; positioning; tracking; weighted sign algorithm; wireless sensor networks I. INTRODUCTION Given the increasing demand for location-aware applica- tions in wireless sensor networks, target positioning and track- ing have received a great deal of attention over the past ten years [1]-[3]. A wireless sensor network typically consists of a large number of sensor nodes to measure the desired physical information in the real environment, and the local sensor nodes are easy to deploy, programmable, and dynamically reconfigurable in the entire network [4]-[8]. Recently, theoret- ical research has led to many localization methods being pro- posed and analyzed based on the decentralized approach [9]- [11]. This approach is favored because a decentralized locali- zation system requires less transmission energy when com- pared with the centralized system in large-scale and dense wireless sensor networks. The performance of these decentra-
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  • Spring '10
  • brown
  • Sensor node, Wireless sensor network, Wireless Sensor Networks, IEEE Communications Society, path loss exponent

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