This paper develops an explicit solution that estimates the location of a stationary source using Time Difference of Arrival (TDOA) measurements of a signal received by a number of receivers that have random error in their positions. The proposed solution accounts for the error from receiver positions, is algebraic, and does not have convergence problem as in the Taylor-series linearization method. The Cramer-Rao Lower Bound (CRLB) of the source location estimate in the presence of sensor position error is derived. Simulation results indicate that the proposed solution achieves an accuracy close to the CRLB under Gaussian noise. * He is presently with the

The purpose of this paper is to investigate the use of Ultra Wideband (UWB) technology for indoor precise positioning systems that can be used by fire fighters. Two promising techniques to achieve indoor positioning accuracy of better than 1 m are Impulse Radio Ultra Wideband (IR-UWB) and Multicarrier Ultra Wideband (MC-UWB). This paper provides insight into key concepts such as receiver synchronization and practical system implementation for both these techniques from the positioning system perspective. This is followed by a system level comparison listing advantages and disadvantages of both these techniques. Basic simulation results comparing performance of a precise positioning system using IR-UWB and MC-UWB are presented, followed by indoor ranging test results using a MC-UWB based prototype. It is demonstrated that such an MC-UWB based positioning system achieves ranging accuracy of better than 1 m in indoor multipath environments without occupying GHz of bandwidth and without interfering with other existing wireless systems.

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There exist various applications for indoor positioning, amongst which indoor positioning and tracking in urban environments has gained significant attention. Some user communities, like fire fighters, ideally require indoor accuracy of less than one metre, with accuracies of less than six metres acceptable by some other user communities. Achieving this level of accuracy requires a detailed profiling of error sources so that they can be better understood so that, in turn, indoor positioning accuracy in the presence of these errors can be further improved. Some well known error sources like multipath, NLOS (non line of sight), oscillator drift, dilution of precision and others have been studied and can be found in the literature. A less well known error source that can substantially affect indoor positioning accuracy are the effects of the dielectric properties of building materials on propagation delay.Various RF and non-RF based prototypes that claim to be suitable for indoor positioning can be found in the literature. Most of the existing literature discusses algorithms and summarizes the positioning results that were achieved during field tests using a prototype system or, more commonly, simulations. Little of this existing literature provides a breakdown of the total navigation system errors observed with the objective of analyzing the contribution of each error source independently.The paper will first provide a brief overview of the precision personnel locator system developed at the Worcester Polytechnic Institute. The field tests and observed indoor positioning results using this RF prototype will then be summarized and used to provide a baseline to establish a system error budget. The total observed error will be broken down and a detailed analysis of each of the error sources will be presented based on actual measured data in a variety of indoor environments. This leads to a better understanding of how each error source affects indoor positioning accuracy. Each of the error sources can then be independently optimized to minimize the observed errors. Specifically, the interplay between the dielectric properties and multipath profiles will be highlighted. This paper will conclude by presenting an error budget which can be used as a practical lower bound when designing precise indoor positioning systems.K E Y W O R D S 1. Indoor positioning.2. Dielectric properties.