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Created by Olivier Bonaventure, last modified at June 27, 2013, at 07:23 AM

Achraf MALLAT will defend his Ph.D. thesis on "Parameter Estimation for Ultra Wideband Based Positioning" in Louvain-la-Neuve on Wednesday July 3rd, 2013 in room a.105, Maxwell building

Abstract

Positioning a node can be performed either directly from the signals received at/from the reference nodes, or by estimating some position-related parameters in a first step then combining them in an optimal way to get the position in a second step. In two- step positioning strategies different types of parameters can be considered like: time of arrival (TOA) and angle of arrival (AOA). Impulse radio (IR) ultra wideband (UWB) signals are characterized by their pulses shorter than 2 ns (bandwidth larger than 500 MHz). Such signals represent an excellent candidate for highly accurate positioning when the TOA technique is employed. In this thesis we consider the problem of parameter estimation for UWB-based positioning. We consider the general case of non-linear estimation, study the threshold and ambiguity phenomena, and derive some approximations of the mean squared error (MSE) and some approximate upper and lower bounds. The obtained results are applied in the context of TOA estimation using IR-UWB signals, and exploited in the design of the pulses that achieve the lowest attainable MSE. We consider multi-user (MU) time-hopping IR-UWB systems. We propose a new TOA estimator, compute its asymptotic, local and global performances, and compare to some existing estimators. We study the potential of the proposed estimator in the cases of deterministic and random MU interference. We propose a family of TOA estimators based on the discrete Fourier transform (DFT) for AWGN and multi-path channels. We derive the Cramer-Rao lower bounds (CRLB) for joint TOA and AOA estimation, AOA-based positioning, and hybrid TOA-AOA based positioning, in multipath UWB channels. We study the impact of the overlapping between the multipath components (MPC) on the joint MPC gain and TOA estimation. We derive the CRLBs for the joint TOA and AOA estimation in single-input-single-output (SISO), single-input-multiple- output (SIMO), MISO and MIMO systems. We present a testbed realized at UCL for IR-UWB based positioning using the TOA technique. Two TOA estimators are considered. We have studied from experimental results the impacts of the multipath channel and the shape of the used pulses on the positioning performances.

Tags: phd