Parameter estimation for ultra wideband based positioning
(2013)
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- Authors
- Supervisors
- Vandendorpe, Luc
- Abstract
- Positioning an unknown location 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, and then combining them in an optimal way to get the desired position in a second step. In two-step positioning strategies, different types of parameters can be considered such as the time of arrival (TOA) and the angle of arrival (AOA). On the other hand, 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 positioning using IR-UWB signals. We treat the general setting of non-linear estimation, study the threshold and ambiguity phenomena, propose some approximations of the statistics of the maximum likelihood estimator (MLE), and derive some approximate upper and lower bounds of the mean squared error (MSE). 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 deal with TOA estimation in multiuser time-hopping IR-UWB systems. We introduce a new receiver that we call "delaying-and-multiplying" receiver, and propose a new estimator based on that receiver and named it "maximum delaying-and-multiplying estimator". We compute the asymptotic, local and global performances of the proposed estimator and compare it with some existing benchmark estimators. We study the potential of the proposed estimator in the presence of deterministic and random multiuser interference. We also propose a family of TOA estimators based on the discrete Fourier transform of the received signal for both AWGN and multipath channels. We derive the Cramer-Rao lower bounds (CRLB) for joint TOA and AOA estimation, for AOA based positioning, and for hybrid TOA-AOA based positioning, in UWB multipath channels. We investigate the impact of the overlapping between the different multipath components (MPC) on the joint estimation of the MPCs gains and TOAs. We also derive the CRLBs for the joint estimation of the TOA and the AOA in single-input-single-output (SISO), single-input-multiple-output (SIMO), multiple-input-single-output (MISO) and multiple-input-multiple-output (MIMO) systems. We present a testbed that we realized at Université catholique de Louvain (UCL) for ranging and positioning by using IR-UWB signals based and employing the TOA technique. Two TOA estimators are considered: the MLE and a threshold-based estimator. We have studied from measurement data the impact of the multipath aspect of the channel and that of the shape of the transmitted pulses on the positioning performances. The obtained results are compared with the theoretical limits.
- Affiliations
Citations
Mallat, A. (2013). Parameter estimation for ultra wideband based positioning. https://hdl.handle.net/2078.5/25046