Improved Position Estimation Using Hybrid TW-TOA and TDOA in Cooperative Networks
Artikel i vetenskaplig tidskrift, 2012

This paper addresses the problem of positioning multiple target nodes in a cooperative wireless sensor network in the presence of unknown turn-around times. In this type of cooperative networks, two different reference sensors, namely, primary and secondary nodes, measure two-way time-of-arrival (TW-TOA) and time-difference-of-arrival (TDOA), respectively. Motivated by the role of secondary nodes, we extend the role of target nodes such that they can be considered as pseudo secondary nodes. By modeling turn-around times as nuisance parameters, we derive a maximum likelihood estimator (MLE) that poses a difficult global optimization problem due to its nonconvex objective function. To avoid drawbacks in solving the MLE, we linearize the measurements using two different techniques, namely, nonlinear processing and first-order Taylor series, and obtain linear models based on unknown parameters. The proposed linear estimator is implemented in three steps. In the first step, a coarse position estimate is obtained for each target node, and it is refined through steps two and three. To evaluate the performance of different methods, we derive the Cramer-Rao lower bound (CRLB). Simulation results show that the cooperation technique provides considerable improvements in positioning accuracy compared to the noncooperative scenario, especially for low signal-to-noise-ratios.

Cooperative positioning

maximum-likelihood estimator (MLE)

time-of-arrival (TOA)

linear estimator

time-difference-of-arrival (TDOA)

two-way time-of-arrival (TW-TOA)

Cramer-Rao lower bound (CRLB)

wireless sensor network


Mohammad Reza Gholami

Chalmers, Signaler och system, Kommunikations- och antennsystem, Kommunikationssystem

Sinan Gezici

Bilkent Universitesi

Erik Ström

Chalmers, Signaler och system, Kommunikations- och antennsystem, Kommunikationssystem

IEEE Transactions on Signal Processing

1053-587X (ISSN)

Vol. 60 7 3770-3785 6183529


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