Robust Time-Based Localization for Asynchronous Networks

Abstract

Localization is indispensable for the successful deployment of wireless sensor networks (WSNs). Time-based localization approaches attract a lot of interest due to their high accuracy and potentially low cost. However, time-based localization is intensively coupled with clock synchronization. Thus, the reliability of timestamps in the time-based localization becomes an important yet challenging task to deal with. In this paper, we propose a robust time-based localization approach to locate a target node with the assistance of anchors (nodes with known positions) in an asynchronous network with clock offsets. We employ the asymmetric trip ranging (ATR) protocol to obtain time-of-arrival (TOA) measurements and facilitate clock offset cancellation. Regardless of the reliability of the timestamp report from the target node, closed-form least-squares (LS) and weighted LS estimators are derived to accurately estimate the target node position. As a result, we counter the uncertainties caused by the target node by ignoring the timestamps from this node. Furthermore, Cramér-Rao Bounds (CRBs) and simulation results corroborate the efficiency of our localization scheme.

Synchronization and Localization in Wireless Networks

“…Practical implementations and the combination of recently proposed methods from both fields are analyzed. In Chapter 6, an overview of simultaneous approaches is presented, with a distinction in centralized and distributed computation [1,19,26,35,36,37,75,89,124,129,137,138,139,141,143,144]. In this review we provide a comprehensive orientation in this novel topic.…”

Localization algorithms for asynchronous time difference of arrival positioning systems

“…Efforts have been made in the literature to relax the synchronization requirements, and two common methods are two-way ranging [1,2] and elliptical localization [3][4][5]. In two-way ranging, an anchor node transmits a packet to a target node, which replies by an acknowledgment packet to the anchor node after a response delay.…”

“…Hence, the target node lies on the trajectory of an ellipse with anchor Tx and anchor Rx as the two foci. Several elliptical localization systems have been studied in the literature [3][4][5]. These systems work in a similar manner, and they differ in one or two respects.…”

“…The system deployment in [3] has a designated anchor Tx emitting an ultra-wideband pulse, and three anchor Rx nodes to perform the time difference arrival measurements. Wang et al [4] proposed an asymmetric trip ranging protocol, and the system deployment is similar to [3], but it involves a timing logic at the target node, which suffers from clock non-idealities. In [5], a distributed localization scheme is proposed, and it uses the target node to measure the TDOA.…”

Dual-satellite source geolocation with time and frequency offsets and satellite location errors

“…They did not consider sensor position errors and an iterative ML location estimator was used. The algorithm developed in [28] eliminated the clock bias via the use of asymmetric trip ranging (ATR). This protocol required the node to be located to be cooperative, which may not be fulfilled in the dual-satellite geolocation problem considered in this paper.…”