Abstract
Received signal strength (RSS) changes of static wireless nodes can be used for device-free localization and tracking (DFLT). Most RSS-based DFLT systems require access to calibration data, either RSS measurements from a time period when the area was not occupied by people, or measurements while a person stands in known locations. Such calibration periods can be very expensive in terms of time and effort, making system deployment and maintenance challenging. This paper develops an Expectation-Maximization (EM) algorithm based on Gaussian smoothing for estimating the unknown RSS model parameters, liberating the system from supervised training and calibration periods. To fully use the EM algorithm’s potential, a novel localization-and-tracking system is presented to estimate a target’s arbitrary trajectory. To demonstrate the effectiveness of the proposed approach, it is shown that: (i) the system requires no calibration period; (ii) the EM algorithm improves the accuracy of existing DFLT methods; (iii) it is computationally very efficient; and (iv) the system outperforms a state-of-the-art adaptive DFLT system in terms of tracking accuracy.
Highlights
Academic Editor: Gregor KlančarReceived: 6 July 2021Accepted: 13 August 2021Published: 18 August 2021Publisher’s Note: MDPI stays neutral with regard to jurisdictional claims in published maps and institutional affiliations.In developed nations, the demographic change in the population is creating many challenges both from a societal and an economic standpoint
The threshold is a tuning parameter between two extremes: if γ = 0 all pixels are taken into account and if γ = 1 only a single pixel is accounted for, and we have empirically found that γ = 0.7 provides a good overall performance
The results demonstrate that the implemented smoother and EM algorithm can be used with other devicefree localization and tracking (DFLT) methods, and it is an effective method to improve system performance
Summary
Academic Editor: Gregor KlančarReceived: 6 July 2021Accepted: 13 August 2021Published: 18 August 2021Publisher’s Note: MDPI stays neutral with regard to jurisdictional claims in published maps and institutional affiliations.In developed nations, the demographic change in the population is creating many challenges both from a societal and an economic standpoint. Is the European Union’s funding program that aims at developing “information and communication technologies (ICT) in a person’s daily living and working environment to enable them to stay active for longer duration, remain socially connected and live independently into old age” (www.aal-europe.eu, accessed on 17 August 2021). This can be achieved by developing both preventive and monitoring systems for aging safely at home, in the community, and at work.
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