{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2026,3,22]],"date-time":"2026-03-22T05:59:29Z","timestamp":1774159169273,"version":"3.50.1"},"reference-count":190,"publisher":"MDPI AG","issue":"4","license":[{"start":{"date-parts":[[2020,9,23]],"date-time":"2020-09-23T00:00:00Z","timestamp":1600819200000},"content-version":"vor","delay-in-days":0,"URL":"https:\/\/creativecommons.org\/licenses\/by\/4.0\/"}],"funder":[{"DOI":"10.13039\/100010661","name":"Horizon 2020","doi-asserted-by":"publisher","award":["813278"],"award-info":[{"award-number":["813278"]}],"id":[{"id":"10.13039\/100010661","id-type":"DOI","asserted-by":"publisher"}]}],"content-domain":{"domain":[],"crossmark-restriction":false},"short-container-title":["Data"],"abstract":"<jats:p>Some of the recent developments in data science for worldwide disease control have involved research of large-scale feasibility and usefulness of digital contact tracing, user location tracking, and proximity detection on users\u2019 mobile devices or wearables. A centralized solution relying on collecting and storing user traces and location information on a central server can provide more accurate and timely actions than a decentralized solution in combating viral outbreaks, such as COVID-19. However, centralized solutions are more prone to privacy breaches and privacy attacks by malevolent third parties than decentralized solutions, storing the information in a distributed manner among wireless networks. Thus, it is of timely relevance to identify and summarize the existing privacy-preserving solutions, focusing on decentralized methods, and analyzing them in the context of mobile device-based localization and tracking, contact tracing, and proximity detection. Wearables and other mobile Internet of Things devices are of particular interest in our study, as not only privacy, but also energy-efficiency, targets are becoming more and more critical to the end-users. This paper provides a comprehensive survey of user location-tracking, proximity-detection, and digital contact-tracing solutions in the literature from the past two decades, analyses their advantages and drawbacks concerning centralized and decentralized solutions, and presents the authors\u2019 thoughts on future research directions in this timely research field.<\/jats:p>","DOI":"10.3390\/data5040087","type":"journal-article","created":{"date-parts":[[2020,9,23]],"date-time":"2020-09-23T09:28:08Z","timestamp":1600853288000},"page":"87","update-policy":"https:\/\/doi.org\/10.3390\/mdpi_crossmark_policy","source":"Crossref","is-referenced-by-count":58,"title":["Survey of Decentralized Solutions with Mobile Devices for User Location Tracking, Proximity Detection, and Contact Tracing in the COVID-19 Era"],"prefix":"10.3390","volume":"5","author":[{"ORCID":"https:\/\/orcid.org\/0000-0001-8178-5652","authenticated-orcid":false,"given":"Viktoriia","family":"Shubina","sequence":"first","affiliation":[{"name":"Faculty of Information Technology and Communication Sciences, Tampere University, Korkeakoulunkatu 1, 33720 Tampere, Finland"},{"name":"Faculty of Automatic Control and Computers, University \u201cPolitehnica\u201d of Bucharest, Splaiul Independen\u021bei 313, 060042 Bucharest, Romania"}]},{"ORCID":"https:\/\/orcid.org\/0000-0002-1028-0160","authenticated-orcid":false,"given":"Sylvia","family":"Holcer","sequence":"additional","affiliation":[{"name":"Institute of New Imaging Technologies, Universitat Jaume I, Avda. Sos Baynat, 12071 Castell\u00f3n de la Plana, Spain"},{"name":"Faculty of Electrical Engineering and Communication, Brno University of Technology, Technick\u00e1 3058\/10, 616 00 Brno, Czechia"}]},{"ORCID":"https:\/\/orcid.org\/0000-0002-6431-1794","authenticated-orcid":false,"given":"Michael","family":"Gould","sequence":"additional","affiliation":[{"name":"Institute of New Imaging Technologies, Universitat Jaume I, Avda. Sos Baynat, 12071 Castell\u00f3n de la Plana, Spain"}]},{"ORCID":"https:\/\/orcid.org\/0000-0003-1718-6924","authenticated-orcid":false,"given":"Elena Simona","family":"Lohan","sequence":"additional","affiliation":[{"name":"Faculty of Information Technology and Communication Sciences, Tampere University, Korkeakoulunkatu 1, 33720 Tampere, Finland"}]}],"member":"1968","published-online":{"date-parts":[[2020,9,23]]},"reference":[{"key":"ref_1","unstructured":"Asaf, G., Davis, H., McCorkell, L., Wei, H., O\u2019Neill, B., and Akrami, A. (2020, September 17). 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