{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2025,10,11]],"date-time":"2025-10-11T06:40:46Z","timestamp":1760164846070,"version":"build-2065373602"},"reference-count":28,"publisher":"MDPI AG","issue":"9","license":[{"start":{"date-parts":[[2021,5,10]],"date-time":"2021-05-10T00:00:00Z","timestamp":1620604800000},"content-version":"vor","delay-in-days":0,"URL":"https:\/\/creativecommons.org\/licenses\/by\/4.0\/"}],"content-domain":{"domain":[],"crossmark-restriction":false},"short-container-title":["Sensors"],"abstract":"<jats:p>The outbreak of COVID-19 has resulted in many different policies being adopted across the world to reduce the spread of the virus. These policies include wearing surgical masks, hand hygiene practices, increased social distancing and full country-wide lockdown. Specifically, social distancing involves keeping a certain distance from others and avoiding gathering together in large groups. Automatic crowd density estimation is a technological solution that could help in guaranteeing social distancing by reducing the probability that two persons in a public area come in close proximity to each other while moving around. This paper proposes a novel low complexity RF sensing system for automatic people counting based on low cost UWB transceivers. The proposed system is based on an ordinary classifier that exploits features extracted from the channel impulse response of UWB communication signals. Specifically, features are extracted from the sorted list of singular values obtained from the singular value decomposition applied to the matrix of the channel impulse response vector differences. Experimental results achieved in two different environments show that the proposed system is a promising candidate for future automatic crowd density monitoring systems.<\/jats:p>","DOI":"10.3390\/s21093296","type":"journal-article","created":{"date-parts":[[2021,5,10]],"date-time":"2021-05-10T10:49:51Z","timestamp":1620643791000},"page":"3296","update-policy":"https:\/\/doi.org\/10.3390\/mdpi_crossmark_policy","source":"Crossref","is-referenced-by-count":10,"title":["CIR-Based Device-Free People Counting via UWB Signals"],"prefix":"10.3390","volume":"21","author":[{"ORCID":"https:\/\/orcid.org\/0000-0002-5712-1204","authenticated-orcid":false,"given":"Mauro","family":"De Sanctis","sequence":"first","affiliation":[{"name":"Department of Electronics Engineering, University of Rome \u201cTor Vergata\u201d, 00133 Roma, Italy"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"Aleandro","family":"Conte","sequence":"additional","affiliation":[{"name":"Department of Electronics Engineering, University of Rome \u201cTor Vergata\u201d, 00133 Roma, Italy"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"ORCID":"https:\/\/orcid.org\/0000-0002-2580-7324","authenticated-orcid":false,"given":"Tommaso","family":"Rossi","sequence":"additional","affiliation":[{"name":"Department of Electronics Engineering, University of Rome \u201cTor Vergata\u201d, 00133 Roma, Italy"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"Simone","family":"Di Domenico","sequence":"additional","affiliation":[{"name":"Department of Electronics Engineering, University of Rome \u201cTor Vergata\u201d, 00133 Roma, Italy"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"Ernestina","family":"Cianca","sequence":"additional","affiliation":[{"name":"Department of Electronics Engineering, University of Rome \u201cTor Vergata\u201d, 00133 Roma, Italy"}],"role":[{"role":"author","vocabulary":"crossref"}]}],"member":"1968","published-online":{"date-parts":[[2021,5,10]]},"reference":[{"key":"ref_1","doi-asserted-by":"crossref","first-page":"153479","DOI":"10.1109\/ACCESS.2020.3018140","article-title":"A Comprehensive Survey of Enabling and Emerging Technologies for Social Distancing\u2014Part I: Fundamentals and Enabling Technologies","volume":"8","author":"Nguyen","year":"2020","journal-title":"IEEE Access"},{"key":"ref_2","doi-asserted-by":"crossref","unstructured":"Bouhlel, F., Hazar, M., and Hammami, M. 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