{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2026,5,27]],"date-time":"2026-05-27T12:38:34Z","timestamp":1779885514302,"version":"3.53.1"},"reference-count":57,"publisher":"MDPI AG","issue":"19","license":[{"start":{"date-parts":[[2022,9,27]],"date-time":"2022-09-27T00:00:00Z","timestamp":1664236800000},"content-version":"vor","delay-in-days":0,"URL":"https:\/\/creativecommons.org\/licenses\/by\/4.0\/"}],"funder":[{"DOI":"10.13039\/501100012166","name":"National Key Research and Development Program of China","doi-asserted-by":"publisher","award":["2021YFB3900800"],"award-info":[{"award-number":["2021YFB3900800"]}],"id":[{"id":"10.13039\/501100012166","id-type":"DOI","asserted-by":"publisher"}]}],"content-domain":{"domain":[],"crossmark-restriction":false},"short-container-title":["Sensors"],"abstract":"<jats:p>With the emergence of COVID-19, social distancing detection is a crucial technique for epidemic prevention and control. However, the current mainstream detection technology cannot obtain accurate social distance in real-time. To address this problem, this paper presents a first study on smartphone-based social distance detection technology based on near-ultrasonic signals. Firstly, according to auditory characteristics of the human ear and smartphone frequency response characteristics, a group of 18 kHz\u201323 kHz inaudible Chirp signals accompanied with single frequency signals are designed to complete ranging and ID identification in a short time. Secondly, an improved mutual ranging algorithm is proposed by combining the cubic spline interpolation and a two-stage search to obtain robust mutual ranging performance against multipath and NLoS affect. Thirdly, a hybrid channel access protocol is proposed consisting of Chirp BOK, FDMA, and CSMA\/CA to increase the number of concurrencies and reduce the probability of collision. The results show that in our ranging algorithm, 95% of the mutual ranging error within 5 m is less than 10 cm and gets the best performance compared to the other traditional methods in both LoS and NLoS. The protocol can efficiently utilize the limited near-ultrasonic channel resources and achieve a high refresh rate ranging under the premise of reducing the collision probability. Our study can realize high-precision, high-refresh-rate social distance detection on smartphones and has significant application value during an epidemic.<\/jats:p>","DOI":"10.3390\/s22197345","type":"journal-article","created":{"date-parts":[[2022,9,28]],"date-time":"2022-09-28T03:30:37Z","timestamp":1664335837000},"page":"7345","update-policy":"https:\/\/doi.org\/10.3390\/mdpi_crossmark_policy","source":"Crossref","is-referenced-by-count":12,"title":["Smartphone-Based Social Distance Detection Technology with Near-Ultrasonic Signal"],"prefix":"10.3390","volume":"22","author":[{"given":"Naizheng","family":"Jia","sequence":"first","affiliation":[{"name":"College of Control Science and Engineering, Zhejiang University, Hangzhou 310000, China"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Haoran","family":"Shu","sequence":"additional","affiliation":[{"name":"College of Control Science and Engineering, Zhejiang University, Hangzhou 310000, China"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"ORCID":"https:\/\/orcid.org\/0000-0001-8771-8901","authenticated-orcid":false,"given":"Xinheng","family":"Wang","sequence":"additional","affiliation":[{"name":"School of Advanced Technology, Xi\u2019an Jiaotong-Liverpool University, Suzhou 215123, China"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Bowen","family":"Xu","sequence":"additional","affiliation":[{"name":"College of Control Science and Engineering, Zhejiang University, Hangzhou 310000, China"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Yuzhang","family":"Xi","sequence":"additional","affiliation":[{"name":"College of Control Science and Engineering, Zhejiang University, Hangzhou 310000, China"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Can","family":"Xue","sequence":"additional","affiliation":[{"name":"College of Control Science and Engineering, Zhejiang University, Hangzhou 310000, China"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Youming","family":"Liu","sequence":"additional","affiliation":[{"name":"College of Control Science and Engineering, Zhejiang University, Hangzhou 310000, China"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Zhi","family":"Wang","sequence":"additional","affiliation":[{"name":"College of Control Science and Engineering, Zhejiang University, Hangzhou 310000, China"}],"role":[{"vocabulary":"crossref","role":"author"}]}],"member":"1968","published-online":{"date-parts":[[2022,9,27]]},"reference":[{"key":"ref_1","doi-asserted-by":"crossref","first-page":"860","DOI":"10.1126\/science.abb5793","article-title":"Projecting the transmission dynamics of SARS-CoV-2 through the postpandemic period","volume":"368","author":"Kissler","year":"2020","journal-title":"Science"},{"key":"ref_2","doi-asserted-by":"crossref","first-page":"c54","DOI":"10.1093\/nsr\/nwac054","article-title":"Strategies for reopening in the forthcoming COVID-19 era in China","volume":"9","author":"Guan","year":"2022","journal-title":"Natl. Sci. Rev."},{"key":"ref_3","doi-asserted-by":"crossref","first-page":"587","DOI":"10.1038\/s41467-020-20817-6","article-title":"A population-based controlled experiment assessing the epidemiological impact of digital contact tracing","volume":"12","author":"Rodriguez","year":"2021","journal-title":"Nat. Commun."},{"key":"ref_4","doi-asserted-by":"crossref","first-page":"113478","DOI":"10.1016\/j.socscimed.2020.113478","article-title":"Motivating social distancing during the Covid-19 pandemic: An online experiment","volume":"265","author":"Lunn","year":"2020","journal-title":"Soc. Sci. Med."},{"key":"ref_5","doi-asserted-by":"crossref","first-page":"1","DOI":"10.1007\/s10462-020-09852-3","article-title":"CovidSens: A vision on reliable social sensing for COVID-19","volume":"54","author":"Rashid","year":"2021","journal-title":"Artif. Intell. Rev."},{"key":"ref_6","doi-asserted-by":"crossref","first-page":"245","DOI":"10.1177\/0033354920976575","article-title":"The immediate effect of COVID-19 policies on social-distancing behavior in the United States","volume":"136","author":"Abouk","year":"2021","journal-title":"Public Health Rep."},{"key":"ref_7","doi-asserted-by":"crossref","unstructured":"Adiyoso, W. (2021). Social distancing intentions to reduce the spread of COVID-19: The extended theory of planned behavior. BMC Public Health, 21.","DOI":"10.1186\/s12889-021-11884-5"},{"key":"ref_8","doi-asserted-by":"crossref","first-page":"9","DOI":"10.1016\/j.comcom.2020.11.007","article-title":"Do we need a contact tracing app?","volume":"166","author":"Maccari","year":"2021","journal-title":"Comput. Commun."},{"key":"ref_9","doi-asserted-by":"crossref","first-page":"1422","DOI":"10.1126\/science.abc6197","article-title":"Reducing transmission of SARS-CoV-2","volume":"368","author":"Prather","year":"2020","journal-title":"Science"},{"key":"ref_10","unstructured":"(2022, August 03). China Publishes White Paper on Fight against COVID-19 (Full Text), Available online: http:\/\/en.nhc.gov.cn\/2020-06\/08\/c_80724.htm."},{"key":"ref_11","doi-asserted-by":"crossref","first-page":"24","DOI":"10.1186\/s43020-021-00054-y","article-title":"GNSS smartphones positioning: Advances, challenges, opportunities, and future perspectives","volume":"2","author":"Zangenehnejad","year":"2021","journal-title":"Satell. Navig."},{"key":"ref_12","doi-asserted-by":"crossref","unstructured":"Atroner, M., Urban, R., Reindl, T., Seidl, J., and Brou\u010dek, J. (2020). Evaluation of the Georeferencing Accuracy of a Photogrammetric Model Using a Quadrocopter with Onboard GNSS RTK. Sensors, 20.","DOI":"10.3390\/s20082318"},{"key":"ref_13","doi-asserted-by":"crossref","unstructured":"Yang, T., Cabani, A., and Chafouk, H. (2021). A Survey of Recent Indoor Localization Scenarios and Methodologies. Sensors, 21.","DOI":"10.3390\/s21238086"},{"key":"ref_14","doi-asserted-by":"crossref","first-page":"1","DOI":"10.1145\/2146417.2146421","article-title":"BeepBeep: A High-Accuracy Acoustic-Based System for Ranging and Localization Using COTS Devices","volume":"11","author":"Peng","year":"2012","journal-title":"ACM Trans. Embed. Comput. Syst."},{"key":"ref_15","doi-asserted-by":"crossref","first-page":"211","DOI":"10.1504\/IJSNET.2008.019006","article-title":"The impact of fading and shadowing on the network performance of wireless sensor networks","volume":"3","author":"Liu","year":"2008","journal-title":"Int. J. Sen. Netw."},{"key":"ref_16","doi-asserted-by":"crossref","first-page":"3062","DOI":"10.1109\/JIOT.2021.3095185","article-title":"AIPS: An Accurate Indoor Positioning System With Fingerprint Map Adaptation","volume":"9","author":"Tao","year":"2022","journal-title":"IEEE Internet Things J."},{"key":"ref_17","doi-asserted-by":"crossref","first-page":"740","DOI":"10.1109\/TMC.2020.3012563","article-title":"Wi-Fi RTT Ranging Performance Characterization and Positioning System Design","volume":"21","author":"Ma","year":"2022","journal-title":"IEEE Trans. Mob. Comput."},{"key":"ref_18","doi-asserted-by":"crossref","first-page":"10662","DOI":"10.1109\/JSEN.2019.2929580","article-title":"Device-Free Tracking via Joint Velocity and AOA Estimation With Commodity WiFi","volume":"19","author":"Zhang","year":"2019","journal-title":"IEEE Sens. J."},{"key":"ref_19","doi-asserted-by":"crossref","first-page":"4476","DOI":"10.1109\/JIOT.2021.3104666","article-title":"Eliminating the Barriers: Demystifying Wi-Fi Baseband Design and Introducing the PicoScenes Wi-Fi Sensing Platform","volume":"9","author":"Jiang","year":"2022","journal-title":"IEEE Internet Things J."},{"key":"ref_20","doi-asserted-by":"crossref","unstructured":"Leith, D.J., and Farrell, S. (2021, January 21). Google\/Apple Exposure Notification Due Diligence. Proceedings of the Innovative Secure IT Technologies against COVID-19 Workshop, Online.","DOI":"10.14722\/coronadef.2021.23005"},{"key":"ref_21","doi-asserted-by":"crossref","first-page":"71","DOI":"10.1109\/MCE.2020.3002492","article-title":"Behind COVID-19 Contact Trace Apps: The Google-Apple Partnership","volume":"9","author":"Michael","year":"2020","journal-title":"IEEE Consum. Electron. Mag."},{"key":"ref_22","doi-asserted-by":"crossref","first-page":"66","DOI":"10.1145\/3431832.3431840","article-title":"Coronavirus contact tracing","volume":"50","author":"Leith","year":"2020","journal-title":"ACM SIGCOMM Comp. Com."},{"key":"ref_23","doi-asserted-by":"crossref","unstructured":"Chen, L., Kuusniemi, H., Chen, Y., Liu, J., Pei, L., Ruotsalainen, L., and Chen, R. (September, January 31). Constraint Kalman filter for indoor bluetooth localization. Proceedings of the 2015 23rd European Signal Processing Conference (EUSIPCO), Nice, France.","DOI":"10.1109\/EUSIPCO.2015.7362717"},{"key":"ref_24","doi-asserted-by":"crossref","unstructured":"Suryavanshi, N.B., Reddy, K.V., and Chandrika, V.R. (2019, January 8\u201310). Direction Finding Capability in Bluetooth 5.1 Standard. Proceedings of the Second EAI International Conference, Bangalore, India.","DOI":"10.1007\/978-3-030-20615-4_4"},{"key":"ref_25","doi-asserted-by":"crossref","first-page":"1540","DOI":"10.1109\/TII.2016.2579265","article-title":"Smartphone Inertial Sensor-Based Indoor Localization and Tracking with iBeacon Corrections","volume":"12","author":"Chen","year":"2016","journal-title":"IEEE Trans. Ind. Inform."},{"key":"ref_26","first-page":"105","article-title":"Real Time Localization of Assets in Hospitals Using Quuppa Indoor Positioning Technology","volume":"12","author":"Ham","year":"2016","journal-title":"ISPRS Ann. Photogramm. Remote Sens. Spat. Inf. Sci."},{"key":"ref_27","doi-asserted-by":"crossref","first-page":"2106","DOI":"10.1109\/TIM.2017.2681398","article-title":"Comparing Ubisense, BeSpoon, and DecaWave UWB Location Systems: Indoor Performance Analysis","volume":"66","author":"Ruiz","year":"2017","journal-title":"IEEE Trans. Instrum. Meas."},{"key":"ref_28","unstructured":"Zhiming, C., and Yuanjin, Z. (2009, January 14\u201316). A CMOS low-power variable-gain amplifier with RSSI for a noncoherent low data rate IR-UWB receiver. Proceedings of the 2009 12th International Symposium on Integrated Circuits, Singapore."},{"key":"ref_29","doi-asserted-by":"crossref","first-page":"1","DOI":"10.1109\/TIM.2021.3069486","article-title":"A Low-Cost Indoor Real-Time Locating System Based on TDOA Estimation of UWB Pulse Sequences","volume":"70","author":"Bottigliero","year":"2021","journal-title":"IEEE Trans. Instrum. Meas."},{"key":"ref_30","doi-asserted-by":"crossref","first-page":"612","DOI":"10.1109\/LMWC.2005.855392","article-title":"Using enhanced-TDOA measurement for indoor positioning","volume":"15","author":"Bocquet","year":"2005","journal-title":"IEEE Microw. Wirel. Co."},{"key":"ref_31","doi-asserted-by":"crossref","first-page":"3743","DOI":"10.1109\/TSP.2019.2916016","article-title":"Joint Time-of-Arrival Estimation for Coherent UWB Ranging in Multipath Environment with Multi-User Interference","volume":"67","author":"Wang","year":"2019","journal-title":"IEEE Trans. Signal Proces."},{"key":"ref_32","doi-asserted-by":"crossref","unstructured":"Schmid, L., Salido-Monz\u00fa, D., and Wieser, A. (October, January 30). Accuracy Assessment and Learned Error Mitigation of UWB ToF Ranging. Proceedings of the 2019 International Conference on Indoor Positioning and Indoor Navigation (IPIN), Pisa, Italy.","DOI":"10.1109\/IPIN.2019.8911769"},{"key":"ref_33","doi-asserted-by":"crossref","unstructured":"Etzlinger, B., Nusbaummuller, B., Peterseil, P., and Hummel, K.A. (July, January 30). Distance Estimation for BLE-based Contact Tracing-A Measurement Study. Proceedings of the 2021 Wireless Days (WD), Paris, France.","DOI":"10.1109\/WD52248.2021.9508280"},{"key":"ref_34","doi-asserted-by":"crossref","first-page":"2906","DOI":"10.1109\/JSEN.2014.2382568","article-title":"SmartPDR: Smartphone-Based Pedestrian Dead Reckoning for Indoor Localization","volume":"15","author":"Kang","year":"2015","journal-title":"IEEE Sens. J."},{"key":"ref_35","doi-asserted-by":"crossref","first-page":"1398","DOI":"10.1109\/COMST.2021.3058296","article-title":"Hybrid LiFi and WiFi Networks: A Survey","volume":"23","author":"Wu","year":"2021","journal-title":"IEEE Commun. Surv. Tutor."},{"key":"ref_36","doi-asserted-by":"crossref","unstructured":"Gualda, D., P\u00e9rez-Rubio, C., Ure\u00f1a, J., P\u00e9rez-Bachiller, S., Villadangos, J.M., Hern\u00e1ndez, \u00c1., Garc\u00eda, J., and Jim\u00e9nez Mart\u00edn, A. (2021). LOCATE-US: Indoor Positioning for Mobile Devices Using Encoded Ultrasonic Signals, Inertial Sensors and Graph-Matching. Sensors, 21.","DOI":"10.3390\/s21061950"},{"key":"ref_37","doi-asserted-by":"crossref","first-page":"29","DOI":"10.1016\/j.pmcj.2014.09.003","article-title":"Accurate smartphone indoor positioning using a WSN infrastructure and non-invasive audio for TDoA estimation","volume":"20","author":"Lopes","year":"2015","journal-title":"Pervasive Mob. Comput."},{"key":"ref_38","doi-asserted-by":"crossref","first-page":"779","DOI":"10.1109\/JIOT.2015.2502486","article-title":"A Smartphone Compatible SONAR Ranging Attachment for 2-D Mapping","volume":"3","author":"Graham","year":"2016","journal-title":"IEEE Internet Things J."},{"key":"ref_39","doi-asserted-by":"crossref","unstructured":"Mao, W., He, J., and Qiu, L. (2016, January 3\u20137). CAT: High-precision acoustic motion tracking. Proceedings of the 22nd Annual International Conference on Mobile Computing and Networking, New York, NY, USA.","DOI":"10.1145\/2973750.2973755"},{"key":"ref_40","doi-asserted-by":"crossref","first-page":"7341","DOI":"10.1109\/TIM.2020.2981985","article-title":"Effective Audio Signal Arrival Time Detection Algorithm for Realization of Robust Acoustic Indoor Positioning","volume":"69","author":"Cao","year":"2020","journal-title":"IEEE Trans. Instrum. Meas."},{"key":"ref_41","first-page":"1","article-title":"Precise Indoor Positioning Based on Acoustic Ranging in Smartphone","volume":"70","author":"Chen","year":"2021","journal-title":"IEEE Trans. Instrum. Meas."},{"key":"ref_42","doi-asserted-by":"crossref","first-page":"355","DOI":"10.1109\/TIM.2018.2844942","article-title":"TOA Estimation of Chirp Signal in Dense Multipath Environment for Low-Cost Acoustic Ranging","volume":"68","author":"Zhang","year":"2019","journal-title":"IEEE Trans. Instrum. Meas."},{"key":"ref_43","doi-asserted-by":"crossref","unstructured":"Lee, H., Kim, T.H., Choi, J.W., and Choi, S. (May, January 26). Chirp signal-based aerial acoustic communication for smart devices. Proceedings of the 2015 IEEE Conference on Computer Communications (INFOCOM), Hong Kong, China.","DOI":"10.1109\/INFOCOM.2015.7218629"},{"key":"ref_44","doi-asserted-by":"crossref","first-page":"605","DOI":"10.1109\/TCSS.2021.3092942","article-title":"Maintaining Social Distancing in Pandemic Using Smartphones with Acoustic Waves","volume":"9","author":"Rupapara","year":"2022","journal-title":"IEEE Trans. Comput. Soc. Syst."},{"key":"ref_45","doi-asserted-by":"crossref","unstructured":"Shan, F., Zeng, J., Li, Z., Luo, J., and Wu, W. (2021, January 10). Ultra-Wideband Swarm Ranging. Proceedings of the IEEE INFOCOM 2021-IEEE Conference on Computer Communications, Vancouver, BC, Canada.","DOI":"10.1109\/INFOCOM42981.2021.9488717"},{"key":"ref_46","doi-asserted-by":"crossref","first-page":"155","DOI":"10.1016\/0378-5955(79)90025-X","article-title":"Calculating virtual pitch","volume":"1","author":"Terhardt","year":"1979","journal-title":"Hearing Res."},{"key":"ref_47","doi-asserted-by":"crossref","first-page":"256","DOI":"10.1016\/j.ijnaoe.2016.09.004","article-title":"Multiuser chirp modulation for underwater acoustic channel based on VTRM","volume":"9","author":"Yuan","year":"2017","journal-title":"Int. J. Nav. Arch. Ocean"},{"key":"ref_48","doi-asserted-by":"crossref","first-page":"373","DOI":"10.1109\/TASSP.1979.1163269","article-title":"Optimum estimation of time delay by a generalized correlator","volume":"27","author":"Hassab","year":"1979","journal-title":"IEEE Trans. Acoust. Speech Signal Process."},{"key":"ref_49","unstructured":"Misra, P.K., Ostry, D., Kottege, N., and Jha, S. (November, January 31). TWEET: An envelope detection based broadband ultrasonic ranging system. Proceedings of the 14th ACM International Conference on Modeling, Analysis and Simulation of Wireless and Mobile Systems, Miami, FL, USA."},{"key":"ref_50","doi-asserted-by":"crossref","first-page":"2141","DOI":"10.1109\/78.536672","article-title":"Digital computation of the fractional Fourier transform","volume":"44","author":"Ozaktas","year":"1996","journal-title":"IEEE Trans. Signal Proces."},{"key":"ref_51","doi-asserted-by":"crossref","first-page":"107163","DOI":"10.1016\/j.apacoust.2019.107163","article-title":"Chirp-rate quasi-orthogonality based DSSS-CDMA system for underwater acoustic channel","volume":"161","author":"Yuan","year":"2020","journal-title":"Appl. Acoust."},{"key":"ref_52","first-page":"1","article-title":"Temporal Correlation Enhanced Multiuser Detection for Uplink Grant-Free NOMA","volume":"1","author":"Wu","year":"2021","journal-title":"IEEE Trans. Mob. Comput."},{"key":"ref_53","doi-asserted-by":"crossref","first-page":"6375","DOI":"10.1109\/JSEN.2018.2846481","article-title":"Design of chirp waveforms for multiple-access ultrasonic indoor positioning","volume":"18","author":"Khyam","year":"2018","journal-title":"IEEE Sens. J."},{"key":"ref_54","doi-asserted-by":"crossref","first-page":"523","DOI":"10.1109\/JCN.2018.000085","article-title":"Cooperative control feedback: On backoff misbehavior of CSMA\/CA MAC in channel-hopping cognitive radio networks","volume":"20","author":"Liu","year":"2018","journal-title":"J. Commun. Netw.-S. Kor."},{"key":"ref_55","doi-asserted-by":"crossref","unstructured":"Luu, G., Ravier, P., and Buttelli, O. (2011, January 25\u201326). The generalized correlation methods for estimation of time delay with application to electromyography. Proceedings of the 1st International Symposium on Engineering Physics and Mechanics (ISEPM), Pune, India.","DOI":"10.1145\/2093698.2093879"},{"key":"ref_56","unstructured":"Meng, L., Li, X.-H., Zhang, W.-G., and Liu, D.-Z. (2015, January 18\u201320). The Generalized Cross-Correlation Method for Time Delay Estimation of Infrasound Signal. Proceedings of the 2015 Fifth International Conference on Instrumentation and Measurement, Computer, Communication and Control (IMCCC), Singapore."},{"key":"ref_57","doi-asserted-by":"crossref","first-page":"1","DOI":"10.1109\/TIM.2021.3083558","article-title":"An Echo Suppression Delay Estimator for Angle-of-Arrival Ultrasonic Indoor Localization","volume":"70","author":"Gabbrielli","year":"2021","journal-title":"IEEE Trans. Instrum. Meas."}],"container-title":["Sensors"],"original-title":[],"language":"en","link":[{"URL":"https:\/\/www.mdpi.com\/1424-8220\/22\/19\/7345\/pdf","content-type":"unspecified","content-version":"vor","intended-application":"similarity-checking"}],"deposited":{"date-parts":[[2025,10,11]],"date-time":"2025-10-11T00:40:47Z","timestamp":1760143247000},"score":1,"resource":{"primary":{"URL":"https:\/\/www.mdpi.com\/1424-8220\/22\/19\/7345"}},"subtitle":[],"short-title":[],"issued":{"date-parts":[[2022,9,27]]},"references-count":57,"journal-issue":{"issue":"19","published-online":{"date-parts":[[2022,10]]}},"alternative-id":["s22197345"],"URL":"https:\/\/doi.org\/10.3390\/s22197345","relation":{},"ISSN":["1424-8220"],"issn-type":[{"value":"1424-8220","type":"electronic"}],"subject":[],"published":{"date-parts":[[2022,9,27]]}}}