{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2025,12,31]],"date-time":"2025-12-31T20:14:56Z","timestamp":1767212096744,"version":"build-2065373602"},"reference-count":37,"publisher":"MDPI AG","issue":"12","license":[{"start":{"date-parts":[[2022,6,13]],"date-time":"2022-06-13T00:00:00Z","timestamp":1655078400000},"content-version":"vor","delay-in-days":0,"URL":"https:\/\/creativecommons.org\/licenses\/by\/4.0\/"}],"funder":[{"name":"BK21FOUR, Creative Human Resource Education"}],"content-domain":{"domain":[],"crossmark-restriction":false},"short-container-title":["Sensors"],"abstract":"<jats:p>Various sensors are embedded in automobiles to implement intelligent safety technologies such as autonomous driving and front\u2013rear collision avoidance technology. In particular, ultrasonic sensors have been used in the past because they have an accuracy of centimeters to sub-centimeters in air despite their low cost and low hardware complexity. Recently, the crosstalk problem between ultrasonic sensors has been raised because the number of ultrasonic sensors in the unit space has increased as the number of vehicles increases. Various studies have been conducted to solve the crosstalk, but a demodulation error occurs when signals overlap. Therefore, in this paper, we propose a method that is robust to ultrasonic signal overlap, is robust even at shorter code length, and has reduced time of flight (TOF) error compared to the existing method by applying frequency sweep keying modulation based on code division multiple access (CDMA). As a result of the experiment, the code was detected accurately regardless of the overlap ratio of the two signals, and it was robust even in situations where the power of the two signals was different. In addition, it shows an accurate TOF estimation even if the ID code length is shorter than the existing on\u2013off-keying, frequency shift keying, and phase shift keying methods.<\/jats:p>","DOI":"10.3390\/s22124462","type":"journal-article","created":{"date-parts":[[2022,6,13]],"date-time":"2022-06-13T06:31:59Z","timestamp":1655101919000},"page":"4462","update-policy":"https:\/\/doi.org\/10.3390\/mdpi_crossmark_policy","source":"Crossref","is-referenced-by-count":6,"title":["Frequency Sweep Keying CDMA for Reducing Ultrasonic Crosstalk"],"prefix":"10.3390","volume":"22","author":[{"ORCID":"https:\/\/orcid.org\/0000-0002-8379-1754","authenticated-orcid":false,"given":"Ga-Rin","family":"Park","sequence":"first","affiliation":[{"name":"School of Electric and Electronic Engineering, Pusan National University, Busan 46241, Korea"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"ORCID":"https:\/\/orcid.org\/0000-0001-6380-301X","authenticated-orcid":false,"given":"Sang-Ho","family":"Park","sequence":"additional","affiliation":[{"name":"School of Electric and Electronic Engineering, Pusan National University, Busan 46241, Korea"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"ORCID":"https:\/\/orcid.org\/0000-0002-2928-2043","authenticated-orcid":false,"given":"Kwang-Ryul","family":"Baek","sequence":"additional","affiliation":[{"name":"School of Electronic Engineering, Pusan National University, Busan 46241, Korea"}],"role":[{"role":"author","vocabulary":"crossref"}]}],"member":"1968","published-online":{"date-parts":[[2022,6,13]]},"reference":[{"key":"ref_1","first-page":"71","article-title":"Distance measurement via using of ultrasonic sensor","volume":"3","author":"Kelemen","year":"2015","journal-title":"J. Autom. Control"},{"key":"ref_2","doi-asserted-by":"crossref","first-page":"032189","DOI":"10.1088\/1742-6596\/1015\/3\/032189","article-title":"Application of ultrasonic sensor for measuring distances in robotics","volume":"1015","author":"Zhmud","year":"2018","journal-title":"J. Phys. Conf. Ser."},{"key":"ref_3","doi-asserted-by":"crossref","first-page":"143","DOI":"10.1109\/JSEN.2001.936931","article-title":"An ultrasonic sensor for distance measurement in automotive applications","volume":"1","author":"Carullo","year":"2001","journal-title":"IEEE Sens. J."},{"key":"ref_4","doi-asserted-by":"crossref","unstructured":"Shen, M., Wang, Y., Jiang, Y., Ji, H., Wang, B., and Huang, Z. (2019). A new positioning method based on multiple ultrasonic sensors for autonomous mobile robot. Sensors, 20.","DOI":"10.3390\/s20010017"},{"key":"ref_5","doi-asserted-by":"crossref","first-page":"1349","DOI":"10.1007\/s12555-010-0622-9","article-title":"A multi-robot positioning system using a multi-code ultrasonic sensor network and a Kalman filter","volume":"8","author":"Moon","year":"2010","journal-title":"Int. J. Control Autom. Syst."},{"key":"ref_6","doi-asserted-by":"crossref","unstructured":"Carotenuto, R., Merenda, M., Iero, D., and Della Corte, F.G. (2020). Mobile Synchronization Recovery for Ultrasonic Indoor Positioning. Sensors, 20.","DOI":"10.3390\/s20030702"},{"key":"ref_7","doi-asserted-by":"crossref","first-page":"20","DOI":"10.1007\/s10921-010-0086-0","article-title":"Automatic defect classification in ultrasonic NDT using artificial intelligence","volume":"30","author":"Sambath","year":"2011","journal-title":"J. Nondestruct. Eval."},{"key":"ref_8","doi-asserted-by":"crossref","first-page":"524","DOI":"10.1016\/j.ndteint.2009.03.002","article-title":"3D finite element simulations of an air-coupled ultrasonic NDT system","volume":"42","author":"Ke","year":"2009","journal-title":"NDT E Int."},{"key":"ref_9","doi-asserted-by":"crossref","first-page":"671","DOI":"10.1088\/0034-4885\/62\/5\/201","article-title":"Ultrasonic imaging of the human body","volume":"62","author":"Wells","year":"1999","journal-title":"Rep. Prog. Phys."},{"key":"ref_10","doi-asserted-by":"crossref","first-page":"621","DOI":"10.1111\/1523-1747.ep12319741","article-title":"Assessment of aging of the human skin by in vivo ultrasonic imaging","volume":"93","author":"Escoffier","year":"1989","journal-title":"J. Investig. Dermatol."},{"key":"ref_11","first-page":"26","article-title":"Calculation of muscle strength per unit cross-sectional area of human muscle by means of ultrasonic measurement","volume":"26","author":"Ikai","year":"1968","journal-title":"Int. Z. Angew. Physiol. Einschl. Arb."},{"key":"ref_12","doi-asserted-by":"crossref","unstructured":"Jin, Y., Li, S., Li, J., Sun, H., and Wu, Y. (2018, January 19\u201323). Design of an intelligent active obstacle avoidance car based on rotating ultrasonic sensors. Proceedings of the 2018 IEEE 8th Annual International Conference on CYBER Technology in Automation, Control, and Intelligent Systems, Tianjin, China.","DOI":"10.1109\/CYBER.2018.8688326"},{"key":"ref_13","doi-asserted-by":"crossref","first-page":"11420","DOI":"10.1109\/TVT.2018.2870995","article-title":"Design of collision detection system for smart car using li-fi and ultrasonic sensor","volume":"67","author":"Krishnan","year":"2018","journal-title":"IEEE Trans. Veh. Technol."},{"key":"ref_14","first-page":"55","article-title":"Smart parking system (SPS) architecture using ultrasonic detector","volume":"6","author":"Kianpisheh","year":"2012","journal-title":"Int. J. Softw. Eng. Its Appl."},{"key":"ref_15","doi-asserted-by":"crossref","first-page":"11464","DOI":"10.3390\/s111211464","article-title":"Ultrasonic array for obstacle detection based on CDMA with Kasami codes","volume":"11","author":"Diego","year":"2011","journal-title":"Sensors"},{"key":"ref_16","doi-asserted-by":"crossref","first-page":"173","DOI":"10.1016\/j.ymssp.2017.04.041","article-title":"Kalman filter-based tracking of moving objects using linear ultrasonic sensor array for road vehicles","volume":"98","author":"Li","year":"2018","journal-title":"Mech. Syst. Signal Process."},{"key":"ref_17","doi-asserted-by":"crossref","unstructured":"Xue, W., Yang, M., Hong, D., Wu, D., Wang, Y., and Qing, X. (2020). The design and verification of an active SAMSR ultrasonic guided wave monitoring system with ultra-low crosstalk. Sensors, 20.","DOI":"10.3390\/s20030898"},{"key":"ref_18","doi-asserted-by":"crossref","first-page":"599","DOI":"10.1109\/TIM.2012.2218056","article-title":"A synchronous TDMA ultrasonic TOF measurement system for low-power wireless sensor networks","volume":"62","author":"Medina","year":"2012","journal-title":"IEEE Trans. Instrum. Meas."},{"key":"ref_19","doi-asserted-by":"crossref","first-page":"3836","DOI":"10.1109\/TIE.2012.2208439","article-title":"A distributed TDMA scheduling algorithm for target tracking in ultrasonic sensor networks","volume":"60","author":"Cheng","year":"2012","journal-title":"IEEE Trans. Ind. Electron."},{"key":"ref_20","doi-asserted-by":"crossref","first-page":"3501","DOI":"10.3390\/s130303501","article-title":"Ultrasound indoor positioning system based on a low-power wireless sensor network providing sub-centimeter accuracy","volume":"13","author":"Medina","year":"2013","journal-title":"Sensors"},{"key":"ref_21","doi-asserted-by":"crossref","unstructured":"Chen, X., Chen, Y., Cao, S., Zhang, L., Zhang, X., and Chen, X. (2019). Acoustic indoor localization system integrating TDMA+ FDMA transmission scheme and positioning correction technique. Sensors, 19.","DOI":"10.3390\/s19102353"},{"key":"ref_22","doi-asserted-by":"crossref","first-page":"5325","DOI":"10.1109\/JSEN.2016.2557817","article-title":"High-precision OFDM-based multiple ultrasonic transducer positioning using a robust optimization approach","volume":"16","author":"Khyam","year":"2016","journal-title":"IEEE Sens. J."},{"key":"ref_23","doi-asserted-by":"crossref","unstructured":"Perez, M.C., Ure\u00f1a, J., Hernandez, A., Jimenez, A., Ruiz, D., Alvarez, F.J., and De Marziani, C. (2009, January 2\u201328). Performance comparison of different codes in an ultrasonic positioning system using DS-CDMA. Proceedings of the 2009 IEEE International Symposium on Intelligent Signal Processing, Budapest, Hungary.","DOI":"10.1109\/WISP.2009.5286574"},{"key":"ref_24","doi-asserted-by":"crossref","unstructured":"P\u00e9rez-Rubio, M.C., Hern\u00e1ndez, \u00c1., Gualda-G\u00f3mez, D., Murano, S., Vicente-Ranera, J., Ciudad-Fern\u00e1ndez, F., and Nieto, R. (2022). Simulation Tool and Online Demonstrator for CDMA-Based Ultrasonic Indoor Localization Systems. Sensors, 22.","DOI":"10.3390\/s22031038"},{"key":"ref_25","doi-asserted-by":"crossref","unstructured":"Suzuki, A., Kumakura, K., Choi, Y., and Iyota, T. (2014, January 27\u201330). Accuracy of distance measurements using signal tracking of spread-spectrum ultrasonic waves with CDMA. Proceedings of the 2014 International Conference on Indoor Positioning and Indoor Navigation (IPIN), Busan, Korea.","DOI":"10.1109\/IPIN.2014.7275530"},{"key":"ref_26","doi-asserted-by":"crossref","unstructured":"Oberdorfer, M., Esslinger, D., Benz, G., Sawodny, O., and Tarin, C. (2020, January 7\u201311). Robustness enhancements of time-of-flight measurements in a CDMA ultrasonic channel of an opto-acoustic indoor positioning system using MEMS microphones. Proceedings of the 2020 IEEE International Ultrasonics Symposium (IUS), Las Vegas, NV, USA.","DOI":"10.1109\/IUS46767.2020.9251546"},{"key":"ref_27","doi-asserted-by":"crossref","unstructured":"Fan, Z., Rudlin, J., Asfis, G., and Meng, H. (2019). Convolution of Barker and Golay Codes for Low Voltage Ultrasonic Testing. Technologies, 7.","DOI":"10.3390\/technologies7040072"},{"key":"ref_28","doi-asserted-by":"crossref","first-page":"158","DOI":"10.1088\/0957-0233\/1\/2\/010","article-title":"A new Golay code system for ultrasonic pulse echo measurements","volume":"1","author":"Ding","year":"1990","journal-title":"Meas. Sci. Technol."},{"key":"ref_29","doi-asserted-by":"crossref","first-page":"1752","DOI":"10.1109\/TCOM.1979.1094370","article-title":"A comparison of modulation techniques for digital radio","volume":"27","author":"Oetting","year":"1979","journal-title":"IEEE Trans. Commun."},{"key":"ref_30","doi-asserted-by":"crossref","first-page":"423","DOI":"10.1109\/TCOM.1986.1096561","article-title":"A BPSK\/QPSK timing-error detector for sampled receivers","volume":"34","author":"Gardner","year":"1986","journal-title":"IEEE Trans. Commun."},{"key":"ref_31","unstructured":"Watson, B. (1980). FSK: Signals and Demodulation, Watkins\u2013Johnson Company."},{"key":"ref_32","doi-asserted-by":"crossref","unstructured":"Schr\u00f6der, A., and Henning, B. (2014, January 3\u20136). Signal optimization of PSK modulated gold-sequences for narrow band transducers. Proceedings of the 2014 IEEE International Ultrasonics Symposium, Chicago, IL, USA.","DOI":"10.1109\/ULTSYM.2014.0136"},{"key":"ref_33","doi-asserted-by":"crossref","unstructured":"Kumakura, K., Suzuki, A., and Iyota, T. (2013, January 28\u201331). Code division positioning by continuous signals using spread spectrum ultrasonic waves. Proceedings of the International Conference on Indoor Positioning and Indoor Navigation, Montbeliard, France.","DOI":"10.1109\/IPIN.2013.6817904"},{"key":"ref_34","doi-asserted-by":"crossref","first-page":"189","DOI":"10.14257\/ijca.2016.9.6.18","article-title":"Improvement of measurement range via chaotic binary frequency shift keying excitation sequences for multichannel ultrasonic ranging system","volume":"9","author":"Zhenjing","year":"2016","journal-title":"Int. J. Control Autom."},{"key":"ref_35","first-page":"1271","article-title":"The use of binary coded frequency shift keyed signals for multiple user sonar ranging","volume":"2","author":"Nakahira","year":"2004","journal-title":"IEEE Int. Conf. Netw. Sens. Control"},{"key":"ref_36","doi-asserted-by":"crossref","first-page":"804","DOI":"10.1088\/0022-3735\/22\/10\/001","article-title":"Piezoelectric ceramics and ultrasonic transducers","volume":"22","year":"1989","journal-title":"J. Phys. E Sci. Instrum."},{"key":"ref_37","first-page":"397","article-title":"Fast signal reconstruction from magnitude STFT spectrogram based on spectrogram consistency","volume":"10","author":"Kameoka","year":"2010","journal-title":"Proc. DAFx"}],"container-title":["Sensors"],"original-title":[],"language":"en","link":[{"URL":"https:\/\/www.mdpi.com\/1424-8220\/22\/12\/4462\/pdf","content-type":"unspecified","content-version":"vor","intended-application":"similarity-checking"}],"deposited":{"date-parts":[[2025,10,10]],"date-time":"2025-10-10T23:28:39Z","timestamp":1760138919000},"score":1,"resource":{"primary":{"URL":"https:\/\/www.mdpi.com\/1424-8220\/22\/12\/4462"}},"subtitle":[],"short-title":[],"issued":{"date-parts":[[2022,6,13]]},"references-count":37,"journal-issue":{"issue":"12","published-online":{"date-parts":[[2022,6]]}},"alternative-id":["s22124462"],"URL":"https:\/\/doi.org\/10.3390\/s22124462","relation":{},"ISSN":["1424-8220"],"issn-type":[{"type":"electronic","value":"1424-8220"}],"subject":[],"published":{"date-parts":[[2022,6,13]]}}}