{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2026,5,29]],"date-time":"2026-05-29T19:41:56Z","timestamp":1780083716937,"version":"3.54.0"},"reference-count":20,"publisher":"MDPI AG","issue":"11","license":[{"start":{"date-parts":[[2011,10,31]],"date-time":"2011-10-31T00:00:00Z","timestamp":1320019200000},"content-version":"vor","delay-in-days":0,"URL":"https:\/\/creativecommons.org\/licenses\/by\/3.0\/"}],"content-domain":{"domain":[],"crossmark-restriction":false},"short-container-title":["Sensors"],"abstract":"<jats:p>In this article, a time-of-flight detection technique in the frequency domain is described for an ultrasonic Local Positioning System (LPS) based on encoded beacons. Beacon transmissions have been synchronized and become simultaneous by means of the DS-CDMA (Direct-Sequence Code Division Multiple Access) technique. Every beacon has been associated to a 255-bit Kasami code. The detection of signal arrival instant at the receiver, from which the distance to each beacon can be obtained, is based on the application of the Generalized Cross-Correlation (GCC), by using the cross-spectral density between the received signal and the sequence to be detected. Prior filtering to enhance the frequency components around the carrier frequency (40 kHz) has improved estimations when obtaining the correlation function maximum, which implies an improvement in distance measurement precision. Positioning has been achieved by using hyperbolic trilateration, based on the Time Differences of Arrival (TDOA) between a reference beacon and the others.<\/jats:p>","DOI":"10.3390\/s111110326","type":"journal-article","created":{"date-parts":[[2011,10,31]],"date-time":"2011-10-31T11:59:28Z","timestamp":1320062368000},"page":"10326-10342","update-policy":"https:\/\/doi.org\/10.3390\/mdpi_crossmark_policy","source":"Crossref","is-referenced-by-count":31,"title":["Measuring Time-of-Flight in an Ultrasonic LPS System Using Generalized Cross-Correlation"],"prefix":"10.3390","volume":"11","author":[{"given":"Jos\u00e9 Manuel","family":"Villladangos","sequence":"first","affiliation":[{"name":"Department of Electronics, Polytechnic School, University of Alcal\u00e1, Ctra. Madrid-Barcelona Km. 33,600, Alcal\u00e1 de Henares, Madrid 28805, Spain"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Jes\u00fas","family":"Ure\u00f1a","sequence":"additional","affiliation":[{"name":"Department of Electronics, Polytechnic School, University of Alcal\u00e1, Ctra. Madrid-Barcelona Km. 33,600, Alcal\u00e1 de Henares, Madrid 28805, Spain"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Juan Jes\u00fas","family":"Garc\u00eda","sequence":"additional","affiliation":[{"name":"Department of Electronics, Polytechnic School, University of Alcal\u00e1, Ctra. Madrid-Barcelona Km. 33,600, Alcal\u00e1 de Henares, Madrid 28805, Spain"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Manuel","family":"Mazo","sequence":"additional","affiliation":[{"name":"Department of Electronics, Polytechnic School, University of Alcal\u00e1, Ctra. Madrid-Barcelona Km. 33,600, Alcal\u00e1 de Henares, Madrid 28805, Spain"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"\u00c1lvaro","family":"Hern\u00e1ndez","sequence":"additional","affiliation":[{"name":"Department of Electronics, Polytechnic School, University of Alcal\u00e1, Ctra. Madrid-Barcelona Km. 33,600, Alcal\u00e1 de Henares, Madrid 28805, Spain"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Ana","family":"Jim\u00e9nez","sequence":"additional","affiliation":[{"name":"Department of Electronics, Polytechnic School, University of Alcal\u00e1, Ctra. Madrid-Barcelona Km. 33,600, Alcal\u00e1 de Henares, Madrid 28805, Spain"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Daniel","family":"Ru\u00edz","sequence":"additional","affiliation":[{"name":"Department of Electronics, Polytechnic School, University of Alcal\u00e1, Ctra. Madrid-Barcelona Km. 33,600, Alcal\u00e1 de Henares, Madrid 28805, Spain"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Carlos De","family":"Marziani","sequence":"additional","affiliation":[{"name":"Department of Electronic Engineering, National University of Patagonia San Juan Bosco, Ciudad Universitaria, Ruta Provincial n\u00b0 1 s\/n, km. 4, Comodoro Rivadavia (Chubut) 9000, Argentina"}],"role":[{"vocabulary":"crossref","role":"author"}]}],"member":"1968","published-online":{"date-parts":[[2011,10,31]]},"reference":[{"key":"ref_1","unstructured":"Kolodziej, K.W., and Hjelm, J. Local Position Systems\u2014LBS Applications and Services."},{"key":"ref_2","unstructured":"Sukaviriya, N., Podlaseck, M., Kjeldsen, R., Levas, A., Pingali, G., and Pinhanez, C. (2003, January 1\u20135). Embedding interactions in a retail store environment: The design and lessons learned. 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