title: Measuring time-of-flight in an ultrasonic LPS system using generalized cross-correlation.
abstract: 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.
authors.affiliation: Department of Electronics, Polytechnic School, University of Alcalá, Ctra. Madrid-Barcelona Km. 33,600, Alcalá de Henares, Madrid 28805, Spain. villa@depeca.uah.es
authors.forename: José Manuel
authors.initials: JM
authors.lastname: Villladangos
authors.forename: Jesús
authors.initials: J
authors.lastname: Ureña
authors.forename: Juan Jesús
authors.initials: JJ
authors.lastname: García
authors.forename: Manuel
authors.initials: M
authors.lastname: Mazo
authors.forename: Alvaro
authors.initials: A
authors.lastname: Hernández
authors.forename: Ana
authors.initials: A
authors.lastname: Jiménez
authors.forename: Daniel
authors.initials: D
authors.lastname: Ruíz
authors.forename: Carlos
authors.initials: C
authors.lastname: De Marziani