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Sensors 2015, 15(8), 18641-18665; doi:10.3390/s150818641

An Ultrasonic Multiple-Access Ranging Core Based on Frequency Shift Keying Towards Indoor Localization

1
Department of Industrial Sciences and Technology (INDI), Vrije Universiteit Brussel, Pleinlaan 2, Elsene 1050, Belgium
2
Department of Electronics and Informatics (ETRO), Vrije Universiteit Brussel, Pleinlaan 2, Elsene 1050, Belgium
*
Author to whom correspondence should be addressed.
Academic Editor: Leonhard M. Reindl
Received: 27 May 2015 / Revised: 20 July 2015 / Accepted: 23 July 2015 / Published: 30 July 2015
(This article belongs to the Section Sensor Networks)

Abstract

This paper describes a new approach and implementation methodology for indoor ranging based on the time difference of arrival using code division multiple access with ultrasound signals. A novel implementation based on a field programmable gate array using finite impulse response filters and an optimized correlation demodulator implementation for ultrasound orthogonal signals is developed. Orthogonal codes are modulated onto ultrasound signals using frequency shift keying with carrier frequencies of 24.5 kHz and 26 kHz. This implementation enhances the possibilities for real-time, embedded and low-power tracking of several simultaneous transmitters. Due to the high degree of parallelism offered by field programmable gate arrays, up to four transmitters can be tracked simultaneously. The implementation requires at most 30% of the available logic gates of a Spartan-6 XC6SLX45 device and is evaluated on accuracy and precision through several ranging topologies. In the first topology, the distance between one transmitter and one receiver is evaluated. Afterwards, ranging analyses are applied between two simultaneous transmitters and one receiver. Ultimately, the position of the receiver against four transmitters using trilateration is also demonstrated. Results show enhanced distance measurements with distances ranging from a few centimeters up to 17 m, while keeping a centimeter-level accuracy. View Full-Text
Keywords: indoor ultrasound localization; indoor ultrasound ranging; FPGA ranging; FPGA correlator; ultrasound orthogonal frequency shift keying; ultrasound MEMS indoor ultrasound localization; indoor ultrasound ranging; FPGA ranging; FPGA correlator; ultrasound orthogonal frequency shift keying; ultrasound MEMS
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This is an open access article distributed under the Creative Commons Attribution License which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. (CC BY 4.0).

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MDPI and ACS Style

Segers, L.; Van Bavegem, D.; De Winne, S.; Braeken, A.; Touhafi, A.; Steenhaut, K. An Ultrasonic Multiple-Access Ranging Core Based on Frequency Shift Keying Towards Indoor Localization. Sensors 2015, 15, 18641-18665.

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