Ultrasound Indoor Positioning System Based on a Low-Power Wireless Sensor Network Providing Sub-Centimeter Accuracy

Abstract

This paper describes the TELIAMADE system, a new indoor positioning system based on time-of-flight (TOF) of ultrasonic signal to estimate the distance between a receiver node and a transmitter node. TELIAMADE system consists of a set of wireless nodes equipped with a radio module for communication and a module for the transmission and reception of ultrasound. The access to the ultrasonic channel is managed by applying a synchronization algorithm based on a time-division multiplexing (TDMA) scheme. The ultrasonic signal is transmitted using a carrier frequency of 40 kHz and the TOF measurement is estimated by applying a quadrature detector to the signal obtained at the A/D converter output. Low sampling frequencies of 17.78 kHz or even 12.31 kHz are possible using quadrature sampling in order to optimize memory requirements and to reduce the computational cost in signal processing. The distance is calculated from the TOF taking into account the speed of sound. An excellent accuracy in the estimation of the TOF is achieved using parabolic interpolation to detect of maximum of the signal envelope at the matched filter output. The signal phase information is also used for enhancing the TOF measurement accuracy. Experimental results show a root mean square error (rmse) less than 2 mm and a standard deviation less than 0.3 mm for pseudorange measurements in the range of distances between 2 and 6 m. The system location accuracy is also evaluated by applying multilateration. A sub-centimeter location accuracy is achieved with an average rmse of 9.6 mm.

Improvement of Ultrasound-based System Using Sine Wave Detector and CAN Network

“…Another method was also applied is interpolation or interpolation -phase correction combination which are implemented in [22]. It enables user to decrease not only their sampling frequency to under 40kHz but also the error of measurement to sub-cm range.…”

A State-of-the-Art Survey of Indoor Positioning and Navigation Systems and Technologies

“…The advantage of the Dolphin system is that it requires only a few nodes to determine all the position of nodes, hence improving performance. However, one general problem that is inherent in this system is low accurate positioning caused by multipath effects and LOS (Gu et al, 2009;Fallah et al, 2013;Medina et al, 2013). In some cases, privacy concern is an issue regarding where a server stores and computes users' position information.…”

“…This is because the receiver or sensor processes the signal one at a time and many tags will need to be deployed. Therefore, implementation on a large scale will degrade accuracy, and performance due to noise and multipath effects (Gu et al, 2009;Fallah et al, 2013;Medina et al, 2013). The large number of sensors deployed will result in a complex and costly system, with privacy concerns still an issue because of the server that computes position (Gu et al, 2009).…”

“…Furthermore, other newer Ultrasound positioning systems address some of the issues in the Active Bat system. For example, Medina et al (2013) gave a summary of their study using trilateration and TOA techniques to improve positioning accuracy and performance. The study of Holm (2012) used the trilateration, TOA and RSS techniques to improve accuracy and coverage area, and hence scalability, while Lopes, Vieira, and Albuquerque (2012) made use of TOA and broadband ultrasonic transducers, as against the narrowband ultrasonic transducers that the afore-discussed systems use, to improve accuracy on a large scale.…”

“…Ultrasound positioning systems involve the use of ultrasonic tags or nodes on users and objects. These tags or nodes serve as receivers or transmitters; when one is stationary or fixed, the other will be in motion (Holm, 2012;Medina, Segura, & De la Torre, 2013). The widely known Ultrasound positioning systems include the Active Bat (Woodman & Harle, 2010), Cricket system (Priyantha, 2005) and Dolphin system (Fukuju et al, 2003;Minami et al, 2004).…”