TDoA Based Positioning using Ultrasound Signals and Wireless Nodes
📝 Abstract
In this paper, a positioning technique based on Time Difference of Arrival (TDoA) measurements is analyzed. The proposed approach is designed to consent range and position estimation, using ultrasound transmissions of a stream of chirp pulses, received by a set of wireless nodes. A potential source of inaccuracy introduced by lack of synchronization between transmitting node and receiving nodes is identified and characterized. An algorithm to identify and correct such inaccuracies is presented.
💡 Analysis
In this paper, a positioning technique based on Time Difference of Arrival (TDoA) measurements is analyzed. The proposed approach is designed to consent range and position estimation, using ultrasound transmissions of a stream of chirp pulses, received by a set of wireless nodes. A potential source of inaccuracy introduced by lack of synchronization between transmitting node and receiving nodes is identified and characterized. An algorithm to identify and correct such inaccuracies is presented.
📄 Content
TDoA Based Positioning using Ultrasound Signals and Wireless Nodes
Alessio De Angelis, Antonio Moschitta, Antonella Comuniello Dept. of Engineering University of Perugia Perugia, Italy {alessio.deangelis,antonio.moschitta}@unipg.it
Abstract—In this paper, a positioning technique based on Time Difference of Arrival (TDoA) measurements is analyzed. The proposed approach is designed to consent range and position estimation, using ultrasound transmissions of a stream of chirp pulses, received by a set of wireless nodes. A potential source of inaccuracy introduced by lack of synchronization between transmitting node and receiving nodes is identified and characterized. An algorithm to identify and correct such inaccuracies is presented. Keywords—ranging; positioning; ultrasound; embedded; wireless; TDoA I. INTRODUCTION Ultrasound transmissions are a well-known and deeply studied technique, with applications ranging from biomedical scanning to industrial and automotive applications [1]-[3]. Positioning techniques have been studied as well in the literature, because ultrasound transmissions consent accurate short range distance measurement and positioning, using low- cost and low-power hardware [4]-[12]. Recently, an ultrasound system for indoor positioning has been proposed in [13]. Such solution is based on handheld consumer devices using the Android platform and is capable of real-time operation with decimeter-order accuracy. Furthermore, in [14], a positioning system that allows for measuring range and bearing has been proposed, achieving an accuracy better than 10 cm in multipath environments. Typical ultrasound positioning systems are based on time domain measurements, such as Time of Flight (ToF) and Time Difference of Arrival (TDoA) between the mobile node and a set of know position anchors. These measurements can either directly feed a positioning algorithm or they can be converted into range estimations using knowledge of speed of sound, prior feeding a lateration algorithm. It is worth noticing that, while several ultrasound positioning systems have been proposed in the literature, most of them use some synchronization scheme. In some systems wired connection between anchors and the mobile node are used, while in some other cases wireless nodes are synchronized using industrial oriented radio protocols, such as ZigBee or Radio Frequency Identification (RFID) [15][16][17]. Wireless implementations are often a desirable solution, since wireless nodes can be easily deployed and flexibly relocated when installing and operating a positioning system. Moreover, recently several low power chips capable of radio communication were proposed on the market implementing the 4.0 Bluetooth low power protocol, also known as Bluetooth Low Energy (BLE) [18]. BLE is a good candidate for wireless implementations of ultrasound positioning systems. Not only BLE solutions are low cost, but they are usually implemented in hand held devices such as smartphones. Hence, using BLE as communication infrastructure to operate a distributed positioning system based on ultrasound techniques may consent to easily implement and support user-oriented Location Based Services. The main drawback of BLE is in its very same user-oriented nature. In fact, protocols like BLE are transparent to the user, and cannot easily be programmed and configured. In particular, BLE networks use adaptive frequency hopping Time Division Multiple Access (TDMA), where the hopping sequence is often hardware coded. Thus, the frequency hopping random latencies may not be compatible with the synchronization accuracy required by an ultrasound ToF positioning system. This issue may be overcome by realizing a TDoA system, that works in absence of synchronization. Consequently, in this paper an ultrasound based TDoA positioning architecture is investigated, assuming that the mobile node acts as an active beacon, while fixed anchors act as listeners. The performance of the proposed TDoA approach is analyzed. It is shown that TDoA may be prone to uncertainty because of ambiguities in measuring time delays, that can be identified and removed using a proper algorithm.
II. ARCHITECTURE OF THE ANALYZED SYSTEM A. System architecture and signaling The proposed approach is summarized by Fig. 1, showing a mobile node acting as active beacon, a set of wireless anchors, acting as listeners, and a Master node, acting as supervisor. All © 2017 IEEE. Personal use of this material is permitted. Permission from IEEE must be obtained for all other uses, in any current or future media, including reprinting/republishing this material for advertising or promotional purposes, creating new collective works, for resale or redistribution to servers or lists, or reuse of any copyrighted component of this work in other works Preprint version. Presented at:IEEE International Instrumentatio
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