A Preliminary Research on Time-difference-of-arrival (TDOA) Based Indoor Optical Positioning

H. Xu, M. Niu, X. Zhang, X. Zhan

Abstract:	Indoor positioning is a difficult issue towards ubiquitous positioning. Since Global Navigation Satellite System (GNSS) does not satisfy the requirements in both means of coverage and accuracy, various alternate and enhancing methods have been introduced, including: pseudolite, WiFi/RFID/UWB and other signals-of-opportunity (SOOP), integration with inertial sensors, visual navigation, pedestrian navigation, etc. The use of optical spectrum instead of radio-frequency (RF) or other physical sources in indoor positioning applications provides many advantages in means of interference minimization, spectrum compatibility and multipath rejection in particular. It is also rather easy to generate, modulate and detect the light. Principle of positioning is the other major issue. The measurement of a physical source can be direction, signal strength and/or time-of-fly, with examples of angle-of-arrival (AOA), received-signal-strength-indicator (RSSI) and time-of-arrival (TOA) or time-difference-of-arrival (TDOA) respectively. Among the three ways, measuring the signal’s time-of-fly is the most sophisticated and accurate one, where the range or pseudorange can be measured directly. There are a number of successful implementations, with GNSS as the most notable one. In this way, the use of TDOA algorithm in optical spectrum is of value. In this paper, a new method based on time-difference-of-arrival (TDOA) measurement in optical spectrum is proposed and analyzed. In such a system, a few light sources will be mounted on the ceiling emitting different yet synchronized light pulses with a moderate beam covering the whole room, functioning in a similar manner as the Pseudolite positioning system. The user device is composed of an optical lens, a light sensor with high sensitivity and fast response, and a computing unit to decorrelate, detect and measure the relative delay of light signal. Having all the pseudorange measurements of visible light sources, the standard triangulation algorithm can be performed to calculate the user positioning within the room. A number of issues of implementation TDOA method in optical spectrum are identified and discussed, including: the wavelength, modulation, codes and receiving scheme in this paper. Besides, a centralized architecture of light positioning system is also proposed providing simplified infrastructure.
Published in:	Proceedings of the 25th International Technical Meeting of the Satellite Division of The Institute of Navigation (ION GNSS 2012) September 17 - 21, 2012 Nashville Convention Center, Nashville, Tennessee Nashville, TN
Pages:	2417 - 2421
Cite this article:	Xu, H., Niu, M., Zhang, X., Zhan, X., "A Preliminary Research on Time-difference-of-arrival (TDOA) Based Indoor Optical Positioning," Proceedings of the 25th International Technical Meeting of the Satellite Division of The Institute of Navigation (ION GNSS 2012), Nashville, TN, September 2012, pp. 2417-2421.
Full Paper:	ION Members/Non-Members: 1 Download Credit Sign In