Evaluating Measurement-based AOA Indoor Location using WLAN Infrastructure

Carl M. Wong, Geoffrey G. Messier, and Richard Klukas

Abstract:	This paper assesses the potential use of close range angle of arrival (AOA) estimates made using wireless local area network (WLAN) access points (APs) in determining indoor user position. AOA estimation using WLAN APs is possible since next generation WLAN APs will be equipped with multiple antennas. Firstly the error in the AOA estimation is characterized with real indoor wireless channel measurements using a multiple-input multipleoutput (MIMO) channel characterization system. The AOA is then estimated from the resulting channel measurements using the Space Alternating Generalized Expectation-Maximization (SAGE) algorithm. The SAGE algorithm is a modification of the Expectation- Maximization (EM) algorithm, with reduced computational complexity while retaining the ability to estimate multipath arrivals that arrive within the same sampling interval. The estimation error is described in terms of its probability density function (PDF), derived from the histogram of the difference between the actual and estimated angle of arrival from the measurements taken. This information is used to generate random AOA error in a 2D least squares positioning simulation. A typical WLAN AP geometry based on common WLAN transmission distances is used and the resulting RMS positioning accuracy was found to be less than 2 m, suitable for some types of indoor positioning.
Published in:	Proceedings of the 20th International Technical Meeting of the Satellite Division of The Institute of Navigation (ION GNSS 2007) September 25 - 28, 2007 Fort Worth Convention Center Fort Worth, TX
Pages:	1139 - 1145
Cite this article:	Wong, Carl M., Messier, Geoffrey G., Klukas, Richard, "Evaluating Measurement-based AOA Indoor Location using WLAN Infrastructure," Proceedings of the 20th International Technical Meeting of the Satellite Division of The Institute of Navigation (ION GNSS 2007), Fort Worth, TX, September 2007, pp. 1139-1145.
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