A Low Overhead Receive Only Wi-Fi Based Location Mechanism

Erik Lindskog, Hong Wan, Raja Banerjea, Naveen Kakani, Dave Huntingford

Abstract:	Determining the location of a wireless portable device typically uses GPS or trilateration based on mobile phone signals. These methods, however do not work well indoors due to limited availability of GPS satellite signals and mobile phone signals, or simply are not providing the desired accuracy. Accurate indoor location is important for positioning in buildings such as malls, hotels, offices, train stations etc. Using Wi-Fi for such indoor navigation is a very attractive choice given the ubiquitous deployment of Wi-Fi hotspots. However, the use of Wi-Fi for indoor navigation should ideally not adversely affect the mobile phone power consumption or the Wi-Fi network communication throughput. In this paper we describe a method for determining the location of a client device in a wireless network where access points transmit ranging packets between themselves. The client device listens to the traffic between the access points and measures the time of arrival of the ranging packets. Using the location of access points, the time of arrival of ranging packets at the client device and at access points, the client determines its differential distance to pairs of access points. The client’s differential distance to multiple such access point pairs is then used to compute the location of the client using the principles of hyperbolic navigation. As compared to a more straight forward tri-lateration method using the round-trip time measurements mechanism in 802.11, this mechanism has lower overhead as the ranging packets are only transmitted between the access points themselves and not individually to each client device. We compare the location accuracy and associated overhead using the traditional round-trip time based location and the proposed receive-only method.
Published in:	Proceedings of the 27th International Technical Meeting of the Satellite Division of The Institute of Navigation (ION GNSS+ 2014) September 8 - 12, 2014 Tampa Convention Center Tampa, Florida
Pages:	1661 - 1668
Cite this article:	Lindskog, Erik, Wan, Hong, Banerjea, Raja, Kakani, Naveen, Huntingford, Dave, "A Low Overhead Receive Only Wi-Fi Based Location Mechanism," Proceedings of the 27th International Technical Meeting of the Satellite Division of The Institute of Navigation (ION GNSS+ 2014), Tampa, Florida, September 2014, pp. 1661-1668.
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