Efficient Indoor Localization via Switched-Beam Antennas

Abstract

Location-based services have become extremely popular. As a result, indoor localization has received a lot of attention from both industry and academia. Despite the plethora of existing approaches, no method can achieve high accuracy without major, expensive changes to existing systems. For example, to achieve good accuracy, fingerprinting methods require many APs within range of a client, time-of-arrival methods require tight synchronization, client hardware changes and line-of-sight, and direction-of-arrival methods require expensive antenna front ends and line-of-sight. In this paper, we take advantage of inexpensive, off-the-shelf switched-beam antennas (SBAs) to increase the diversity of measurements used for fingerprint-based localization. We show using experiments that a single AP equipped with $n$ n SBAs may infer equally rich localization information as $n$ n APs equipped with $n$ n omnidirectional antennas each, as long as the SBAs are properly configured. We then establish via extensive experiments that a single packet reception from a commodity client at a single AP equipped with a handful of SBAs (e.g., eight SBAs costing a couple of dollars more than omni antennas) achieves localization accuracy in the order of half a meter with or without line-of-sight, in any indoor environment, with zero airtime overhead and zero client support.