Visible Light Localization Using Conventional Light Fixtures and Smartphones

Owing to dense deployment of light fixtures and multipath-free propagation, visible light localization technology holds potential to overcome the reliability issue of radio localization. However, existing visible light localization systems require customized light hardware, which increases deployment cost and hinders near-term adoption. In this paper, we propose LiTell, a simple and robust localization scheme that employs unmodified fluorescent lights (FLs) as location landmarks and commodity smartphones as light sensors. LiTell builds on the key observation that each FL has an inherent characteristic frequency which can serve as a discriminative feature. It incorporates a set of sampling, signal amplification, and camera optimization mechanisms, that enable a smartphone to capture the extremely weak and high-frequency (greater than 80 kHz) features. We have implemented LiTell as a real-time localization and navigation system on Android. Our experiments demonstrate LiTell's high reliability in discriminating different FLs, and its potential to achieve sub-meter location granularity. Our user study in a multi-story office building, parking lot, and grocery store further validates LiTell as an accurate, robust, and ready-to-use indoor localization system.

1 Introduction

Indoor localization technology is bringing huge impacts on human activities, in the same way that GPS did in revolutionizing outdoor navigation. Existing market research predicts that location-based services in retail industry alone will generate 10 billion revenues by 2020 [1]. However, after decades of research, there still lacks a solution with desired simplicity and robustness. Recent field tests of state-of-the-art localization schemes [2], [3] revealed a common set of problems including high deployment overhead and low reliability, concluding that robust meter-level indoor localization remains an open problem, even in a small sandbox environment (300 $\text{m}^2$) with simple layout [2].