LIPS: A light intensity-based positioning system for indoor environments

This article presents a Light Intensity-based Positioning System (LIPS) for indoor environments. The system uses off-the-shelf light-emitting diode lamps as signal sources and light sensors as signal receivers. The design is inspired by the observation that a light sensor has deterministic sensitivity to both the distance and incident angle of a light signal, an under-utilized feature of photodiodes now widely found on mobile devices. We develop a stable and accurate light intensity model to capture the phenomenon, based on which a new positioning principle, Multi-Face Light Positioning, is established that uses three collocated sensors to uniquely determine the receiver's position, assuming merely a single source of light. We have implemented a prototype on both dedicated embedded systems and smartphones. Experimental results show average positioning accuracy within 0.4m across different environments, with high stability against interferences from obstacles, ambient lights, temperature variation, and so on.