LIPS: A Light Intensity Based Positioning System For Indoor Environments
  This paper presents LIPS, a Light Intensity based Positioning System for indoor environments. The system uses off-the-shelf LED lamps as signal sources, and uses light sensors as signal receivers. The design is inspired by the observation that a light sensor has deterministic sensitivity to both distance and incident angle of 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 (MFLP), 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 0.4 meters across different environments, with high stability against interferences from obstacles, ambient lights, temperature variation, etc. 
Bo Xie, Guang Tan, Yunhuai Liu, Mingming Lu, Kongyang Chen, and Tian   He
cs.NI