Device-free positioning using a ceiling-based visible light sensing system

Positioning systems to determine the coordinates of a person inside a building or a room have been gaining popularity in recent years. Device-free positioning can be of use in many applications; for example, in a smart home, it would be useful for the lights in the bedroom to turn on once a person enters, and for it to turn off once they get into bed. However, existing solutions need expensive hardware installation, or require the user to hold a device to act like a receiver in order to be positioned, which is inconvenient. In addition, due to factors such as multipath and wall attenuation in closed areas, common localization strategies such as trilateration and triangulation struggle to provide a low localization error. LED bulbs are steadily becoming ubiquitous in modern society due to their energy efficiency and shelf life, so using visible light sensing for indoor localization is a good way to reduce the amount of external hardware needed to be installed. When a person is in a particular location in the room, shadows form on the floor due to the LED lamps on the ceiling. A highly sensitive prototype is designed and developed to detect the exact position and length of these shadows. These unique shadow patterns can be used in turn to estimate the position of the person. Using this setup, a low localization error of 2 feet is obtained. Finally, this setup is compared to existing technology, showing it to be more suitable for these applications while leveraging existing infrastructure.M.S.Includes bibliographical referencesby Minitha Jawaha