LiCamPos : An Indoor Positioning System using Light to Camera Communication

Due to the limitations of the Global Positioning System to track or locate ultra-small resolutions, Indoor Positioning System(IPS) came into existence. IPS is used to provide useful indoor location-based information. Mostly Radio Frequency (RF) based system is used to achieve IPS. However, alternatives to RF are getting popular due to the debatable health risks of RF. In this paper, a light-based camera communication technique for IPS is proposed and evaluated. The proposed method uses a light aperture to encode location beacon information and is decoded using image processing techniques on the user's mobile phone. An On-Off Keying (OOK) modulation technique is employed to encode and broadcast beacon information, and software-based custom modified mobile camera parameters are used for position estimation. A phenomenon called the "Rolling Shutter" effect is used to extract useful information from the beacon. During experimentation, it was observed that the number of observable rolling shutter stripes is inversely proportional to the distance between the beacon and the receiver, and it is directly proportional to the frequency of OOK. It was also observed that the stripe's width is independent of the distance between beacon and receiver. Finally, an android application is built to show location-relevant messages/ads based on the identified beacon.