Wide receiver orientation using diffuse reflection in camera-based indoor visible light communication

Camera-based visible light communication (CVLC) is a versatile and potential optical wireless communication using rapidly developing smartphone cameras as the receiver. In CVLC, the provision of both flicker-free illumination and high data rate has been a challenging issue. To some extent, however, this issue can be resolved by utilizing a rolling shutter property that is inherited from complementary metal-oxide semiconductor sensors adopted in all smartphone cameras. We propose a practical and versatile wide receiver orientation in CVLC on the basis of this rolling shutter property. That is, unlike previous studies focused on either a line-of-sight (LOS) or non-line-of-sight (NLOS) link only, an orientation independent rolling shutter based CVLC is presented. Based on a unique method of exploiting diffuse reflection of illumination, a wide orientation of the receiver is adequately supported in an indoor environment, thus making the CVLC data reception more practical and convenient. A special transmitter for this wide orientation is designed to ensure that adequate diffuse reflection is present in all directions, regardless of whether a LOS or NLOS link is established. In addition, adaptive algorithms are proposed to ensure an efficient and reliable wide orientation CVLC. Experiments are conducted and analyzed for practical orientations of the receiver in an indoor CVLC environment. While providing sufficient illumination and various orientations, it is found that the proposed scheme achieves a data rate of 6.72 kbps at a distance of up to 50 cm in a small-scale indoor experiment.