A Fixed-scale Pixelated MIMO Visible Light Communication System

Abstract

Visible light communication (VLC) systems take advantage of ubiquitous light-emitting diodes (LED) and leverage existing illumination infrastructure to provide broadband optical communication links. Multiple-input multiple-output (MIMO) VLC systems are among the well studied topics in VLC research. However, most traditional MIMO VLC systems require accurate alignment and have to adjust to different magnifications at various link distances. Consequently, the alignment and calibration modules increase the complexity of the receiver structures. A pixelated MIMO VLC system is introduced in this thesis, which transmits a series of time-varying coded images that can be received and decoded by commercial digital cameras. Using a convex lens placed in front of the transmitter at its focal length, the system exploits the Bokeh effect to obtain fixed-scale images at all link distances. Compared with traditional pixelated MIMO VLC systems, which send information directly in space, this spatial-angular mapping system sends information in different angles instead. In contrast to the complex receiver structures in traditional setups, the proposed system can capture fixed-scale images with a simple receiver requiring no re-focusing as the camera moves. The channel model of the system is measured and modeled and a rateless code is applied to track the truncation of receive images for various link ranges and angular offsets. A proof-of-concept optical communication system is implemented with an LCD display and a high speed CMOS camera. Performance of the system is measured and analysed. The experimental system can achieve a throughput of approximately 10 bit per frame over 90 cm. This fixed-scale pixelated MIMO wireless optical communication system provides a less expensive option for short-range indoor broadcasting optical links and inter-vehicle communications due to its mobility, stability and simpler receiver structure compared to traditional designs in different working conditions.