Short-Range Wireless Optical Communication using Pixelated Transmitters and Imaging Receivers

Short-range wireless optical channels provide high-data rate indoor links free of spectral licensing issues. In this work, we present a point-to-point, multiple-input/multiple output (MIMO) optical channel, termed the pixelated wireless optical channel, which exploits the inherent spatial diversity of the channel to achieve gains in spectral efficiency. Information is conveyed through the transmission of a series of pixelated images to a receiver array. An experimental prototype point-to-point link is constructed using a $512\times 512$ pixel LCD panel and $154\times 154$ pixels of a CCD camera. Based on channel measurements, a channel model amenable to computer simulation is developed. Spatial discrete multitone modulation is proposed for this MIMO wireless optical channel to combat the low pass spatial response of the channel. The capacity of a given channel realization is estimated by way of the water-pouring spectrum. Multi-level coding and multi-stage decoding over the spatial frequency bins is shown to yield spectral efficiencies of approximately 1.7 kbit/s/Hz over a range of 2 m.