Multilevel Error Diffusion for Wireless Optical MIMO Channels

In this paper, two techniques to improve channel capacity for wireless optical MIMO channels are presented. The first technique uses multilevel half toning to reduce quantization noise power. For quantization noise-limited systems, increasing the number of quantizer levels provides gains in capacity. For example, at a rate of 200fps, a four-level quantizer gives approximately a two-fold increase in capacity over a binary-level quantizer for all frame sizes considered. The second technique uses higher order noise shaping to shape the quantization noise to the out-of-band spatial frequency spectrum, and hence improves capacity. This technique is shown to be useful when the number of levels is small, i.e., near 2.