The Multiple-Input/Multiple-Output Wireless Optical Channel

Conclusions

The MIMO wireless optical channel exploits spatial degrees of freedom inherent in the channel to provide gains in spectral efficiency. Pixel-matched systems provide a spatial multiplexing gain at the expense of requiring that all transmitters and receivers be in perfect alignment. The pixelated wireless optical channel with SDMT spatial modulation provides a means to generate spatial modulation which is well suited to the spatial frequency constraint. Additionally, the use of these bases eliminates the need for exact spatial alignment of the transmit and receive pixels and requires only that the spatial frequency resolutions be matched.

The gain in using MIMO wireless optical links over single element links arises only at high optical SNRs. Potential applications for the pixelated wire- less optical channel are in the areas of high-speed, short range links where this high SNR condition exists. One example is optical backplane applications connecting a number of circuit boards. High OSNR wireless channels also exist in a host of inter-device connection applications to provide a high-rate, secure, fixed wireless link between a portable computer and host network. For example, a pixelated wireless optical link could be designed to improve the data rate of present day links to all for the transfer gigabytes of data, video and high-quality audio to hand-held computing devices, while providing a secure link free of mechanical wear and interface issues.

In next chapter, an experimental channel is characterized to produce a channel model for computer simulation studies. The capacity of a number of spatial bases is computed for uncoded and SDMT modulated spatial signalling. Some candidate spatio-temporal coding schemes are considered for the pixelated wireless optical channels to quantify the gains available by using this channel topology.