UC Riverside

Scattering and turbulence are two major obstacles posed by the optical channel such that almost every outdoor wireless optical communication (WoC) system has to overcome. This thesis is devoted to studying their effects on the performance limits of communications in terms of the error probability and outage probability. Two typical WoC systems are considered in our scope of discussion. One is so-called non-line-of-sight (NLOS) ultraviolet (UV) communication system while the other has a line-of-sight (LOS) transmission path, working in the range of infrared (IR) and falls into the category of free-space-optical (FSO) links.

With regard to an NLOS UV communication link, the author characterizes the scattering phenomena in terms of the channel path loss model and delay spread in the impulse response. By integrating an empirical model of path loss, NLOS UV communication link is comprehensively investigated for the first time to reveal its potential and fundamental tradeoffs of range versus rate are reported. Furthermore, in view of realistic implementation options of UV transceivers, the author effectively extends above results by coining typical device probabilistic models. This work presents more realistic insights on designing an NLOS UV system, weighing over device choices and tweaking the key parameters.

For a FSO IR link over the range above 1km, the turbulence effect comes into play as a fading effect to overshadow the system performance. Traditionally, techniques such as error-control coding (ECC) and spatial diversity have been introduced to enhance the FSO link. By contrast, the author has proposed a novel method by employing an opportunistic cooperative relay to improve the performance of LOS FSO communications. It is shown the cooperative scheme indeed provides a more robust way of transmission through an information theoretic analysis.

Along with the analytical study, the author adopt both numerical methods and Monte-Carlo simulation to illustrate the performance limits and advantages of proposed scheme. The results are expected to provide valuable reference to the link budget and system design of outdoor WoC links.