Binary-input non-line-of-sight solar-blind UV channels: Modeling, capacity and coding

There has been recent interest in establishing non-line-of-sight links in the solar-blind ultraviolet region for outdoor optical wireless communications. This paper presents a novel channel model combining both photon propagation and detection statistics. The channel capacity with binary inputs is numerically computed for on-off keying and 4-pulse-position modulation (4-PPM) at different baud rates. To approach the capacity, error control coding is applied and a message passing decoding technique is outlined. Simulation results for a running example through the paper indicate that, at a given power, there is an optimum transmitted baud rate that maximizes the achievable data rate on such links. With the application of proper coding techniques, it is demonstrated that a near fifty-fold increase in rate over previous reported designs for this channel is feasible.