UC Riverside

In this thesis, the characteristics of long-distance non-line-of-sight (NLOS) ultraviolet(UV) communication channel are studied through experiment and theoretical analysis. The research focuses on the validation of different channel models, long distance NLOS link loss and received signal energy distribution based on outdoor experiment results and numerous simulations. All the previous research on NLOS UV only considered short communication range scenarios, in which turbulence effects were assumed to be negligible. In fact, with the increasing of communication distance, optical turbulence effects may degrade UV communication performance because the fading irradiance significantly deteriorates the received signal in two aspects: received energy fluctuation and extra path loss.

In the beginning, the author conducts a comprehensive outdoor channel measurement from several hundreds meters up to four thousand meters. To the best of our knowledge, this experiment represents the most comprehensive examination of the NLOS UV communication channel at such distances. By reporting experimentally collected data, we illustrate two approaches to measuring path loss. In addition to highlighting practical issues, which is death time, that must be considered when performing such measurement , the data provide validation of a previously reported Monte Carlo multiple-scattering channel model. In addition, we examine the distribution of received photon counts for evidence of the effects of turbulence in the NLOS channel. In this case, however, there is less agreement with predictions from existing turbulence models, suggesting the need for additional research on the refinement of turbulence modeling.

For this reason, we then propose a MC channel model to capture the multiple scattering channel behavior under turbulence condition. In addition, we present a serial experimental results and study the characteristic of NLOS UV turbulence channel with farthest distances up to 1 km. Through the experiment and simulation, we discuss the

turbulence effect on NLOS UV channel with focus on received-signal energy distribution and channel path loss. What’s more, a special characteristic of NLOS UV channel is proposed and studied as well, which is turbulence strength trade off between path length and common volume size. This is the first experiment to study NLOS UV turbulence channel characteristic. These experimental and simulated results are valuable for studying NLOS UV channel and communication system design.