Ultraviolet Communication Network Modeling and Analysis
With recent advances in ultraviolet (UV) sources and detectors, UV communication and networking has received increasing interest for diverse applications. This thesis studies corresponding non-line-of-sight (NLOS) scattering channels, UV system and network performance, neighbor discovery and network connectivity issues.
Based on NLOS communication link geometry and UV signal interaction with the atmosphere, the author develops two analytical channel models that describe the path loss in an integral form and closed-form respectively. Utilizing curve-fitting with field measurements, an easy-to-use empirical model is further developed. The results are then applied to study performance of a NLOS UV network, from outage probability to transmission throughput and network connectivity in a multi-user interference environment. Different UV transceiver structures and pointing geometry are incorporated, and fundamental relations of network k-connectivity with network parameters such as network scale and node density are studied. Subsequently, a neighbor discovery protocol for UV communication networks is proposed, using a novel handshake mechanism and direction synchronization technique. The protocol is further improved in terms of significantly reduced neighbor discovery time by assigning a leader node for node coordination. Meanwhile, the author also investigates the effects of channel delay spread on communication quality, i.e., data rate limitation from the induced self inter-symbol interference. These analyses and results provide valuable guidance for UV system and network design in a real environment.