Study On Channel Turbulence And System Design For The Ultraviolet Communication

Non-line-of-sight(NLOS)ultraviolet(UV)optical communication is an emerging optical wireless communication technique.Due to the scattering effects in the UV spec-trum,the transmitted optical signals can arrive at the receiver from the NLOS scattering links for the NLOS UV communication,which relieves the requirement on the align-ment between the transmitter and receiver.The contents of this paper mainly contain the study of channel turbulence and system design for the NLOS UV optical communi-cation.In this work,we extend the NLOS UV communication range to 500 meters using a UV laser as the transmitter and a single photon-counting block as the receiver.The receiver-side signal processing part is designed based on the Poisson distribution as-sumption for the detected photoelectron numbers.Computer-based simulation was car-ried out to evaluate the performance of our proposed frame synchronization approach and the baseband signal processing part.We also realized a real-time UV communica-tion system,with both optical devices and baseband signal processing implementation in the hardware.The outdoor real-time communication experiment showed that the data rate can reach 400 kbps at the frame error rate(FER)below 10-5,for a transceiver distance up to 500 meters.We adopt the mixed Poisson distribution to characterize the channel turbulence for the NLOS UV optical communication.The expectation-maximization(EM)algorithm is applied to estimate each component of the mixed Poisson distribution.We analyze the temporal correlation of the turbulence-incuded fading.Computer simulation is also carried out to evaluate the performance of the proposed estimation approaches for the mixed Poisson distribution and the temporal correlation.We also applied the proposed estimation approaches to the outdoor experiments with the transceiver distance of 1500 meters.We address the full-duplex relaying communication for the NLOS UV optical com-munication with stochastic and non-negligible self interference at the relay node.We propose two full-duplex relay protocols,namely the detect-and-forward relaying proto-col and the decode-and-forward relay protocol.We provide the performance analysis of the proposed protocols,especially the comparison with the half-duplex relay system.