Study On Non-Orthogonal Relay And Full-Duplex Optical Wireless Communication System

Compared with traditional wireless communication,optical wireless communica-tion has various advantages such as no spectrum authentication,ultra-wide bandwidth,low power consumption,high data rate,good information confidentiality,and flexible infrastructure assumption.The research in this paper addresses two application sce-narios that are non-line-of-sight UV-scattering communication and close-range visible light-emitting diode(LED)-based communication.It aims to increase the performance of wireless optical communication systems,including increasing the transmission rate and transmission distance and reduce error probability.In terms of non-line-of-sight UV-scattering communications,due to the scattering effect,the signal received by receiver is often very weak and the transmission distance is limited.In response to this problem,we designed a two-way relay protocol in the scattering communication in which the transmitter uses On-Off Keying(OOK)modu-lation and the receiver uses a photon counter to receive in the meantime and the linear minimum mean square error(LMMSE)estimation is adopted by theoretical research and simulation optimization.The linear coefficient of LMMSE and the optimal power mapping table are provided,which greatly improves the communication performance,reduces the error probability of the communication system,saves power,and increases the transmission distance.In addition,in term of the non-line-of-sight UV scattering communication,a scheme of adding a relay node to perform full-duplex relay communication between commu-nication peers is proposed,and the achievable rate is studied from the perspective of information theory.Based on the UV-scattering communication link coplanar model and the approximate calculation method of its link loss,the theoretical analysis of the achievable rate of the full-duplex relay communication channel is carried out.And the numerical simulations of OOK modulation under different conditions are performed.Achievable rate are given under different channel parameters including link loss,rela-tive positions of communication nodes and relay nodes,transceiver angle for the case of whether the relay node has self-interference.Several typical system parameter selec-tion schemes are given,which provide solutions and data support for the deployment of communication facilities in practical applications.On the other hand,regarding to the LED visible light communication application scenario,a full-duplex communication scheme is proposed based on the photoelectric characteristics of the LED.Theoretical analysis of the channel achievable rate and the design and optimization of the transmitter constellation diagram for pulse amplitude modulation(PAM)are given as well.At the same time,the variation of the achievable rate under different modulation levels and gain-to-noise ratios is given.Compared with applying the LED to the receiver of the optical wireless communication by time division multiplexing,the communication rate of the appropriate LED full-duplex communica-tion scheme is greatly improved.