Research On Design And Key Technologies Of Wideband Digital Communication System For Visible Light Communication

Visible light communication(VLC)is a kind of emerging communication way,which based on environmental protection and energy saving lighting source LED(Light emitting Diode),has no electromagnetic interference,healthy,safe and reliable,low cost,and can perfectly solve the problem of wireless radio frequency communication spectrum resources shortage and a series of advantages,is considered to be geared to the needs of the sixth generation(6G)mobile communication system is an important direction of development,will be an important complementary means of wireless communication technology.There are two main factors that currently limit the performance of VLC systems.One is that the very limited modulation bandwidth of LEDs severely limits the transmission rate of VLC systems.On the other hand,the non-linear sources in the VLC system can cause signal distortion and reduce system performance.The thesis focuses on the design of high-speed VLC system and related key technologies.The market demand and application potential of current VLC development are deeply analyzed,the research background and status quo of this topic are systematically summarized.And the possible development direction of VLC in the future is summarized in combination with the latest scientific research progress.The main contents and innovations of this thesis are as follows:1.A comprehensive overview of some basic characteristics of VLC is analyzed.For LED light source,some important optical concepts are introduced.In view of the inherent characteristics of LEDs,several typical nonlinear modeling methods are given;Aiming at the limited modulation bandwidth of LED,several methods of bandwidth expansion are provided.According to the channel characteristics of VLC,several channel models and noise models are described.2.A VLC digital wideband transmission system based on white LED and PIN(positive-intrinsic-negative)tube was successfully designed and set up.The transmission rate of the system is 32 Mbps under the condition that the two ends of receiver(Rx)and transmitter(Tx)are 90 cm apart,only one set of optical lens is used,and no other technologies such as equalization and weighting are adopted.When the distance between Tx and Rx is 30 cm,the system still achieves a signal-to-noise ratio greater than 10 dB at a higher symbol rate of 100 MHz3.The simulation models of Direct Current Optical-OFDM(DCO-OFDM)system and Single-Carrier Frequency Domain Equalization(SC-FDE)system in VLC are built.Based on Ray Traying(RT)simulation channel environment,a physical mechanism based LED numerical model was used to verify and analyze the performance of the two systems.