Research On OFDM Technology In Visible Light Communication System

Visible light communication uses visible light as the information carrier,which has the advantages of rich resources,high security,low power consumption,and no limits to spectrum bandwidth.In the meantime,OFDM has so many outstanding features like high spectral efficiency,efficient implementation of FAST Fourier Transform,simple implementation,and robustness to inter-symbol interference that has been one of the most widely used modulations technologies in VLC.Based on the application of OFDM in VLC,research on theory,off-line transmission,and its implementation is discussed in this thesis.The main work is as follows:1.This thesis describes the VLC system framework and its architecture,and then its modulation principles and key technologies of OFDM are explained.To apply OFDM to VLC,DCO-OFDM and ACOOFDM are introduced.By comparing the realization principle and system performance of the two technologies,a DCO-OFDM system architecture with higher spectral efficiency is built.2.Based on the DCO-OFDM system,synchronization,channel estimation,channel equalization,and other algorithm are comprehensively studied.What’s more,we apply the algorithm of k-Medoids clustering to the equalization and demodulation algorithm of the DCO-OFDM.The signal format and system parameters are designed,and the process of modulation and demodulation on the receiver and transmitter is simulated comprehensively.3.Designed and constructed an off-line experimental platform for the indoor VLC system.The off-line circuit transmission system,DCO-OFDM off-line transmission system based on a single LED,and DCO-OFDM offline transmission system based on a single laser diode are demonstrated through experiments.And also,through multiple experiments and offline processing and analysis of experimental data to optimize the optical transmission system.Finally,under the forward error correction standard,a communication link with a communication distance of 1.37 Gb/s in the free space of 1 m based on blue LED and a transmission rate of 4.55 Gb/s in the free space of 2 m based on blue LD was realized respectively.