Research On Channel Coding And Modulation Technology In Indoor Visible Light Communication

The visible light communication(VLC)compares with the traditional radio frequency(RF)communications and other means of communication,it has many advantages such as high transmission power,does not occupy the radio frequency spectrum resources,no electromagnetic radiation,strong anti-interference,environmental protection,energy conservation good security,and gradually become a research focus in the field of communication.This paper mainly studies the indoor VLC.Paths between communication access point(CAP)and LED array access point(LAAP),paths between LEDs and LAAP are taked into consideration based on the original typical channel model of indoor VLC.Reflection channel of the light source is more perfect.Early adoption of the on-off keying(OOK),pulse width modulation(PPM),absolute binary phase modulation(BPSK)modulation mode can not effectively overcome the multipath effect caused by intersymbol interference(ISI)in indoor VLC and improve the system performance,limits the high-speed transmission of data.Orthogonal frequency division multiplexing(OFDM)not only can effectively overcome the inter symbol interference,but also can realize high-speed transmission of data.This paper analyzes the basic principle of OFDM modulation,and puts forward the necessity of introducing OFDM modulation in the indoor VLC.Symbol information in the visible light channel will occur is neither random and independent also is not a single burst error,but a mixed errors,which will reduce the performance of the system.In order to correct the error code to improve the performance of the system,it is necessary to use the channel coding technology in indoor VLC.Communication system often uses RS error correcting code and fixed interleaving as the channel coding,but weaving width is designed for maximum value in channel in the worst situation,it causes unnecessary memory loss and communication delay because the channel is less in the worst situation.In this paper,an adaptive interleaving scheme isproposed to dynamically change the interleaving width according to the channel state information.This paper studies the RS error correcting code and adaptive interleaving impact on the performance of indoor OFDM VLC system.And establishing the indoor OFDM VLC system model based on adaptive interleaving,designing adaptive interleaving scheme and system parameter of easy simulation.Simulation results show that the adaptive interleaving can effectively improve the quality of the system compare with the mixed interleaving in the indoor OFDM VLC system.