Research On Channel Model And Coding Technology Of LED Visible Light Communication

Visible light communication takes account of communication and lighting functions,has many advantages that other communication means do not possess,such as long life,small volume,high energy efficiency,environmental protection and energy saving.LED has become the focus of lighting field in recent years,and has gradually become the ideal fourth generation solid point light source.Visible light communication is also concerned by all over the word.Its application area is also expanding,and the market prospect is very broad.At present,there is no definite channel model in visible light communication.Only the accurate simulation of the propagation path of visible light communication can ensure the performance of the whole visible light communication system.Therefore,building a channel which is suitable for visible light communication is the key.On the other hand,in order to reduce the impact of obstacles in the transmission process,efficient channel error correction coding techniques should be used to test and correct the errors produced in the transmission.Therefore,the main contents of this paper are as follows:1?Introduce the light source LED and explain the basic principle of visible light communication.The transmitter,channel and receiver of the visible light communication system are introduced in detail.The performance comparison of different light sources and the optional types of detectors are given.2?The radiation model of visible light communication is analyzed.Through the calculation of luminous intensity and other parameters,we build the mathematical model of the visible optical communication channel.The parameters of channel transmission are simulated,and the most suitable parameters,such as the launching angle,the maximum field angle and the effective area of the detector,are selected.The multiple reflection routes in the channel are simulated,and the influence of the reflection path on the transmission results is analyzed.Then we build channel module and system model with Simulink software platform.3?Four typical codes are selected:Linear block code,RS,Turbo,LDPC.Assign parameters to every module in Simulink.Through Matlab programming,the papercall the visible optical communication model in Simulink,and analyze the coding performance under different channels.Finally,the paper choose the code that is most suitable for the transmission of visible optical communication channel.The experimental results show that the performance of LDPC code is the best in channel transmission of visible light communication.4?The influence of code length and bit rate on code is analyzed,and the encoding and decoding algorithms of LDPC are compared.Combining the advantages of the algorithm and the MS algorithm,and introduce the multiplicative factor to improve the algorithm.The simulation results show that the improved algorithm compromises the shortcomings of the above two algorithms and improves the overall performance of the system.