Development Of OFDM Visible Light Communication System Based On DSP

Visible Light Communication (VLC) is a new and promising wirelesstransmission technology recent years, designed on the fourth generation lightingsource-LEDs, which is a green and energy-efficient lighting resource. As acomplementary way of RF in short distance wireless communication, it has shown itsextraordinary potential in intelligent lighting, intelligent control and indoorpositioning and many other areas. Because of its wide coverage, security, high speedand free of electromagnetic interference and radio spectrum licenses, it is so attractiveto researchers all around the world that it has become the focus of research in the fieldof communication.This paper developed an OFDM (Orthogonal Frequency Division Multiplexing)visible light communication system based on DSP. Specific work is as follows:At first the hardware circuit of the sender and receiver were designed anddebugged. The sender hardware circuit is mainly constitute of the DSP core controller,D/A converter circuit, LED drivers circuit and signal coupling circuit,; the receiverhardware circuit is mainly constitute of a photo-detector circuit, pre-amplifier/mainamplifier, gain self-adjusting circuit, single-ended to differential circuit, AD convertercircuit, LCD display circuit and DSP core controller.And then for the software according to the basic theory of OFDM modulationtechnology and with the help of FFT and other auxiliary algorithms, the generationand recovery process of an OFDM symbol was designed and achieved. It includes16PSK/16QAM modulation, serial to parallel conversion, IFFT/FFT calculationsand channel estimation. In this section the correctness and feasibility of this codeswere tested on the conditions of software simulation mode of CCS.At last the overall hardware circuit of this system was integrated, the effects ofthe LED light source driving voltage to channel nonlinear distortion response was studied, and the optimal working range was defined according to the experimentalresults. The SNR level of the sender and receiver hardware circuit was observed. Atthe same time communication experiment was done with16PSK (Phase Shift Keying)and16QAM (Quadrature Amplitude Modulation) modulation respectively in order tomeasure the communication performance of this system. The test results show that:the system’s stability with16QAM is superior than16PSK; the reliablecommunication distance is40-100cm, communication rate is up to66Kbps, BER isabout10-3.