| As a new type wireless optical communication technology with the combination of lighting and communication, visible light communication(VLC)technology has many advantages. Recent years, study of VLC technology has become a focus of research at home and abroad, with the rapid popularization of smart devices and computer, the requirements of rate and coverage for access network will be further enhanced, VLC technology is expected to become the next generation access network of high-speed data transmission.Orthogonal frequency division multiplexing(OFDM) modulation technology has been widely used in communication field. Based on the above ideas, this paper studies the visible light communication system based on OFDM modulation and demodulation technology and implements several key modules of the system with field programmable gate array(FPGA), mainly including quadrature amplitude modulation(QAM) modulation module, channel estimation and equalization module and QAM demodulation module. At present, the FPGA implementation on QAM modulation demodulation module is mostly low-order. In this paper, the implementation of the highest order of QAM modulation and demodulation module is 1024. We use verilog to implement the complex QAM modulation and demodulation algorithm, and laid a foundation for the implementation of high-order QAM modulation OFDM VLC system.On the basis of the above implementation on each module, we have studied the adaptive OFDM VLC, we adopt high-order QAM modulation and demodulation adaptive OFDM VLC scheme, using FPGA technology to build a simulation system for this program. The modulation mode can be switched between 16,64,256,1024. Compared with the lower order QAM adaptive scheme, the system can transmit more data per one symbol, data transfer rate and communication system capacity are improved. The simulation system provides a theoretical basis for the practical application of adaptive OFDM VLC system. |
