The Research of High-Level Modulation in Visible Light Communication

Visible light communication system using light emitting diode as light source, the system has the dual role of lighting and communication, thereby greatly saving energy .The bandwidth of LED modulation is a major obstacle to development of VLC technology. Researchers have put forward a variety of techniques to extend the modulation bandwidth and improve the transmission rate, such as Blu-ray filtering, equalization, multiple-input multiple-output (MIMO) technology, high ray modulation format, the wavelength division multiplexing technology, discrete multi-tone modulation and so on. The transmission rate of VLC system can be greatly improved by a combination of these techniques in a technical or several techniques. This paper analyzes the effect of OFDM technology each sub-carrier modulation with MQAM to visible light communication. It gives a brief introduction of the visible light communication system; it also shows the average power spectral density and error rate from SIMULINK simulation. It proves further the high-level quadrature amplitude modulation (MQAM) with higher bandwidth efficiency and smaller error rate, the bandwidth efficiency of 256QAM modulation is the twice of 16QAM modulation.