可见光通信中高阶调制格式研究

Research on High-level Modulation in Visible Light Communication

可见光通信(VLC)系统采用发光二极管(LED)作为光源,使得系统具有照明与通信的双重作用,从而极大地节约了能源。LED调制带宽有限是VLC技术发展的主要障碍,研究者们已经提出了用于扩展调制带宽、提高传输速率的多种技术,如蓝光过滤、均衡技术、多输入多输出(MIMO)技术、高阶调制格式、波分复用技术、离散多音调调制等。VLC系统的传输速率可以通过这些技术中的某种技术或者几种技术相结合得到大大提高。本文采用各子载波调制为MQAM的OFDM技术对可见光通信的影响,介绍了可见光通信系统,并通过SIMULINK仿真分析了MQAM调制的星座图,平均功率谱密度及误码率,进一步证明了高阶正交幅度调制(MQAM)可以调高频带利用率并降低误码率,采用256QAM调制频带利用率提高为16QAM调制的2倍。

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 band-width and improve the transmission rate, such as Blu-ray filtering, equalization, multiple-input multiple-output （MI-MO） technology, high ary 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 tech-niques in a technical or several techniques. In this paper the affect of OFDM technology each sub-carrier modulation with MQAM to visible light communication is analyzed. A brief introduction of the visible light communication system is given, the constellation diagram of MQAM modulation is also showed, the average power spectral density and error rate are simulated by SIMULINK. The high-level quadrature amplitude modulation （MQAM） with higher bandwidth efficiency and smaller error rate is proved further, the bandwidth efficiency of 256QAM modulation is the twice of 16QAM modulation.