基于激光二极管的可见光通信技术研究和硬件设计

发布时间：2018-07-15 11:48

【摘要】：随着无线通信技术的不断发展和用户数量的持续增多,人们对移动通信网络的带宽需求也不断提高。然而当今世界无线频谱资源紧张,大多数可用频段都已被占用。传统的射频通信越来越难以满足当今人们日益增长的信息需求。在这种情况下,可见光通信技术应运而生。由于可见光通信使用的可见光波段还是空白频谱,所以无需授权即可使用。除此之外,可见光通信还具有安全性高、保密性好以及绿色节能等特点。可见光通信技术自从诞生以来就受到了国内外研究人员的广泛关注。本文主要研究了影响可见光通信系统的关键技术,并在此基础之上实现了可见光通信系统的硬件设计。首先,本文研究了可见光通信的信道特性,对在大气衰减、大气湍流和指向误差三种因素影响下的混合大气信道建立了可靠的数学模型。基于该数学模型本文得出了混合信道下通信系统平均误码率的闭合表达式,并通过蒙特卡罗方法得出与理论数据吻合的仿真曲线,证明了表达式的正确性。其次,本文研究了可见光通信系统中的调制技术。本文分析了二进制调制技术与多进制调制技术的性能特点,比较了二进制调制技术中OOK调制、PPM调制以及DPPM调制的频谱效率和功率效率。通过仿真分析可知,与PPM、DPPM调制相比OOK调制系统的频谱利用率更高,因此在通信系统设计初期更适合使用OOK调制以降低设计的复杂度。然后,本文设计了可见光通信系统的硬件电路。分别通过反向并联肖特基二极管的方法提高半导体激光器的调制速度,使用线性均衡的方法解决了半导体光源器件的非线性问题,使用电压缓冲器放大电流信号的方法提高电压信号的驱动能力以及使用T型偏置器解决了半导体光源的使用寿命短的问题。最后,论文通过测试眼图形状定性的验证了硬件电路的性能。最后,本文设计了可见光通信系统的底层硬件,包括A/D转换器、D/A转换器和三速以太网的驱动程序。论文还研究了A/D转换器和D/A转换器的选择对系统性能产生的影响,得出A/D转换器的精度越大、频率越高越有利于系统性能的提高的结论。除此之外,论文研究了网络传输的中媒体访问控制层的作用,并剖析了其数据帧的结构、设计了三速以太网的驱动模块。通过硬件仿真显示了该模块可以实现以太网数据的正确传输,验证了设计的正确性。
[Abstract]:With the development of wireless communication technology and the continuous increase of the number of users, the demand for the bandwidth of mobile communication network is also increasing. However, the world wireless spectrum resources are scarce, most of the available frequency band has been occupied. Traditional RF communication is more and more difficult to meet the increasing information demand. In this case, visible light communication technology came into being. Because the visible spectrum used in visible light communication is still blank spectrum, it can be used without authorization. In addition, visible light communication also has the characteristics of high security, good confidentiality and green energy saving. Since the birth of visible light communication technology, researchers at home and abroad have paid close attention to it. In this paper, the key technologies that affect the visible light communication system are studied, and the hardware design of the visible light communication system is realized. Firstly, this paper studies the channel characteristics of visible light communication, and establishes a reliable mathematical model for the mixed atmospheric channel under the influence of atmospheric attenuation, atmospheric turbulence and pointing error. Based on this mathematical model, the closed expression of the average bit error rate (BER) of the communication system in mixed channels is obtained, and the simulation curve consistent with the theoretical data is obtained by Monte Carlo method, which proves the correctness of the expression. Secondly, the modulation technology in visible light communication system is studied in this paper. In this paper, the performance characteristics of binary modulation and multiary modulation are analyzed, and the spectral efficiency and power efficiency of OOK modulation PPM modulation and DPPM modulation are compared. The simulation results show that the OOK modulation system has higher spectral efficiency than PPM-DPPM modulation, so it is more suitable to use OOK modulation in the early stage of communication system design to reduce the complexity of the design. Then, the hardware circuit of visible light communication system is designed. The modulation speed of semiconductor laser is improved by reverse parallel Schottky diode, and the nonlinear problem of semiconductor light source device is solved by linear equalization method. Using voltage buffer to amplify current signal improves the driving ability of voltage signal and solves the problem of short service life of semiconductor light source by using T-type bias device. Finally, the performance of the hardware circuit is verified qualitatively by testing the shape of the eye diagram. Finally, this paper designs the underlying hardware of visible light communication system, including A / D converter D / A converter and three-speed Ethernet driver. The influence of the selection of A / D converter and D / A converter on the performance of the system is also studied. It is concluded that the higher the precision of the A / D converter, the higher the frequency, the better the performance of the system. In addition, the paper studies the role of media access control layer in network transmission, analyzes the structure of its data frame, and designs the driving module of three-speed Ethernet. The hardware simulation shows that the module can realize the correct transmission of Ethernet data and verify the correctness of the design.
【学位授予单位】：南京航空航天大学
【学位级别】：硕士
【学位授予年份】：2014
【分类号】：TN929.1

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