无线光通信系统调制解调技术研究

发布时间：2018-04-10 15:44

本文选题：可见光通信 + CSK调制　；参考：《东南大学》2017年硕士论文

【摘要】：随着频谱资源被大量的开发利用,频谱资源越来越稀缺,同时随着人们的环保健康意识的增强,射频对人体的辐射危害也逐渐进入人们的视线,这些促使人们寻找一种新兴的接入方式。同时,随着LED技术的逐渐成熟并随之应用于人们的生活,利用LED进行的可见光通信技术由于其潜在带宽资源丰富,绿色安全无辐射的特点,逐渐受到研究人员的关注,并对其进行了大量的研究。本文主要研究了多色可见光通信技术中的调制技术,包括CSK星座点设计,星座点概率分布优化等方面,还针对可见光信道中存在的散弹噪声,给出了相应的检测优化方案。首先,本文介绍了可见光通信的研究背景以及国内外的研究进展,并对可见光通信中的调制技术领域的研究进行了简要介绍。随后针对多色可见光通信系统模型进行建模,对可见光信道特性,信道噪声组成等方面进行了分析,并对本文所涉及的色移键控(CSK)的调制解调方案做了详细描述。随后,本文对四色可见光通信中的等概分布的CSK星座点设计问题进行了研究。在该问题中,为了保证合成白光的质量,我们引入色温以及显色指数约束,并将该非线性约束转换为线性约束,通过迭代优化的方法获得最优星座点分布。然后我们利用该方案在不同光源,亮度以及色温条件下进行了星座点优化和系统仿真,仿真结果显示,该优化方法能有效地增大星座点间的最小距离,相比三色CSK调制在性能上有较大的增益。同时根据仿真结果的特点给出了一个能够使四色LED灯组工作在最佳状态的照明方案。接着,本文对四色可见光通信规则星座图下的概率分布进行了优化。为了减小传输端的硬件复杂度,通信系统通常采用规则的星座图。本章为了减小调制信号的平均发射功率,引入格栅成形(Trellis Shaping)技术,并针对四色通信系统独有的特点,提出了两种Shaping方式:联合Shaping和分组Shaping。联合Shaping是将发射信号看作四维信号,改变四维星座图上的每个星座点出现的概率,增大能量较少的星座点出现概率同时减小能量较大的星座点出现的概率。分组Shaping方案则针对两路信号独立传输,根据四色通信的特点,将数据分成独立的两路进行传输,并对每一路进行Shaping。仿真结果显示,两种Shaping方案均能明显地减小发射功率,同时调制阶数越高,Shaping所带来的性能提升越大。最后,本文还针对可见光通信中散弹噪声对解调器性能的影响展开研究。本章首先提出了一种在光信道下利用导频序列测量信号无关噪声(SIGN)和信号相关噪声(SDGN)比重的方法,随后针对2-PAM检测算法改进了解调信号的似然比计算公式,在采用LDPC码的编码调制系统中,改进方法能明显地提升系统性能,同时在LDPC最小和算法基础上提出了一种简化的似然比计算方案,该种计算方式对噪声估计误差不敏感,计算复杂度低。仿真结果表明,两种似然比计算方式均能带来不同程度的性能增益,而针对最小和算法的改进方案具有较高的鲁棒性。
[Abstract]:With the use of a large number of spectrum resources are developed, the spectrum resources are increasingly scarce, and with the awareness of environmental health, RF radiation harm to human body is gradually into people's attention, which has prompted the search for a new access method. At the same time, with the maturity of LED technology and then applied to the people life, the use of LED visible light communication technology because of its potential bandwidth resources, characteristics of green safe radiation, gradually attention by researchers, and a lot of research. This paper mainly studies the modulation technology of multi-color visible light communication technology, including the CSK constellation design aspect, constellation point probability distribution optimization, in the presence of visible light shot noise in the channel, the corresponding detection optimization scheme. Firstly, this paper introduces the research background and the visible light communication The research progress at home and abroad, and the research of modulation technology in the field of optical communication are introduced. Then the modeling for polychromatic visible light communication system model, the visible light channel characteristics, analyzes the channel noise composition, and are involved in this paper and the color shift keying (CSK). Modulation and demodulation scheme is described in detail. Then, the CSK constellation design problem the probability distribution of color in the visible light communication is studied. In this problem, in order to ensure the quality of the synthesis of white light, we introduce the color temperature and color rendering index constraints, and the nonlinear constraints into linear constraints, obtained the optimal distribution of constellation points through the iterative optimization method. Then we use the method in different light, brightness and color temperature conditions for constellation optimization and system simulation, the simulation results show that the optimization method can To effectively increase the minimum distance between the constellation points, compared to three CSK modulation has a greater gain in performance. At the same time, according to the simulation results presented a four-color LED lamp group can make the work in the best lighting scheme. Then, the probability of four visible light communication constellation diagram under the rules of distribution optimization. In order to reducing transport terminal hardware complexity, communication systems usually adopt rules of the constellation. This chapter in order to reduce the average transmit power modulation signal, (Trellis Shaping) the introduction of grid forming technology, and according to the unique characteristics of four communication system, puts forward two kinds of Shaping: Shaping and Shaping. combined with Shaping group joint the emission signal as a four-dimensional signal, change the probability of each point on the constellation constellation 4D appears, constellation increases the probability of less energy and reduce energy than the big star A little probability appeared. Shaping packet scheme is for two independent signal transmission, according to the characteristics of four communication, the data is divided into two independent transmission, and each path of the Shaping. simulation results show that the two Shaping schemes can significantly reduce the transmit power at the same time, the higher the modulation order, the performance of Shaping bring the greater promotion. Finally, aiming at the influence of visible light communication on the performance of shot noise demodulator is researched. This chapter first proposes the use of a pilot sequence measuring signals in the optical channel independent noise (SIGN) and signal noise (SDGN) proportion method, then the 2-PAM detection algorithm improved understanding of likelihood ratio calculation formula of the modulated signal, the LDPC code encoding modulation system, the improved method can significantly improve the system performance, and proposes a simple algorithm based on minimum and in LDPC The likelihood ratio calculation scheme is not sensitive to the noise estimation error and the computational complexity is low. The simulation results show that the two likelihood ratio methods can bring different performance gains, and the improved algorithm for minimum sum algorithm has high robustness.

【学位授予单位】：东南大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：TN929.1

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