无线光通信信道编码与调制的研究

发布时间：2019-06-06 17:47

【摘要】：自由空间光通信(Free Space Optical, FSO)指利用激光束作为载体在大气中进行图像、数据、语音信息双向传输的一种技术,它具有很多优点,例如保密性好、信息容量大、传输速率高、组网灵活、成本低等。空间光通信在民用、国防等相应领域具有非常广阔的应用前景,已成为无线通信、大容量、保密研究的热点。由于激光在空间中传输时会受到背景光、大气减效应以及大气湍效应等多种因素的影响,从而导致大气信道存在衰落、多径干扰等现象,这些因素的影响导致了空间无通信链路总是存在不同程度质量的下降。因此,研究、开发具有高速率、高抗干扰性能的信道编码技术成为光通信的重要课题之一。本文首先回顾了空间光通信技术的发展状况,介绍了其优势,且对其关键技术进行了分析比较。其次对大气随机信道进行了建模,为后续章节信道参数的设定提供了参考。然后,本文在LDPC码理论基础上,介绍了一种非规则LDPC码的构造方法。分析比较了 OOK、PPM、DPIM这三种调制方式的性能,仿真结果表明PPM调制更适合应用到无线光通信中,所以本文选择将PPM调制作为无线光通信系统的调制方式。基于MATLAB仿真软件,对不同参数下的纠错性能进行了仿真验证,为下文译码算法提供合适参数。将这种非规则LDPC码应用到一种PPM解调与LDPC码联合迭代译码的算法中,通过仿真验证了非规则LDPC码应用到PPM解调与LDPC码联合迭代译码的算法中对无线光通信系统的性能有显著提高。最后,在Quartus Ⅱ仿真平台上,选用Altera公司StratixⅡ系列型号为EP2S15F672I4芯片,利用Verilog硬件语言进行编程,仿真实现了这种非规则LDPC码的编码器和译码器,并通过MATLAB和Quartus Ⅱ软件的联合,对硬件仿真的结果进行了测试。
[Abstract]:Free space optical communication (Free Space Optical, FSO) refers to a technology that uses laser beam as carrier for bidirectional transmission of image, data and voice information in the atmosphere. It has many advantages, such as good confidentiality, large information capacity and high transmission rate. Flexible networking, low cost and so on. Space optical communication has a very broad application prospect in civil, national defense and other corresponding fields, and has become the focus of wireless communication, large capacity and security research. Because the laser propagation in space will be affected by many factors, such as background light, atmospheric subtraction effect and atmospheric turbulence effect, which leads to the fading of atmospheric channel, multi-path interference and so on. The influence of these factors leads to the decline of the quality of space communication links to varying degrees. Therefore, the research and development of channel coding technology with high speed and high anti-interference performance has become one of the important topics in optical communication. In this paper, the development of space optical communication technology is reviewed, its advantages are introduced, and its key technologies are analyzed and compared. Secondly, the atmospheric random channel is modeled, which provides a reference for the setting of channel parameters in the following chapters. Then, on the basis of LDPC code theory, this paper introduces a construction method of irregular LDPC code. The performance of OOK,PPM,DPIM is analyzed and compared. the simulation results show that PPM modulation is more suitable for wireless optical communication, so this paper chooses PPM modulation as the modulation mode of wireless optical communication system. Based on MATLAB simulation software, the error correction performance under different parameters is verified by simulation, which provides suitable parameters for the following decoding algorithms. The irregular LDPC code is applied to a joint iterative decoding algorithm of PPM demodulation and LDPC code. The simulation results show that the performance of wireless optical communication system is significantly improved by the application of irregular LDPC code to the joint iterative decoding algorithm of PPM demodulation and LDPC code. Finally, on the Quartus II simulation platform, the Stratix II series model of Altera company is selected as the EP2S15F672I4 chip, and the Verilog hardware language is used to program the encoder and decoder of the irregular LDPC code, and the encoder and decoder of the irregular LDPC code are simulated and realized by the combination of MATLAB and Quartus II software. The results of hardware simulation are tested.
【学位授予单位】：哈尔滨工程大学
【学位级别】：硕士
【学位授予年份】：2014
【分类号】：TN929.1

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