基于LDPC码的水下通信系统的研究

发布时间：2018-03-01 08:04

本文关键词： 水下通信 LDPC编译码 LMS算法信道均衡瑞利衰落莱斯衰落　出处：《昆明理工大学》2017年硕士论文　论文类型：学位论文

【摘要】：随着通信技术在理论和实践方面的不断发展,水下通信的研究也攻克了一个又一个的难题,技术也越来越进步。水下通信系统模型的建立作为水下通信的重要环节,涉及许多水声学的关键技术,这些技术也成了许多学者研究的热点,包括根据特定的水下环境仿真水声信道,对水声信道进行建模分析,以及真实的水下通信系统存在的问题:多径效应,多普勒频移以及海洋噪声等。通过这些技术实际仿真出的水声信道才能更真实地分析水下环境,并在此基础上研究如何提高水声通信系统的数据传输效率、系统性能、降低传输复杂度和信息误码率,通过使用不同的算法实现模型仿真并比较这些算法性能的优缺点。本文主要研究浅海水声信道特征,应用LDPC码在水下声信道进行信息传输,同时对水声信道进行改进以提高水声通信系统性能,选择合适的LDPC编译码算法进行数据传输,进一步增加水下通信系统的信道带宽利用率和提高数据传输的可靠性。本文首先详细介绍了与水下通信系统相关内容的研究现状,对涉及水声通信的关键技术进行理论研究,包括水声信道特征、信息编译码方式以及影响水下通信系统的环境噪声等,使用计算机仿真的水声信道包括浅海短距离和浅海中远距离信道。主要使用MATLAB建模仿真多径衰落模型,模拟水下通信中存在的问题,分析信息在水下信道传输情况。其次本文在仿真水下信道之前提出了使用归一化LMS算法对水声信道进行均衡,大大地降低了信道模型的复杂度,提高了通信速率。在编译码方面,选择了抗干扰、抗衰落、抗噪声性能较好的LDPC码,详细分析并研究了 LDPC码编译的基本算法思想以及构造方式,选择适合于水声信道的规则化LDPC编码和BF译码,选取合适的参数进行仿真分析,降低了 LDPC码的复杂度。最后将LDPC码应用到水下通信系统中,综合讨论了 LDPC码应用于水声通信的优缺点,进行仿真分析,建立了 LDPC码在不同水声信道的仿真模型,通过MATLAB仿真对比LDPC码在不同调制方式、不同水下信道以及不同码长下的性能。本文主要仿真分析了 LDPC码在不同水声信道、不同码长和不同调制方式下的性能,并对信道进行均衡改进,系统仿真了 LDPC码的编码性能,达到了较好的通信传输效果,为实际应用提供了理论指导。
[Abstract]:With the development of communication technology in theory and practice, the research of underwater communication has overcome one problem after another, and the technology is more and more advanced. The establishment of underwater communication system model is an important link in underwater communication. It involves many key technologies of underwater acoustics, and these technologies have also become the focus of many scholars, including modeling and analysis of underwater acoustic channels according to the underwater environment simulation of underwater acoustic channels. And the problems of real underwater communication system, such as multipath effect, Doppler frequency shift and ocean noise, etc. The underwater environment can be analyzed more realistically by the underwater acoustic channel simulated by these technologies. On this basis, how to improve the data transmission efficiency, system performance and reduce the transmission complexity and bit error rate of underwater acoustic communication system is studied. By using different algorithms to simulate the models and compare the advantages and disadvantages of these algorithms, this paper mainly studies the characteristics of shallow water acoustic channel, and uses LDPC code to transmit information in underwater acoustic channel. At the same time, the underwater acoustic channel is improved to improve the performance of underwater acoustic communication system, and the appropriate LDPC encoding and decoding algorithm is selected for data transmission. Further increase the channel bandwidth utilization rate of underwater communication system and improve the reliability of data transmission. Firstly, this paper introduces the research status of underwater communication system in detail, and studies the key technologies of underwater acoustic communication in theory. Including underwater acoustic channel features, information encoding and decoding methods, and the impact of underwater communication system environment noise, etc. The underwater acoustic channel simulated by computer includes short distance channel in shallow water and medium and long distance channel in shallow water. MATLAB is used to model and simulate multipath fading model to simulate the problems existing in underwater communication. Secondly, a normalized LMS algorithm is proposed to equalize the underwater acoustic channel before simulating the underwater channel, which greatly reduces the complexity of the channel model. In the aspect of encoding and decoding, LDPC codes with good anti-interference, anti-fading and anti-noise performance are selected. The basic algorithm and construction of LDPC coding are analyzed and studied in detail. The regularized LDPC codes and BF codes suitable for underwater acoustic channels are selected, and the appropriate parameters are selected for simulation analysis. The complexity of LDPC codes is reduced. Finally, the LDPC codes are applied to underwater communication systems. The advantages and disadvantages of the application of LDPC codes in underwater acoustic communication are discussed synthetically. The simulation models of LDPC codes in different underwater acoustic channels are established, and the LDPC codes in different modulation modes are compared by MATLAB simulation. In this paper, the performance of LDPC codes in different underwater channels, different code lengths and different modulation modes is simulated and analyzed, and the channel equalization is improved. The system simulates the coding performance of LDPC code and achieves good communication transmission effect, which provides theoretical guidance for practical application.
【学位授予单位】：昆明理工大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：TN929.3;TN911.22

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