多载波定向水声通信系统均衡器的设计与实现

发布时间：2018-01-23 19:49

本文关键词： 水声通信 OFDM 信道估计均衡器　出处：《电子科技大学》2014年硕士论文　论文类型：学位论文

【摘要】：随着人们对海洋的开发和利用,水下通信成为人们在民用及军事活动中必不可少的一项技术。不同于空气等无线电传播介质,海洋及湖泊环境中,声波是目前唯一可以有效进行远距离传播的媒介,而OFDM技术可以有效适应水声信道多途干扰强、可利用带宽少的特点。然而为了尽可能地提高水声通信的性能,增强对频率选择性衰落的抵抗、避免码间干扰,还必须设计良好的信道估计及均衡器。本文在通用的OFDM水声通信系统模型的基础上,对信道估计器和均衡器的算法及结构进行了研究,结合不同的信道环境通过仿真对比不同算法结构下接收机的性能。以此为基础,在考虑FPGA硬件资源的前提下设计出可以在硬件平台上工作并具有较好效果的接收机均衡器,主要完成的工作包括:简单介绍了OFDM水声通信系统的基本原理及发展现状,对目前国内外在信道估计及均衡方面的研究现状做了阐述和概括;分析了OFDM技术在水声通信中的优势以及信道估计和均衡对于提高水声通信性能的重要性;结合水声信道的特点,针对其可利用带宽窄、多途干扰大、频率选择性衰弱强的特点,研究了信道估计及均衡算法的原理,归纳了常用算法的优点和缺陷,提出了适用于本OFDM水声通信系统的信道估计器及均衡器的几种算法和结构作为重点研究对象。在Matlab中建立OFDM水声通信系统接收机的整体模型,并在其中加入信道估计及均衡模块,通过调整信道参数模拟不同的信道环境,将不同的算法及其经过改良后的设计通过Matlab进行仿真,通过对比不同信噪比下的误码率提出最终适合在FPGA硬件系统上进行实现的算法。根据仿真结果,设计了可以在FPGA平台上实现的均衡器以及相应的信道估计和均衡算法,并将其加入接收机系统进行联调。通过分析硬件资源使用情况验证计算复杂度。开发了FPGA与上位机PC之间的数据缓冲器以便于进行实验和应用。最后将设计好的均衡器连同发射机接收机一起进行水桶及浅水实验,并利用水声发生阵列进行普通情况的水声传输及定向传输,验证了所设计的解决方案确实可以有效对抗多径干扰及频率选择性衰落,保证良好的误码率。通过均衡器的加入,可以显著改善水声通信系统抵抗码间干扰的表现,在25dB信噪比环境下,误码率达到10-3以下,而FPGA平台上的实现也增加了本均衡器的实际应用价值。
[Abstract]:With the development and utilization of the ocean, underwater communication has become an indispensable technology in civil and military activities. At present, acoustic wave is the only medium that can effectively propagate over long distance, and OFDM technology can effectively adapt to the strong multi-path interference in underwater acoustic channel. However, in order to improve the performance of underwater acoustic communication as much as possible, enhance the resistance to frequency selective fading and avoid inter-symbol interference. It is also necessary to design a good channel estimator and equalizer. Based on the general model of OFDM underwater acoustic communication system, the algorithm and structure of channel estimator and equalizer are studied in this paper. Combined with different channel environment, the performance of receiver under different algorithm structure is compared by simulation. Based on the consideration of FPGA hardware resources, a receiver equalizer which can work on the hardware platform and has a better effect is designed. The main works are as follows: the basic principle and development status of OFDM underwater acoustic communication system are briefly introduced, and the current research status of channel estimation and equalization at home and abroad is described and summarized. The advantages of OFDM technology in underwater acoustic communication and the importance of channel estimation and equalization in improving the performance of underwater acoustic communication are analyzed. According to the characteristics of underwater acoustic channel, the principle of channel estimation and equalization algorithm is studied, and the advantages and disadvantages of common algorithms are summarized. Several algorithms and structures of channel estimator and equalizer suitable for this OFDM underwater acoustic communication system are proposed as the main research objects. The whole receiver of OFDM underwater acoustic communication system is established in Matlab. Model. The channel estimation and equalization module is added to simulate the different channel environment by adjusting the channel parameters. The different algorithms and their improved design are simulated by Matlab. By comparing the bit error rate under different SNR, the algorithm which is suitable for FPGA hardware system is put forward, and the simulation results are given. The equalizer and the corresponding channel estimation and equalization algorithm are designed on FPGA platform. The data buffer between FPGA and PC is developed to facilitate the experiment and application. Finally, by analyzing the use of hardware resources to verify the computational complexity, a data buffer between FPGA and PC is developed to facilitate the experiment and application. The designed equalizer and transmitter receiver are used for bucket and shallow water experiments. The underwater acoustic transmission and directional transmission are carried out by using underwater acoustic array, which proves that the proposed solution can effectively resist multipath interference and frequency selective fading. With the addition of equalizer, the performance of ISI resistance in underwater acoustic communication system can be significantly improved. Under 25dB SNR, the BER is below 10 ~ (-3). The realization of FPGA platform also increases the practical application value of this equalizer.
【学位授予单位】：电子科技大学
【学位级别】：硕士
【学位授予年份】：2014
【分类号】：TN929.3

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