【作者】 陶毅；

【导师】 许肖梅；

【作者基本信息】 厦门大学 ， 海洋物理， 2008， 博士

【摘要】 浅海水声信道是迄今为止最为复杂的无线通信信道之一。它固有的时-空-频变以及窄带、高噪、强多途干扰、长传输时延、大随机起伏等特征,使得浅海水声通信系统在有效性和可靠性等通信性能的提高上面临着巨大挑战。由于浅海域具有特殊的经济和军事战略地位,涉及到国家的利益与发展,使得浅海水声通信技术成为当今海洋研究的热点。跳频通信是扩展频谱通信的一种重要方式,其具有的抗干扰能力强,特别是抗窄带干扰、抗噪声、抗多途;以及保密性和易于实现码分多址等特点使得跳频通信在复杂浅海水声通信中受到广泛重视。论文基于NI CompactRIO嵌入式模块,利用其具有高速数字信号处理能力和易于编程等优点,针对浅海复杂水声信道特点,构建了抗多途水声跳频通信系统。系统在厦门港浅海域进行了多次海上现场实验,取得了较好的实验结果。论文的主要工作如下:1.系统和全面地介绍了国内外在水声通信技术领域的研究概况,分析了浅海水声信道的特点及其对水声通信性能的影响;2.开展了浅海水声信道传输特性的仿真研究。采用BELLHOP射线模型和快速声场模型分别对台湾海峡水声信道传递函数和浅海脉冲传播多途时延特性进行仿真研究,分析了浅海水声信道中梳状滤波器特性及信道环境参数对水声传输性能的影响;3.基于降低通信系统误码率的需求,进行了信道纠错编码-Turbo码在浅海水声信道中的性能仿真研究;4.针对浅海水声跳频通信中最为关键的同步问题,提出了一种新的基于软件数字信号处理方法的时频编码同步方案,并采用短时傅立叶变换方法实现该方案;5.对于浅海水声通信中面临的信号大幅度起伏和尖脉冲干扰,在数字信号处理方法上采用Hilbert变换及相关算法实现幅度的自动均衡,用小波变换去除突发尖峰噪声,较好的实现了信号调理;6.在上述工作基础上,论文基于NI CompactRIO嵌入式模块,设计并实现了一套浅海水声信道抗多途跳频通信系统。系统在实验室水池和厦门港浅海域进行了多次现场实验。实验结果表明,在距离为6km,水深15m左右,传输速率500bit/s时,传输误码率为10^-2-10^-3。结合Turbo码技术后,可使通信系统的误码率降至10^-4以下,表明系统具有较强的抗干扰能力,能够实现较为稳健的通信性能。本文具有以下创新点:1.提出了基于短时傅立叶变换的一种新的时频联合分析的同步方案;2.采用Hilbert变换和小波变换的软件数字信号处理方法在水声通信接收端中实现幅度自动均衡和去除冲击噪声干扰;3.基于美国NI公司最新开发的CompactRIO嵌入式模块,设计并实现了一套水声跳频通信系统,经厦门港海上实验验证系统具有较高的稳健性。更多还原

【Abstract】 Shallow water acoustic channel is one of the most complex wireless communication channels. The inherent characteristics, such as space-time-frequency varying, narrow-band, high-noise, strong multipath interference, long transmission delay, large fluctuation, etc., making effectiveness and reliability performance of shallow water acoustic communication face enormous challenges. On the other hand, owing to the special economic and military-strategic position of shallow water, which involved the national interest and development, shallow water acoustic communication technique become a hot research area in recent years. Frequency-hopping communication as a major method of Spread-spectrum communication has many advantages, for example, anti-jamming ability, in particular the ability to narrow-band interference, anti-noise, anti-multipath, confidential and easy to implement Code Division Multiple Access （CDMA） technique. Consequently, shallow water acoustic frequency-hopping communication deserved extensive attention.With NI CompactRIO embedded module, an anti-multi-path frequency-hopping acoustic communication system was constructed, benefiting from its high-speed digital signal processing capability and the advantages of easy programming. A number of field test were carried out in Xiamen Harbor, and good results were achieved.The main work of this dissertation is as follows:1. Former researches in the field of underwater acoustic communication were introduced objectively. shallow water acoustic channel features and the impact on the underwater acoustic communication were analyzed;2. The transmission characteristics of the shallow water acoustic channel are studied in simulation. Transfer function and multi-path delay spread in the Taiwan Strait acoustic channel were simulated by BELLHOP ray model and fast field program respectively. The comb filter characteristics of shallow water channel and the impact on sound transmission performance were researched;3. Performance of error correcting coding-Turbo Code in shallow water acoustic channel was studied by simulation for reduce bit error rate;4. For the most critical issues of shallow water acoustic frequency-hopping communication - synchronization, Short-time Fourier Transform was used to fulfill a new software-based digital signal processing method time-frequency coding synchronization programme;5. Hilbert transform with related algorithms and wavelet transform were used to amplitude equilibrium and removing peak noise for the signal large fluctuations and peak pulse interference which will obstruct shallow water acoustic communication. Satisfactory signal conditioning was accomplished;6. An anti-multipath frequency-hopping communication system in shallow water acoustic channel was designed and implemented based on NI CompactRIO embedded module. A number of field experiments had done in the laboratory pond and Xiamen Harbor. Experimental results show that the bit error rate on the order of 10^-2～10^-3, by using Turbo Code, the bit error rate reduce to on the order of 10^-4 on the channel of distance of 6 km, average water depth of 15m, at data rate of 500 bit/s. The system has strong anti-interference capability, achieved a stable communication.The originalities of this dissertation are as follows:1. Proposed a new software-based digital signal processing programme to fulfill a time-frequency coding synchronization;2. Hilbert transform and wavelet transform were used to carry out amplitude equilibrium and removing peak noise ;3. Based on NI CompactRIO embedded module, an anti-multipath frequency-hopping shallow water acoustic communication system was designed and performed in field test in Xiamen Harbor更多还原