基于分数阶Fourier变换的高速Chirp扩频水声通信系统的关键技术研究
发布时间：2018-11-09 11:56
【摘要】：伴随着对海洋开发和利用的深入,人们对于海洋声通信的可靠性和速率提出了更高的要求。但受限于海洋信道的复杂特性,如何实现高速可靠的水声通信是一大挑战。 Chirp信号同时在时域和频域进行扩展,在水下通信过程中具有良好的抗频率选择性衰落和抗多普勒频移的特性。分数阶Fourier变换作为一种以Chirp信号为核函数的时频变换,在对Chirp信号的检测和参数估计上有不可替代的优势。论文首先研究了基于分数阶Fourier变换的多分量Chirp信号的检测方法,并在此基础上结合二进制键控,设计了多载波Chirp扩频系统。为解决在有限的水声通信带宽内提升多载波Chirp扩频系统速率的难题,结合并行组合扩频技术提出了并行组合Chirp扩频系统,并使用单阵元时间反转镜技术作为通信系统的抗码间干扰的技术。上述两个系统分别在厦门大学实验水池及厦门港附近海域进行了实验。结果表明,论文所提出的两个通信系统在特定的水下环境中,具备高速和可靠的通信的能力。 本文的主要工作概括如下： 1.介绍了国内外Chirp水声通信的研究现状,及海洋声信道的特性,分析了信道对通信系统的影响； 2.利用Chirp信号在分数阶Fourier变换域上的能量聚集特性,通过在分数阶Fourier变换域对多分量Chirp信号滤波的方法,完成了多分量Chirp信号的检测和参数估计算法研究。 3.利用Chirp信号自身优异的抗频率选择性衰落和抗多普勒频移的特性,结合二进制正交键控调制,在保障系统稳定性的前提下设计了多载波Chirp扩频水声通信系统,接收端使用分数阶Fourier变换的方法进行解调,相比传统的Chirp扩频系统,速率得到了一定程度的提升。 4.针对多载波Chirp水声通信系统的速率提升依赖于载波数量的问题,结合并行组合扩频技术提出了并行组合Chirp扩频水声通信系统,使得在发送较少载波的情况下实现系统速率的进一步提升。接收端使用分数阶Fourier变换进行解调提高了系统的可靠性,同时降低了接收机的复杂度。 5.针对实际水声信道可能存在强码间干扰的现象,将单阵元被动时间反转镜技术应用到并行组合Chirp扩频系统中。仿真结果表明,通过被动时反技术的使用,并行组合Chirp扩频系统的高速和可靠的通信能力得以发挥得更好。 6.在实验室水池和厦门港附近海域实验表明,多载波Chirp扩频水声通信系统和并行组合扩频Chirp水声系统均可以较高的速率实现通信,同时也具有较高的可靠性。
[Abstract]:With the development and utilization of ocean, the reliability and speed of ocean acoustic communication are required. However, due to the complex characteristics of ocean channel, how to achieve high-speed and reliable underwater acoustic communication is a big challenge. Chirp signal is extended in both time and frequency domain, and it has good anti-frequency selective fading and anti-Doppler frequency shift characteristics in underwater communication process. Fractional Fourier transform, as a time-frequency transform with Chirp signal as its kernel function, has irreplaceable advantages in detecting and parameter estimation of Chirp signal. In this paper, the detection method of multi-component Chirp signal based on fractional Fourier transform is studied, and a multi-carrier Chirp spread spectrum system based on binary keying is designed. In order to solve the problem of increasing the speed of multi-carrier Chirp spread spectrum system in the limited underwater acoustic communication bandwidth, a parallel combined Chirp spread spectrum system is proposed by combining the parallel combined spread spectrum technology. The time reversal mirror of single array element is used as the anti-interference technology of communication system. The two systems were tested in the experimental pool of Xiamen University and the sea area near Xiamen Port. The results show that the two communication systems are capable of high-speed and reliable communication in a specific underwater environment. The main work of this paper is summarized as follows: 1. This paper introduces the research status of Chirp underwater acoustic communication at home and abroad, and the characteristics of ocean acoustic channel, analyzes the influence of channel on communication system; 2. Based on the energy aggregation of Chirp signals in fractional Fourier transform domain, the detection and parameter estimation algorithms of multi-component Chirp signals are studied by filtering multi-component Chirp signals in fractional Fourier transform domain. 3. Based on the excellent anti-frequency selective fading and anti-Doppler frequency shift characteristics of Chirp signal and binary quadrature keying modulation, a multi-carrier Chirp spread spectrum underwater acoustic communication system is designed under the premise of ensuring the stability of the system. The receiver uses fractional Fourier transform to demodulate, and the rate is improved compared with the traditional Chirp spread spectrum system. 4. In order to solve the problem that the rate increase of multi-carrier Chirp underwater acoustic communication system depends on the number of carriers, a parallel combined Chirp spread spectrum underwater acoustic communication system is proposed by combining the parallel combined spread spectrum technology. The system speed can be further improved under the condition of sending fewer carriers. The receiver uses fractional Fourier transform to demodulate the system, which improves the reliability of the system and reduces the complexity of the receiver. 5. Aiming at the phenomenon of strong inter-symbol interference (ISI) in underwater acoustic channel, the passive time reversal mirror technique of single array element is applied to the parallel combined Chirp spread spectrum system. The simulation results show that the high speed and reliable communication ability of the parallel combined Chirp spread spectrum system can be improved by the use of passive time inverse technique. 6. The experiments in the laboratory pool and near Xiamen Port show that both the multi-carrier Chirp spread spectrum underwater acoustic communication system and the parallel combined spread spectrum Chirp underwater acoustic system can realize the communication at a higher rate and have a higher reliability at the same time.
【学位授予单位】：厦门大学
【学位级别】：硕士
【学位授予年份】：2014
【分类号】：TN929.3
本文编号：2320345
[Abstract]:With the development and utilization of ocean, the reliability and speed of ocean acoustic communication are required. However, due to the complex characteristics of ocean channel, how to achieve high-speed and reliable underwater acoustic communication is a big challenge. Chirp signal is extended in both time and frequency domain, and it has good anti-frequency selective fading and anti-Doppler frequency shift characteristics in underwater communication process. Fractional Fourier transform, as a time-frequency transform with Chirp signal as its kernel function, has irreplaceable advantages in detecting and parameter estimation of Chirp signal. In this paper, the detection method of multi-component Chirp signal based on fractional Fourier transform is studied, and a multi-carrier Chirp spread spectrum system based on binary keying is designed. In order to solve the problem of increasing the speed of multi-carrier Chirp spread spectrum system in the limited underwater acoustic communication bandwidth, a parallel combined Chirp spread spectrum system is proposed by combining the parallel combined spread spectrum technology. The time reversal mirror of single array element is used as the anti-interference technology of communication system. The two systems were tested in the experimental pool of Xiamen University and the sea area near Xiamen Port. The results show that the two communication systems are capable of high-speed and reliable communication in a specific underwater environment. The main work of this paper is summarized as follows: 1. This paper introduces the research status of Chirp underwater acoustic communication at home and abroad, and the characteristics of ocean acoustic channel, analyzes the influence of channel on communication system; 2. Based on the energy aggregation of Chirp signals in fractional Fourier transform domain, the detection and parameter estimation algorithms of multi-component Chirp signals are studied by filtering multi-component Chirp signals in fractional Fourier transform domain. 3. Based on the excellent anti-frequency selective fading and anti-Doppler frequency shift characteristics of Chirp signal and binary quadrature keying modulation, a multi-carrier Chirp spread spectrum underwater acoustic communication system is designed under the premise of ensuring the stability of the system. The receiver uses fractional Fourier transform to demodulate, and the rate is improved compared with the traditional Chirp spread spectrum system. 4. In order to solve the problem that the rate increase of multi-carrier Chirp underwater acoustic communication system depends on the number of carriers, a parallel combined Chirp spread spectrum underwater acoustic communication system is proposed by combining the parallel combined spread spectrum technology. The system speed can be further improved under the condition of sending fewer carriers. The receiver uses fractional Fourier transform to demodulate the system, which improves the reliability of the system and reduces the complexity of the receiver. 5. Aiming at the phenomenon of strong inter-symbol interference (ISI) in underwater acoustic channel, the passive time reversal mirror technique of single array element is applied to the parallel combined Chirp spread spectrum system. The simulation results show that the high speed and reliable communication ability of the parallel combined Chirp spread spectrum system can be improved by the use of passive time inverse technique. 6. The experiments in the laboratory pool and near Xiamen Port show that both the multi-carrier Chirp spread spectrum underwater acoustic communication system and the parallel combined spread spectrum Chirp underwater acoustic system can realize the communication at a higher rate and have a higher reliability at the same time.
【学位授予单位】：厦门大学
【学位级别】：硕士
【学位授予年份】：2014
【分类号】：TN929.3
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