宽带水声信道参数估计及应用
发布时间：2018-10-20 09:26
【摘要】：从上世纪90年代至今,由于经济社会发展和国防安全的需求,水声科学技术的研究受到了世界各国的关注,并取得了突飞猛进的发展。相比陆地无线信道,水声信道具有其特殊性和复杂性,表现在其严重的多途效应、时变特性以及带限特性等方面。近年来持续发展的水声相干通信在提高频带利用率和信息传输速率上,较非相干通信有着较明显的优势,但同时对水声信道的参数估计有着越来越高的要求。从信号处理角度上讲,信道估计的精度与效率直接影响着整个水声通信系统的性能,因此该问题一直以来都是水声领域研究的重中之重。本文从水声信道的物理特性出发,抓住其宽带本质,对具有多尺度多时延特性的水声信道参数估计问题,及其在水声通信上的应用展开了深入研究,在以下几个方面具有创新性成果:1)结合对射线理论和水声Doppler效应的分析,系统地描述了宽带水声信道模型的多尺度多时延特性。对于不满足窄带近似条件的信道,以Doppler尺度因子来描述宽带Doppler效应,接收信号表示为发送信号多个时延-尺度副本按照宽带扩散函数的加权叠加。通过对BELLHOP建模工具和Vir TEX算法加以修正和改进,模拟出平静海面以及正弦起伏海面情况下具有多尺度多时延特性的信道。2)研究了现有的基于宽带相关处理的信道估计方法,在此基础上,采用一种基准尺度为有理数的小波作为信道探针信号,提出了宽带解卷积信道估计方法和匹配追踪信道估计方法的离散数值算法。仿真实验表明,当信道具有充分稀疏性时,两种方法均能够获得较理想的宽带扩散函数估计。3)利用线性调频信号在时域和分数阶Fourier变换域的脉冲压缩特性,提出了一种基于分数阶Fourier变换的多尺度多时延水声信道参数估计方法。该方法能够以迭代的方式对多分量线性调频信号按照能量大小顺序进行分离,在每次迭代中,通过一个可以校正最佳变换阶数的子迭代过程来获得尺度、时延等参数的精确估计。仿真实验表明,该方法对宽带扩散函数的估计误差明显优于现有的其它方法。4)针对多尺度多时延水声信道,提出一种双曲调频-扩频通信方案。通信帧以线性调频信号作为帧头,用于信道估计,并采用一系列双曲调频信号对数据进行扩频调制。接收机具有极其简单的系统结构,可直接利用信道参数估计结果将收发信号的相关输出分成多条支路进行分集处理,通过一定的合并技术可以获得多径-尺度分集增益。此外,容易将单带传输系统扩展到多带传输,仿真结果证实了该方案的有效性。
[Abstract]:Since 1990s, due to the demand of economic and social development and national defense security, the research of underwater acoustic science and technology has been paid attention to by many countries all over the world, and has made great progress. Compared with terrestrial wireless channel, underwater acoustic channel has its particularity and complexity, which is manifested in its serious multipath effect, time-varying characteristic and band-limit characteristic. In recent years, the continuous development of underwater acoustic coherent communication has obvious advantages over non-coherent communication in improving the efficiency of frequency band and the rate of information transmission, but at the same time, the parameter estimation of underwater acoustic channel is required more and more. From the point of view of signal processing, the accuracy and efficiency of channel estimation directly affect the performance of the whole underwater acoustic communication system, so this problem has always been a top priority in the field of underwater acoustic research. Based on the physical characteristics of underwater acoustic channel and its wideband nature, the parameter estimation problem of underwater acoustic channel with multi-scale and multi-delay characteristics and its application in underwater acoustic communication are studied in this paper. The main contributions are as follows: 1) combining the analysis of ray theory and underwater acoustic Doppler effect, the multi-scale and multi-delay characteristics of broadband underwater acoustic channel model are systematically described. For the channel which does not satisfy the narrow band approximation condition, the Doppler scale factor is used to describe the wideband Doppler effect, and the received signal is expressed as the weighted superposition of multiple time-delay scale copies of the transmitted signal according to the wideband diffusion function. By modifying and improving the BELLHOP modeling tool and the Vir TEX algorithm, the channel with multi-scale and multi-time delay in the case of calm sea surface and sinusoidal fluctuation sea surface is simulated. 2) the existing channel estimation methods based on wideband correlation processing are studied. On this basis, a wavelet with a benchmark scale of rational number is used as the channel probe signal, and a discrete numerical algorithm for wideband deconvolution channel estimation and matching tracking channel estimation is proposed. Simulation results show that when the channel is sparse enough, both methods can obtain ideal wideband diffusion function estimation. 3) the pulse compression characteristics of LFM signals in time domain and fractional Fourier transform domain are utilized. A multi-scale and multi-delay channel parameter estimation method based on fractional order Fourier transform is proposed. The method can separate the multi-component LFM signals according to the order of energy magnitude in an iterative manner. In each iteration, the scale is obtained by a subiteration process which can correct the optimal order of transformation. Accurate estimation of delay and other parameters. Simulation results show that the estimation error of this method for wideband diffusion function is obviously better than that of other existing methods. 4) A hyperbolic frequency-spread spectrum communication scheme is proposed for multi-scale and multi-time delay underwater acoustic channels. The communication frame uses linear frequency modulation (LFM) signal as the frame head for channel estimation and uses a series of hyperbolic FM signals to modulate the data. The receiver has an extremely simple system structure and can directly use the channel parameter estimation results to divide the correlation output of the transceiver signal into multiple branches for diversity processing. The multipath scale diversity gain can be obtained by a certain combination technique. In addition, it is easy to extend the single band transmission system to multi-band transmission. The simulation results show that the proposed scheme is effective.
【学位授予单位】：华南理工大学
【学位级别】：博士
【学位授予年份】：2016
【分类号】：TN929.3
[Abstract]:Since 1990s, due to the demand of economic and social development and national defense security, the research of underwater acoustic science and technology has been paid attention to by many countries all over the world, and has made great progress. Compared with terrestrial wireless channel, underwater acoustic channel has its particularity and complexity, which is manifested in its serious multipath effect, time-varying characteristic and band-limit characteristic. In recent years, the continuous development of underwater acoustic coherent communication has obvious advantages over non-coherent communication in improving the efficiency of frequency band and the rate of information transmission, but at the same time, the parameter estimation of underwater acoustic channel is required more and more. From the point of view of signal processing, the accuracy and efficiency of channel estimation directly affect the performance of the whole underwater acoustic communication system, so this problem has always been a top priority in the field of underwater acoustic research. Based on the physical characteristics of underwater acoustic channel and its wideband nature, the parameter estimation problem of underwater acoustic channel with multi-scale and multi-delay characteristics and its application in underwater acoustic communication are studied in this paper. The main contributions are as follows: 1) combining the analysis of ray theory and underwater acoustic Doppler effect, the multi-scale and multi-delay characteristics of broadband underwater acoustic channel model are systematically described. For the channel which does not satisfy the narrow band approximation condition, the Doppler scale factor is used to describe the wideband Doppler effect, and the received signal is expressed as the weighted superposition of multiple time-delay scale copies of the transmitted signal according to the wideband diffusion function. By modifying and improving the BELLHOP modeling tool and the Vir TEX algorithm, the channel with multi-scale and multi-time delay in the case of calm sea surface and sinusoidal fluctuation sea surface is simulated. 2) the existing channel estimation methods based on wideband correlation processing are studied. On this basis, a wavelet with a benchmark scale of rational number is used as the channel probe signal, and a discrete numerical algorithm for wideband deconvolution channel estimation and matching tracking channel estimation is proposed. Simulation results show that when the channel is sparse enough, both methods can obtain ideal wideband diffusion function estimation. 3) the pulse compression characteristics of LFM signals in time domain and fractional Fourier transform domain are utilized. A multi-scale and multi-delay channel parameter estimation method based on fractional order Fourier transform is proposed. The method can separate the multi-component LFM signals according to the order of energy magnitude in an iterative manner. In each iteration, the scale is obtained by a subiteration process which can correct the optimal order of transformation. Accurate estimation of delay and other parameters. Simulation results show that the estimation error of this method for wideband diffusion function is obviously better than that of other existing methods. 4) A hyperbolic frequency-spread spectrum communication scheme is proposed for multi-scale and multi-time delay underwater acoustic channels. The communication frame uses linear frequency modulation (LFM) signal as the frame head for channel estimation and uses a series of hyperbolic FM signals to modulate the data. The receiver has an extremely simple system structure and can directly use the channel parameter estimation results to divide the correlation output of the transceiver signal into multiple branches for diversity processing. The multipath scale diversity gain can be obtained by a certain combination technique. In addition, it is easy to extend the single band transmission system to multi-band transmission. The simulation results show that the proposed scheme is effective.
【学位授予单位】：华南理工大学
【学位级别】：博士
【学位授予年份】：2016
【分类号】：TN929.3
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