极端海况下的稳健水声通信关键技术研究

Extreme ocean conditions such as surface winds, waves, rainfalls, typhoons, etc, cause sea surface roughness and water column variation, that change the coherence of acoustic signals, affect multipath structure (amplitude and arrival time), phase shifts and Doppler spreads, and increase ocean ambient noise, so they can severely influence the performance of underwater acoustic communication systems. How to overcome these extreme conditions and achieve reliable under communication is a key problem to be solved for current underwater acoustic communication to be practically useful.. This project is the first to propose an interdisciplinary research for reliable underwater communication through combining “ocean environment, underwater acoustic channel, and acoustic communication” as a unity. Effects of ocean environments on acoustic channel characteristics and further on underwater acoustic communication systems will be studied via field experiments and theoretical analysis of various extreme ocean conditions including winds, waves, rainfalls and typhoons. Three key issues will be addressed here: (a) Study channel estimation and channel modeling for different ocean conditions, and search for new signal processing methods for tolerant channel matching; (b) Design an adaptive mode for underwater acoustic communication (including adjustable operating frequency, transmitting power and modulation schemes, adaptive channel coding, etc) for various ocean conditions; (c) Design a reliable, non-coherent acoustic communication system based on a fractional Fourier domain hopping (FrFDH) method, and analyze its performance in different ocean conditions.

海面上的风浪、降雨和台风等极端海况引起海面粗糙度和海水水体的变化，改变水声信号的相关性，影响多途幅度-时延、相位变化、多普勒扩展，提高海洋环境噪声，从而严重影响现有水声通信系统的性能。如何在极端海况下实现稳健通信是当前水声通信走向实际应用亟待解决的关键问题。.项目首次提出以“海洋环境-水声信道-水声通信”为一整体进行稳健水声通信技术研究。通过对海浪、降雨和台风等极端海况下水声信道特征参数的实验研究和理论分析，获取不同海况对水声通信系统性能影响的信道特征主要参数。项目将解决三个关键问题：一是建立不同海况下的信道估计和信道模型，寻求与信道模型宽容匹配的新型信号处理方法；二是根据不同海洋环境条件，设计自适应水声通信系统的通信模式，包括工作频率、发射功率和通信调制体制、自适应信道编码；三是基于分数域跳频（FrFDH）非相干思想设计一套稳健水声通信系统并在不同海况下比较系统的性能。

海面上的风浪、降雨、台风和海洋生物、海洋工程噪声等突发水下噪声所引起的极端海况将引起海面粗糙度和海洋噪声的显著变化，改变水声通信中信号的相关性，影响多途幅度-时延、相位变化、多普勒扩展和海洋噪声级，从而严重影响现有水声通信系统的性能。如何在极端海况下实现稳健水声通信技术是当前水声通信走向实际应用亟待解决的关键问题之一。. 基于海洋环境中的风浪、突发噪声等对水下声场的显著影响，项目首次提出以“海洋环境-水声信道-水声通信”作为一整体进行稳健水声通信系统设计研究。通过对海浪、海洋生物和海洋工程噪声等极端海况下水声信道特征参数的实验研究和理论分析，采用PE模型分析了海面风浪对水声信道冲激响应的影响，研究了极端海况下水声信道的特征。项目研究了三个关键问题：一是建立不同海况下的信道估计和信道模型，研究了风浪、海洋生物和海洋工程等强噪声背景对水声信道的影响；二是根据不同海洋环境条件，研究了稳健可靠、宽容匹配的水声通信系统，设计了采用分数域跳频（FrFDH）和OCDM调制的水声通信系统方案；三是基于NI Compact RIO平台，设计了基于OCDM调制的稳健水声通信软、硬件系统，并比较了系统在不同调制方式和不同海况下的通信性能。