基于多载波差分混沌调制的稳健水声通信关键技术研究

Underwater acoustic communication is a main method for underwater information transmission. It is a frontier research field of ocean technology and information technology. Due to severe environment of underwater acoustic channels, there are many challenges to develop low complexity and robust underwater acoustic communication systems. Based on the previous systemic architecture of the multi-carrier differential-chaos-shift-keying (DCSK) scheme, 1) we will design multi-carrier DCSK system with index modulation and M-ary modulation to upgrade the transmission efficiency of multi-carrier DCSK. 2) Through analyzing performance of the systems, we will clarify the principle that the systems how to gain multipath diversity and Doppler diversity, and optimize the system performance. 3) In order to ensure high reliable information transmission of the proposed systems, we will design LDPC/Turbo coded-modulation chaotic systems and study the algorithms to decrease impulse noise interference. The proposed systems arrange the reference and data-bearing chaotic chips into the same time and frequency unit, so the proposed systems can obtain time and frequency diversity over doubly selective underwater acoustic channel. Thus, the proposed systems not only have robust performance over underwater acoustic channel but also have low complexity transceiver. It is an efficiency technique for low-cost robust underwater acoustic communications. To carry out the related system design and theoretical study has important application value and scientific significance.

水声通信是水下信息传输的主要方式，是海洋技术与信息技术交叉的前沿研究领域。由于水声传播环境的复杂性，使得研制性能稳健、复杂度低的水声通信系统仍然面临许多挑战。本项目基于前期设计的多载波与差分混沌调制相结合的系统架构，1) 研究融合下标调制和多元调制的多载波差分混沌通信系统，以改善传输效率；2) 理论分析系统性能，阐明系统获取多径分集与多普勒分集的原理机制，进而优化其系统性能；3) 研究基于LDPC/Turbo码的编码混沌调制技术，以及脉冲噪声降低算法，以保障水声带限信道下信息传输的可靠性。所提的系统架构将混沌扩频后的参考码片和信息承载码片放到相同的时频单元中传输，能够同时获得水声时频双选择性信道的时频分集，其不仅继承了差分混沌调制复杂度低的特点，还具有性能稳健的优点，是解决低成本、稳健水声信息传输的有效技术。开展相关的系统设计与理论研究具有重要的应用价值与科学意义。

本项目针对复杂水声信道环境，以稳健水声通信系统为研究目标。基于混沌多载波的系统架构，通过深入研究，解决了一系列混沌扩频水声通信的关键问题。（1）基于参考信号与信息承载信号重叠传输的思想，提出了采用正交码复用的多载波差分混沌通信系统架构，由于参考信号与信息承载信号在相同的时频资源上传输，使得该多载波系统具备良好的抗水声时变的性能，此外，该多载波系统采用了OFDM的结构，使其抗符号间干扰的能力得到增强。（2）基于该多载波架构，通过对码、时、频资源的激活模式的研究，提出了一系列索引调制方法，这些索引调制方法能够带来以下好处：增强比特能量效率，提升系统误码性能；合理选取激活参数，可有效提升系统的传输效率；降低多载波系统的峰均功率比。（3）利用差分混沌通信系统中参考信号与信息承载信号之间存在的冗余，设计了多种有效降低接收机噪声的方法，通过定量分析系统的误码性能，阐明了系统关键参数与系统性能的关系。最后通过大量的仿真与水声通信实验，验证了项目设计的系统在复杂水声信道环境下的适应性和稳健性。通过该项目的资助，发表期刊论文26篇，会议论文6篇，国家发明专利6项。