正交信分复用（OSDM）调制水声通信技术研究

Currently, orthogonal frequency-division multiplexing (OFDM) and single-carrier frequency domain equalization (SC-FDE) are two primary physical layer techniques widely adopted in underwater acoustic communications. In comparison, OFDM suffers from a large peak-to-average power ratio and high sensitivity to Doppler effects, while SC-FDE leads to an inflexible management of signal energy and bandwidth resources. Orthogonal signal-division multiplexing (OSDM) is a newly-emerging generalized modulation framework, in which by introducing the concept of "symbol vector," OFDM and SC-FDE can be treated as two special cases. Therefore, OSDM promises to bridge the gap between OFDM and SC-FDE. However, the mathematical model of OSDM is fundamentally different from OFDM and SC-FDE, where the channel impairments are embodied as intra-vector intersymbol interference (ISI) and inter-vector interference (IVI). So far, most of these effects have not been studied yet. To this end, this project is dedicated to developing new methods for OSDM systems over underwater acoustic channels. Specifically, our research aims to propose a partial FFT demodulation algorithm for IVI cancellation, per-vector equalization for ISI mitigation, phase rotation based processing for MIMO detection, and kernel function based adaptive compensation for nonlinear distortion. Furthermore, numerical simulations, pool tests and lake/sea field trials will be conducted to evaluate the performances of all the proposed algorithms. The outcomes of this project can enrich the physical layer techniques of underwater acoustic communications and provide new possibilities for practical use.

当前水声通信物理层技术存在多载波正交频分复用（OFDM）与单载波频域均衡（SC-FDE）两大阵营。其中，OFDM具有峰平功率比高、多普勒敏感等缺点；SC-FDE亦有调制信号能量、带宽管理不灵活等问题。正交信分复用（OSDM）是一种新兴的泛化调制框架，其引入“符号矢量”概念，使OFDM与SC-FDE被统一为此框架下的两个极端特例。因此，OSDM有望实现两大技术阵营的融合。然而，OSDM的数学模型明显区别于OFDM与SC-FDE，其信道干扰体现为矢量内码间干扰（ISI）与矢量间干扰（IVI），相关研究大部分尚属空白。鉴于此，本课题拟针对水声信道特点，研究并提出OSDM系统的部分FFT解调IVI抵消、逐矢量ISI均衡、相位旋转MIMO检测与核函数自适应非线性畸变补偿算法，并通过仿真、水池与湖海实验对关键技术进行验证。本课题研究成果有望为进一步推动水声通信物理层技术的发展提供理论基础与有效方法。

目前水声通信物理层使用较为广泛的两大主流调制技术多载波正交频分复用（OFDM）和单载波频域均衡（SC-FDE）虽各自具有一定的优势，但也都存在局限性。为此，本项目对新兴泛化调制框架正交信分复用（OSDM）技术与其对应的接收信号处理方法进行了研究。具体而言，本项目首先构建了OSDM时变水声通信系统模型，随后重点对OSDM矢量间干扰（IVI）建模与抵消、OSDM矢量内码间干扰（ISI）的低复杂度均衡、多输入多输出（MIMO）OSDM水声通信系统进行了研究，提出了基于特征分解的差分调制部分FFT解调水声通信方法、基于时域过采样的OSDM水声通信方法、基于迭代检测的时变信道接收方法、基于基扩展模型的时变信道接收方法、基于对角分块带状矩阵增强的OSDM均衡优化方法、联合信道冲激响应和多普勒估计方法，构建了空间分集、空间复用MIMO-OSDM水声通信系统。同时，本项目为了缓解功放等系统非线性对OSDM水声通信系统性能的影响，还开展了非线性自适应补偿方法的研究，可进一步提高水声通信链路的能量效率。此外，已通过数值仿真、水池与湖上试验对关键技术进行了验证。本项目的研究成果可为水声通信物理层技术的发展提供理论基础与有效方法，也可推广应用于水下无线网络建设，为实现我国信息化海洋开发提供强有力支撑。