基于OCDM的动态信道环境下变速率水声通信研究

水声信道具时频双选性，信道容量随时空显著变化，研究环境自适应的变速率通信具重要意义。面临主要问题有二：一是现有水声通信调制方式难以实现谱效与鲁棒性的平滑置换，通信机的信道适应能力受限；二是水声信道时变快而传播时延大，信道反馈信息易“过时”。针对问题一，本项目创新性地运用OCDM（正交Chirp复用）调制技术，通过调节激活Chirp的数量实现谱效-鲁棒性的灵活置换。 针对问题二，本项目创新性地基于多尺度视角分析信道，在大尺度时间内预测信道统计参数，实现大传播延迟下部分信道信息的有效反馈。主研内容包括：符号级快变信道估计与均衡、大尺度时间内信道统计参数的预测、系统信息可达率最大化的功率分配（含Chirp激活）。解决以下关键问题：1）水声信道不同路径多普勒因子的高分辨求解; 2）信道统计参数预测模型建模; 3）双选信道下OCDM信息可达率。成果有望为信道环境自适应变速率水声通信提供理论支撑。

UWA (Underwater Acoustic) channel is doubly selective in time and frequency domain, and its communication capacity changes significantly over time and space. It is of great significance to study channel adaptive communications with variable rate. There are two main problems: First, the existing UWA modulation methods cannot achieve smooth trade-off between spectral efficiency and robustness. Thus the adaptability of the transceivers is limited. Second, the channel feedback information is easy to be outdated, because of the fast varying channel and the large propagation delay. For the first problem, we adopt a novel modulation technology , OCDM (Orthogonal Chirp Multiplexing) , to achieve flexible trade-off between spectral efficiency and robustness, by adjusting the number of activated Chirps. For the second problem, we analyze the channel in different time scales, predict the channel statistical parameters in large time scale, and realize effective feedback of partial channel information under large propagation delays. The main research contents of the project include: estimation and equalization of fast-varying UWA Channel , channel statistical parameter prediction in large time scale, and power allocation (including Chirp activation) to maximize the achievable rate. Solve the following scientific issues: 1) the high-resolution solution of Doppler factors for different paths of the UWA Channel; 2) the prediction models of channel statistical parameter; 3) the achievable rate of OCDM under doubly selective channels. The results are expected to provide theoretical support for channel adaptive UWA communications with variable-rate.