水下异步全速率协作通信关键技术研究

Cooperative Communication techniques can provide MIMO diversity to the nodes with single antenna in the multi-user communication network environments, which will reduce the requirements of size and cost of the network nodes effectively and be attractive to the underwater applications that need a large amount of small and cheap nodes, for example, the underwater sensor networks. However, the current underwater cooperative communication techniques are based on the conventional synchronous cooperative mode, which brings several limitations to their efficiencies: (1) The source node has to transmit its data intermittently when the relays are half duplex, which reduces its transmission rates significantly; (2) Long synchronization time is needed due to the large delay in the underwater environment, which reduces the transmission efficiency greatly. To overcome these problems, key techniques of the underwater asynchronous full-rate cooperative communication is studied in this project, which includes the underwater asynchronous full-rate cooperative communication strategy, the diversity technique of asynchronous intercurrent signals, and the underwater distributed best relay selection and grouping. Because the source node can transmit data continuously in the full-rate cooperative mode, and the asynchronous cooperative mechanism can reduce the waiting time in the transmission, the asynchronous full-rate cooperative communication is expected to acheive higher transmission rates than the current underwater cooperative techniques. Since the studies of the underwater cooperative communication techniques are still in their early stages, our work is important to the developments of both underwater communication techniques and underwater acoustic network products of our country.

协作通信可以在多用户环境下用单天线实现MIMO的分集功能，能有效地降低网络节点对体积和成本的要求，在水下传感器网络等需要较多小型、廉价节点的水声应用中有着广阔的应用前景。但目前水下协作通信研究中普遍采用的传统同步协作模式存在以下不足：（1）中继节点半双工时源节点只能间歇地发送信息，降低了信息的传输速率；（2）同步协作机制在长时延的水下环境使用时同步时间长、传输效率低。为此，本项目将对异步的水下全速率协作通信技术进行研究，重点解决其中的异步全速率协作策略、异步信息的分集接收、中继节点的选择和分组等关键问题。全速率协作模式下源节点可以连续地发送信息，异步协作机制可以减少等待时间，因此异步的全速率协作将有望能有效地提高现有水下协作通信的传输速率。目前国内外在水下协作通信方面的研究刚起步，因此本项目对促进我国水声通信理论和技术的发展、研制具有自主知识产权的水声通信系统方面具有重要的意义。

我国海域辽阔，海洋资源丰富，随着水下资源开发和利用的深入，对水声通信和组网技术有着迫切的需求，但水声信道时-空-频变化、有限频带、强多途干扰、长时延、大多普勒频移和高噪声等特点使得水下通信和组网非常困难。协作通信可以在多用户环境下用单天线实现MIMO的分集功能，能有效地降低网络节点对体积和成本的要求，在水下传感器网络等应用中有着广阔的应用前景。本项目针对传统水下协作通信中同步协作模式的不足，围绕异步的水下全速率协作通信技术及其应用展开研究，主要研究成果包括：.1、在水声通信的物理层技术方面，提出了水下异步全速率协作通信方法、阴影Nakagami衰落信道中SWIPT协作通信系统性能分析方法、基于迭代的双选水声信道估计方法、基于PPM的抗多途水声通信方法、非连续子载波OFDM系统的最佳导频设计方法等，能有效提高水声通信物理层的性能，相关成果已发表和录用三大索引论文13篇，获发明专利授权3项，申请发明专利5项。.2、在水声网络的MAC层技术方面，针对水声信道时延长的特点，提出了一系列基于分布式发送时间规划的水声网络MAC协议，能有效提高水声网络的吞吐量，减少多节点传输的时延。相关成果已发表三大索引论文2篇，获发明专利授权1项，申请发明专利4项。.3、在水下探测方面，提出了水下信号、速度、加速度、波达方向等检测新方法，相关成果已发表三大索引论文2篇，获发明专利授权4项，申请发明专利10项。.4、在水下语音通信方面，提出了动态分配频谱的水下多用户语音通信方法、基于模型的多数据流语音增强方法、基于模型的麦克风阵列语音增强方法等，相关成果已发表和录用三大索引论文3篇，获发明专利授权1项，申请发明专利6项。. 本项目针对水声信道的特点，对水声通信的物理层和MAC层的若干问题进行了理论分析并提出新的解决方法，在此基础上还对水声探测和水下语音通信等应用技术进行了研究，其成果可以广泛用于水声点对点通信、水声监测网、水下语音通信网等多种应用中。