移动Ad Hoc网络中支持协作通信的媒体访问控制跨层设计理论研究

Adopting cooperative communication in the physical layer of Mobile Ad Hoc Networks (MANET) to mitigate the channel fading requires the link-layer Media Access Control (MAC) to coordinate and manage the cooperation and support the multiple-access simultaneously. It is critical to take into account the statistical characteristics of the channel fading and the prosperities of cooperative communication, in the design and analysis of cooperative MAC. However, due to the complexity and randomness of the signal propagation and detection, this is difficult to achieve and has become the bottleneck in the study of cooperative MAC. In this project, we plan to investigate the statistical characteristics of the received Signal-to-Noise Ratio (SNR) and Packet-Error-Rate (PER) of cooperative communication in typical mobile fading channels. Then, the link-layer packet-level model is to be established, which can be incorporated into the mathematical description and fast simulation of MAC protocol readily. Thus, the bottleneck problem of combining the physical and link layers together may be solved, and the new cross-layer design approach will be explored. Furthermore, we plan to study a novel distributed, auto-adaptive "Hybrid-Cooperative MAC". Based on the packet-level model of cooperative communication and the cross-layer design approach, the theories and methods to reduce the protocol overhead, increase the channel utilization and improve the adaptability to the node movement and channel fading will be developed. The issues studied in this project are common and fundamental for self-organized, Ad Hoc communication networks. Particularly, the packet-level model for cooperative communication and the cross-layer design approach are novel and have not been reported in the literature. The achievements of the project will bridge the gap between the physical-layer communication systems and upper-layer protocols, and will be very useful for the further research and application of the mobile Ad Hoc networks.

移动Ad Hoc网络在物理层使用协作通信抵抗信道衰落，需要链路层媒体访问控制（MAC）进行协调管理，并支持多址接入。结合信道衰落和协作通信的统计特性，是协作MAC设计和分析的关键。但是，由于信号传播与接收的复杂性和随机性，这已成为协作MAC研究的难点和瓶颈。本项目拟研究典型移动衰落信道中协作通信的信噪比和误包率的统计规律，进而建立其链路层数据包级模型，可方便地加入到MAC协议的数学描述和快速仿真中，从而克服物理层难以与链路层结合的瓶颈，探索跨层设计的新方向。其次，研究分布式、自适应"混合型-协作MAC"，并基于数据包级模型，进行一体化跨层设计，研究降低协议开销、提高信道利用率、提高对节点移动和信道衰落的自适应性的理论与方法。该研究是自组织移动通信网的共性基础性问题，以协作通信数据包级模型和跨层设计为特色，架起物理层与上层网络协议之间的桥梁，对Ad Hoc网络的研究和应用有重要的学术价值。

协作通信能够有效抵抗信道衰落，提高频谱利用率和网络吞吐量，并降低能耗。在移动ad hoc网络（MONET）中需要链路层介质接入控制（MAC）协议来协调网络节点的多址接入，以便公平、高效地使用共享信道，同时建立并维护节点间的协作传输，实现协作通信。而且，有效的协作通信和MAC协议是建立在无线信道的衰落与干扰特性上。本项目针对无线网络协作MAC协议，开展基于物理层信道特性的跨层设计与性能分析，主要研究内容及实现的目标如下。（1）无线通信信道的空-时域测量与建模：得到了移动网络中宽带信道在频域的衰落相关性模型和多径传播空间随机散射模型。进而建立了数据包级信道模型，描述了无线网络中链路层信干（噪）比和误包率的随机过程，可用于上层网络协议的理论分析和快速仿真。以上工作为跨层设计提供了基础。（2）研究了ad hoc网络协作MAC协议。首先，提出了三种基于网络编码的协作传输方法，能够有效抵抗信道衰落，提高网络吞吐量。其次，针对无线传感器网络（WSN），提出了由节点簇和移动元素进行协作数据收集的新方法，包括MAC协议和多跳路由策略，可提高网络寿命并改善数据收集时延。（3）协作ad hoc网络容量分析。针对ad hoc和蜂窝网络，推导了多个随机协作节点下的网络容量的统计分布。对于MONET，分别对具有相关性和非相关性（独立）的节点移动模式，理论推导了网络吞吐量和平均时延，并证明了网络容量的边界。本项目共培养了1名博士生和8名硕士生，发表论文23篇，其中SCI论文7篇。在IEEE Globecom、ICC等通信技术领域重要国际会议做学术报告9次。本课题的开展为后续研究奠定了良好基础。基于无线信道特性的网络协议设计与优化，是实现移动网络高吞吐量、多业务支持、复杂环境下应用的重要途径。针对新的通信技术，例如FD-MIMO和Massive MIMO，需要深入研究其无线信道特性和模型，并对无线网络进行跨层设计。