【作者】 吕品；

【导师】 徐明； 王旭东；

【作者基本信息】 国防科学技术大学 ， 计算机科学与技术， 2012， 博士

【摘要】 无线Mesh网络具有成本低廉、部署便捷、覆盖范围广、网络带宽高等显著优势，非常适合作为Internet”最后一公里”接入方案，已经受到了多国政府和运营商的重视，在实际中得到了越来越广泛的部署。然而，无线Mesh网络在实际部署过程中也面临着很多挑战性问题，如用户接入带宽难以保证、丢包率较高、移动用户通信容易中断等等。本文提出采用无线Mesh网络虚拟化的方案来克服这些问题。通过建立虚拟网络，无线Mesh网络虚拟化技术对用户屏蔽了底层物理网络的细节，使用户能够按需地获得服务。这对无线Mesh网络的进一步发展具有极为重要的意义。本文建立了无线Mesh网络虚拟化的理论框架，包括隔离式网络虚拟化、聚合式网络虚拟化和混合式网络虚拟化等三个方面，并分别以典型应用场景为出发点，从这三个方面对无线Mesh网络的虚拟化关键技术进行了研究。其中，在隔离式网络虚拟化方面，分别为单播服务和多播服务设计了资源分配机制以确保虚拟网络之间的隔离性，从而能够保证用户的服务质量；在聚合式网络虚拟化方面，设计了网络主导型关联机制，将多个无线Mesh接入点聚合抽象为统一的接入点，避免了用户因切换接入点而造成的通信中断；而混合式网络虚拟化则将上述两个方面的结合，虚拟网络之间的隔离性与异构物理网络的聚合性都需要考虑。本文主要研究内容和贡献包括以下几个方面。第一，提出了无线Mesh网虚拟接入网的概念并设计了相应的网络系统结构和虚拟接入网络映射算法。本文针对以无线Mesh网作为Internet接入网的应用场景，通过构建虚拟接入网络来满足用户的端到端带宽需求。为了实现这一目标，本文设计了基于OFDMA技术的双射频无线Mesh网节点、基于部分交叠信道的信道分配算法和相应的无线Mesh网络体系结构，能够确保虚拟网络之间相互隔离。本文还提出了基于贪心算法和遗传算法的虚拟接入网络映射算法，在网络中存在多个Internet网关且虚拟网络带宽总需求大于网络容量的条件下，使得物理网络资源得到了尽可能充分的利用。第二，提出了无线Mesh网中面向多播服务的虚拟网络映射算法。本文针对在无线Mesh网中运行面向多播服务的虚拟网络的需求，设计了基于机会主义重传的虚拟网络映射算法，能够在物理无线链路不可靠的条件下满足虚拟链路的传输可靠性要求。算法还通过适当的链路调度使每个多播虚拟网络的激活时间最小化，从而提高了物理网络资源的利用率。第三，提出了无线Mesh网网络主导型关联机制。本文针对移动客户机在接入无线Mesh网络时由于接入点发生切换而导致网络连接中断的问题，提出了网络主导型关联机制以实现移动客户机在无线Mesh网覆盖范围的无缝漫游。在这种机制下，整个无线Mesh网被虚拟为一个逻辑的接入点，客户机只与这个虚拟的接入点相关联而无需进行切换。网络主导型关联机制能够自适应地在客户机通信范围内的多个物理接入点中选择最佳的接入点为其提供报文转发服务，从而提高了网络吞吐率，降低了端到端传输时延和丢包率。第四，提出了基于无线Mesh网和电力线通信网的智能配电网通信框架与虚拟网络映射算法。本文针对智能配电网的通信需求，设计了结合无线Mesh网和电力线通信网的混合式通信框架。在此框架的基础上，为不同类型的业务分别建立虚拟网络并将其映射到异构的物理网络中，通过增加传输分集来保证实时业务的可靠性。映射算法在保证实时业务可靠性的基础上，使尽力而为型业务的吞吐率最大化。无线Mesh网络虚拟化理论的提出和关键技术的研究有助于解决无线Mesh网所面临的挑战性问题，对无线Mesh网络的发展将具有巨大的推动作用。更多还原

【Abstract】 Wirelessmeshnetwork(WMN)haslotsofobviousadvantagesincludinglowcost,convenien-t deployment, wide coverage, high throughput, etc. These advantages make WMN quite suitablefor last-mile Internet access. Governments and operators in many countries have paid attention toWMNs, and deployed increasingly more WMNs in practice. However, several challenging prob-lems emerge in actual deployments, such as a user cannot get guaranteed bandwidth, packet lossrate is relatively high, and a mobile user tends to suffer from link disruption. Wireless mesh net-work virtualization is adopted to overcome these problems. Though establishing virtual networks,wireless mesh network virtualization technologies shield details of substrate networks to users,and serve users on their demands. Therefore, the wireless mesh network virtualization has greatsignificance for the evolution of WMNs.A theoretical framework for wireless mesh network virtualization is established in this the-sis. The framework contains three aspects, i.e., separation, aggregation and hybrid wireless meshnetwork virtualization. Based on typical application scenarios, key techniques of wireless meshnetwork virtualization are studied from these three aspects. For separation wireless mesh net-work virtualization, resource allocation mechanisms are designed for both unicast and multicastservices to guarantee the isolation among virtual networks. For aggregation wireless mesh net-work virtualization, cooperation protocols are designed to abstract multiple physical devices intoa unified logical device. The hybrid wireless mesh network virtualization is the combination ofthe above-mentioned two aspects, in which both separation of virtual networks and aggregation ofheterogeneous physical networks should be considered. The main contents and contributions ofthis thesis are described as follows.First, the concept of virtual access network is firstly proposed, and the corresponding WM-N architecture and the virtual access network embedding algorithm are designed. Virtual accessnetworks are built to guarantee the end-to-end bandwidth requirements of users when a WMNis deployed as an access network for the Internet. In order to achieve this goal, OFDMA-baseddual-radio mesh node, partially overlapped channel-based channel assignment algorithm, and theWMN architecture are designed to insure the separation among the virtual access networks. Agreedy and genetic-based algorithm for virtual access network embedding is also represented inthis thesis. When multiple Internet gateways exist in the WMN and the total bandwidth require-ment of users exceeds the total capacity of these Internet gateways, the algorithm can enhance the utilization of the substrate network resources.Second, an algorithm for multicast service-oriented virtual network embedding in the WMNis proposed for the first time. Based on opportunistic rebroadcasting, the algorithm can satisfy thereliability requirements of virtual links under the condition that physical wireless links are lossy.According to appropriate scheduling, the algorithm also minimizes the activation time of eachvirtual network, which improves the utilization of substrate network resources.Third, a network-leading association scheme is firstly proposed. Movement of a station maytrigger its handoff between access points, which can incur interruption of network connection.Aiming at this problem, the network-leading association scheme is designed to achieve seamlessroaming of the moving station in the coverage of the WMN. With this scheme, the whole WMN isvirtualized as a single access point with which the station is associated, and no explicit handoff isneeded. Theschemecanadaptivelyselecttheoptimalmeshaccesspointwithinthecommunicationrange of the station to forward its packets, which improves the throughput and reduces end-to-endairtime and packet loss rate.Finally, WMN and powerline-based communication framework for smart grid communica-tions as well as algorithms for virtual network embedding is proposed for the first time. Accordingto communication requirements of smart grid, a hybrid framework combining both WMN andpowerline communication network is designed. Based on the framework, virtual networks areestablished for various types of services respectively, and are embedded onto the heterogeneoussubstrate networks. Reliability of realtime services is satisfied through transmission diversity en-hancement, while throughput of best-effort service is maximized.The theoretical framework and the key technologies of wireless mesh network virtualizationare conducive to solve challenging problems of WMNs. Thus, wireless mesh network virtualiza-tion is a powerful impetus WMNs.更多还原