【作者】 束永安；

【导师】 洪佩琳；

【作者基本信息】 中国科学技术大学 ， 通信与信息系统， 2007， 博士

【摘要】 近年来，无线技术得到飞速发展，无线网络的应用日益普及。越来越多的人希望提供无处不在的、高质量的无线通信。对需要高带宽支持、有QoS保证的应用(如实时性较强的视频传输)的需求日益增长，有力地推动了无线接入网的技术变革。无线网状网(wireless mesh network，WMN)是一种新型的宽带无线网络架构，它由对等的骨干节点构成多跳环境，单跳无线链路距离较短，可以实现较高的带宽且对节点的发射功率要求不高，因而建设成本较低。由于WMN具备不同于传统无线网络的特点，该技术在鲁棒性、灵活组网、提高网络覆盖率、增加网络容量、减少前期投资等诸多方面都显现出很大的优势，尤其适合用于宽带无线接入骨干网。目前WMN在世界范围内迅速引起了学术界与工程界的关注，成为一项热点技术。可以肯定，WMN必将成为下一代因特网技术的重要组成部分。在WMN中，多信道分配策略、MAC协议以及路由协议是非常重要的研究课题。高效的信道分配策略能充分利用有限的信道资源，显著提高网络吞吐量；有效支持多跳数据包转发的MAC协议对提高WMN的性能至关重要；WMN路由协议的关键在于能够自适应WMN中常见的快速变化(如链路质量的变化)，迅速转发报文。本文着重研究WMN中MAC协议和路由协议，其主要内容包括：无线网状网介绍、支持无线网状网结构的IEEE 802系列协议、多信道分配策略、多信道MAC协议以及自适应路由策略。论文的主要研究工作和创新如下：第二章介绍和分析了可以构建覆盖不同范围无线网状网的IEEE 802系列协议。既包括了可用于建立城域网的IEEE 802.16协议，也包括了构建个域网状网的IEEE 802.15.5协议草案。重点讨论了无线局域网状网标准草案IEEE 802.11s。第三章介绍了有代表性的集中式信道分配策略和分布式信道分配策略。集中式信道分配策略需要先获得网络流量模型，扩展性差，不能自适应网络流量的变化。分布式信道分配策略虽然扩展性较好，但也存在信道依赖性等问题。第三章最后提出了基于干扰模型的多信道分配策略，仿真结果表明，该策略可以有效地降低整个网络的信道干扰，从而提高网络的吞吐量。第四章分析了一些典型的MAC协议。基于竞争的分布式单信道IEEE 802.11 DCF协议在激活的节点数目增加时，吞吐量会显著下降。2P协议的不足之处是主干链路使用同一信道，形成整个网络吞吐量的瓶颈。IEEE 802.11s草案提出的共同信道框架下单接口多信道MAC协议的性能受共同控制信道的制约。第四章设计了一种新的多信道无线网状网MAC协议Mesh—MAC，该协议通过有向天线构建WMN相邻骨干节点间的链路，使得WMN能覆盖较大的区域，并提高多个正交信道的空间复用度。为实现全网内可靠的数据转发，第四章提出了一种新的时间同步机制。通过仿真表明，与IEEE802.11及2P协议相比，Mesh—MAC协议在性能和效率上有着大幅度的提高。无线网状网的路由协议需要自适应快速多变的环境，如动态变化的流量以及快速多变的无线链路质量等。那些为有线网络所设计的传统路由协议，并不能很好处理无线网状网中常见的快速变化。第五章首先介绍了与无线网状网路由协议关联性较强的Ad hoc路由协议，然后分析了比较有代表性的无线网状网路由协议，最后提出了一种基于干扰模型的无线网状网自适应路由策略IBAR，通过选择具有最小干扰的路径，显著提高路由的效率。为适应动态变化的网络环境，IBAR定期对路由进行分布式自适应调整，在WMN网关节点进行负载均衡。为解决自适应路由策略引起的路由振荡，本文提出了行之有效的解决方法。通过仿真表明，与AODV和HWMP协议相比，IBAR能显著改善WMN吞吐量等性能。论文中提出的算法和机制经过了理论分析和计算机仿真的验证，可以用于无线网状网络中，对设计无线网状网MAC协议和路由协议也具有较高的参考价值。更多还原

【Abstract】 In recent years, with the tremendous development in wireless technology, wireless network has been widely applied. More and more people expect easy-to-access quality wireless communication. There is an increasing demand for services that need high bandwidth support and QoS guarantee, such as video transmission, which pushes forward the technical innovation of wireless access networks.Wireless mesh network (WMN) is a new broadband wireless network framework. It is a multi-hop network formed by peer-to-peer backbone nodes. Because of the short distance within one hop, nodes in WMN can transmit with lower power and higher bandwidth can be achieved, which reduce the cost. Because of its robustness, easy deploy, wider network coverage, larger network capacity, and lower early phrase investment, WMN is advanced to the traditional wireless networks. It is particularly suitable for broadband wireless access backbone networks. WMN has drawn the attentions form both the world of academy and the world of engineering, thus becoming a hot technology. WMN will definitely become an essential part of the Internet of the next generation.In WMN, multiple channel allocation strategies, MAC protocols, and routing protocols are very important issues. High effective channel allocation strategies can take full advantage of the limited channel resources and highly enhance the network throughput. The MAC protocol that effectively supports multi-hop data packets forwarding is crucial to enhance the performance of WMN. The key to WMN routing protocols is to automatically adapt to the frequent rapid changes in WMN and to quickly forward the packets.This dissertation focuses on the MAC protocols and routing protocols in WMN and includes the following parts: an introduction to WMN, IEEE802 series protocols, multiple channel allocation strategies, multiple MAC protocols, and self-adaptive routing strategies that support WMN structure. The research topics and contributions are as follows:In Chapter Two, I introduce and analyze the WMN IEEE802 series protocols that can cover different geographic ranges. These protocols consist of IEEE802.16 for constructing metropolitan area networks and IEEE802.15.5 for building personal area networks. The focus is on wireless local area network standard draft IEEE 802.11s.Chapter Three discusses the representative centralized channel allocation strategies and distributed channel allocation strategies. Centralized channel allocation strategies require the network traffic model in advance. They are of lower extension and can not self-adapt to network traffic changes. Although distributed channel allocation strategies have good extension, problems like channel dependence still exist. Therefore, a multiple channel allocation strategy based on interference model is proposed. The simulation results demonstrate that this strategy can effectively reduce channel interference in the whole network, and therefore enhance the network throughput.Chapter Four examines some typical MAC protocols and points out their weakness. When the number of active stations increases, the throughput performance of distributed single channel IEEE802.11DCF protocol based on contention deteriorates significantly. The disadvantage for 2P protocol is that the backbone links share a common channel, resulting in the bottleneck of the network throughput. The performance of the single interface multiple channel MAC protocol under common channel framework proposed in IEEE802.11s draft is restricted by the common control channel. A new multiple channel WMN MAC protocol MESH-MAC is designed. Forming links among neighboring backbone nodes by directional antennas, this protocol enables WMN to cover larger area and increases multiple orthogonal channel spatial reuse. To achieve reliable data forwarding, a new time synchronization mechanism is also proposed. The simulation results indicate that compared to IEEE 802.11 and 2P protocols, Mesh-MAC protocol is much better in performance and effectiveness.The routing protocol for WMN should self-adapt to the fast changing environments like dynamically changing traffic and fast changing wireless link quality. The traditional routing protocols designed for wired networks can not handle well the rapid changes in WMN.Chapter Five first introduces some Ad hoc routing protocols that are more closely related to WMN routing protocols, followed by analyzing some typical WMN routing protocols. The last part presents a WMN self-adaptive routing strategy based on interference model (IBAR). By selecting minimum interference route, it notably improves routing effectiveness. In order to adapt to the dynamically changing network environment, IBAR periodically adjusts the routes self-adaptively and balance the load in WMN gateway nodes. An effective method is proposed to solve the oscillation caused by self-adaptive routing strategy. By simulation, IBAR improves WMN throughput performance notably compared to AODV and HWMP protocols.The novel algorithms and mechanisms proposed in this dissertation have been theoretically explored and verified by computer simulations. They can be applied to the designing of WMN MAC and routing protocols.更多还原