【作者】 宋甲英；

【导师】 钟章队；

【作者基本信息】 北京交通大学 ， 通信与信息系统， 2012， 博士

【摘要】 随着人们对宽带无线通信需求的不断增长,无线Mesh网络正在逐渐成为实现宽带互联网接入的高性能、低成本的理想解决方案。无线Mesh网络是一种新型宽带无线网络结构,具有动态自组织、自配置、自愈的特点,便于快速部署,易于维护,成本低,可扩展性强,服务可靠。基于TDMA (Time Division Multiple Access,时分多址接入)的无线Mesh网络与基于CSMA/CA(Carrier Sensing Multiple Access/Collision Avoidance,载波监听冲突避免多址接入)的无线Mesh网络在MAC(Medium Access Control,媒体接入控制)层技术、拓扑感知、信息交互和分布式调度方面都存在较大差异,很多技术和结论无法共用。因此,本文研究基于IEEE802.16的无线Mesh网络关键性能与资源调度算法中存在的若干问题。传统无线Mesh网络性能分析没有考虑基于TDMA的网络中控制时隙与总时隙比例太大或太小都会降低网络吞吐量以及网络中转发业务与新业务并存的特性。在定量分析基于TDMA的无线Mesh网络中控制时隙数目对节点碰撞概率影响的基础上,进一步分析节点密度、传输速率、传输距离、跳数、控制时隙与总时隙比等因素与有效吞吐量的关系,并通过仿真寻找理想的控制时隙与总时隙比。同时,考虑网络中不同位置的节点对网络连通性的影响不同,定量分析节点传输距离与网络连通性的关系。现有的IEEE802.16协议Mesh规范中定义的分布式传输调度算法存在控制时隙利用率低和三次握手时延高的缺点,且没有定义详细的链路调度算法。提出一种基于IEEE802.16的无线Mesh网络传输调度算法——随机自学习传输调度算法,有效克服上述两个缺点。同时,由于基于TDMA的无线Mesh网络需要支持实时业务传输,提出一种基于IEEE802.16的无线Mesh网络启发式链路调度算法——分布式端到端链路调度算法,通过有效结合路由发现过程和链路端到端传输时隙调度过程以及连续的时隙预约机制,有效降低实时业务的端到端时延。并在此基础上对端到端时延进行定量分析。现有的IEEE802.16协议Mesh规范中没有定义无线Mesh网络切换管理算法,但基于IEEE802.16的骨干无线Mesh网络要为不同业务提供不同优先级的服务。借鉴协作传输的优点,提出基于IEEE802.16的骨干无线Mesh网络预切换协作算法,利用空闲Mesh路由器和关联Mesh路由器之间的协作传输降低Mesh客户机在切换过程中的误码率。同时,提出基于IEEE802.16的骨干无线Mesh网络带QoS保障的Mesh路由器选择算法,综合考虑RSSI (Receive Signal Strength Indicator,接收信号强度指示)、业务优先级和节点的带宽需求等因素选择合适的Mesh路由器,有效降低总阻塞业务量。更多还原

【Abstract】 Wireless mesh networks are currently emerging as an efficient and promising solution for low-cost broadband Internet access. Wireless mesh networks are characterized by dynamic self-organization, self-configuration and self-healing to enable quick deployment, easy maintenance, low cost, high scalability and reliable services. Time Division Multiple Access-based (TDMA-based) wireless mesh networks and Carrier Sensing Multiple Access/Collision Avoidance-based (CSMA/CA-based) wireless mesh networks differ significantly in Medium Access Control (MAC) layer technology, topology awareness, information exchange and distributed scheduling scheme, so they cannot use same technologies. This thesis studies some theoretical and technical problems in performance analysis and resource schedule.In traditional performance analysis for wireless mesh networks, the ratio of control slots number to total slots number and coexisting of relay traffic and forwarding traffic are not considered. The relation between the collision probability and the ratio of control slots number to total slots number is derived. Further derivation leads to the relationship between the available capacity and node density, transmission rate, transmission range, hop counts, and the ratio of control slots number to total slots number. Simulation results show the optimal ratio of control slots number to total slots number. Moreover, the transmission range that achieves100%connectivity probability is formulated.The transmission scheduling scheme specified in the mesh mode of IEEE802.16protocol has two disadvantages, low control slots utilization ratio and high three-way handshake delay. A transmission scheduling scheme, randomized self-learning transmission scheduling scheme is proposed for IEEE802.16-based wireless mesh networks to overcome these two weaknesses. Meanwhile, because the IEEE802.16protocol lacks link scheduling scheme and TDMA-based wireless mesh networks should support real-time traffic transmission, a heuristic distributed end-to-end link scheduling scheme is presented. The scheme utilizes hop-aware route discovery and sequential slots reservation scheme to reduce the end-to-end delay for delay sensitive traffic. The end-to-end delay carried out by the scheme is formulated.The mesh mode of IEEE802.16protocol does not have the specification for handoff management scheme, and IEEE802.16-based backbone wireless mesh networks are expected to support various types of applications with diverse priorities. A pre-handoff cooperation scheme is proposed to increase the transmission reliability of roaming mesh client by the cooperation between the associated mesh router and the new routers. In addition, a QoS-aware mesh router selection scheme is presented to decrease the total blocking traffic by considering the RSSI (Receive Signal Strength Indicator), traffic priority and bandwidth requirements together.更多还原