【作者】 扈鹏；

【导师】 刘元安；

【作者基本信息】 北京邮电大学 ， 电磁场与微波技术， 2010， 博士

【摘要】 随遇计算是一种让人们随时随地都能获得信息服务的一种通信模式。移动Ad Hoc网络作为实现随遇计算的一种新型技术,通过节点之间的相互协作和无线多跳的方式完成网络通信。这种网络技术具有无中心、自组织、可快速展开的特点,并且运行时不依赖于基站一类的固定基础设施。因此Ad Hoc网络在军事和民用领域都具有广泛的应用前景并发挥着越来越重要的作用。本文对移动Ad Hoc网络的若干关键技术进行了研究。这些技术主要包括了单信道接入协议IEEE 802.11e EDCA、广播算法以及适用于Ad Hoc网络的发布订阅路由算法等。本文的主要研究贡献归纳如下：(1)提出了一种可以为无线多跳网络提供端到端时延保障的动态接入控制算法。该算法的设计思路是：首先为移动节点的各个接入等级提供估算从本节点到达目的节点传输时延的功能；随后为具有分布式特性的Ad Hoc网络提供估算分组在网络中传输时间的功能,然后根据分组在网络中的传输时间、端到端时延要求和本节点各个接入等级到达目的节点的传输时延来判断分组传输的快慢,由此移动节点灵活的调整分组的优先级。仿真结果表明与EDCA相比动态接入控制算法提供了端到端时延保障,与APHD算法相比该算法减小了端到端时延并提高了的吞吐量。(2)提出了一种适用于按需路由协议的动态广播算法。首先建立数学模型分析了广播中的额外覆盖面积问题和信道竞争问题,然后在此基础上提出了动态广播算法。该算法根据节点之间的相对距离信息和邻居节点的密度信息来决定控制分组的广播概率。通过动态调整控制分组的广播概率,该算法降低了冗余控制分组的转发概率,减少了网络中冗余信息的传输并减轻了网络中的信道竞争问题。仿真结果表明动态广播算法有效的减少了网络中的冗余控制分组,提高了数据分组递交率,减小了数据分组的端到端时延。(3)提出了一种适用于移动Ad Hoc网络的发布订阅路由算法—PSRBSC。该算法的主要设计思想是：根据发布者发出的Publisher Query分组和订阅者回应的Subsciber Reply分组建立网格类型的多播转发结构,然后在网络层实现基于内容的路由机制和订阅覆盖策略。基于内容的路由机制可以为网络中传送的事件分组提供过滤,滤除那些订阅者不感兴趣的事件。订阅覆盖策略能够提高这种路由机制的效率,进二步的减少订阅者不感兴趣的事件在网络中的传输。仿真结果表明该算法降低了事件传输时延并提高了订阅成功率。(4)首次将Gossip算法和移动Ad Hoc网络的发布订阅路由算法相结合,提出了改善发布订阅系统订阅成功率的PSRBSC+GA算法。在该算法中,网络中的订阅者和发布者会缓存接收到事件信息,订阅者向网络发送GS(Gossip Subscription)分组来传送订阅,具有匹配事件的移动节点将产生GE(Gossip Event)分组并传送给订阅者,从而使订阅者收到更多的匹配事件以提高订阅成功率。仿真结果表明该算法有效的提高了Ad Hoc网络发布订阅系统的订阅成功率。(5)最后,本文针对发布订阅系统做了一部分的外延工作,为有线网络中的发布订阅系统设计了一种应用层多播路由协议。该协议中,每一个发布者、订阅者都会加入到多播组中并形成一颗多播共享树。订阅者发送的订阅将被传送到多播共享树中的每一个节点,而发布者发布的事件将在多播共享树中进行有选择的传输。实验结果表明该协议能有效的减小事件的传输时延。更多还原

【Abstract】 Ubiquitous computing is a communication mode which can provide information services anywhere and anytime.The mobile ad hoc network is a new important technology to realize ubiquitous computing, in which the communication between nodes relies on mutual cooperation in the manner of wireless multi-hop.This technology has the characteristics such as self organized, fast deployment and independent of infrastructure, which make it have wide prospects in both the fields of civilian and military. Therefore this type of networking plays a more important role in many aspects of people’s daily life and military applications.Under this background, this dissertation carries out deep researches in several important techniques of mobile ad hoc network, which include the mechanism of IEEE 802.11e EDCA, broadcast algorithm and publish subscribe routing algorithm for ad hoc network. The main contributions of this dissertation are as follows:(1)This dissertation proposes a dynamic access control algorithm which can provide end to end delay assurance in multihop wireless network. The design idea of this algorithm is:Individual node estimates the transmitting delay from itself to every destination for each access categories; This algorithm provides the function of estimating the transmitting time of each packet in MAC layer. By subtracting end to end delay requirement from the packet transmitting time, the remaining time of this packet is obtained; An intermediate node will compare the packet’s remaining time and each access categories’transmitting delay when it receives a packet.Then the node adjusts packets’priority. The simulation results show that:compared with EDCA, this algorithm achieving the end to end delay assurance;compared with APHD, this algorithm improves the network throughput and transimting delay.(2) This dissertation proposes a dynamic broadcasting algorithm. Firstly, a mathematic model is proposed by which the contention problems and additional coverage area are analyzed.Inspired by these analysis results,a dynamic broadcasting algorithm for on-demand routing protocol is proposed, which computes the broadcast probability of control message by neighbor node density and relative distance.By dynamically adjusting the broadcast probability, the redundant control message is reduced and the contention problem is alleviated.The simulation results show that:by applying this algorithm to on demand routing protocol,control messages’overhead is reduced, the packet delivery ratio is improved and the end to end delay is decreased.(3)This dissertation put forwards a publish subscribe routing algorithm for the ad hoc network. The design idea of this algorithm is:a).Construct the forwarding mesh topology through publisher query packet originated by publisher and subscriber reply packet from subscriber.b).Implement the content based routing strategy and subscription cover strategy in network layer. Content based routing strategy can filter unnecessary events which are not subscribed by subscribers.Subscription cover strategy will improve this routing strategy and further reduce the transmission of unnecessary events. The simulation results indicate that:PSRBSC can reduce the total cost of the network, improve subscription rate and average routing delay for events.(4) Based on our research of PSRBSC, this dissertation integrates the gossip algorithm and publish subscribe routing algorithm for ad hoc network. A new algorithm is proposed, which can improve subscription rate for publish subscribe system. In this algorithm, the publishers and subscribers will buffer the events received from network. The subscribers will send Gossip Subscription packets to subscribe and the mobile nodes will response Gossip Event packets to subscriber if it buffered the corresponding events.The simulation results show that this algorithm improves subscription rate effectively.(5) Finally, some extened researches for publish subscribe system in wired network are carried out.An application level multicast routing protocol for publish subscribe system is proposed. Every publisher and subscriber will join the session group and construct a shared multicast tree.The subscriptions generated by subscribers will be delivered to every node of the multicast tree and the events generated by publishers will be selectively transfered on the multicast tree.Experiment results show that this protocol can effectively reduce the routing delay for events’transmission.更多还原