【作者】 王玉明；

【导师】 杨宗凯；

【作者基本信息】 华中科技大学 ， 信息与通信工程， 2005， 博士

【摘要】 传统的局域网技术,被广泛应用于学校、企业、组织,仍然是现在最为普及的网络接入方式之一。此外,ADSL宽带技术也为家庭用户接入互联网提供了方便。随着无线技术的发展,人们对接入网络的便利性提出了更高的要求。无线局域网技术为小区域的移动提供了可能,被越来越多的人所采用。新兴的WiMAX技术更是支持城域范围的移动,被网络提供商和用户所看好。无论是传统的局域网、ADSL宽带,还是新兴的无线局域网和WiMAX技术,均为有基础设施的接入方式,它们存在的问题是,用户不能实现全局IP漫游,而且一旦基础设施毁坏,主机将失去所有连接。无线接入要真正普及,研究者必须面临以下几大挑战:网络为用户提供全局IP漫游的能力。用户能全局移动,并始终保持互联网连接; 其它用户始终能通过其永久不变的IP地址连接上相应的移动用户。网络应对突发紧急情况的能力。用户在突发紧急情况下,不会因为固定设施遭到破坏而失去一切联系,始终能跟身边的人保持通信。网络应对拓扑变化的快速路由能力。节点不断移动,导致拓扑频繁变化。发现链路断开后,用户能以较小的信令开销实现快速修复路由,减少丢包率。快速切换及服务质量保证的能力。用户频繁移动时,能实现快速切换,始终保持宽带互联网连接,并能在一定程度上保证用户服务质量。本文针对上述问题,对支持IP漫游的多跳接入方式进行研究,包括其组网设计及协议扩展、路由技术、快速切换及服务质量保证技术。本文的研究从这几个方面展开:(1)支持IP漫游的多跳接入组网设计及协议扩展; (2)边缘接入部分的多跳网络路由重建机制; (3)主干接入部分的资源预留快速无缝切换机制。这些工作得到国家自然科学基金“基于媒体传输特性的无线多媒体技术的研究”(No.60202005)和“基于Internet的交互式流媒体分发技术研究”(No.60302004)的资助。取得的研究成果包括如下几个方面:1. 提出了支持IP漫游的多跳接入组网设计及协议扩展。边缘接入部分采用多跳Ad hoc技术,主干接入部分采用分层移动IPv6技术。多跳网络提高了网络更多还原

【Abstract】 The traditional LAN technology is widely used in the campuses, enterprises andorganizations, and is still one of the most widespread access manner. Besides, ADSLalso makes it convenient for family users to access internet. With the developmentof wireless technology, people expect more convenient access to the internet. WLANis adopted by more and more people, because it allows users to move in a smallrange. Network providers and users are bullish for the rising WiMAX technologywhich allows users to move in a larger metropolitan-area. Whether the technologyof LAN, ADSL, WLAN or WiMAX, they are all based on a fixed infrastructure.The problem is, the mobile users cannot process global IP roaming, in addition, itwill lose all connections if the fixed infrastructures are broken down. Therefore, theresearchers must face the following challenges before the wireless access technology iswidely used:The ability of network to provide global IP roaming for users. Mobile user isallowed to move in a global range while keeping connected with the internet, andanyone can contact the user through a permanent IP address.The ability of network to deal with emergency. In some urgent situation, con-nections with the nearby persons can still survive after the fixed infrastructuresare broken down.The ability of network to route packets in changeful topology. The networktopology changes frequently because of the ?oating users. Once a broken linkoccurs, the mobile user can process a fast recovery with low signaling cost toreduce packet drop ratio.The ability of fast handover and QoS assurance. Under frequent movements,the mobile user can handle fast handovers while keeping broadband internetconnections all the time, and guarantee QoS in a way.To solve the above problems, this thesis addresses on the scheme of global IProaming multi-hop access manner, including its implementing framework and proto-col extension, routing, fast handover and QoS assurance. The content of this the-sis includes issues about: (1) multi-hop access framework and protocol extension; (2) route reconstruction for the edge multi-hop access networks; (3) fast seamlesshandover of backbone resource reservation. The works in this thesis have been sup-ported by the National Science Foundation of China “Investigation of Wireless Mul-timedia Techniques based on Multimedia Transmission Property”(No.60202005) and“Internet-based interactive streaming delivery technique”(No.60302004) respectively.The contributions of this thesis include:1. Proposing a global IP roaming multi-hop access framework and its protocol ex-tension. The new framework merges multi-hop Ad hoc into its edge part andHMIPv6 into its backbone part. The multi-hop networks improve toughness,expand coverage, thus reduces disposal cost, and broadband access is also sup-ported; while HMIPv6 reduces signaling cost and handover delay in the intra-domain handovers. The existed HMIPv6 protocol is extended to support theregistrations with the internet gateways. This makes it possible for the MNsin the same edge MANET to communicate with each other directly. Thus, ithelps to reduce the backbone transmission burden, and is also helpful for theMN to establish internet connections quickly and handover seamlessly betweengateways.2. Proposing a cache bypass and local recovery based route reconstruction scheme.In the edge part of the global IP roaming multi-hop access manner, a routereconstruction scheme is proposed to reduce the rerouting signaling cost, increasethe amount and timeliness of backup routes, and further reduce packet dropratio and latency. The MN listens in all frames including data packets androuting control signaling in its free time, and maintains a neighbor list and localroute cache, thus well reduces signaling cost brought by the periodical HELLOmessages, and gains more usable route information. Once the intermediate nodedetects a broken link, fast route discovery and local recovery will be achievedaccording to local route cache and neighbors’route caches, thus routing controlsignaling and packet drop ratio are well reduced.3. Proposing a fast seamless handover scheme for resource reservation in the ping-pong type of movement. In the backbone part of the global IP roaming multi-hop access manner, in order to reduce signaling cost and handover delay ofresource reservation, the typical ping-pong type of movement is studied, and afast seamless handover scheme is proposed under a hierarchical architecture. TheMN is allowed to keep the old reservation for some time and to retrieve it quicklywhen the MN returns soon. Based on the simulation results, it can be observedthat, by setting the Reservation Active Flag (RAF) and the o?ine Count DownTimer (CDT), the scheme significantly reduces QoS signaling cost and handoverdelay. This helps to reduce network transmission burden and service interruptionfor ping-pong mobile user.4. Proposing an optimizing policy for the o?ine count down timer in the fast seam-less handover scheme. The fast seamless handover scheme well reduces QoShandover signaling and delay in case of a ping-pong type of movement by keep-ing the old reservation before the CDT expires. Whereas, in order to improvenetwork utilization, and to reduce the waste of resources and the e?ect on the cellcapacity due to withholding resources, the CDT cannot be increased infinitelyand need to be optimized. A simple expression for CDT optimization is derivedbased on a poisson mobility model. According to the previous mobility charac-teristic, the MN can easily set the optimal CDT for the best cost performanceof resource reservation.更多还原