【作者】 张竹；

【导师】 郭庆；

【作者基本信息】 哈尔滨工业大学 ， 信息与通信工程， 2013， 博士

【摘要】 近年来，随着人们通信需求的日益增高，全球信息化、网络化成为了发展的必然趋势，通信网络也因此面临着巨大的变革。在地面通信网络已不能满足人们日益增长的多媒体通信需求的情况下，利用卫星接入互联网已经成为卫星通信发展的主要方向，也是未来空天地一体化网络的重要组成部分。利用IP/LEO卫星保证网络的全球覆盖，是未来移动通信更好地提供个人通信服务的坚实基础。IP/LEO卫星网络能够支持用户移动性的服务，使得用户可以在更大的地域范围内方便地进行通信，但是全IP卫星网络的特殊网络架构、卫星上受到限制的数据存储容量和数据处理能力，以及卫星网络中传输延迟增加等特点，均为IP/LEO卫星网络中移动性管理问题带来了严峻的挑战。移动IP协议是当前IP网络中的基础移动性管理协议，能够实现IP网络中的移动性需求，但其也有一些明显的不足。针对移动IP的不足之处，相继出现了很多从不同角度对其进行改进的算法，如提出分层的概念、增加预测算法、支持快速切换、加入寻呼机制及解决网络移动问题等。但是这些移动IP的优化算法运用在卫星网络中存在着网络结构不匹配，优化性能下降等缺陷。所以，在IP/LEO卫星网络中，分析其移动性管理问题并设计移动性管理算法将成为重要的研究课题。在归纳总结了国内外最新研究成果的基础之上，本论文以IP/LEO卫星网络为背景，针对其移动性管理中的位置管理、切换管理以及网络移动性技术三个方面进行了深入研究，并获得了一些新的研究结论。主要研究工作如下：第一，在分析了IP/LEO卫星网络中移动用户不同移动特性的基础上，提出了一种基于位置信息的双重位置区位置管理方法。通过采用卫星、地面站双重位置区的方式在保证卫星网络中低速运动用户低位置更新频率的基础上，进一步降低了高速以及在位置区边界往复运动用户的位置更新次数。算法引入的寻呼机制降低了网络中用户位置更新消息的负荷，同时在用户发起的位置更新消息中加入用户位置信息，网络在寻呼用户时首先在用户最近一次进行位置更新区域进行，从而增加了首次寻呼成功的概率。通过理论推导及仿真，证明了基于位置信息的双重位置区位置管理策略相对于其他方法在网络位置管理开销、寻呼开销上都有了明显的改进；进一步分析了地面站覆盖范围的选择与本策略性能的关系。第二，针对IP/LEO卫星网络由于传输延时大而造成的用户切换延时增加的问题，提出了基于位置信息的预测SIGMA切换优化方案。该方法利用传输层协议mSCTP多家乡的特点，允许用户在一个SCTP关联中加入两个IP地址，避免了用户进入新位置区后新IP地址需要经过家乡代理处注册才可使用所造成的传输时延。提出了IP/LEO卫星网络中基于位置信息的用户切换时刻预测算法，利用卫星网络的星历信息和用户的位置信息，预测用户需要进行链路切换的时刻，在节省SCTP关联信令的基础上，保证用户在切换发生的时刻准确地将SCTP关联中的备用IP地址设置为主地址从而完成切换过程。通过仿真证明，该方案相对于传统的SIGMA方案，在用户切换延时、丢包率性能上都有了明显的改进。第三，利用IP/LEO卫星网络的网络移动特性，提出了一种面向NEMO基本支持协议的卫星网络结构设计思想。卫星网络作为地面因特网络的子网，通过一个或多个卫星接入路由器与地面网络相连。详细分析了卫星作为通信对端以及卫星作为路由转发装置时，应用NEMO基本支持协议的路由过程，以及网络移动性用户通过移动卫星网络与地面网络通信时的两种路由方式。经过分析，此网络结构可以减少卫星网络对地面网络的依赖，从而更好的保证通信的连通性。仿真表明，在此网络结构下应用NEMO基本支持协议在信令开销、丢包率方面性能均表现更佳。更多还原

【Abstract】 In recent years, communication network as the information infrastructure hasundergone tremendous and profound changes with the rapid development of worldwidenetwork and information technology. Since the ground communication network cannotdemand the increasing demand for multimedia communication, satellites are used toaccess the Internet, which is main direction of the development of satellitecommunication and also is an important part of the air-space-ground integrated network.Guaranteeing the network global coverage by IP/LEO satellite is a solid foundation forproviding better personal communication services in future mobile communication.IP/LEO satellite network is capable of supporting users’ mobility services and providingwider region for users. But the special network architecture, the satellites’ limited datastorage capacity and data processing ability, and the longer transmission delay all havebrought severe challenge for mobility management in IP/LEO satellite network.Mobile IP protocol is the basic mobility management protocol which can achieve themobility need in IP network. But Mobile IP protocol also has some obvious deficiencies.Aimed at those deficiencies, there have been many improved algorithms such as thehierarchical concept, the prediction algorithm, supporting fast handover, adding pagingmechanism and so on. But while using in satellite network, these optimizationalgorithms of MIP need to face the mismatching of the network structure, the decline ofoptimization performance and some other problems. Therefore, analyzing the problemof mobility management and designing the suitable mobility management algorithm isan important research topic in IP/LEO satellite network.On the basis of analyzing ahd absorbing the latest research results both here andabroad, this paper focuses on the three aspects of mobility management which are thelocation management, handover and the network mobility technology in IP/LEOsatellite network, and several new conclusins are obtained. The main research works areas follows.First, after analyzing the different mobility of the mobile users in IP/LEO satellitenetwork, this paper persents a dual-location area location management method based onlocation information. By using both the satellite and ground location areas, the locationupdate frenquency of high-speed users and flip-flop users is declined on the basis ofkeeping the low location update frenquency of low-speed users in the network. Pagingscheme is added to decrease the location upadate messages in the network. At the sametime, by adding MN’s location information in the location update messages, the networkis able to paging the users within the area the users latest updated, and the successsprobability of first paging is increased. Through the theoretical analysis and simulation, the preformance of location information based dull-location area location managementtheod is proved to be lower in location management and paging cost compared withother strategies. The relationship between the ground sation coverage area and theperformance of the strategy is further discussed.Second, aiming at the problem of increasing handover time dely caused by the longtransimission delay in satellite network, a SIGMA handover prioritization scheme basedon location information is proposed in this paper. The characteristic of multi-homing oftransport layer protocol mSCTP is used in this method. Two IP adresses can be added inone SCTP association by the users. After access to the new router, the users can use theirnew IP adress first instead of registering the new IP adress at the home agent first. Andthe handover delay can be decreased. The prediction algorithm of users’ handover timebased on location information in IP/LEO satellite network is also proposed. In theprediction algorithm, the satellites’ ephemeris information and the users’ locationinformation are both used. The SCTP association set up signalling is saved and the usersalso can set the new IP adress as the primary adress during the handover time. Thesimulation proverd that the proposed scheme performance better in handover delay andpassage loss rate campared to the traditional SIGMA scheme.Third, a design idea of NEMO based satellite network structure based on thecharacteristic of network mobility of IP/LEO satellite. The satellite network whis act asthe subnet of the ground Internet network is connected to the ground network throughone or more satellite access routers. The routing processes of the satellite act as both thecorresponding node and the access router based on NEMO basic support protocol areanalysed. Two types of routings which make sure the network mobility users canconnect to the ground Internet network through satellite network are also analysed.Analysis shows that the network structure can reduce the dependence of the satellitenetwork on the ground network, the communication connectivity is also betterguaranteed. Simulation results show that applicating NEMO basic support protocal insuch network structure can get better performances in signalling cost and packet lossrate.更多还原