【作者】 许辉；

【导师】 吴诗其；

【作者基本信息】 电子科技大学 ， 通信与信息系统， 2008， 博士

【摘要】 在卫星通信中,宽带卫星通信的主要目标是为多媒体和高数据速率的Internet应用提供一种无所不在的通信方式。对于时延要求低以及具有广播/组播性质的高速数据业务(如大容量数据传输、多媒体广播、因特网宽带接入、卫星远程应用、多媒体双向互动等业务)来说,卫星具有极大的优越性。宽带卫星网络也称下一代卫星通信网络。宽带卫星通信网具有地面覆盖面广、承载业务种类多、可快速部署、带宽利用率较高、星上交换快捷、可提供一体化网络等特点,能满足不同用户的业务需求。发展宽带卫星系统已成为当前通信的新热点之一。Internet是当今发展最快的业务,各种网络技术都在向提供高质量IP(InternetProtocol)业务的方向发展,在大范围覆盖和长距离传输方面具有优势的卫星通信与IP技术的结合无疑是通信发展的一个重要方向。TCP(Transport Control Protocol)是Internet上应用的传输协议,它是为地面有线网络设计的,用于卫星信道时会出现长时延、较高的差错率、上/下行信道非对称等很多问题,需加以解决才能顺利工作。卫星网络固有的信道广播特性使得它很适合实现组播服务。随着在Internet上支持多媒体业务的发展,在LEO(LOW Earth Orbit)网络中需要提供服务质量(QoS-Qualityof Service)保证。组播传输和QoS路由是卫星网络可靠传输的关键技术。星间链路是卫星间的双向通信通路,采用星间链路可降低系统地面段的成本,又提高了空间段的灵活性。编队飞行中星间链路的设计是非常关键的,它直接影响整个系统的性能。编队飞行要实现可靠的数据传输,底层协议方案是核心。本文研究了宽带卫星IP通信网络的可靠传输技术,内容涵盖了传输层TCP拥塞控制策略,可靠组播传输技术和网络层QoS路由算法设计,物理层/链路层可靠数据传输方案设计等,取得了以下研究成果:1.提出了两种宽带卫星TCP解决方案:基于优先级的TCP和卫星智能TCP拥塞控制策略。仿真结果显示:在卫星IP网络中,可以使系统吞吐率性能得到显著提高,在混合网络连接环境中,它们对资源具有较好的公平共享性。2.提出一种基于Agent的宽带卫星网络可靠组播传输协议。该协议利用接收端Agent来实现卫星组播传输,采用分组级FEC和本地差错恢复纠正传播中的非相关错误和相关错误,利用优先级分组实现拥塞控制。解决了卫星网络中可靠组播传输的一些关键问题,同时具有较好的可扩展性。3.提出了一种LEO卫星网络分布式组播路由算法,仿真结果表明该算法具有较短的端到端时延,生成的组播树长度较短,并维持较低的网络开销。4.提出了一种基于启发式蚂蚁算法的LEO卫星网络分布式QoS路由策略,提出了新的信道预留方案,在保证公平的前提下,实现切换优先。仿真结果显示该算法具有较低的呼叫阻塞概率,在网络负载较高时产生较低的开销。5.提出了用超宽带(UWB-Ultra WideBand)实现编队飞行可靠数据传输方案,给出了系统链路预算和星间定位方法,分析了一种采用MB(MultiBand)-UWB的星间链路方案的系统吞吐率。结果表明该方案具有可行性和较好的性能。更多还原

【Abstract】 In satellite communication, broadband satellite communication is focused on providing ubiquitous communication mode for multimedia and high bit rates Internet application. The satellites have very great advantage for that high speed data services with low time delay requirement and broadcast/multicast character (for example, the large pipe data transport, multimedia broadcast, broadband access of Internet, satellite remote application and bidirectional interactive multimedia, and so on). The broadband satellite networks could be named next generation satellite networks. They have traits as wide area coverage, bearing many kinds of application, deploying quickly, high bandwidth utilization, fast on-board switching and providing integrative network, etc. Developing the broadband satellite systems has become one of the new communication hotspots.Internet grows very fast; all kinds of network technologies develop to provide high quality IP service. Satellite systems have the inherent advantages of wide area coverage, and long distance transmission; so it is the important direction of communication development that combining with satellite and IP technology.TCP is the transport protocol of Internet application. TCP is designed for terrestrial wire networks; in satellite environments, it will appear long time delay, high bit error rate, and forward/reverse channel asymmetric, and so on; so it should be solved and could work well.The satellite systems have inherent advantages of unique broadcast capability, and it is very fit for multicast service. Along with the development of multimedia service on internet, LEO networks need to guarantee QoS. The multicast and QoS routing are the key technologies of satellite networks reliable transport.ISL (Inter-Satellite Link) is the bidirectional communication thoroughfare between satellites. The adoption of ISL can reduce the system ground segment cost, and improve the agility of space segment. ISL design in formation flying is the key point, and influences the system performance directly. In order to realize the reliable data transmission in formation flying ISL, the protocol of low layer is the core.This dissertation mainly focuses on reliable transport technology in broadband satellite IP networks, which includes TCP congestion control strategy, reliable multicast transport technology, QoS routing algorithm design, and reliable data transmission scheme of physical/link layer. This dissertation has contributions as follows:1.Proposes two broadband satellite TCP solution schemes: based on priority satellite TCP and satellite intelligent TCP congestion control stategy. The simulation results indicate: these two schemes improve the system throughputs markedly, at the same time, achieve fair share of network resources in heterogeneous scenarios.2.Presents a reliable multicast transport protocol based on agent.The protocol realizes satellite multicast by using agent of receivers. Packet FEC and ARQ are used. The congestion control is implemented by different priorities packets. It solves some key problems of reliable transmission in satellite networks. Algorithm has expansibility.3.Proposes a distributed multicast routing algorithm for LEO networks.The simulation results indicate this algorithm can achieve shorter end-2-end delay and multicast tree length and keep lower cost.4.Brings forward a distribute QoS routing policy based on heuristic ant algorithm. It gives the guarantee-channel scheme that achieves high priority of handover under the fair condition. The simulation results indicate it has lower call blocking rates. The cost is lower under higher load.5.A study has made on a reliable transmission scheme that deploying UWB technology into formation flying. It gives the system link budgets and the method that how to positioning the satellites, analyzes system throughput of MB-UWB ISL scheme.The results indicate the scheme has feasibility and good performance.更多还原