基于OPNET的LEO卫星网络协议仿真平台研究

在OPNET仿真环境下,通过对LEO卫星网络协议构架分析,合理简化协议体系结构,构建通用卫星节点模块,实现了LEO卫星网络协议仿真平台。该平台能够模拟无连接LEO卫星网络路由表的建立更新和数据包选路等过程,以及切换、长时延等一些卫星网络特性给其他协议带来的影响。最后通过对作者提出的一种路由算法进行仿真,验证了该仿真平台能够在一定精度上模拟LEO卫星网络环境。     

LEO卫星网QoS遗传算法路由协议

为了满足多媒体应用的QoS要求,卫星路由协议应该更有效地利用网络资源,提供更好的QoS保障。为此提出了一个基于遗传算法的LEO卫星网络QoS路由协议,称为遗传卫星路由协议（GSRP）。改进了新的操作函数,如适应度函数、终止函数,以及变异率和路由表。仿真结果表明,GSRP能够实现较少CBP和HBP的可靠的点对点时延约束,以及比传统的算法更有效的负载平衡。     

基于虚拟拓扑的低轨卫星路由切换算法仿真

针对低轨卫星网络中星地链路、星间链路的不断切换会造成路由重构,而星地路由重构时间过长将严重影响数据传输时延稳定性的问题,提出一种卫星路由切换算法.算法结合了卫星网络拓扑可预测性和地面电台动态性的特点,在动态路由计算的过程中加入静态可预测信息以降低动态路由的计算开销,并基于OPNET搭建了一个低轨卫星系统仿真平台来验证该协议.仿真结果表明,上述协议能有效的解决低轨卫星系统路由重构的问题,降低了丢包率,减少了系统端到端时延.     

LEO卫星网中基于地理位置的分布式动态路由算法的研究

LEO卫星网络中进行信息交换，首先要解决的就是星际链路网络上路由问题，而运行于地面网络的路由算法，在卫星网络中并不适用．将针对LEO卫星网络星际链路的特点进行深入研究，提出一种新型的符合LEO卫星网络拓扑高速变化等特点的基于地理位置的分布式动态路由算法，并构建地面网络对该算法和现在流行的路由算法的性能进行仿真验证和比较，证明我们提出的新型动态路由算法能适应LEO卫星网络环境，能够提供较好的通信质量，就有较短的通信时延．     

基于空间光链路的启发式低轨卫星网络路由算法

任何时间任何地点提供互联网络接入服务的需求使得卫星网络通信的研究不断深入.本文在充分考虑空间光链路及低轨卫星系统的特点,提出一个基于空间光链路的低轨宽带卫星通信系统.同时在路由算法中利用星座时变拓扑的可预测性,基于有限路径的启发式路径搜索策略,提出符合LEO卫星通信特点的QoS路由算法(QHRL).仿真结果证明算法在卫星网络整体性能基本不变的情况下有着良好的路由性能.     

面向LEO卫星网的轻量级按需QoS源路由算法

接入卫星切换、流量分布不均匀和星上处理能力受限等因素使LEO卫星网的QoS路由面临巨大挑战。提出了一种引入移动代理技术的轻量级按需QoS源路由算法。首先结合星际链路队列占用情况设计了星际链路可用指数;接着基于卫星网承载流量分布特点提出了卫星可用指数;综合星际链路和卫星可用指数给出了移动代理迁移策略、星际QoS路由及其重建算法。仿真结果表明,提出的路由算法信令开销低,时延抖动、新呼叫阻塞率和切换呼叫阻塞率等QoS性能明显优于传统路由算法。     

LEO/MEO卫星网络动态多径路由协议

针对LEO/MEO卫星网络的特点,提出了快速、自重构且支持多径的空间信息网络路由协议,并进行了仿真和性能分析。该协议不仅大大降低了端到端路由建立的时间,同时多径路由也为实现网络可靠性传输、负载均衡等提供了条件。     

一个Ad Hoc网络中的组合QoS路由协议

本文提出了一种新型的组合QoS路由协议:Hi-ACQoS-TORA。给出了分簇策略下的簇间簇内路由协议。在提案方式中,作者将蚁群算法应用于簇间路由,解决了满足时延、延迟抖动、线路带宽、分组丢失率和费用多个指标的簇内QoS路由,与DSDV、DSR、ZRP、TORA等协议比较分析了Hi-ACQoS-TORA的性能。     

一种AODV跨层优化方法及仿真测试分析

针对Ad Hoc网络中传统AODV协议不支持QoS的缺陷,提出了一种多约束QoS AODV跨层优化方法MQ-AODV（Multi-Constrained QoS AODV）。该方法采用跨层设计的思想,除以传统AODV协议的转发跳数作为路由选择判据之外,而且加入应用层的QoS需求信息和MAC层的多种QoS指标作为路由选择判据,并通过改进AODV路由表结构和路由查找算法,提高AODV路由协议性能。仿真测试结果表明MQ-AODV协议缩短了传输时延,增强了路由协议的适应性和鲁棒性。     

具有高效确认机制的双层卫星网络多径路由协议

针对资源受限的LEO卫星网络中传统单路径路由协议数据传输速率较低的问题,基于GEO/LEO双层卫星网络模型提出一种基于网络编码（NC）的双层卫星网络多径路由协议（N-NCMR）。首先,通过GEO卫星为LEO卫星网络计算路由减轻LEO卫星的负担,结合NC技术动态地沿着多个不相交路径传输数据流的不同部分;其次,设计了一种高效的延迟确认机制加速数据传输,源节点在接收到前一组的确认（ACK）消息之前可以连续发送后续的组。仿真结果表明,该路由协议显著提高了LEO卫星网络的吞吐量和数据传输效率。     

Routing for predictable Multi-Layered Satellite Networks

Multi-Layered Satellite Network (MLSN), especially LEO/MEO satellite network, consisting of low and medium earth orbit satellites, is capable of providing higher coverage and better service than single-layered one. Its performance in deployment, however, is mainly encumbered by obsolete routing protocols and algorithms. This paper takes the predictability of satellite movements into consideration, based on which a novel routing protocol Predictable Satellite Network Routing Protocol (PSNRP)—is proposed. In this protocol, every topology change due to satellite movement is either described as a predictable or an unpredictable change. On the basis of PSNRP, we import a heuristic routing algorithm for satisfying Quality-of-Service (QoS) requirements from network users, which is convinced as a Non-deterministic Polynomial Complete problem. The QoS requirements in this paper mainly refer to end-to-end delay, bandwidth and package loss rate. In addition to obtaining better routing performance, PSNRP successfully allocates calculation tasks evenly among all nodes, separates user data from protocol control data and achieves stronger robustness against satellite failures and link congestions. The superiority of our routing scheme is proved by simulation results.     

Packet routing algorithm for polar orbit LEO satellite constellation network

The proliferation of Internet motivates the need of integrating IP with Low Earth Orbit (LEO) satellite networks that are well known for their global coverage and their ability of providing services with different QoS specifications. There is no doubt tha…     

卫星移动通信网络切换算法的研究

低轨卫星移动通信网络在实现全球移动通信方面具有很大优势.切换方案对于控制低轨卫星网络通信时延,提高卫星网络服务质量和链路带宽资源利用率具有重要意义.深入分析了星地链路切换和重计算路由问题,提出了一种低轨移动通信卫星链路切换算法.仿真实验表明,提出的卫星链路切换算法有较小的端到端时延、较好的稳定性和可定制性.     

基于移动Agent的双层卫星网动态路由算法

新一代LEO/MEO卫星体系结构成为当今卫星网通信研究的热点。结合移动Agent技术解决卫星网动态路由问题,在LEO／MEO卫星网平台上构建了核心层功能,并较好地处理了受复杂的星际链路切换影响的数据包转发。在OPNET仿真软件下模拟了卫星节点受算法工作的影响,结果表明,卫星处理数据包时延在理想性上处理能力和合理的链路容量条件下是可以接受的,且数据包端到端时延是较小的。     

End-to-end support for statistical quality of service in heterogeneous mobile ad hoc networks

In heterogeneous mobile ad hoc networks (MANETs), different types of mobile devices with diverse capabilities may coexist in the same network. The heterogeneity of MANETs makes end-to-end support for quality of service (QoS) guarantees more difficult than in other types of networks, not to mention the limited bandwidth and frequent topology changes of these networks. Since QoS routing is the first step toward achieving end-to-end QoS guarantees in heterogeneous MANETs, we propose a QoS routing protocol for heterogeneous MANETs. The proposed protocol, called virtual grid architecture protocol (VGAP), uses a cross-layer approach in order to provide end-to-end statistical QoS guarantees. VGAP operates on a fixed virtual rectilinear architecture (virtual grid), which is obtained using location information obtained from global positioning system (GPS). The virtual grid consists of a few, but possibly more powerful, mobile nodes known as ClusterHeads (CHs) that are elected periodically. CHs discover multiple QoS routes on the virtual grid using an extended version of the open shortest path first (OSPF) routing protocol and an extended version of WFQ scheduling policy that takes into account the wireless channel state. Moreover, VGAP utilizes a simple power control algorithm at the physical layer that provides efficient energy savings in this heterogeneous setting. Simulation experiments show that VGAP has a good performance in terms of packet delivery ratio, end-to-end packet delay, call blocking probability, and network scalability.     

Performance analysis of multicast algorithms for mobile satellite communication networks

With the rise of mobile computing and an increasing need for ubiquitous high-speed data connections, Internet-in-the-sky solutions are becoming increasingly viable. To reduce the network overhead of one-to-many transmissions, the multicast protocol has been devised. The implementation of multicast in these low earth orbit (LEO) constellations is a critical component to achieving an omnipresent network environment. This paper examines the system performance associated with two terrestrial-based multicast mobility solutions, distance vector multicast routing protocol (DVMRP) with mobile IP and on demand multicast routing protocol (ODMRP). These protocols are implemented and simulated in a satellite LEO constellation. Results from the simulation trials show the ODMRP protocol provided greater than 99% reliability in packet deliverability, at the cost of more than 8 bits of overhead for every 1 bit of data for multicast groups with multiple sources. In contrast, DVMRP proved robust and scalable, with data-to-overhead ratios increasing logarithmically with membership levels. DVMRP also had less than 70 ms of average end-to-end delay, providing stable transmissions at high loading and membership levels.     

卫星网络基于信任的认证路由协议

安全路由协议是保障卫星网络安全运行的一个重要因素。针对现有卫星网络路由大多缺少安全机制的问题,运用基于椭圆曲线的签名方案保证路由报文的合法性,通过改进的信任评估机制排除内部恶意节点参加选路,设计了适用于高空通信平台(HAP)/低轨道(LEO)结构的层次式安全路由协议。分析表明该协议能够抵御多种常见的路由攻击。     

Topological dynamics characterization for LEO satellite networks

The highly topological dynamics characterizes the most fundamental property of satellite networks with respect to terrestrial ones. The manifest feature directs the researches on various aspects of satellite networks, including protocol architecture investigations, routing protocol and reliable transmission control protocol design and enhancement, etc. This paper systematically quantifies the dynamical activities of regular low earth orbit (LEO) satellite network topologies. The number and length of network snapshots are formulated concisely. With this work, it compensates for the simplified topological assumptions in many LEO satellite network related researches. The thorough understanding of this basic feature not only provides for an accurate quantification of network behavior for researchers on satellite network community, but also could act as a guidance for future satellite constellation design and optimization.