LEO卫星IP网络组播路由算法

为了解决低轨(low earth orbit,LEO)卫星网络中需要快速高效组播路由协议的问题,提出一种新型LEO卫星IP网络组播路由算法。在分析建立LEO卫星网络拓扑模型的基础上,该算法利用LEO卫星网络的自身特点,采用分布式迭代的计算模式,生成基于源端的组播路由树,大幅度地降低了算法的计算复杂度。仿真结果表明:与传统的LEO卫星网络组播路由算法相比,该算法具有较低的计算复杂度,生成的组播路由树具有较小的开销。相比于传统MRA算法,该算法生成的组播树中源点到组播成员节点的平均延时大约为前者的90%。     

LEO卫星IP网络组播路由算法

为了解决低轨(lowearthorbit,LEO)卫星网络中需要快速高效组播路由协议的问题,提出了一种新型LEO卫星IP网络组播路由算法。在分析建立LEO卫星网络拓扑模型的基础上,该算法利用了LEO卫星网络的自身特点,采用分布式迭代的计算模式,生成基于源端的组播路由树,大幅度地降低了算法的计算复杂度。仿真结果表明,和传统的LEO卫星网络组播路由算法相比,该算法具有较低的计算复杂度,生成的组播路由树具有较小的开销。相比于传统MRA算法,该算法生成的组播树中源点到组播成员节点的平均延时大约为前者的90%。     

基于深度图强化学习的低轨卫星网络动态路由算法

为了解决高移动性导致卫星网络路由难以计算的问题,融合图神经网络和深度强化学习,提出一种基于深度图强化学习的低轨卫星网络动态路由算法。考虑卫星网络拓扑和卫星间链路的可用带宽、传播时延等约束,构建卫星网络状态,通过图神经网络对其进行表示学习;根据此状态的图神经网络表示,深度强化学习智能体选择相应的决策动作,使卫星网络长期平均吞吐量达到最大并保证平均时延最小。仿真结果表明,所提算法在保证较小时延的同时,还能提升卫星网络吞吐量和降低丢包率。此外,图神经网络强大的泛化能力使所提算法具有更好的抗毁性能。     

A multi-path routing algorithm of LEO satellite networks based on an improved ant colony system

Geography rectangle is used to reduce signaling overhead of the LEO satellite networks.Moreover,a multi-path routing algorithm based on an improved ant colony system （MPRA-AC） is proposed.Matrix indicating the importance of the link between satellites is introduced into MPRA-AC in order to find the optimal path more quickly.Simulation results show that MPRA-AC reduces the number of iterations to achieve a satisfactory solution.At the same time,the packet delivery ratio of LEO satellite networks when running MPRA-AC and DSR-LSN （dynamic source routing algorithm for LEO satellite networks） is compared.The packet delivery ratio is about 7.9％ lower when running DSR-LSN.Moreover,because of the mechanism of active load balancing of MPRA-AC,simulation results show that MPRA-AC outperforms DSR-LSN in link utilization when data packets are transmitted in the networks.     

卫星网络中基于蚁群优化的概率路由算法

为了提高空间信息传输的有效性和可靠性,针对传统蚁群优化(ant colony optimization,ACO)容易造成最优路径负载过重而发生拥塞的问题,提出了一种基于蚁群优化的概率路由算法(ant colony optimization based proba-bilistic routing algorithm,ACO-PRA).根据卫星网络拓扑动态周期时变的固有特点,将拓扑周期均匀分为若干个时间片,形成基于不同时间片的卫星网络拓扑连通图;根据网络拓扑连通图,将星间链路带宽和链路容量引入到目标函数中,建立时延最小的优化模型;根据蚁群算法的节点概率函数选择下一跳节点,进而找到一条能同时满足时延带宽和链路容量要求的最佳信号传输路径.仿真结果表明,提出的基于蚁群优化的概率路由算法不仅能够降低平均端到端时延和丢包率,而且能够有效地提高网络吞吐量、平衡网络负载.     

分布式星群网络中基于联系图的路由技术研究

随着卫星技术和通信技术的发展,由全功能大型卫星组成的卫星星座网络正逐渐被由大量微小型卫星组成的分布式自组织星群网络所替代.这种新型卫星网络架构给星间数据通信和路由带来了自组织、自适应能力方面的问题.本文从延迟容忍的角度考虑,提出利用卫星周期性运动的特点构建网络结构,建立联系图来计算和选择路由.针对异常情况,采用被动发现和重路由机制重构网络拓扑,并利用满消息和空消息的传递来避免拥塞和控制流量.使用OPNET搭建网络仿真场景,分析对比该方案的性能.实验结果表明:与Flood路由、Spray-and-wait路由、Random路由相比,本文提出的路由技术具有更高的抗毁性能,且在平均端到端时延上从2 377s降到16s,平均吞吐量上从1 696bit/s提高到2 895bit/s.     

A distributed routing and wavelength assignment algorithm for online multicast in all-optical WDM networks

Routing and wavelength assignment for online real-time multicast connection setup is a difficult task due to the dynamic change of availabilities of wavelengths on links and the consideration of wavelength conversion delay in WDM networks. This paper presents a distributed routing and wavelength assignment scheme for the setup of real-time multicast connections. It integrates routing and wavelength assignment as a single process, which greatly reduces the connection setup time. The proposed routing method is based on the Prim’s MST (Minimum Spanning Tree) algorithm and the K-restricted breadth-first search method, which can produce a sub-minimal cost tree under a given delay bound. The wave-length assignment uses the least-conversion and load balancing strategies. Simulation results show that the proposed algorithm is suitable for online multicast connection establishment in WDM networks. Biography: Huang Chuan-he(1963-), male, Associate professor, research direction: computer networks, distributed computing systems, quantum computation.     

具有星际链路的LEO/MEO卫星网络动态路由协议

针对具有星际链路的LEO/MEO卫星网络,设计了一种具有自主运行能力的卫星网络动态路由协议(SDRP).采用时间离散化的链路状态增量更新的虚拟拓扑路由算法,降低了网络开销.提出的多点转发节点选举算法,提高了路由收敛速度和网络资源利用率.仿真结果表明,卫星网络动态路由协议的路由收敛时间远小于网络稳态保持时间,路由收敛时间是OSPF的1/10,平均协议带宽占用率也大大小于OSPF,可以保证卫星网络的信息可靠传送.     

基于阶梯式拓扑结构的WSN半动态路由算法

针对全动态路由算法随着网络规模的增大其拓扑管理能耗剧增的不足,提出一种半动态路由算法.该算法创建了以簇为基本单元的阶梯式网络拓扑模型,根据无线信道传输模型确定簇的覆盖并建立簇到基站的多跳梯度场,在梯度场中采用有序、定向的数据传送方式,实现信息以链路最短的距离向基站汇聚,并在簇内创建了一套簇头轮转机制,以实现簇内能耗平衡.对该算法能耗的定量分析和具体场景的仿真结果表明,该算法大大减少了拓扑管理和数据传送过程中的通信能耗,尤其是随着网络规模的增大,与LEACH算法相比具有明显的节能效果.     

LEO卫星网络的重构与自恢复

针对使用星际链路ISL(intersatellitelinks)的LEO(lowearthorbiting)卫星系统,提出一种基于动态路由策略的网络重构与自恢复算法,通过该算法管理卫星能够尽可能快地检测出故障链路,并通过快速的、自主的测试可精确定位故障链路·重构网络拓扑,当故障链路恢复后,再在拓扑图中恢复该链路·通过在卫星网络上的仿真表明,具有实时性、精确性且可能不占用或只占用很少的额外带宽·     

Distributed multicast routing algorithm with dynamic performance in multimedia networks

The delay and DVBMT problem is known to be NP-complete. In this paper,an efficient distributed dynamic multicast routing algorithm was proposed to produce routing trees with delay and delay variation constraints. The proposed algorithm is fully distributed,and supports the dynamic reorganizing of the multicast tree in response to changes for the destination. Simulations demonstrate that our algorithm is better in terms of tree delay and routing success ratio as compared with other existing algorithms,and performs excellently in delay variation performance under lower time complexity,which ensures it to support the requirements of real-time multimedia communications more effectively.     

一种集成网络编码的低轨卫星网络多径路由方法

针对星际链路的时变性、不可靠性和间断性连接的特点使得在低轨卫星网络中应用多径路由技术产生报文乱序和报文丢失现象,提出一种集成网络编码的多径路由方法。理论分析表明,在同等多路径数目和报文丢失率条件下达到相等的报文投递率,该方法的传输性能优于传统的多径路由方法。通过扩展ns-2软件并进行仿真实验,比较2种方法在不同的多路径数目、冗余因子和链路报文丢失率条件下的报文投递性能,仿真结果验证了理论分析的正确性,表明采用该方法可显著提高多径路由传输的可靠性,节省星上通信资源并在一定报文丢失范围内提升多径路由的容错能力。     

A new approach to VC routing in ATM networks

A new ant-algorithm-based routing approach is proposed for the VC routing problem with considering the comprehensive effect between the resource utilization and the load balance in ATM networks. In the approach, the backup paths are calculated first, and then an ant algorithm based on the ability of ants to find the shortest path between their nest and the food source during their searching food, is constructed to optimize the VC global route. Simulation results show that the proposed approach can realize VC routing effectively according to the current traffic states in the networks and the user-specified delay requirements. Foundation item: Supported by Shanghai Post & Telecom Administration-SJTU Information and Telecom Joint Lab Project (1999-GR1-3) Biography: Li Sheng-hong (1971-), male, Postdoctor, research direction: intelligent technology application in broadband networks and statistical signal processing.     

A mesh based routing protocol in vehicular ad hoc networks

This paper studies a routing protocol used in the application of collecting real-time traffic information using mobile vehicles to monitor traffic status. The biggest challenge of vehicular ad hoc network routing protocol lies in the mismatch between the direction of moving vehicles and routed data. In order to deal with this mismatch, a mesh based routing protocol with a two-tier network architecture is proposed. By using mesh nodes deployed at intersections, data can be routed through an optimized path which can improve the delivery ratio and reduce the consumption of network resources. The simulation uses the mobility model processed from the GPS data of taxis running in Shanghai urban areas. The result shows that the proposed protocol outperforms the existing flooding protocol.     

DTNs中一种基于节点有效交互度和效用的节能路由算法

延迟容忍网络是一种通过节点机会通信的网络类型.由于该网络中节点不易预测的移动性模式和容易中断的连接,路由算法一直是DTNs中研究的重点.但是目前从节省能量消耗角度提出的路由算法较少.文章提出一种基于节点有效交互度和效用的节能路由策略.首先,从节点有效交互度出发来进行转发传输速率控制,在节能与转发成功率之间自适应调整.其次,从节点效用出发设置消息携带者转发概率,选择合适的节点进行消息转发,避免网络产生过多消息副本.再次,仿真实验结果显示,与其他路由算法相比,该文提出的算法在保障网络消息传递率的基础上可以降低约6%～15%节点能量消耗.     

一种新颖的多信道多接口无线Mesh网络的接入调度算法

无线Mesh网络信道接入调度问题是指在一个调度周期内为网络中每个节点在信道上分配时隙,在该时隙上节点可以向邻居发送控制信息,问题的目标是最小化调度周期长度.提出采用饱和度(staturation degree)的方法来研究这个问题,与现有方法关键不同之处是,饱和度算法的每一步不是对节点本身,而是对节点的邻居依次分配时隙.在第一步完成对网络中邻居最多的节点的分配后,调度周期的长度已逼近理论下界,从而在随后分配过程中可充分实现时隙的空间复用.同时也提出了该算法的分布式实现,并对算法性能进行了理论分析.仿真实验结果表明,算法在各种情况下实验结果均非常接近理论的下限.