一种基于QoS的空间延迟/中断容忍网络拥塞控制方法

为缓解网络拥塞对空间延迟/中断容忍网络产生的影响,该文提出一种基于QoS的网络拥塞控制算法。该算法包括接触拥塞判断和基于QoS的数据转发两种机制,分别从接触剩余可用容量和节点剩余存储空间两方面对每一段接触的拥塞程度进行预测,将接触划分为不同的拥塞等级。在计算路由时,以整段路径中所包含接触的最高拥塞等级为该路径的拥塞等级,并根据该拥塞等级发送不同优先级的数据。实验表明,基于QoS的拥塞控制算法可以提高低优先级数据的传递率并在节点存储空间不足时降低最高优先级数据的传递时延。     

延迟容忍网络中拥塞控制算法分析

先引入延迟容忍网络中拥塞控制的概念与基础知识,其中介绍了几种常用的拥塞检测方式和拥塞研究方向,然后重点介绍了3种拥塞控制算法的实现并在仿真平台下对这3种算法进行仿真分析,最后对延迟容忍网络中拥塞控制算法的发展前景进行了展望.     

节点状态感知的延迟容忍网络拥塞控制策略

为了有效提高延迟容忍网络中的数据传输效率,节点普遍采用多副本方式转发数据,然而此种方式将造成网络中冗余数据增多,导致网络拥塞.本文提出了一种带有节点状态感知的拥塞控制策略,根据运动过程中所获知的相关历史信息,节点以直接获取及间接推荐的方式准确地感知网络中各个节点的拥塞状态,进而以分布式的方式动态地为数据选择中继节点,达到更加合理地利用有限的网络资源的目的.结果表明所提出的拥塞控制能有效地改善数据成功投递概率和网络负载率.     

延迟/中断可容忍网络路由中的关键技术

容迟网络是一种受限网络,以频繁的间断性和高而可变的延迟为特点,在某段时间内可能不存在端到端的路径,使得数据传输受到限制。对路由算法的研究是解决这种网络中数据传输问题的关键。虽然已经有大量的路由算法被提出,但不同的算法的侧重点不一样,有必要对路由涉及到的关键问题和技术做分析研究和总结,以便于将来的研究,目的正是如此,分析了与延迟/中断容忍网络（DTN）路由相关的关键技术。     

延迟容忍网络中的路由算法研究

研究了延迟容忍网络的几种路由算法并通过仿真比较它们的性能。仿真结果表明已知的拓扑信息越多，算法表现越好。为在延迟容忍网下寻找合适的路由算法提供了参考数据。     

基于运动状态的延迟容忍网络受控传输路由算法

根据延迟容忍网络(Delay/Disruption Tolerant Networks,DTN)中节点移动特性,提出基于移动节点运动状态的延迟容忍网络受控传输路由协议。通过获取信息传输范围内各邻居节点的运动信息,筛选符合预期要求的节点作为中继节点进行消息转发。     

延迟容忍网络自适应差错控制方法

根据延迟容忍网络的时延较大、误码率较高等特点,在现有的传输控制层和MAC层差错控制的基础上改进,结合IEEE 802.11 DCF机制的特点,提出一种基于MAC层丢包率的自适应差错控制方案.该方案能有效改善延迟容忍网络的传输时延,满足对时延要求比较敏感的业务的要求.     

基于信誉的延迟容忍网络双重Spray and Wait增强方案

引入转发证据的概念,设计了节点行为观测协议,提出一种基于信誉的双重Spray and Wait增强方案。通过对原始协议直接传输阶段的建模,使得信誉门限的确定建立在概率计算的基础上。仿真结果表明,在自私节点存在的环境中,与原始方案相比,增强方案能够减少自私行为对网络的危害,提高网络性能。     

延迟容忍网络中能量有效的接触探测研究

在延迟容忍网络中,为了发现在其通信范围内的邻居节点,网络中的节点必须不断地探测周围的环境。这个接触探测过程极其耗费能量。如果网络中的节点探测太过频繁,会耗费很多能量,且使得网络能量的使用效率降低。另一方面,稀疏的探测可能导致节点失去和其它节点的接触,从而错失交换数据的机会。因此,在延迟容忍网络中能量效率和接触机会之间存在着一种折中的关系。为了研究这种折中关系,该文首先对基于随机路点模型(Random Way-Point model, RWP)的接触探测过程进行建模,得到恒定探测间隔下接触探测概率的表达式,并且证明在所有平均探测间隔相同的策略中,以恒定间隔探测的策略是最优的。其次,基于提出的理论模型,分析不同情况下能量效率和接触探测概率之间的折中。最后,通过仿真实验验证该理论模型的正确性。     

延迟容忍网络状态感知的路由策略研究

延迟容忍网络具有间歇连通的特点,这为数据传输提出了很大的挑战。目前的路由算法没有充分考虑节点的整个状态(位置、速度),该文提出了一种节点状态感知的路由策略SARM(Situation-Aware Routing Method)。SARM根据节点的状态估计它能把消息传送到汇聚节点的可能性,并把消息复制到那些比自身可能性大的节点上。该文根据消息的生存时间、剩余时间及复制次数提出了一种消息队列管理机制。仿真实验表明,SARM在不增加消息副本数量的情况下提高了传输成功率并降低了传输延迟。     

Congestion management techniques for disruption‐tolerant satellite networks

Delay and disruption‐tolerant networks are becoming an appealing solution for extending Internet boundaries toward challenged environments where end‐to‐end connectivity cannot be guaranteed. In particular, satellite networks can take advantage of a priori trajectory estimations of nodes to make efficient routing decisions. Despite this knowledge is already used in routing schemes such as contact graph routing, it might derive in congestion problems because of capacity overbooking of forthcoming connections (contacts). In this work, we initially extend contact graph routing to provide enhanced congestion mitigation capabilities by taking advantage of the local traffic information available at each node. However, since satellite networks data generation is generally managed by a mission operation center, a global view of the traffic can also be exploited to further improve the latter scheme. As a result, we present a novel strategy to avoid congestion in predictable delay‐ and disruption‐tolerant network systems by means of individual contact plans. Finally, we evaluate and compare the performance improvement of these mechanisms in a typical low Earth orbit satellite constellation.     

基于蚁群优化的高性能拥塞控制路由机制

为了有效地解决偏远地理区域通信网络存在的网络拥塞严重、数据成功传输率低、数据冗余率高以及网络整体性能不佳等问题,通过考虑网络节点运动区域性特点,基于蚁群优化机制,设计出一种新型的容延容断网络 (DTN) 拥塞控制路由优化算法。该算法结合蚁群优化机制中的信息素因子,在同一对源、目的网络节点之间进行多次数据信息传输操作。在数据信息传输方向上,获取各个网络节点的中转跳数平均值,评估各个网络节点的中转价值;参考蚁群优化机制中的启发值因子,将网络节点的中转价值与剩余存储容量相关联,构成网络节点作为中转节点的评定参数,选取评定参数最大的网络节点完成其中转任务。实验表明：该算法有效控制了网络拥塞,提高了数据成功传输率,降低了数据信息冗余率,使网络整体性能得到进一步优化。     

Local information-based congestion control scheme for space delay/disruption tolerant networks

Wireless Networks - The storage resources and communication opportunities in space delay/disruption tolerant networks (DTN) are usually very limited. Moreover, as the links in space DTN are often...     

Early detection and rejection probability‐based congestion control scheme for deep space networks

Deep Space Networks (DSNs) are a class of DTNs. In such networks, owing to limited radio range and node mobility, end‐to‐end paths between source and destination nodes are not available. Messages are relayed by store‐and‐forward strategy and may be buffered for long periods before being forwarded to the next hop. Therefore, the buffer of message carriers may overflow, and congestion follows. To address this issue, this paper proposes an early detection and rejection probability‐based congestion control algorithm, named ERBA, in which every intermediate node estimates rejection probability when a new message arrives and refuses to receive the message with the rejection probability, so as to avoid congestion. To validate its effectiveness, ERBA is merged into static routing (SR) and dynamic routing (DR). SR and DR are classical routing algorithms for DSNs. The simulation results show that when working with ERBA, the routing overhead of SR and DR decreases rapidly. However, the message delivery ratio also decreases. To deal with this problem, we propose a buffer‐compensation mechanism that effectively reduces the routing overhead for SR and DR without causing the reduction of the message delivery ratio.Copyright © 2014 John Wiley & Sons, Ltd.     

Caching algorithms for broadcasting and multicasting in disruption tolerant networks

In delay and disruption tolerant networks, the contacts among nodes are intermittent. Because of the importance of data access, providing efficient data access is the ultimate aim of analyzing and exploiting disruption tolerant networks. Caching is widely proved to be able to improve data access performance. In this paper, we consider caching schemes for broadcasting and multicasting to improve the performance of data access. First, we propose a caching algorithm for broadcasting, which selects the community central nodes as relays from both network structure perspective and social network perspective. Then, we accommodate the caching algorithm for multicasting by considering the data query pattern. Extensive trace‐driven simulations are conducted to investigate the essential difference between the caching algorithms for broadcasting and multicasting and evaluate the performance of these algorithms. Copyright © 2016 John Wiley & Sons, Ltd.     

Optimal mobility control with energy constraint in delay tolerant networks

Owing to the uncertainty of transmission opportunities between mobile nodes, the routing in delay tolerant networks (DTNs) exploits the mechanism of store‐carry‐and‐forward. In this routing mechanism, mobility plays an important role, and we need to control the mobility of nodes around the network to help with carrying messages from the source to the destination. This is a difficult problem because the nodes in the network may move arbitrarily and it is difficult for us to determine when the nodes should move faster to help the data transmission while considering the complicated energy consumption in such a network. At the same time, for most DTNs, the system energy is limited, and energy efficient algorithms are crucial to maximizing the message delivery probability while reducing the delivery cost. In this paper, we investigate the problem of energy efficient mobility speed control in epidemic routing of DTN. We model the message dissemination process under variable mobility speed by a continuous‐time Markov model. With this model, we then formulate the optimization problem of the optimal mobility control for epidemic routing and obtain the optimal policy from the solution of this optimization problem. Furthermore, extensive numerical results demonstrate that the proposed optimal policy significantly outperforms the static policy with constant speed, in terms of energy saving. Copyright © 2012 John Wiley & Sons, Ltd.     

基于社团结构的容迟传感器网络多副本数据传输策略研究

在社团结构网络模型下,建立社团间多副本数据转发策略的传输概率模型,提出一种基于社团结构的多副本数据传输(CMDD)策略。CMDD策略动态计算社团间移动节点的平均相遇间隔时间,并根据传输概率模型估算借助该社团分发副本可获得的成功传输概率。模拟实验表明,CMDD策略能以较低的传输延迟和较低的传输开销获得较高的数据传输成功率。