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在Ad hoc网络中保证组播通信的可靠性要面对Ad hoc网络高误码率、带宽受限、节点能量有限和拓扑结构频繁变化等技术挑战。该文将协同的思想引入到组播丢失恢复设计中,设计了新的基于协同的可靠组播丢失恢复算法(CoreRM)。根据各个节点经历的不同丢失情况,通过自适应选择本地恢复、全局恢复或发送端恢复,分布式地处理整个网络的丢失恢复。CoreRM还设计了恢复路径缓存、NAK抑制机制,以及源路由数据包(SPM)发送机制来应对Ad hoc网络中的拓扑变化。性能分析和NS2的仿真实验表明相对于UDP和PGM可靠组播通信,CoreRM算法可以在网络吞吐量和丢失恢复延时方面有显著性能改善。 相似文献
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Ad hoc网络中的路由技术 总被引:6,自引:0,他引:6
Ad hoc网络是一些移动节点组成一个多跳的临时性无线自治系统,这种新型的通信网络具有动态变化的拓扑结构和分布控制的网络机制。文中针对Ad hoc网络作了简单的介绍并重点介绍了针对Ad hoc网络特性而提出的路由协议。 相似文献
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在Ad hoc网络(自组织网络)的路由建立过程中,由于AODV(Ad hoc按需距离矢量)路由采用洪泛方式转发RREQ(路由请求)消息会产生很多不必要的重传,很可能引发广播风暴而影响网络性能。文章提出了一种基于动态概率转发RREQ消息的改进方案,该方案根据邻居节点的个数选择不同的概率转发RREQ消息。仿真结果表明,在网络节点较多且网络比较稠密的情况下,改进方案能有效减少网络端到端时延,提高网络吞吐量和分组投递率。 相似文献
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该文主要研究了无线Ad hoc网络中节点失效的情况下,如何维护网络的连通性和拓扑的性能,并且尽可能地降低拓扑维护的开销。提出了基于最短路径树的拓扑维护算法。该算法在拓扑变化时首先触发失效节点的邻节点响应(即重新运行拓扑控制算法),在不增加额外通信开销的情况下,响应的节点根据相互发送的Hello分组来判断网络是否连通;如果不能确定网络是连通的,再触发失效节点的其它可达邻近节点响应。仿真研究表明,算法显著地减少了拓扑维护的开销,维护后的拓扑结构在功率有效性和功率扩展因子等方面也取得了好的性能。 相似文献
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Ad hoc网络是一种具有有限生存期的无基础设施网络。它具有动态网络拓扑、多跳通信、分布式结构、有限带宽和功率、抗毁坏、入侵性差等特点。文章围绕Ad hoc网络,从Ad hoc的发起开始,简要介绍了Ad hoc的应用方向,然后结合后3G(B3G),着重介绍了Ad hoc在B3G中所面临的挑战。 相似文献
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Ad hoc网络中的分簇算法 总被引:10,自引:0,他引:10
分簇算法是根据系统要求将节点组织成可管理的结构,它的好坏直接影响着Ad hoc网络的各种性能指标。本文阐述了Ad hoc网络的体系结构和存在的问题,介绍了与分簇算法相关的一些定义和分簇算法的目标。对Ad hoc网络中的分簇算法进行了详尽的分类和比较分析。 相似文献
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《Selected Areas in Communications, IEEE Journal on》2009,27(7):1297-1304
Traditionally, the performance of distributed algorithms has been measured in terms of time and message complexity.Message complexity concerns the number of messages transmitted over all the edges during the course of the algorithm. However, in energy-constrained ad hoc wireless networks (e.g., sensor networks), energy is a critical factor in measuring the efficiency of a distributed algorithm. Transmitting a message between two nodes has an associated cost (energy) and moreover this cost can depend on the two nodes (e.g., the distance between them among other things). Thus in addition to the time and message complexity, it is important to consider energy complexity that accounts for the total energy associated with the messages exchanged among the nodes in a distributed algorithm. This paper addresses the minimum spanning tree (MST) problem, a fundamental problem in distributed computing and communication networks. We study energy-efficient distributed algorithms for the Euclidean MST problem assuming random distribution of nodes. We show a non-trivial lower bound of ω(log n) on the energy complexity of any distributed MST algorithm. We then give an energy-optimal distributed algorithm that constructs an optimal MST with energy complexity O(log n) on average and O(log n log log n) with high probability. This is an improvement over the previous best known bound on the average energy complexity of ?(log2 n). Our energy-optimal algorithm exploits a novel property of the giant component of sparse random geometric graphs. All of the above results assume that nodes do not know their geometric coordinates. If the nodes know their own coordinates, then we give an algorithm with O(1) energy complexity (which is the best possible) that gives an O(1) approximation to the MST. 相似文献
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为了实现车载自组织网络中车辆节点之间信息传输的安全认证,该文设计了一种无证书聚合签名方案。提出的方案采用无证书密码体制,消除了复杂的证书维护成本,同时也解决了密钥托管问题。通过路侧单元生成的假名与周围节点进行通信,实现了车辆用户的条件隐私保护。在随机预言模型下,证明了方案满足自适应选择消息攻击下的存在性不可伪造。然后,分析了方案的实现效率,并模拟实现了车载自组网(VANET)环境中车流密度与消息验证的时间延迟之间的关系。结果表明,该方案满足消息的认证性、匿名性、不可伪造性和可追踪性等性质,并且通信效率高、消息验证的时延短,更适合于动态的车载自组织网络环境。 相似文献
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Iyengar S.S. Sharma M.B. Kashyap R.L. 《Signal Processing, IEEE Transactions on》1992,40(12):3012-3021
Communication issues and problems in information routing in distributed sensor networks (DSNs) are considered. Two important communication constraints, viz., the delay constraint and the reliability constraint, are identified, and their impact on information routing is discussed. It is shown that the maximum end-to-end delay in a network depends on the diameter of the network, and efficient distributed algorithms are presented to determine the diameter of asynchronous networks. A distributed algorithm that determines the diameter of an asynchronous tree network when an arbitrary node in the network initiates the algorithm is introduced. An efficient algorithm for determining the diameter when multiple nodes initiate the algorithm is presented. An algorithm to determine the diameter of arbitrary networks is presented, and its message complexity is shown. Effects of link/node failures on network delay are studied, and important network structure design criterion are discussed. The distributed, dynamic routing algorithms are reviewed, and their adaptation to DSN environments is discussed 相似文献
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公平、健壮和易于实现的分布式互斥算法对分布式系统保证数据一致性、逻辑一致性及时序一致性至关重要.除Lamport算法,RA算法和N0.63算法外,以前提出的分布式互斥算法都只是在节点数目与请求集大小存在一定关系时才是公平和对称的,在大多数情况下是不对称的.这些算法的同步时间,容错性能与消息复杂度之间存在着不可调和的矛盾,不能三者兼顾.本文提出了一种基于循环编码的互斥请求集产生算法,并在此基础上改进了已有的基于请求集的分布式互斥算法,使该算法在系统节点数为任意值时都能公平和对称地产生请求集.其消息复杂度较低,同步时间为T,节点容错能力达到N-1. 相似文献
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A Mutual Exclusion Algorithm for Ad Hoc Mobile Networks 总被引:2,自引:0,他引:2
A fault-tolerant distributed mutual exclusion algorithm that adjusts to node mobility is presented, along with proof of correctness and simulation results. The algorithm requires nodes to communicate with only their current neighbors, making it well-suited to the ad hoc environment. Experimental results indicate that adaptation to mobility can improve performance over that of similar non-adaptive algorithms when nodes are mobile. 相似文献
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张书奎 《微电子学与计算机》2007,24(3):45-48
针对无线移动Ad Hoc网络(Mobile Ad Hoc Network,MANET),采用一种基于随机化分布式QoS路由算法RBAD(Random-Based Distributed QoS Routing Algorithm),该算法依据信道条件和业务量优化分组在多条路径上的路由,及寻找路由和存储路由表的代价,通过对结点排序,达到实现网络平均时延和平均消息复杂度最小的目标。仿真结果表明该算法能够以较小的路由消息开销获得较高的路由成功率,此外,算法具有可扩展性,可以应用于较大规模的Ad Hoc网络。 相似文献
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Password authentication has been accepted as one of the commonly used solutions in network environment to protect resources from unauthorized access. The emerging mobile Ad hoc network, however, has called for new requirements for designing authentication schemes due to its dynamic nature and vulnerable-to-attack structure, which the traditional schemes overlooked, such as availability and strong security against off line guessing attacks in face of node compromise. In this paper, we propose a threshold password authentication scheme, which meets both availability and strong security requirements in the mobile Ad hoc networks. In our scheme, t out of n server nodes can jointly achieve mutual authentication with a registered user within only two rounds of message exchanges. Our scheme allows users to choose and change their memorable password without subjecting to guessing attacks. Moreover, there is no password table in the server nodes end, which is preferable since mobile nodes are usually memory-restricted devices. We also show that our scheme is efficient to be implemented in mobile devices. 相似文献