共查询到19条相似文献,搜索用时 173 毫秒
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基于XML-RPC技术的分布式教育资源库系统 总被引:5,自引:0,他引:5
针对目前教育资源分布分散,无法被有效地利用和共享等问题,提出了分布式教育资源库系统的设计思想,系统为多个分布式资源库节点建立统一的资源目录中心,采用XML-RPC技术解决资源目录中心和分布式资源库节点之间信息的同步问题,有效地实现了教育资源的共建共享。 相似文献
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时间同步算法作为无线传感器网络的支撑技术,成为近些年研究的一个热点。其中集中式时间同步算法一直以来被广泛研究,它依靠参考节点通过广播、泛洪或者多跳的方式达到全网时间同步,取得了良好的同步精度,但同时鲁棒性和可扩展性差。提出了一种分布式时间同步算法,通过融合全网节点的时间信息来达到时间同步,这种算法消除了网络拓扑变化和节点密度变化对集中式算法的影响。实验结果表明,针对典型的网络拓扑,分布式时间同步算法实现了全网时间同步,并且对于网络变化和节点数目变化具有鲁棒性。 相似文献
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自适应Ad hoc分布式互斥算法 总被引:1,自引:0,他引:1
Ad hoc网络的动态拓扑结构和节点自组织给分布式算法的实现带来了诸多困难.针对Ad hoc分布式互斥算法研究滞后的现状,提出了一种自适应的Ad hoc分布式算法ADMUTEX. ADMUTEX算法基于令牌查询方法,它采用Lamport逻辑时戳保证消息的时序性,避免了节点饿死.同时,它在消息复杂度与同步延迟之间作了折衷,而且它不需要节点了解系统的全局信息,能够适应Ad hoc网络的动态拓扑结构和节点频繁出入的情况.分析与仿真结果表明该算法具有较低的消息复杂度、小响应延迟和公平性. 相似文献
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时钟同步是分布式网络内各节点设备协同工作的重要前提,网络内许多任务的完成都需以时钟同步作为基础;为了实现分布式系统中高精度的时钟同步,文章在现有的时钟同步技术的基础上,设计了一种分布式时钟同步技术,以北斗卫星授时技术作为主同步机制,单向时钟同步技术作为辅助同步机制;即在正常情况下网络中的节点设备利用北斗卫星进行授时,而在无法顺利接收北斗授时信号的少数情况下,节点设备之间利用单向时钟同步技术完成时钟同步,两者结合共同实现不同情况下高精度的时钟同步;在LabVIEW编程环境下设计仿真程序对方案进行验证,结果表明,该方案可以实现分布式系统中的时钟同步,方案的可行性可以得到验证,然后通过进一步的误差分析可知,误差处在一个可接受的范围内. 相似文献
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《中国科学:信息科学(英文版)》2012,(4):805-814
In this paper,a beamforming (BF) based cooperation scheme with decode-and-forward (DF) protocol is proposed and its performance analysis is provided.Firstly,to solve the issue of carrier synchronization in distributed networks,a backward synchronization (B-Sync) method is introduced,where participating relays synchronize to the reference carrier broadcast by the destination and make signals superimposed coherently at the destination without any phase feedback.Then,based on B-sync,a cooperation scheme with DF protocol is proposed to carry out BF forwarding among relays.The outage probability of this scheme is derived and analyzed,which shows that the full diversity order can be achieved by the proposed scheme.Furthermore,symbol error probability (SEP) analysis is presented to evaluate the practical performance.Simulation results validate the analysis,and show that the proposed scheme outperforms other existing ones in terms of outage probability and SEP. 相似文献
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Mohsen Heydarian 《The Journal of supercomputing》2014,68(1):214-244
Developing new mathematical frameworks such as distributed dynamic routing algorithms for constructing optimal incremental paths from a node to another node is an important challenge in data communication networks. These new algorithms can model network resources optimally and increase network performances. A bundle of single routes in a current communication path, which starts from a source node and ends to a destination node, can consist of several successive nodes and links. The Incremental term emphasizes that the number of routes (links and nodes) in a current path can change so that achieving more data rate and optimal efficiency in the network. In this paper, our problem is to add/omit some routes consisting of some nodes and links to/from the current unicast path dynamically and optimally. We call this problem the Optimal Dynamic Distributed Unicast Routing (ODDUR) problem and it is a NP-complete problem. This problem can be formulated as a new type of Linear Programming Problem (LPP) for finding a minimum cost multichannel unicast path, which this path will minimize end-to-end delay and bandwidth consumption along the routes from the source node to the destination node. In this paper, at first a new mathematical framework will be constructed and then this framework will propose the new optimal dynamic distributed unicast routing algorithm for solving our LPP problem. This algorithm will compute an optimal solution for our LPP based on the simplex method and postoptimality computations and will reduce computations and consumed time. Simulation results will show that our new algorithm is more efficient than other available algorithms in terms of utilization of bandwidths and data rate. 相似文献
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Behrouz Maham Mérouane Debbah Are Hj?rungnes 《Frontiers of Computer Science in China》2009,3(2):263-271
Due to the limited energy supplies of nodes, in many applications like wireless sensor networks energy-efficiency is crucial
for extending the lifetime of these networks. We study the routing problem for multihop wireless ad hoc networks based on
cooperative transmission. The source node wants to transmit messages to a single destination. Other nodes in the network may
operate as relay nodes. In this paper, we propose a cooperative multihop routing for the purpose of power savings, constrained
on a required bit error rate (BER) at the destination. We derive analytical results for line and grid network topologies.
It is shown that energy savings of 100% are achievable in line and grid networks with a large number of nodes for BER = 10−4 constraint at the destination. 相似文献
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Given a source node and a set of destination nodes in a network, multicast routing problem is usually treated as Steiner tree problem. Unlike this well-known tree based routing model, multicast routing under multi-path model is to find a set of paths rooted at the source node such that in each path at most a fixed number of destination nodes can be designated to receive the data and every destination node must be designated in a path to receive the data. The cost of routing is the total costs of paths found. In this paper we study how to construct a multicast routing of minimal cost under multi-path model. We propose two approximation algorithms for this NP-complete problem with guaranteed performance ratios. 相似文献
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A simple fault-tolerant adaptive and minimal routing approach in 3-D meshes 总被引:4,自引:1,他引:3 下载免费PDF全文
吴杰 《计算机科学技术学报》2003,18(1):0-0
In this paper we propose a sufficient codition for minimal routing in 3-dimensional (3-D) meshes with faulty nodes,It is based on an early work of the author on minial routing in 2-dimensional(2-D) meshes,Unlike many traditional models that assume all the nodes know global fault distribution or just adjacent fault information,our approach is based on the concept of limited global fault information,First,we propose a fault model called faulty cube in which all faulty nodes in the system are contained in a set of faulty cubes.Fault information is then distributed to limited number of nodes while it is still sufficeint to support minimal routing.The limited fault information collcted at each node is represented by a vector caaled extended safety level.The extended safety level associated with a node can be used to determine the existence of a minimal path from this node to a given destination .Specifically,we study the existence of minimal paths at a given source node,limited distribution of fault information,minimal routing,and deadlock-free and livelock-free routing.our results show that any minimal routing that is partially adaptive can be applied in our model as long as the dstination node meets a certain conditon.We also propose a dynamic planar-adaptive routing scheme that offers better fault tolerance and adaptivity than the planar-adaptive routing scheme in 3-D meshes.Our approach is the first attempt to address adaptive and minimal routing is 3-D meshes with faulty nodes using limited fault information. 相似文献
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《Journal of Parallel and Distributed Computing》1993,17(3):259-265
A passive optical star is an ideal shared medium, from both fault tolerant and access synchronization points of view. The communication over an optical star merges to a single point in space and then broadcasts back to all the nodes. This circular symmetry facilitates the solution for two basic distributed synchronization problems, which are presented in this work: (i) the generation of a global event clock for synchronizing the nodes′operation, and (ii) distributed scheduling for accessing the shared passive medium, which is a hybrid (deterministic and random) technique. We present, prove, and analyze this hybrid scheduling algorithm, which is equivalent to a distributed queue, and, therefore, is also algorithmically fair. Furthermore, our solution has two additional properties: destination overflow prevention and destination fairness. The effective solution of these problems can be used for efficiently implementing a local area network based on a passive optical star. 相似文献
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为了提高多群多点广播中继网络系统的性能,提出一种改进的协作中继多点广播码分多址(CDMA)系统设计。该方案利用协作中继辅助的分布式波束形成 实现单天线基站多播,获得了较好的空间分集增益。在该系统中,多个基站利用多个中继节点向多个目的地的各个小组传播消息;利用CDMA技术来减少中继节点以及目的地节点的多址干扰(MAI)障碍,同时每个中继节点作为线性预编码波束合成器,可以在合适的代码空间重塑基站信号;对线性波束形成矩阵进行优化,使得中继节点的功率最小化,从而满足QoS在信号干扰噪声比方面的要求。系统性能仿真对比实验的结果表明,提出的改进方案明显优于传统的正交复用方案(FDMA / TDMA)。 相似文献
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本文提出了一种公平分配代价的组播路由算法 DFC_ DCMT- -分布式公平分配代价的延迟受限组播路由算法 ,该算法在优化 tree- cost的条件下 ,能够计算出满足延迟限制的、各目的节点公平负担网络代价的点到多点的组播路由树 .本文还给出一种近似算法 ,可减少节点间交换的信息量 ,同时在一般情况下仍保持各目的节点公平负担网络代价 . 相似文献
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无线传感器网络(WSN)路由中,节点未充分考虑路径剩余能量及链路状况进行的路由会造成网络中部分节点网络寿命减少,严重影响网络的生存时间。为此,将蚁群优化算法与非均匀分簇路由算法相结合,提出一种基于蚁群优化算法的无线传感器非均匀分簇路由算法。该算法首先利用考虑节点能量的优化非均匀分簇方法对节点进行分簇,然后以需要传输数据的节点为源节点,汇聚节点为目标节点,利用蚁群优化算法进行多路径搜索,搜索过程充分考虑了路径传输能耗、路径最小剩余能量、传输距离和跳数、所选链路的时延和带宽等因素,最后选出满足条件的多条最优路径,完成源目的节点间的信息传输。实验表明,该算法充分考虑路径传输能耗和路径最小剩余能量、传输跳数及传输距离,能有效延长无线传感器网络的生存期。 相似文献