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复杂网络的网络结构与传播动力学都与网络的度分布有着一定的联系。所以,想要进行复杂网络的研究,首先就要进行复杂网络的度分布问题的研究。因此,基于这种认识,本文从复杂网络的结构和传播动力学与度分布指数的关系角度入手,对复杂网络的度分布问题进行了探讨。 相似文献
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基于校园网论坛评论的数据统计,从群体层面和个体层面深入挖掘学生用户在校园网论坛上活动行为的时间间隔分布的统计特性,以及给出学生群体兴趣度消失模型的实证研究.研究发现,论坛整体评论时间间隔以及用户个体活动时间隔服从幂律分布,学生群体兴趣度消失模型中,学生群体对于某个话题的兴趣逐渐消失,评论的时间间隔服从幂率分布,且对于比较敏感的话题,会存在兴趣再次上升的情况. 相似文献
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针对延迟容忍网络中节点运动状态变化频繁、通信路径不完整,使得转发消息仅能通过节点相遇而获得连接机会来完成,以及在不知节点间相关性的延迟容忍网络中盲目转发消息易导致其转发成功率较低等问题,提出了基于相遇紧密程度动态估测的延迟容忍网络路由策略。通过设计节点间的条件相遇时间间隔和连接持续时间的计算模型,来确定节点间关系的紧密程度;定义延迟容忍网络模型,构造最短路径择取机制,动态地选出条件最短路径,对消息进行转发。仿真数据对比显示,所提策略可有效改善网络性能,提高消息成功投递率,降低传输时延和负载率。 相似文献
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动态查询是无结构点对点(P2P)网络中经常采用的查询技术,该方法使用尽可能少的对等节点得到所需的查询结果。分布式哈希表是结构化P2P网络查询过程中采用的机制。近年来将非结构化查询和结构化查询结合起来提出了混合式P2P查询机制以此来提高查询性能。在结构化网络模型ML-Chord中加入了动态查询,同时根据文件的受欢迎程度调整查询范围,减少了网络负载,从而提高了查询效率。 相似文献
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网络论坛BBS是中国网民一个重要的信息传播渠道,而其中的热点话题自然就成为舆情调控和效果评估的首要目标。提出一个快速有效的用于挖掘网络论坛中热点话题并分析预测其发展态势的方法,利用统计的方法为同一版面下帖子的热度打分并排序,并使用相关的数学模型对热度较高的帖子的发展态势进行分析与预测。通过实验验证了该模型的可行性和有效性,为进一步研究复杂网络中热点话题的演化奠定了基础。 相似文献
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首先介绍了ASP的特点和利用ASP访问数据库的方法,其次设计了基于ASP技术的教育网站的BBS系统。该系统主要提供了网上交谈和网上留言板两个主要板块,实现了受教育者在不受时间和空间等条件的约束下,教育资源的最大共享和教育方法的重大突破。 相似文献
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Bang Wang Kee Chaing Chua Vikram Srinivasan Wei Wang 《Wireless Communications and Mobile Computing》2009,9(6):745-757
In this paper, we study the problem of scheduling sensor activity to cover a set of targets with known locations such that all targets can be monitored all the time and the network can operate as long as possible. A solution to this scheduling problem is to partition all sensors into some sensor covers such that each cover can monitor all targets and the covers are activated sequentially. In this paper, we propose to provide information coverage instead of the conventional sensing disk coverage for target. The notion of information coverage is based on estimation theory to exploit the collaborative nature of geographically distributed sensors. Due to the use of information coverage, a target that is not within the sensing disk of any single sensor can still be considered to be monitored (information covered) by the cooperation of more than one sensor. This change of the problem settings complicates the solutions compared to that by using a disk coverage model. We first define the target information coverage (TIC) problem and prove its NP‐completeness. We then propose a heuristic to approximately solve our problem. Simulation results show that our heuristic is better than an existing algorithm and is close to the upper bound when only the sensing disk coverage model is used. Furthermore, simulation results also show that the network lifetime can be significantly improved by using the notion of information coverage compared with that by using the conventional definition of sensing disk coverage. Copyright © 2008 John Wiley & Sons, Ltd. 相似文献
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分布式声探测无线网络时间同步算法研究 总被引:1,自引:0,他引:1
分布式声探测无线网络是一种基于声达时间差(TDOA)进行目标定位的无线传感器网络;而基于TDOA算法的分布式定位需要节点之间严格时间同步,本文正是对节点之间严格时间同步进行了重点研究.文中系统分析了分布式声探测无线网络的应用环境、工作机制和硬件平台,在此基础上提出节点之间的采样同步和全网同步问题,并基于后同步思想和分级同步机制,设计了分布式声探测无线网络节点同步的整体解决方案.该方案已经进行了组网测试,有效解决了分布式身探测的时间同步问题.本文对相关工程实践具有一定的指导意义. 相似文献
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Time synchronization is essential for several ad‐hoc network protocols and applications, such as TDMA scheduling and data aggregation. In this paper, we propose a time synchronization framework for clustered, multi‐hop sensor networks. We assume that relative node synchronization is sufficient, that is, consensus on one time value is not required. Our goal is to divide the network into connected synchronization regions (nodes within two‐hops) and perform inter‐regional synchronization in O(LLSync) × Niter time, where O(LLSync) denotes the complexity of the underlying low‐level synchronization technique (used for single‐hop synchronization), and Niter denotes the number of iterations where the low‐level synchronization protocol is invoked. Thus, our main objective is rapid convergence. We propose novel fully distributed protocols, SYNC‐IN and SYNC‐NET, for regional and network synchronization, respectively, and prove that Niter is O(1) for all protocols. Our framework does not require any special node capabilities (e.g., being global positioning systems (GPS)‐enabled), or the presence of reference nodes in the network. Our framework is also independent of the particular clustering, inter‐cluster routing, and low‐level synchronization protocols. We formulate a density model for analyzing inter‐regional synchronization, and evaluate our protocols via extensive simulations. Copyright © 2007 John Wiley & Sons, Ltd. 相似文献
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Ali F. Almutairi Awatef K. Ali Mehmet Hakan Karaata 《Wireless Communications and Mobile Computing》2005,5(2):209-217
In this paper, we propose a new Generalized Distribution‐Based Handover (DBHO) to deal with the inefficient utilization of spectral resources due to the non‐uniform cell loads. The DBHO scheme is different from the existing adaptive schemes since it uses a new criterion to initiate handover when moving from/to a congested cell. Two risk factors are used to dynamically change handover boundaries according to the distribution of traffic loads. This controls the handover initiation process such that a user in a congested cell that is moving to a free cell is allowed to initiate a handover to a new cell earlier, as long as the signal received from the target cell is higher than a certain threshold. While delaying the handover initiation process for a user moving in the opposite direction, as long as the signal received from the serving cell is not lower than a certain threshold. Our results show a substantial reduction in the handover and call dropouts rates. Our scheme is complementary to the existing adaptive schemes proposed in the literature. The proposed scheme also gives cellular system designers a new tool to optimize the overall network performance by initiating handovers based on the traffic intensities. Frequent handovers increase the load on switching networks, which consequently degrades the Quality of Service (QoS). Existing handover schemes usually use parameters such as the received signal strength for initiating a handover with some additional measurements to reduce unnecessary handovers and call dropouts. These schemes perform well when cell loads are somewhat evenly distributed, but fail to account for nonuniform traffic, as is often the case in microcells. Hence, it is desirable to design efficient handover schemes to avoid unnecessary handovers, reduce call dropouts and yet dynamically adapt to the variation of traffic among cells. In this paper, we present a new adaptive handover scheme that dynamically changes the handover boundaries to balance cell loads and to effectively reduce the average number of handovers. Copyright © 2004 John Wiley & Sons, Ltd. 相似文献
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现有的CDN-P2P缓存替换机制没有关注内容文件中各片段的个体流行度差异性,而无法提高预缓存内容片段的访问命中率。鉴于此,提出了基于流行度差异性的缓存替换机制Diff-Attribute。同时考虑了内容文件的整体流行度和文件中各个片段的个体流行度。此外,基于分布熵,定义了一种内容流行度均衡性度量方法:若流行度均衡,就提前缓存各文件的前缀片段;否则提前缓存热门文件或其中最热门的内容片段。仿真结果表明:在缓存命中率和字节命中率方面,Diff-Attribute机制分别高出LFU、LRU等传统机制约6%和8%;在访问延迟启动率和传输成本消耗率方面,Diff-Attribute机制则降低了约13%和7%。 相似文献