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本文将WSN中所有节点都看作处于不同层次的sink节点,通过对网络应用语义性描述得到任务模型,将其作为传感器节点传输及处理的基本单位,就此提出了一种基于任务(Task-based,TB)的混合MAC协议。TB-MAC中簇头(上层sink)首先广播任务,接收到广播且能部分或全部完成任务的节点采用竞争方式发送应答,簇头确定参与任务执行的节点及子任务要求并确定各节点的TDMA发送时序。由于簇头进行了任务协商,使得参与任务的节点能够有效地去除节点数据间的冗余性,提高网络的性能。仿真结果显示,TB-MAC的能耗和时延性能较典型的S-MAC、Z-MAC以及ECR-MAC均有较大改善。 相似文献
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首先介绍4种经典的无线传感器网络(WSN)介质接入控制(MAC)层信道接入方式,并在基于MSP430单片机的温湿度无线传感平台上进行性能验证。随后比较4种经典MAC接入方式的实测值,并分析存在差异的原因。最后提出无线传感器网络MAC层信道接入方式研究的可能方向。 相似文献
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无线传感器网络节点流量的带宽分配策略 总被引:1,自引:1,他引:1
本文分析了WSN中几种MAC协议和数据流的特点,提出了一种基于节点流量的带宽分配策略。该策略将较忙的节点设为高优先级,而将空闲节点设为低优先级,优先调度高优先级节点的分组。应用OPNET进行了网络仿真。仿真结果表明,WSN在一定网络负荷下丢包数更低,能有效缓解某些节点的拥塞,更有利于节能。 相似文献
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基于行为的信任体系是适应于无线传感器网络资源受限特性的一种安全增强机制.该体系通过节点的过往行为来评估节点的可信度,从而提高任务完成的质量.现有NS2上的WSN仿真方法往往只模拟网络中的某一个层次,不能满足该体系层次融合和网内逐跳信息处理的两个基本特点.在AD HOC仿真平台的基础上进行改动,在MAC层和网络接口层之间增加信任处理层,实现对节点完成不同类型的任务的能力进行评估.同时,对路由算法进行改进,使其选择信任度更高的节点作为路由的下一跳,从而降低不良节点对无线传感器网络中路由功能的影响.利用该文的仿真框架对基于行为的信任体系进行仿真验证,结果表明该体系的存在有效地提高了路由的成功率. 相似文献
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无线传感网络(WSN)目前在工业领域得到了越来越广泛的应用,主流的WSN协议包括ZigBee、WIA-PA和Wireless HART.这三种无线短程通信协议在物理层上均兼容IEEE 802.15.4物理层(PHY)协议规范,但在媒介访问控制(MAC)及以上各层则完全不同.通过对这三种WSN协议的MAC层进行分析和对比,以及对MAC网络性能的模拟分析计算,给出了三种WSN的适用条件. 相似文献
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分级环片上网络互连 总被引:1,自引:0,他引:1
在大规模、超大规模片上互连网络中,因为二维互连方式的性能较差而使多维互连方式成为可选方案之一.文中首先基于区域划分设计了一种分级环互连结构,分析了其静态互连特性,然后基于卡诺图编码设计了一种分级环互连的路由结构以及寻径方法,在均匀通信模式测试了不同的分级环级联链路缓冲区设置方法下网络的性能,详细分析了按照等比序列设置分级环级联链路缓冲区时分级环互连方式的动态网络特性,最后根据互连性能与Mesh等二维片上互连方式比较的结果,给出了分级环互连方式的使用场合.实验结果表明,虽然在较小规模网络中性能较差,但是分级环互连方式能以较低的成本、较高的性能实现大规模、超大规模片上网络的互连,其中单环分级互连方式在较低网络负载下综合性能更好,而双环分级互连方式则具有更大的网络负载能力,在较高网络负载下性能更好. 相似文献
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组合原则表明句子的语义由其构成成分的语义按照一定规则组合而成,由此基于句法结构的语义组合计算一直是一个重要的探索方向,其中采用树结构的组合计算方法最具有代表性。但是该方法难以应用于大规模数据处理,主要问题是其语义组合的顺序依赖于具体树的结构,无法实现并行处理。该文提出一种基于图的依存句法分析和语义组合计算的联合框架,并借助复述识别任务训练语义组合模型和句法分析模型。一方面,图模型可以在训练和预测阶段采用并行处理,极大地缩短计算时间;另一方面,联合句法分析的语义组合框架不必依赖外部句法分析器,同时两个任务的联合学习可使语义表示同时学习句法结构和语义的上下文信息。我们在公开汉语复述识别数据集LCQMC上进行评测,实验结果显示准确率接近树结构组合方法,达到79.54%,预测速度最高可提升30倍以上。 相似文献
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互连网络的数学建模在大规模并行系统的研究和设计中有重要的作用,而Infiniband网络是一种广泛运用于高性能计算机系统的互连网络标准。本文对基于Infiniband的互连网络进行了分析,建立了网络延时模型,并使用该模型分析了2D-mesh和m-portn-tree两种拓扑的互连网络特性。最后通过仿真对分析模型进行了测试和评价,仿真结果表明,该模型能够合理地反映互连网络的特性。 相似文献
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《Computer Networks》2008,52(11):2189-2204
In the WSNs, the nodes closer to the sink node have heavier traffic load for packet forwarding because they do not only collect data within their sensing range but also relay data for nodes further away. The unbalanced power consumption among sensor nodes may cause network partition. This paper proposes efficient node placement, topology control, and MAC scheduling protocols to prolong the sensor network lifetime, balance the power consumption of sensor nodes, and avoid collision. Firstly, a virtual tree topology is constructed based on Grid-based WSNs. Then two node-placement techniques, namely Distance-based and Density-based deployment schemes, are proposed to balance the power consumption of sensor nodes. Finally, a collision-free MAC scheduling protocol is proposed to prevent the packet transmissions from collision. In addition, extension of the proposed protocols are made from a Grid-based WSN to a randomly deployed WSN, enabling the developed energy-balanced schemes to be generally applied to randomly deployed WSNs. Simulation results reveal that the developed protocols can efficiently balance each sensor node’s power consumption and prolong the network lifetime in both Grid-based and randomly deployed WSNs. 相似文献
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Sensors cooperate and coordinate with each other to disseminate sensed data in the network. In establishing coordination among sensors such that they can access the shared wireless medium, Medium Access Control (MAC) protocol plays an important role. In this article, we presented an analytical study on some popular MAC protocols for Wireless Sensor Networks (WSNs). Based on the design techniques, MAC protocols for WSNs are classified into two main categories: single-layer and cross-layer. MAC protocols such as S-MAC, T-MAC, B-MAC and X-MAC are selected to study the design approaches of single-layer genre. BoX-MAC-1 and BoX-MAC-2 are selected to analyze cross-layer design approaches. This survey paper aims at reporting an implementation viewpoint of different design approaches of MAC protocols in WSN. We have considered mixed WSNs that exhibits node movement (e.g., static, mobile) and changes in communication medium (e.g., air, water). Representative protocols are implemented in Castalia simulator and evaluated on the basis of important performance metrics such as energy consumption, network lifetime, throughput and end-to-end delay. The merits and demerits of different protocols are also compared. 相似文献
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For TDMA MAC protocols in wireless sensor networks (WSNs), redundancy and retransmission are two important methods to provide high end-to-end transmission reliability. Since reliable transmissions will lead to more energy consumption, there exists an intrinsic tradeoff between transmission reliability and energy efficiency. For each link, we name the number of its reserved time slots in each MAC superframe as a replicator factor. In the following paper, we propose a reliability-lifetime tradeoff framework (RLTF) for WSNs to study replicator factor control problem. First, for the redundancy TDMA MAC, we formulate replicator factor control problem as convex programming. By the gradient projection method, we develop a fully distributed algorithm to solve the convex programming. Second, for the retransmission TDMA MAC, we set the retransmission upper bound for each link according to the optimal replicator factors under the redundancy MAC and compute the total communication overhead for the retransmission MAC. Finally, we compare the communication overhead of these two MAC protocols under different channel conditions. 相似文献
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Suat Özdemir Bara’a A. Attea Önder A. Khalil 《Soft Computing - A Fusion of Foundations, Methodologies and Applications》2013,17(9):1573-1584
A wireless sensor network (WSN) generally consists of a large number of inexpensive power constrained sensors that are small in size and communicate over short distances to perform a predefined task. Realizing the full potential of WSN poses many design problems, especially those which involve tradeoffs between multiple conflicting optimization objectives such as coverage preservation and energy conservation. While both energy conservation routing protocols in a cluster-based WSNs and coverage-maintenance problems have been extensively studied in the literature, these two problems have not been integrated in a multi-objective optimization (MOO) manner. This paper employs a recently developed MOO algorithm, the so-called multi-objective evolutionary algorithm based on decomposition (MOEA/D) to solve simultaneously the energy conservation and coverage preservation design problems in cluster-based WSNs. The performance of the proposed approach, in terms of network lifetime and coverage is compared with the heuristic LEACH and SEP clustering protocols and with another prominent MOEA, the so-called non-dominated sorting genetic algorithm II (NSGA II). Simulation results reveal that MOEA/D provides a more efficient and reliable behavior over other approaches. 相似文献
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无线传感器网络MAC协议研究进展 总被引:17,自引:3,他引:14
近年来, 无线传感器网络 (WSNs) 作为国内外一个新兴的研究方向, 吸引了许多研究者和机构的广泛关注. 无线传感器网络具有与传统无线网络不同的特点, 且与应用高度相关. 无线传感器网络主要的一个设计目标是有效地使用网络节点的受限资源 (能量、内存和计算能力), 以最大化网络的服务寿命. 传统网络的介质访问控制 (MAC) 协议, 并不能直接应用于无线传感器网络. 针对无线传感器网络的特点和应用背景, 研究人员提出了很多 MAC 协议. 本文通过分析无线传感器网络的特点, 讨论了影响 MAC 协议设计的有关问题, 着重研究和比较了当前一些重要的无线传感器网络 MAC 协议. 结果表明, 不存在一种适用于无线传感器网络应用的标准 MAC 协议, 好的 MAC 协议必须能在能量有效性和网络性能之间进行折中. 最后, 展望了无线传感器网络 MAC 协议的进一步研究策略和发展趋势. 相似文献
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一种无线传感器网络MAC协议优化算法 总被引:11,自引:0,他引:11
在无线传感器网络中,各节点采集的信息以多跳的方式传送到汇聚点.从各节点到汇聚点形成一棵以汇聚点为根的传输树.文中在对无线传感器网络传输特点分析的基础上,剖析了基于CSMA/CA(载波多路监听/冲突避免)的MAC协议在树状结构无线传感器网络中的弊端,提出了一种基于CSMA/CA的MAC协议优化算法.算法基于节点在传输树中的位置信息调整其MAC信道接入分配,将CSMA/CA采用的各节点均等竞争信道的方法优化为各节点依据在传输树中的位置情况竞争信道的方式,这一优化提高了节点公平性,使MAC信道接入分配与树状结构的无线传感器网络传输特点相契合,解决了基于CSMA/CA的MAC协议与树状结构无线传感器网络不匹配的问题,从而减少了信道资源浪费,提高了网络传输效率,降低了能耗.实验结果表明该算法在网络丢包率、吞吐量和能耗方面的性能均有较大改进. 相似文献
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