并行下载最优机制

建立并行下载模型,并基于这一模型,从下载节点效益的角度出发,分析并提出最优机制.这种最优机制包括最优的选择源节点集合和文件分块方案.理论分析表明,这种机制能够使下载节点代价函数最小.仿真结果说明了这种机制的有效性.     

基于节点最优发送概率的EDCA能源优化

通过分析IEEE802.11 EDCA网络中各优先级节点的能源消耗,利用全概率理论建立网络能源利用率和各优先级节点发送概率的关系模型。针对最优化最小竞争窗口设置问题,提出一种基于最大化网络能源利用率求各优先级节点最优发送概率的算法。在保证每类业务Qo S条件下,首先求出在最大化网络能源利用率下的节点最优发送概率,然后根据节点数目和节点最优发送概率来优化最小竞争窗口的大小,实现最优最小竞争窗口设置,从而提高网络能源利用率。仿真结果表明:该算法相对于EDCA在网络能源利用率方面有较好的表现。     

基于蚁群的无线传感网最大化生存时间路由

为提高无线传感网的生存时间,对基于蚁群算法的最大化生存时间路由(MLRAC)进行了研究。该路由利用链路能耗模型和节点发送数据概率,计算一个数据收集周期内节点总能耗。同时考虑节点初始能量,建立了最大化生存时间路由的最优模型。为求解该最优模型,在经典蚁群算法的基础上,提出修正的蚁群算法。该算法采用新的邻居节点转发概率公式、信息素更新公式和分组探测方法,经过一定的迭代计算获得网络生存时间的最优值和每个节点的最优发送数据概率。最后,Sink节点洪泛通知网络中所有节点。节点根据接收到的最优概率,选择数据分组未经过的邻居节点发送数据。仿真实验表明,经过一定时间的迭代,MLRAC的生存时间可以收敛到最优值。该算法能延长网络生存时间,在一定的条件下,MLRAC算法比PEDAP、LET、Ratio-w、Sum-w等算法更优。     

基于最小费用最大流问题的“排序”算法

由于现有的求解最小费用最大流问题的方法都存在其局限性,为了更好地解决实际问题,在已有最短路算法以及最小费用算法的基础上作了改进,给出了一种求解基于最大流的最小费用问题的算法.文中针对小规模网络给出求两点之间最小费用的一种简单易行的方法,此外该算法可以在一个图上完成,这样可以节省许多画图时间,增强了算法的直观性和可控性.并且构建石油运输的网络模型,结合最小费用最大流算法,给出该模型从产地到销地的最优运输方案,最后通过具体的模型实例验证了该方法的效率和实用性.     

一种基于遗传算法的流媒体多播路由算法

流媒体多播路由算法要寻找连接源节点和所有目的节点的最小生成树,不仅要使网络费用最小还要求适合于流媒体这一较新的服务.本文通过对最小代价多播路由问题进行分析,给出网络模型及其数学描述,结合模糊逻辑控制提出一种性能优越的基于遗传算法的多播路由算法.     

一种求解最少时间最小费用路问题的算法

针对同时带有弧费用和弧时间的运输网络中最少时间最小费用路的问题,本文提出了一种算法。该算法能高效地求出此类网络中从源节点到目的节点的双目标最短路（最少时间最小费用路）。实例计算表明,该算法是有效的。     

声纳阵列网络基于移动信标到达角的渐进最优节点自定位算法

针对水下声纳阵列网络节点自定位问题,提出一种基于移动信标到达角的三维总体最小二乘（TLS）节点自定位算法。首先给出了基于方位角和俯仰角的变量含误差模型,并根据该模型提出三维TLS算法,证明三维TLS算法随信标广播次数增加是渐进最优估计,仿真结果验证所提出算法的均方根误差渐进达到CRLB。     

基于能量水平的多Sink节点传感器网络路由算法

单Sink节点传感器网络存在着部分关键路径上节点能量消耗过快、路由选择算法单一以及Sink节点失效等问题.首先提出了多Sink节点传感器网络数据收集的系统框架;给出了拓扑发现和维护策略;然后提出了基于最小能量消耗路由算法.在分析了该算法的不足后提出了基于能量水平的路由算法,按照计算得到的能量水平选择最优的路径进行数据传送.实验证明,基于能量水平的路由算法比基于最小能量消耗路由算法能更有效提高传感器网络的使用寿命.     

无线传感器网络TPSN-RBS联合时间同步算法

针对大规模多跳传感器网络节点间所存在的同步误差及其累积误差问题,提出了一种基于加权最小二乘法的TPSN-RBS联合时间同步算法.该算法充分利用可监听到的消息,通过加权最小二乘法估计得到节点逻辑时钟的时间偏移和频率偏移的最优解.用Cramér-Rao下界对本算法进行性能分析,同时与TPSN算法进行仿真对比,结果表明:该算法提高了节点间的同步精度,且在节点密集的大规模无线传感器网络中,在保证较低通信量的同时降低了累积误差.     

自组网中基于自适应波束天线的拓扑控制算法

定向天线自组网拓扑的构建问题比全向天线网络复杂.基于自适应波束定向天线模型提出一种分布式拓扑控制算法,通过调整节点发射功率,改变天线波束的朝向、宽度和增益来构建拓扑.网络中每个节点收集其邻居节点信息,采用功率控制调度策略选择最优相邻节点,并选取覆盖所有最优相邻节点的最小发射功率为此节点的发射功率.算法在保证网络连通性与无向性的同时,降低了节点的发射功率,减小了节点的平均度数,从而降低节点能耗,减少了节点间干扰,提高了网络吞吐量.仿真结果表明,算法显著提高了网络性能.     

物流配送网络环境中移动代理路径寻优

将蚁群算法的基本原理用到物流配送网最短路径搜索中,对降低配送成本有重要意义。针对物流配送网带约束的路由选择问题,分析了自然界中蚂蚁卓越的选路行为,提出了一种基于ant-like移动代理的路径选择算法（ORA）。该算法利用ant-like移动代理采集物流配送网络中各节点的详细信息,以网络延迟和费用为QoS参数,建立了一个满足延迟约束达到费用最小化模型;同时采用多个ant-like代理选径策略来求路径最优解,以缩短路由重构的时间,延长了网络的生存时间。分析和仿真实验结果都证明该算法是有效的。     

能量高效的ZigBee网络改进路由策略

在分析现有ZigBee网络路由策略的基础上,以节省网络能耗和均衡网络负载为目的,提出一种能量高效的改进路由策略。该策略分别对ZigBee网络的簇树拓扑结构以及基于簇树算法和AODVjr算法的ZBR路由策略进行改进。改进后的路由策略在尽量减少路由开销的同时充分考虑对能量偏低节点的保护。仿真实验验证,改进策略能有效减少网络能耗,均衡网络负载,最大化网络的生存时间。     

A note on distributed multicast routing in point-to-point networks

The distributed algorithm for a multicast connection set-up, based on the ‘cheapest insertion’ heuristic, is reviewed. The multicast routing problem is translated into a Steiner tree problem in point-to-point networks where nodes have only a limited knowledge about the network. A solution is proposed in which the time complexity and the amount of information exchanged between network nodes are proportional to the number of members of the multicast group. The Steiner tree is constructed by means of a distributed table-passing algorithm. The analysis of the algorithm presented, backed up by simulation results, confirms its superiority over the algorithm based on ‘waving technique’.Scope and purposeMulticasting is a mechanism used in communication networks that allows distribution of information from a single source to multiple destinations. The problem of finding a multicast connection for a static group of communicating entities in connection-oriented point-to-point network can be formulated in graph theory as a minimum Steiner tree problem. Due to NP-completeness of the Steiner tree problem multicast, routing algorithms are based on heuristics. The diversity of network environments and the lack of centralised information about network topology require an effective distribution of the multicast routing algorithms among the network nodes. This article presents an alternative to the distributed algorithm proposed by Rugelj and Klavzar that implements the same heuristics for the construction of a minimum cost multicast connection in point-to-point networks. The present algorithm constitutes a substantial improvement over that previously proposed with regard to running time and the amount of the information exchanged between network nodes.     

WSN中基于能量代价的能量优化路由算法

针对无线传感器网络路由算法中的节点能耗问题,提出了一种基于能量代价的能量优化路由算法。算法综合考虑数据传输中节点能耗的有效性和均衡性,设计了一种新的能量代价函数,实现了二者的优化匹配。传感器节点按此函数计算前向部居节点的能量代价,选择能量代价最小的节点作为下一跳。算法基于部居节点信息进行路由选择,具有较低的计算时间复杂度。最后,对路由算法的性能进行了仿真分析,并与典型的路由算法进行了对比,结果表明,本路由算法能够有效延长网络生存时间,节约并均衡节点的能量消耗。     

Strategies for utility maximization in social groups with preferential exploration

Social Group is group of interconnected nodes interested in obtaining common content (Scott, in Social network analysis, 2012). Social groups are observed in many networks for example, cellular network assisted Device-to-Device network (Fodor et al., in IEEE Commun Mag 50:170–177, 2012, Lei et al., in Wirel Commun 19:96–104, 2012), hybrid Peer-to-Peer content distribution (Christos Gkantsidis and Miller, in 5th International Workshop on Peer-to-Peer Systems, 2006, Vakali and Pallis, in IEEE Internet Comput 7:68–74, 2003) etc. In this paper, we consider a “Social Group” of networked nodes, seeking a “universe” of data segments for maximizing their individual utilities. Each node in social group has a subset of the universe, and access to an expensive link for downloading data. Nodes can also acquire the universe by exchanging copies of data segments among themselves, at low cost, using inter-node links. While exchanges over inter-node links ensure minimum or negligible cost, some nodes in the group try to exploit the system by indulging in collusion, identity fraud etc. We term such nodes as ‘non-reciprocating nodes’ and prohibit such behavior by proposing the “Give-and-Take” criterion, where exchange is allowed iff each participating node provides at least one segment to the node which is unavailable with the node. While complying with this criterion, each node wants to maximize its utility, which depends on the node’s segment set available with the node. Link activation between pair of nodes requires mutual consent of the participating nodes. Each node tries to find a pairing partner by preferentially exploring nodes for link formation. Unpaired nodes download data segments using the expensive link with pre-defined probability (defined as segment aggressiveness probability). We present various linear complexity decentralized algorithms based on the Stable Roommates Problem that can be used by nodes for choosing the best strategy based on available information. We present a decentralized randomized algorithm that is asymptotically optimal in the number of nodes. We define Price of Choice for benchmarking the performance of social groups consisting of non-aggressive nodes (i.e. nodes not downloading data segments from the expensive link) only. We evaluate performances of various algorithms and characterize the behavioral regime that will yield best results for nodes and social groups, spending the least on the expensive link. The proposed algorithms are compared with the optimal. We find that the Link For Sure algorithm performs nearly optimally.     

基于人工鱼群算法的无线传感器网络覆盖优化

针对网络节点严重冗余而导致的网络成本增加、生命周期过短等缺陷,提了一种基于人工鱼群算法的覆盖优化方法.首先以节点的利用率和网络有效覆盖率作为优化目标,建立相应的数学模型,然后采用人工鱼群算法对模型进行求解,得到无线传感器网络的最优覆盖方案.仿真结果表明,人工鱼群算法提高了无线传感器网络节点的覆盖率,减少了传感器节点冗余,有效降低了网络成本,网络生存时间得到了延长.     

WSN中有效的最小单位圆集覆盖算法*

针对具有不同传输半径的无线传感器网络覆盖与广播数据转发问题,提出了一种以最小单位圆覆盖集作为广播数据转发集的算法。该算法能有效计算出覆盖范围的轮廓集,具有最优的时间复杂度O(n log n)。对每个节点,该算法以其最少数量的邻居节点子集实现所有邻居节点的覆盖,并证明了该算法找到的最小单位圆覆盖集与其轮廓集是相等的。详细的仿真实验及与现有算法的比较表明,提出的覆盖算法不仅以最少数量的节点实现了网络覆盖与广播数据转发,同时延长了网络生命期。     

A scheduling algorithm for applications in a cloud computing system with communication changes

This paper proposes a scheduling algorithm to solve the problem of task scheduling in a cloud computing system with time‐varying communication conditions. This algorithm converts the scheduling problem with communication changes into a directed acyclic graph (DAG) scheduling problem for existing fuzzy communication task nodes, that is, the scheduling problem for a communication‐change DAG (CC‐DAG). The CC‐DAG contains both computation task nodes and communication task nodes. First, this paper proposes a weighted time‐series network bandwidth model to solve the indefinite processing time (cost) problem for a fuzzy communication task node. This model can accurately predict the processing time of a fuzzy communication task node. Second, to address the scheduling order problem for the computation task nodes, a dynamic pre‐scheduling search strategy (DPSS) is proposed. This strategy computes the essential paths for the pre‐scheduling of the computation task nodes based on the actual computation costs (times) of the computation task nodes and the predicted processing costs (times) of the fuzzy communication task nodes during the scheduling process. The computation task node with the longest essential path is scheduled first because its completion time directly influences the completion time of the task graph. Finally, we demonstrate the proposed algorithm via simulation experiments. The experimental results show that the proposed DPSS produced remarkable performance improvement rate on the total execution time that ranges between 11.5% and 21.2%. In view of the experimental results, the proposed algorithm provides better quality scheduling solution that is suitable for scientific application task execution in the cloud computing environment than HEFT, PEFT, and CEFT algorithms.     

无线传感器网络部分覆盖算法及连通性研究

研究了无线传感器网络在部分覆盖下的节点配置及网络连通性问题。首先,基于最优正六边形拓扑架构,给出了节点密集分布条件下的覆盖率与相邻工作节点间距的解析关系,并在已有的最优完全覆盖算法OGDC的基础上进行了扩展和改进,从而得到了一种新的网络节点配置算法EGDC（Extended OGDC Algorithm）。该算法可以有效地选择出合适的工作节点以达到任意给定覆盖率下的部分覆盖。此外,还给出了一种检验和评价网络连通性的方法,通过该方法可以对网络的连通性进行量化分析,并给出了一项评价网络连通性的指标。仿真表明,EGDC可以有效地实现任意期望覆盖率下的网络配置并保持网络的连通。