Fast and proximity-aware multi-source overlay multicast under heterogeneous environment

Overlay multicast has been considered as one of the most important developments for the next generation Internet infrastructure. In this paper, we consider overlay multicast in the scenarios where any participant node is a potential data source. Existing multicast algorithms for single-source always require a long time to deliver messages or have high maintenance overhead when multiple data sources are allowed. There are other algorithms that are designed for multi-source scenarios. But they consume too much network resources and have a long convergence time because of proximity ignorance. To address the issues, we present FPCast, which leverages node heterogeneity and proximity information at the same time. Physically close nodes are grouped into clusters and each cluster selects a powerful, stable node as its rendezvous point. The rendezvous nodes form a DHT-based structure. Data messages are replicated and forwarded along implicit, source specific, and heterogeneity-aware multicast trees. We further reduce the delivery delay by introducing probabilistic forwarding scheme. We show the average delivery path length converges to O(logn) automatically (n is the number of nodes in the overlay). The simulation results demonstrate the superiority of our algorithm in terms of message delivery time and network resource consumption, in comparison with the previous randomized algorithms. The algorithm is also resilient to node failures.     

一种异构多接口多信道无线网络的信道分配算法

多接口多信道技术是无线网络环境中减少链路干扰、提高网络吞吐量的有效途径,但如何合理有效地进行信道分配已成为多接口多信道无线网络所面临的主要问题之一.针对自私的网络节点,本文使用非合作博弈对异构条件下多接口节点的信道分配问题进行建模分析,其纳什均衡解为解决该问题所需的稳定的信道分配方案.本文首先讨论纳什均衡的存在条件并提出实现纳什均衡的分布式算法.此外,考虑到实际网络中节点仅能感知局部信道信息以及接口工作信道受限等因素,本文进一步改进算法并通过仿真实验对其收敛性进行证明.     

基于簇的无线传感器网络交会路由协议

针对现有无线传感器网络(WSN)协议中更多消耗sink附近节点能量导致网络寿命短的问题,本文提出一种基于簇的无线传感器网络交会路由协议(Cluster-based Rendezvous Routing Protocol, CRRP)。该协议是基于交会的路由协议,其中在网络的中间构建交会区域,该交会区域划分整个网络区域并在传感器节点之间分配网络负载,这延长了网络寿命。此交会区域内的节点分为不同的簇,每个簇的簇头(CH)负责不同簇之间的通信,sink在此交会区域内发送其更新的位置信息,并且当传感器节点想要发送数据时,会从该交会区域检索sink的当前位置信息并直接将数据发送到sink。仿真实验结果表明,在能耗与网络寿命性能方面,本文CRRP协议优于Rendezvous协议、LBDD协议、Railroad协议和Ring协议。     

Channel assignment in heterogeneous multi-radio multi-channel wireless networks: A game theoretic approach

Channel assignment is a challenging issue for multi-radio multi-channel wireless networks, especially in a competing environment. This paper investigates channel assignment for selfish nodes in a heterogeneous scenario, in which nodes may have different QoS requirements and thus compete for different channels with unequal bandwidth. The interaction among nodes is formulated as a non-cooperative Multi-radio Channel Assignment Game (MCAG), where Nash Equilibrium (NE) corresponds to a stable channel assignment outcome from which no individual node has the incentive to deviate. The NEs in MCAG are characterized in this paper. Since multiple NEs may exist in this game, it is natural to choose the NE that maximizes the network utility, i.e., the sum of node utilities. It is shown that the optimal NE outcome can be derived by solving an integer non-linear programming problem. Based on some observations on the radio number distribution of NE, we propose a two-stage optimization algorithm to achieve an optimal channel assignment. Finally, computer simulations validate the effectiveness of the proposed algorithm.     

WMN中的干扰避免部分重叠信道分配算法

针对无线mesh网络(wireless mesh networks,WMN)中存在的信道干扰问题,提出一种基于部分重叠信道(partially overlapping channels,POC)的负载平衡且干扰避免的信道分配算法。通过基于Huffman树的通信接口分配方法连接邻居节点的接口;根据网络干扰情况,对链路进行迭代信道分配,使用静态链路调度保证网络连接;利用启发式算法优先为重要程度较高的链路分配无干扰时隙,对链路调度进行优化。仿真结果表明,在具有混合流量的WMN中,所提算法可以显著提升网络吞吐量,降低网络干扰与平均丢包率,改善网络性能。     

Advertisement timeout driven bee's mating approach to maintain fair energy level in sensor networks

In wireless sensor network, dynamic cluster-based routing approach is widely used. Such practiced approach, quickly depletes the energy of cluster heads and induces the execution of frequent re-election algorithm. This repeated cluster head re-election algorithm increases the number of advertisement messages, which in turn depletes the energy of overall sensor network. Here, we proposed the Advertisement Timeout Driven Bee's Mating Approach (ATDBMA) that reduces the cluster set-up communication overhead and elects the standby node in advance for current cluster head, which has the capability to withstand for many rounds.Our proposed ATDBMA method uses the honeybee mating behaviour in electing the standby node for current cluster head. This approach really outperforms the other methods in achieving reduced number of re-election and maintaining fair energy nodes between the rounds.     

Deterministic Rendezvous in Graphs

Two mobile agents having distinct identifiers and located in nodes of an unknown anonymous connected graph, have to meet at some node of the graph. We seek fast deterministic algorithms for this rendezvous problem, under two scenarios: simultaneous startup, when both agents start executing the algorithm at the same time, and arbitrary startup, when starting times of the agents are arbitrarily decided by an adversary. The measure of performance of a rendezvous algorithm is its cost: for a given initial location of agents in a graph, this is the number of steps since the startup of the later agent until rendezvous is achieved. We first show that rendezvous can be completed at cost O(n + log l) on any n-node tree, where l is the smaller of the two identifiers, even with arbitrary startup. This complexity of the cost cannot be improved for some trees, even with simultaneous startup. Efficient rendezvous in trees relies on fast network exploration and cannot be used when the graph contains cycles. We further study the simplest such network, i.e., the ring. We prove that, with simultaneous startup, optimal cost of rendezvous on any ring is Θ(D log l), where D is the initial distance between agents. We also establish bounds on rendezvous cost in rings with arbitrary startup. For arbitrary connected graphs, our main contribution is a deterministic rendezvous algorithm with cost polynomial in n, τ and log l, where τ is the difference between startup times of the agents. We also show a lower bound Ω (n²) on the cost of rendezvous in some family of graphs. If simultaneous startup is assumed, we construct a generic rendezvous algorithm, working for all connected graphs, which is optimal for the class of graphs of bounded degree, if the initial distance between agents is bounded.     

Community Discovery Algorithm Based on Multi-Relationship Embedding

Complex systems in the real world often can be modeled as network structures, and community discovery algorithms for complex networks enable researchers to understand the internal structure and implicit information of networks. Existing community discovery algorithms are usually designed for single-layer networks or single-interaction relationships and do not consider the attribute information of nodes. However, many real-world networks consist of multiple types of nodes and edges, and there may be rich semantic information on nodes and edges. The methods for single-layer networks cannot effectively tackle multi-layer information, multi-relationship information, and attribute information. This paper proposes a community discovery algorithm based on multi-relationship embedding. The proposed algorithm first models the nodes in the network to obtain the embedding matrix for each node relationship type and generates the node embedding matrix for each specific relationship type in the network by node encoder. The node embedding matrix is provided as input for aggregating the node embedding matrix of each specific relationship type using a Graph Convolutional Network (GCN) to obtain the final node embedding matrix. This strategy allows capturing of rich structural and attributes information in multi-relational networks. Experiments were conducted on different datasets with baselines, and the results show that the proposed algorithm obtains significant performance improvement in community discovery, node clustering, and similarity search tasks, and compared to the baseline with the best performance, the proposed algorithm achieves an average improvement of 3.1% on Macro-F1 and 4.7% on Micro-F1, which proves the effectiveness of the proposed algorithm.     

一种基于图形数据库的快速电力网络拓扑分析方法

提出了一种基于图形数据库的通用拓扑分析方法,将多状态设备映射为多节点,每个节点的父对象都为此设备,将设备连接抽象为连接电缆节点和连接关系,每种设备的电气属性都抽象为节点和关系的属性,在将网络的拓扑信息入库后,组合利用图形数据库中的多种图形分析算法,并结合电力网络应用开发出相连节点连通性分析和停电范围检测算法,基于此开发的电网停电范围监测系统和变电站智能开票操作票程序该方法具备高可用性和高性能,取得了良好的效果．     

移动自组网基于跨层协作的负载均衡队列调度算法

传统的路由协议都是基于"最短路径"的考虑,节点在对数据包进行调度转发的时候,无条件的为路由控制消息赋予较高的优先转发权,这样就会导致网络中处于骨干位置的节点负载过重,从而进一步影响整个网络的性能.本文提出一种新的基于跨层协作的负载均衡队列调度算法(CLLBS),通过在MAC层与网络层监视节点网络负载,配合路由协议,根据节点的负载状况实时动态地对数据流的转发优先权进行调整,在整个网络进行负载均衡,缓解那些拥塞节点的负载压力.仿真结果表明本文算法较之传统的简单优先权算法有明显的性能提高,可以有效地提高网络的吞吐量,降低丢包率.     

Energy-Efficient Communication in Multi-interface Wireless Networks

We study communication problems in wireless networks supporting multiple interfaces. In such networks, two nodes can communicate if they are close enough and share a common interface. The activation of each interface has a cost reflecting the energy consumed when a node uses this interface. We distinguish between the homogeneous and heterogeneous case, depending on whether all nodes have the same activation cost for each interface or not. For the homogeneous case, we present a (3/2+?)-approximation algorithm for the problem of achieving connectivity with minimum activation cost, improving a previous bound of 2. For the heterogeneous case, we show that the connectivity problem is not approximable within a sublogarithmic factor in the number of nodes and present a logarithmic approximation algorithm for a more general problem that models group communication.     

LPR MAC:一种采用并行协商机制的低功耗多信道MAC协议

本文通过分析不同类型的多信道MAC协议的特点,指出了并行协商类多信道MAC协议存在的消失节点问题和通信竞争问题。针对上述问题,基于无线传感器网络节点的能量有效性,本文提出了一种新的多信道MAC协议：LPR MAC。本协议采用全网同步,时间上划分为多个时间片,节点在网络建立时随机选择某个时间片作为自己的固定接收周期,在接收周期按各自的伪随机序列在多个信道之间进行跳跃,并行协商,在其余时间片休眠。仿真结果表明,该协议减少了通信竞争程度,降低了能量消耗。     

基于密集连接卷积神经网络的链路预测模型

现有的基于网络表示学习的链路预测算法主要通过捕获网络节点的邻域拓扑信息构造特征向量来进行链路预测，该类算法通常只注重从网络节点的单一邻域拓扑结构中学习信息，而对多个网络节点在链路结构上的相似性方面研究不足。针对此问题，提出一种基于密集连接卷积神经网络（DenseNet）的链路预测模型（DenseNet-LP）。首先，利用基于网络表示学习算法node2vec生成节点表示向量，并利用该表示向量将网络节点的结构信息映射为三维特征数据；然后，利用密集连接卷积神经网络来捕捉链路结构的特征，并建立二分类模型实现链路预测。在四个公开的数据集上的实验结果表明，相较于网络表示学习算法，所提模型链路预测结果的ROC曲线下方面积（AUC）值最大提高了18个百分点。     

结合动态信用机制的PBFT算法优化方案

实用拜占庭容错（PBFT）共识算法被广泛应用于金融机构、电子货币行业、农产品溯源等领域,但存在灵活性较差、拜占庭节点处理方式不足、通信开销和网络时延较大等问题。提出基于动态机制与信用积分机制的实用拜占庭容错共识算法DT-PBFT。引入动态加入或退出机制,使集群内的节点可以按需自由加入或退出,增加信用积分机制,通过分层机制将节点按可信任程度分为备用主节点层、中间层、警告层和清理层,采用惩罚机制降低节点连续作恶的可能性,以保证从备用主节点层中优先选择最优的主节点,大幅提高共识效率。同时,通过剔除网络清理层中的拜占庭节点,提高算法的运行效率。在此基础上,通过优化一致性协议对共识流程进行改进,减少一轮全网节点信息交互确认流程,从而降低通信开销。实验结果表明,当节点数为22时,相比DGPBFT、DDBFT和PBFT算法,DT-PBFT算法具有较优的灵活性,吞吐量和交易请求有效完成率分别为292 transaction/s和83.4%,CPU利用率为50%,相比PBFT算法,延迟降低了350 ms。     

一种联合多信道分配决策的认知Mesh系统数据传输优化算法

在认知Mesh系统进行数据传输的过程中,为了提高数据包投递成功率及网络的吞吐量,减少网络延迟时间,提出一种联合多信道分配决策的认知Mesh系统数据传输优化算法(JCWN)。针对信道的干扰问题,建立了认知Mesh系统的干扰无向图,分析节点链路的网络干扰电平。在节点的路由请求阶段通过提出基于信道干扰电平的路由指标函数,并通过权重阈值来为节点链路分配干扰较小的信道。在路由选择上,联合多路由算法计算每条路由路径的信道干扰程度,为了保障节点传输数据的成功率而选择干扰程度更小的路由。实验仿真结果表明,在数据包投递成功率上,该算法相比POC算法以及基于RL的算法提高了20%以上,在提高网络吞吐量,减少延迟时间上也表现出了更好地效果。     

Improving inter-node communications in multi-core clusters using a contention-free process mapping algorithm

High performance clusters, which are established by connecting many computing nodes together, are known as one of main architectures to obtain extremely high performance. Currently, these systems are moving from multi-core architectures to many-core architectures to enhance their computational capabilities. This trend would eventually cause network interfaces to be a performance bottleneck because these interfaces are few in number and cannot handle multiple network requests at a time. The consequence of such issue would be higher waiting time at the network interface queue and lower performance. In this paper, we tackle this problem by introducing a process mapping algorithm, which attempts to improve inter-node communications in multi-core clusters. Our mapping strategy reduces accesses to the network interface by distributing communication-intensive processes among computing nodes, which leads to lower waiting time at the network interface queue. Performance results for synthetic and real workloads reveal that the proposed strategy improves the performance from 8 % up to 90 % in tested cases compared to other methods.     

代理移动IPv6多接口接入分析与测试

未来移动节点必须支持多个网络接口的应用。代理移动IPv6（PMIPv6）协议可以为移动节点提供基于网络的移动性管理,不需要移动节点参与移动性管理。分析了多接口技术在PMIPv6下的应用,详述了基于虚拟接口实现多接口接入PMIPv6的方法。在实验室集成开发环境下进行了实验测试,测试表明基于虚拟接口的PMIPv6多接口接入基本实现了多家乡和异构切换功能。     

Rendezvous in networks in spite of delay faults

Two mobile agents, starting from different nodes of an unknown network, have to meet at a node. Agents move in synchronous rounds using a deterministic algorithm. Each agent has a different label, which it can use in the execution of the algorithm, but it does not know the label of the other agent. Agents do not know any bound on the size of the network. In each round an agent decides if it remains idle or if it wants to move to one of the adjacent nodes. Agents are subject to delay faults: if an agent incurs a fault in a given round, it remains in the current node, regardless of its decision. If it planned to move and the fault happened, the agent is aware of it. We consider three scenarios of fault distribution: random (independently in each round and for each agent with constant probability \(0<p<1\)), unbounded adversarial (the adversary can delay an agent for an arbitrary finite number of consecutive rounds) and bounded adversarial (the adversary can delay an agent for at most c consecutive rounds, where c is unknown to the agents). The quality measure of a rendezvous algorithm is its cost, which is the total number of edge traversals. For random faults, we show an algorithm with cost polynomial in the size n of the network and polylogarithmic in the larger label L, which achieves rendezvous with very high probability in arbitrary networks. By contrast, for unbounded adversarial faults we show that rendezvous is not possible, even in the class of rings. Under this scenario we give a rendezvous algorithm with cost \(O(n\ell )\), where \(\ell \) is the smaller label, working in arbitrary trees, and we show that \(\varOmega (\ell )\) is the lower bound on rendezvous cost, even for the two-node tree. For bounded adversarial faults, we give a rendezvous algorithm working for arbitrary networks, with cost polynomial in n, and logarithmic in the bound c and in the larger label L.     

一种多路由器多接口的移动网络多宿方案

为了解决移动网络中移动路由器易出现的单点失效和性能瓶颈的问题,针对现有多宿方案不能同时处理多路由器和多接口混合多宿,以及需要修改网络内部节点等不足,提出了一种可以适用于混合多宿场景的移动网络多宿方案MM-NEMO。该方案定义了移动路由器外部接口常用的重要属性以及这些属性的维护方法,并通过多播技术在移动路由器之间动态地交换接口属性,使移动网络中所有外部接口的信息都以分布式存储的形式保存在每个移动路由器中;然后移动路由器对内部节点发起的通信使用基于信息熵的多属性决策机制进行最佳接口的选择、分配或重定向。特性分析表明,该方案可以同时满足多路由器、多接口以及混合场景的需求,并且对网络内部节点保持透明。仿真结果表明,该方案具有较低的端到端时延和较高的总吞吐量。     

Self-organization of unattended wireless acoustic sensor networks for ground target tracking

A distributed, self-organization algorithm for ground target tracking using unattended acoustic sensor network is developed. Instead of using microphone arrays, each sensor node in the sensor network uses only a single microphone as its sensing device. This design can greatly reduce the size and cost of each sensor node and allow more flexible deployment of the sensor network. The self-organization algorithm presented in this paper can dynamically select proper sensor nodes to form the localization sensor groups that can work as a virtual microphone array to perform energy efficient target localization and tracking. To achieve this, we use a time-delay based bearing estimation plus triangulation for source localization in the sensor network. Major error sources of the localization method like time delay estimation, bearing calculation and triangulation are analyzed and sensor selection criteria are developed. Based on these criteria and neighborhood information of each sensor node, a distributed self-organization algorithm is developed. Simulation results show the effectiveness of the proposed algorithm.