Real-time data dissemination in mobile peer-to-peer networks

Mobile peer-to-peer networks have found many uses such as streaming of audio and video data. There are circumstances, such as emergency situations and disaster recovery, when real-time delivery is a fundamental requirement. The problem is challenging due to the limited network capacity, the variable transmission rates and the unpredictability with respect to the network conditions in the mobile peer-to-peer network.In this paper we address the problem of real-time data dissemination of multimedia streams in mobile peer-to-peer networks. Four routing algorithms are proposed based on a packet's deadline, priority or a combination of these metrics. They are simulated under different setups in a mobile peer-to-peer network with Bluetooth connectivity and nodes broadcasting audio and video streams using different priorities. We compare the performance of the algorithms using a number of metrics. Detailed experimental results are presented. Based on these results, propositions on the usage of the algorithms and the design of network requirements are presented.     

Analysis of a CDN–P2P hybrid architecture for cost-effective streaming media distribution

To distribute video and audio data in real-time streaming mode, two different technologies – Content Distribution Network (CDN) and Peer-to-Peer (P2P) – have been proposed. However, both technologies have their own limitations: CDN servers are expensive to deploy and maintain, and consequently incur a cost for media providers and/or clients for server capacity reservation. On the other hand, a P2P-based architecture requires sufficient number of seed supplying peers to jumpstart the distribution process. Compared with a CDN server, a peer usually offers much lower out-bound streaming rate and hence multiple peers must jointly stream a media data to a requesting peer. Furthermore, it is not clear how to determine how much a peer should contribute back to the system after receiving the media data, in order to sustain the overall media distribution capacity.In this paper, we propose and analyze a novel hybrid architecture that integrates both CDN- and P2P-based streaming media distribution. The architecture is highly cost-effective: it significantly lowers the cost of CDN capacity reservation, without compromising the media quality delivered. In particular, we propose and compare different limited contribution policies for peers that request a media data, so that the streaming capacity of each peer can be exploited on a fair and limited basis. We present: (1) in-depth analysis of the proposed architecture under different contribution policies, and (2) extensive simulation results which validate the analysis. Our analytical and simulation results form a rigorous basis for the planning and dimensioning of the hybrid architecture.     

能量有效的无线传感器网络层次型路由协议

为改善LEACH中节点能耗不均而过早失效的情况,提出了一种能量有效的无线传感器网络层次型路由协议EEHRP,它采用一种智能延迟策略选取簇头,尽可能使得剩余能量越高的节点时延越小,它们能够先于周围剩余能量较低的节点发送簇头通告。在路由算法中引入了网关节点,能有效避免簇头远距离传送数据造成的能耗过多。仿真表明,EEHRP可使节点的能量消耗更均匀,有效地延长了网络生存时间。     

服务总线支持Pub-Sub模式的路由研究

近年来,随着电信行业业务应用的发展,对电信业务服务质量提出了更高的要求。面向服务的体系结构（SOA）提供面向业务的系统框架。采用SOA架构的电信业务系统能满足处理性能、稳定性、完整性及其智能化程度等因素上的高要求。本文以电信行业业务服务性能为目的,从SOA架构的核心基础设施企业服务总线（ESB）对服务路由的支持着眼,提供服务跨系统的Pub／Sub交互,在基础设施上满足服务性能需求,并应用到电信行业中。     

Modeling and analyzing the performance of adaptive hierarchical networks

As networks become larger, scalability and QoS-awareness become important issues that have to be resolved. A large network can be effectively formed as a hierarchical structure, such as the inter/intra-domain routing hierarchy in the Internet and the Private Network-to-Network Interface (PNNI) standard, to resolve these critical issues. Methods of modeling and analyzing the performance of QoS-capable hierarchical networks become an open issue. Although the reduced load approximation technique has been extensively applied to flat networks, the feasibility of applying it to the hierarchical network model has seldom been investigated. Furthermore, most of the research in this area has focused on the performance evaluation with fixed routing. This work proposes an analytical model for evaluating the performance of adaptive hierarchical networks with multiple classes of traffic. We first study the reduced load approximation model for multirate loss networks, and then propose a novel performance evaluation model for networks with hierarchical routing. This model is based on a decomposition of a hierarchical route into several analytic hierarchical segments; therefore the blocking probability of the hierarchical path can be determined from the blocking probabilities of these segments. Numerical results demonstrate that the proposed model for adaptive hierarchical routing yields accurate blocking probabilities. We also investigate the convergence of the analysis model in both the originating-destination (O-D) pair and the alternative hierarchical path. Finally, the blocking probability of the adaptive hierarchical O-D pair is demonstrated to depend on the blocking of all hierarchical paths but not on the order of the hierarchical path of the same O-D pair.     

一种多频分级Ad Hoc网络的组网方案

采用多频分级结构的大型移动Ad hoc网络,需要高效的组网机制来实现控制开销少、可扩展性强的有机组织和维护,为此提出了一种分级结构的组网方案,设计并集成了分群、IPv6地址配置、路由及移动管理操作。仿真结果表明该方案能有效提高组网的效率和性能,同时对节点的群移动方式提供了良好的支持。     

无线传感器网络聚类改进层次路由协议

无线传感器网络（WSN）是一种全新的信息获取和处理技术,通常被部署在恶劣的环境中。因此能源供应一直是WSN研究的一个重要问题。层次路由协议能够有效地延长网络生存时间,已经成为无线传感器网络研究中的热点。提出了一个新的层次路由协议MHLAH,结合了LEACH和HeeD的优点,它能够合理地分布簇头节点,采用多跳的路由传输协议,延长网络的生存时间。仿真实验结果表明,与传统的LEACH和HeeD协议相比,MHLAH协议有效地平衡了网络中传感器节点的能量消耗,延长了无线传感器网络的生存周期。     

Graph-theoretic quantum system modelling for neuronal microtubules as hierarchical clustered quantum Hopfield networks

Graph-theoretic quantum system modelling (GTQSM) is facilitated by considering the fundamental unit of quantum computation and information, viz. a quantum bit or qubit as a basic building block. Unit directional vectors “ket 0” and “ket 1” constitute two distinct fundamental quantum across variable orthonormal basis vectors, for the Hilbert space, specifying the direction of propagation of information, or computation data, while complementary fundamental quantum through, or flow rate, variables specify probability parameters, or amplitudes, as surrogates for scalar quantum information measure (von Neumann entropy). This paper applies GTQSM in continuum of protein heterodimer tubulin molecules of self-assembling polymers, viz. microtubules in the brain as a holistic system of interacting components representing hierarchical clustered quantum Hopfield network, hQHN, of networks. The quantum input/output ports of the constituent elemental interaction components, or processes, of tunnelling interactions and Coulombic bidirectional interactions are in cascade and parallel interconnections with each other, while the classical output ports of all elemental components are interconnected in parallel to accumulate micro-energy functions generated in the system as Hamiltonian, or Lyapunov, energy function. The paper presents an insight, otherwise difficult to gain, for the complex system of systems represented by clustered quantum Hopfield network, hQHN, through the application of GTQSM construct.     

基于多agent和分层递阶结构的城市快速路网多模控制*

提出了基于多agent和分层递阶智能结构的城市快速路网多模控制策略。执行级agent采用单点积分反馈控制策略,协调级agent采用多匝道协调控制策略,组织级agent采用路线诱导与匝道控制相集成的控制策略。仿真表明,多模控制能灵活有效地适应路网中各种状况的实时变化,控制效果良好。     

HyMN-injection-based multimedia content distribution in hybrid wireless networks

Infrastructured networks typically employ centralized approaches for group management and information provisioning. In contrast to that, in multi-hop ad hoc networks each node acts as a router as well as sender and receiver. In pure ad hoc networks, no Internet access is available. An additional challenge is to deal with mobility that causes network partitioning and re-organizations. Technically, these problems can be tackled by providing additional uplinks to a backbone network. Those can be used to access resources in the Internet as well as to inter-link multiple ad hoc network partitions, creating a hybrid wireless network. In this paper, we present HyMN, a prototypically implemented hybrid wireless network system optimized for multimedia content providing. Within the ad hoc network, adequate devices are elected to maintain uplinks to a backbone, which can provide for instance multimedia news from certain sports events like Football Championships, Olympic Games and alike. In order to efficiently manage the ad hoc communicating devices, a weighted clustering algorithm is employed. Based on an article presented at the 2nd ACM Workshop on Wireless Multimedia Networking and Performance Modeling, WMuNeP 2006, Torremolinos, Málaga, Spain, October 2006.     

面向无线内容分发网络的树形拓扑生成算法

在无线内容分发网络中,为减轻骨干网络的传输压力,可将网络拓扑结构构建为以基站和Wi Fi接入点为根的若干棵最小生成树,并对生成树的深度和每个节点的度数进行约束。这种深度和度数约束的最小生成树问题是一个NP完全问题。针对该问题,首先提出能够生成优质近似解的启发式算法,该算法在不违反深度以及度数约束的情况下构建生成树,算法思想为在服务性节点相连的边中选择与当前生成树相连且权值最小的边加入生成树。然后在生成初始近似解的基础上采用定制的禁忌搜索算法和模拟退火算法对该近似解实施进一步优化。实验结果表明,在给定的约束条件下,禁忌搜索算法求得的解优于现有的遗传算法,在深度约束为4以及度数约束为10的条件下,解的改进幅度可达18.5%,所提算法的运行速度比遗传算法提高了10倍。     

基于图像内容层次表征的遥感图像 分割方法

提出基于图像内容层次表征的高分辨率遥感图像快速多精度分割方法。首先根据初始分割结果建立区域邻接图(RAG),并将其定义为马尔可夫随机场(MRF);然后引入光谱、形状和边缘等图像特征进行层次合并,通过记录层次合并过程获得图像内容的层次表征;最后根据层次表征中不同层级对象之间的关系快速生成任意不同精度的分割结果,以满足不同应用的需求。利用QuickBird卫星图像进行实验和评价的结果表明,本文方法具有较高的精度和效率。     

Mastering selfishness and heterogeneity in mobile P2P content distribution networks with multiple source download in cellular networks

The performance of Peer-to-Peer (P2P) content distribution networks depends highly on the coordination of the peers. This is especially true for cellular networks with mobile and often selfish users, as the resource constraints on accessible bandwidth and battery power are even more limitating in this context. Thus, it is a major challenge to identify mobile network specific problems and to develop sophisticated cooperation strategies to overcome these difficulties. Cooperation strategies, which are able to cope these problems, are the foundation for efficient mobile file exchange. The detailed performance of the strategies are determined by the peer capabilities and the peer behavior, such as the number of parallel upload connections, the selfishness, or the altruistic re-distribution of data. The purpose of this work is to evaluate and investigate different cooperation strategies which are based on multiple source download and select the best one for mobile scenarios with even leeching peers, i.e. peers which depart as soon as they have finished their download. The question arises whether the cooperation strategy can smoothen the overall performance degradation caused by a selfish peer behavior. As performance indicators the efficiency, fairness, and robustness of the cooperation strategies are applied. The considered scenarios comprise best-case (altruistic peers) and worst-case scenarios (selfish peers). We further propose a new cooperation strategy to improve the file transfer even when mainly selfish peers are present, the CycPriM (cyclic priority masking) strategy. The strategy allows an efficient P2P based content distribution using ordered chunk delivery with only local information available at a peer.     

基于分层压缩激励的ASPP网络单目深度估计

场景深度估计是场景理解的一项基本任务,其准确率反映了计算机对场景的理解程度.传统的深度估计利用金字塔池化(ASPP)模块可以在不改变图像分辨率的情况下处理不同像素特征,但该模块未考虑不同像素特征之间的关系,导致场景特征提取不准确.针对ASPP模块在深度估计中出现的弊端,提出了一种改进型的ASPP模块,解决了该模块在图像...     

Practical design of a proxy agent to facilitate adaptive video streaming service across wired/wireless networks

Thanks to the growing of the wireless networks, the video streaming application becomes a ubiquitous joyful service. In a wireless communication network environment, the service traffic spans across the wired and wireless domains. In this article, we propose a practical design of a proxy agent - SPONGE (Stream Pooler Over a Network Graded Environment) sitting between the wireless User Equipments (UEs) and the video streaming server to facilitate the adaptive video streaming service across wired/wireless networks. To make the wireless streaming service more efficient, an input video session would be encoded as multiple qualities of video streams so that UEs with a similar receiving condition can share streams with the same service quality via SPONGE. SPONGE can alleviate the direct load on the original stream broadcasting server. Meanwhile, it can make each UE get an adaptive streaming service according to the network conditions of the UE by a reduced network condition feedback latency. Our theoretical analysis and simulation results show that SPONGE can help wireless streaming users get a smooth and better playback quality by a quick and accurate reaction to the network condition.     

一种引入阈值的Ad Hoc网络分级转发指针的位置管理策略

在移动Ad Hoc网络中,由于网络具有自组织性和节点的频繁移动,也就使得网络的拓扑结构频繁变化。随着节点数目的增加,网络的开销迅速增大,这就直接影响到网络的可扩展性。目前,在移动Ad Hoc网络中越来越多的引入了位置管理的策略,以达到减少网络开销的目的。引入分级转发指针和阈值的思想,提出了一种新的位置管理策略。通过与其他策略的方针比较,证明其在性能上具有更好的可扩展性。     

Redesign of vaccine distribution networks

In most low- and middle-income countries supported by the World Health Organization's Expanded Program on Immunization, vaccines are distributed through a legacy medical supply chain that is typically not cost-efficient. Vaccines require storage and transport in a temperature-controlled environment; this requires a “cold” distribution chain with capacity constraints on cold storage and cold transport. We propose an approach to redesigning the vaccine distribution chain that includes locating a set of intermediate distribution centers (DCs) and determining the flow paths from the central store (where vaccines are received into a country) through one or more of these to health clinics where vaccination actually occurs. In addition, the transport vehicles to allocate to each flow path, and the cold storage devices to use at each clinic or intermediate DC are determined. The redesigned network does not have to follow the current four-tiered, arborescent structure commonly found in practice, but can use alternative network structures. To redesign this network optimally, we develop a mixed-integer programming (MIP) model that can be used for small-to-medium-sized problems and also present a hybrid heuristic–MIP method to obtain good solutions for larger problems. Numerical results are shown using data reflecting distribution networks in several countries in sub-Saharan Africa.     

基于人工免疫算法的配电网络重构

提出了一种人工免疫算法，有效地提高了算法的收敛速度，避免了不成熟收敛，将该算法应用于配电网络重构中．取得了较好效果。另外本文提出用支路的开关状态（0或1）作为控制参数，避开了繁琐的编码方法，缩短了编码长度，所有这些都有效地提高了计算效率。