基于Chord覆盖网络索引结构的多属性查询

文中给出了一种基于Chord覆盖网络索引结构的多属性查询处理技术.利用卡诺图计算查询结果所在的节点,并以多播树的方式将查询请求发送到对应的节点上,从而实现了相邻数据之间的快速路由.实验证明了该方法在处理多属性查询时的有效性和高效性.     

非结构化P2P网络中基于物理位置与Bloom-filter的副本一致性维护机制

拥有一个有效的一致性维护机制是保证P2P系统正常运行的关键之一。非结构化P2P系统中的消息传播主要通过邻居的转发,会产生大量冗余消息;并且,系统中节点的物理位置和逻辑位置存在着不匹配,会增加消息传播的时间开销。为减少一致性维护代价,该文提出基于物理位置与Bloom-filter的副本一致性维护机制。该机制利用复杂网络中社团划分思想,将网络中的节点按物理位置划分成多个簇,簇中节点物理位置相近,让更新在簇内进行;再引入双层Bloom-filter和冗余二级邻居改进现有更新消息的传播方法。实验表明,该机制可以降低更新消息的冗余传播和一致性维护的时间开销。     

用户簇分布的异构网络建模与覆盖分析

针对第五代/后五代 (The Fifth generation/Beyond The Fifth Generation ,5G/B5G)移动网络以用户为中心的小基站密集部署问题,构建了一个用户簇分布的三层异构网络模型。该网络模型由宏基站(Macro Base Station, MBS)、微微基站(Pico Base Station, PBS)和毫微微基站(Femto Base Station, FBS)组成。采用随机几何理论对三层异构网络的基站部署进行建模。充分分析了毫微微基站层基于SSA干扰管理的网络干扰统计特性,考虑了有序FBS和无序FBS两种情况,给出了FBS下行链路的覆盖概率。通过仿真,验证了理论结果的正确性,分析了覆盖半径、方差以及宏基站密度对覆盖概率的影响,得出有序FBS方案和无序FBS方案在覆盖概率方面的好坏性取决于系统参数。      

基于分类的软件定义网络流表更新一致性方案

软件定义网络是近年来的研究热点,流表更新问题则是其中的一个重要问题。该文提出基于分类的流表更新一致性方案,在保证更新一致性的同时,具有通用性强、有效减轻控制负载等特点。文中引入逻辑证明来验证所提方案能够保证流表更新一致性。多个场景的仿真结果显示,与相关研究相比,该文方案有更好的通用性,更新时间基本一致,能有效降低控制负载。     

带非线性项的异构多智能体系统一致性研究

针对一阶线性、二阶带有非线性项的异构多智能体系统在无向拓扑结构条件下的一致性问题,通过修改现有的一种分布式控制协议,利用图论、Lyapunov稳定性理论和Lasalle不变集理论,得出该异构智能体系统达到一致性的充分条件.使用Simulink搭建四旋翼无人机和智能小车组成的带非线性环节的异构多智能体平台,并将研究理论结...     

基于覆盖树的电路网络分析法

在一般的电路网络分析方法中,割集电压法是选择任意一棵树的树支电压ut作为独立变量,回路电流法是选择任意一棵树的连支电流il作为独立变量,而所选择的任意树并不能以其连支电压ul或树支电流it为独立变量进行分析.本文引进覆盖树的概念,在覆盖树的基础上提出了使树支电压和连支电压、连支电流和树支电流能够互为线性组合的定理,并对该定理进行了证明.以该定理为基础,使得树支上的电压和电流、连支上的电流和电压均可作为独立变量进行分析求解,使电路分析更为灵活简便.     

基于最小生成树的异构传感器网络抗共谋优化方案

基于EBS (Exclusion Basis Systems)的密钥管理协议,以安全性高、动态性和扩展性好,较适用于异构传感器网络,但却存在共谋问题。该文提出了一种基于MST (Minimum Spanning Tree)的密钥共谋问题优化方案。该方案利用Prim算法对由簇内感知节点所构成的无向连通图进行最小生成树求解,并对该树进行遍历,根据所得节点遍历顺序进行密钥的指派与分配,使得相邻节点间所含的密钥重叠程度增大,发生共谋的可能性得到降低。实验结果表明：同比于密钥随机分配方案与SHELL方案,所提方案有效提高了网络的抗捕获能力。     

邻近信息约束下的随机异构无线传感器网络节点调度算法

针对高密度部署的随机异构传感器网络内部存在的覆盖冗余问题,该文提出一种随机异构无线传感器网络的节点调度算法(NSSH)。在网络原型拓扑的支撑下构建Delaunary三角剖分,规划出节点进行本地化调度的局部工作子集。通过折中与邻近节点的空外接圆半径,完成对感知半径的独立配置;引入几何线、面概念,利用重叠面积和有效约束圆弧完成对灰、黑色节点的分类识别,使得节点仅依赖本地及邻居信息进行半径调整和冗余休眠。仿真结果表明,NSSH能以低复杂度的代价,近似追平贪婪算法的去冗余性能,并表现出了对网络规模、异构跨度和参数配置的低敏感性。     

基于节点相似度的CCN社区划分方法

针对内容中心网络(Content Centric Networking,CCN)中路由检索过程造成大量低效的冗余问题,进行了更深一层的研究,结合节点相似度、标签传播等方法,将CCN网络拓扑划分为多个社区。该方法首先将CCN网络中各个请求节点以及节点内容进行名字解析,以便获取用户的兴趣偏好,并将节点中影响力较高的节点作为社区核心节点,再将节点划分社区,实现内容快速缓存,有效地避免了CCN网络检索所造成的数据冗余问题,进一步提高整个网络速度,提高资源利用率,减少数据冗余。     

Proactive load balancing with admission control for heterogeneous overlay networks

The next generation wireless networks will be the coexistence of heterogeneous wireless technologies. Balancing the traffic load among different networks can effectively utilize the overall radio resources in the system. In this paper, we propose an efficient load balancing scheme for the heterogeneous overlay systems, which is applied in the call admission control process. If the available network(s) cannot provide enough resource for the request call without degrading the quality‐of‐service (QoS) obtained by the ongoing calls, the system will perform load balancing operations first by initiating vertical handoffs among networks in order to create more rooms for the request call. The load balancing algorithm is to minimize the variance between the network utilizations of the entire system, which can be formulated as a quadratic binary programming problem. Simulation results show that the proposed scheme can admit more calls into the system compared with the other three reference schemes and then improve the overall throughput. Meanwhile, the scheme can keep the networks working in effective states and provide a better QoS support for users. Copyright © 2011 John Wiley & Sons, Ltd.     

Resource allocation based on dynamic hybrid overlay/underlay for heterogeneous services of cognitive radio networks

In cognitive radio networks (CRNs), hybrid overlay and underlay sharing transmission mode is an effective technique to improve the efficiency of radio spectrum. Unlike existing works in literatures where only one secondary user (SU) uses both overlay and underlay mode, the different transmission modes should dynamically be allocated to different SUs according to their different quality of services (QoS) to achieve the maximal efficiency of radio spectrum. However, dynamic sharing mode allocation for heterogeneous services is still a great challenge in CNRs. In this paper, we propose a new resource allocation method based on dynamic allocation hybrid sharing transmission mode of overlay and underlay (Dy-HySOU) to obtain extra spectrum resource for SUs without interfering with the primary users. We formulate the Dy-HySOU resource allocation problem as a mixed-integer programming to optimize the total system throughput with simultaneous heterogeneous QoS guarantee. To decrease the algorithm complexity, we divide the problem into two sub-problems: subchannel allocation and power allocation. Cutset is used to achieve the optimal subchannel allocation, and the optimal power allocation is obtained by Lagrangian dual function decomposition and subgradient algorithm. Simulation results show that the proposed algorithm further improves spectrum utilization with simultaneous fairness guarantee, and the achieved Dy-HySOU diversity gain is satisfying.     

一种无线异构网络中的分步协作基站分簇方法

为抑制小区间干扰提高系统性能,基于异构网络提出了一种分步基站分簇方法。该方法首先依据期望用户受到的除主服务基站之外的其余基站的信号干扰强度,确定待分簇基站集合;然后根据期望用户接收到待选集合中各个基站的信号强度,确定最终参与协作的基站集合。分步基站分簇方法通过缩小用户选择范围,同时综合考虑用户所在小区的信号强度和周围基站的干扰信号强度进行协作基站分簇。仿真结果表明：相对于现有功率最大法和阈值法,基于分步的基站分簇方法具有更高的用户端传输速率,更好地提升了系统性能。     

Market-based self-optimization for autonomic service overlay networks

Rather than managing their heterogeneity and dynamic behavior through centralized intervention, overlay nodes can be programmed to self-organize and self-manage the network. To achieve the highest performance within a service overlay, they are further expected to self-optimize the network, by cooperatively providing and allocating resources in an optimal manner. However, since nodes are inherently selfish about resources they contribute or consume, self-optimization could not be achieved if they are not given the correct incentives. In this paper, we investigate the effectiveness of a market-based incentive mechanism in directing nodes' behavior and enabling self-optimizations. We have designed an intelligent market model for a service overlay network, based on which individual nodes, being service producers and consumers, determine their own resource contributions, consumptions, or service prices based on their own utility maximization goals. We also propose optimal decision making solutions for nodes to achieve their self-interests; in particular, service providers are provided with a control-based pricing solution based on system identification techniques. With the multicast streaming application as an example, we show through simulations that, even when selfish nodes all seek their maximal utilities, the resulting network still achieves close-to-optimal performance in both steady and dynamic states. The results also indicate that, by encouraging nodes to behave selfishly and intelligently in a designed market, self-optimization in other autonomic systems may be facilitated in the presence of node selfishness.     

可重构服务承载网愈合机理研究

提出了一种服务承载网的快速愈合算法。该算法将服务承载网的愈合问题等价地转化为多商品流问题进行解决。通过大量的仿真实验的验证和量化分析表明,该方法相比较传统的全局重映射方法,能更高效地提高服务承载网的愈合成功率以及愈合效率,从而快速地实现网络服务的恢复,并可显著地降低对底层网络负载的影响。     

Node delay assignment strategies to support end-to-end delay requirements in heterogeneous networks

In a complex, heterogeneous network environment, such as the Internet, packets traversing different networks may be subjected to different treatments and may face different traffic loads across the routing path. This paper addresses the key issue of how to assign delay budgets to each network node along the routing path so that the end-to-end delay requirements of the supported applications are met. First, we describe a methodology to compute for a given flow a set of feasible per-node delays for the class of delay-based servers. We then formalize an optimal per-node delay assignment problem which takes into consideration the workload across the routing path. The solution, for homogeneous and heterogeneous networks, is provided. The resulting solution is optimal, but its implementation overhead is relatively high. To overcome this shortcoming, we propose two heuristics, EPH() and LBH(), to approximate the optimal strategy. EPH() uses the equi-partition concept to compute initial delay values and adjust these delay values to meet the end-to-end delay requirements. LBH() uses a relaxation factor to distribute the load proportionally across all nodes on the routing path. A simulation-based comparative analysis shows that the heuristics perform closely to the optimal schemes.     

一种改进的无结构P2P网络搜索策略

点对点(Peer-to-Peer)网络已发展成为当今最为流行的资源共享系统之一.其中的资源搜索是一个关键性问题.但其常用的基于简单flooding机制的信息资源搜索方法造成了严重的通信消耗,本文借鉴人际传播中谣言传播机制,结合节点吸引因子(在真实系统中,新增节点不仅与网络中已有的度数较高的节点连接,而且与吸引因子较大的...     

Adaptive processing in overlay networks for performance improvement

Wireless Networks - This paper proposes an overlay network wherein a pair of licensed source (LS) and licensed destination (LD) is adaptively assisted by a pair of unlicensed source (US) and...     

Resilient self-organizing overlay networks for security update delivery

Rapid and widespread dissemination of security updates throughout the Internet will be invaluable for many purposes, including sending early-warning signals, updating certificate revocation lists, distributing new virus signatures, etc. Notifying a large number of machines securely, quickly, and reliably is challenging. Such a system must outpace the propagation of threats, handle complexities in a large-scale environment, deal with interruption attacks on dissemination, and also secure itself. Revere addresses these problems by building a large-scale, self-organizing, and resilient overlay network on top of the Internet. We discuss how to secure the dissemination procedure and the overlay network, considering possible attacks and countermeasures. We present experimental measurements of a prototype implementation of Revere gathered using a large-scale-oriented approach. These measurements suggest that Revere can deliver security updates at the required scale, speed and resiliency for a reasonable cost.     

Cooperative cache consistency maintenance for pervasive internet access

Cooperative caching is an important technique to support pervasive Internet access. In order to ensure valid data access, the cache consistency must be maintained properly. However, this problem has not been sufficiently studied in mobile computing environments, especially those with ad hoc networks. There are two essential issues in cache consistency maintenance: consistency control initiation and data update propagation. Consistency control initiation not only decides the cache consistency provided to the users, but also impacts the consistency maintenance cost. This issue becomes more challenging in asynchronous and fully distributed ad hoc networks. To this end, we propose the predictive consistency control initiation (PCCI) algorithm, which adaptively initiates consistency control based on its online predictions of forthcoming data updates and cache queries. In order to efficiently propagate data updates through multi‐hop wireless connections, the hierarchical data update propagation (HDUP) algorithm is proposed. Theoretical analysis shows that cooperation among the caching nodes facilitates data update propagation. Extensive simulations are conducted to evaluate performance of both PCCI and HDUP. Evaluation results show that PCCI cost‐effectively initiates consistency control even when faced with dynamic changes in data update rate, cache query rate, node speed, and number of caching nodes. The evaluation results also show that HDUP saves cost for data update propagation by up to 66%. Copyright © 2009 John Wiley & Sons, Ltd.