A genetic algorithm based approach to transactional and QoS-aware service selection

As there are various risks of failure when Web services are deployed in unreliable environment, the execution of a composite Web service (CWS) requires the transaction mechanism to guarantee its reliable execution. However, the existing service selection approaches consider QoS and transaction separately and have not considered that transactional properties may affect the QoS such as the execution time of a CWS. This work addresses the importance of considering transactional properties and how the transactional properties affect the QoS simultaneously in the process of service selection by a QoS-aware and transactional-aware selection approach. First, a performance evaluation method is proposed to calculate the execution time of a transactional CWS. Then, a genetic algorithm based approach, which takes into account the execution time, price, transactional property and successful execution rate of CWS, is presented to achieve global optimisation service selection. Finally, experimental results show the efficiency and effectiveness of the approach.     

战术Ad Hoc网络中的QoS路由协议设计与仿真

基于TDMA的战术Ad Hoc网络,提出一种分布式的资源预约机制,其中收/发节点采 用协商的方式预约时隙,邻居节点通过侦听方式获得时隙被预约的信息,然后依托该机制提 出一种QoS路由协议,该协议能够在网络节点之间选择一条满足QoS要求且相对短的路径进行 预约时隙,同时对于网络拓扑变化引起的链路故障也能局部修复。仿真表明该协议具有开销 小和可靠性高等特点,能够提高战术Ad Hoc网络的QoS保障能力。     

无线局域网与无线个域网QoS机制的对比分析

无线局域网(WLAN)和无线个域网(WPAN)技术的发展带来的多媒体业务流量的剧增,使无线网络的资源管理、服务质量(QoS)保障等问题日益突出。传统的媒体访问控制(MAC)协议需要重新设计才能对无线网络的QoS问题进行有效地解决。文中研究了IEEEWLAN和WPAN工作组分别于2002年5月和2003年2月提出的IEEE802.11eD3.0和IEEE802.15.3D16两种协议标准的工作机制并对两者的性能作出了比较分析。     

OSGi及其QoS获益驱动动态软件体系结构研究

随着软件领域中移动计算、分布计算和Web Service等技术的迅速发展,软件计算环境变得越来越开放、复杂、多元。如何应对不断变化的计算环境,构建一个自适应的动态软件架构,受到了越来越多的关注。文章首先介绍一个成功的软件系统结构框架实例——Open Service Gateway Initiative(OSGi)。然后,以请求质量QoS为核心,对面向服务的OSGi框架进行扩展,提出了一个动态自适应软件架构解决方案,它以用户QoS属性为目标驱动,通过动态调整软件自身结构,以进一步提高用户期望的服务质量。实验结果证明了该调度框架的有效性。     

PTN关键技术及发展应用

PTN技术是业务向ALLIP转型对承载网的需求，首先介绍了PTN技术的概念及特点，其次重点研究了PTN中的关键技术，最后提出了PTN技术的发展应用方向。     

非静止轨道卫星系统考虑通信中断的服务质量分析

基于Globalstar和Odyssey两个Walker delta星座,建立星间链路网络,重点分析网络中的不同轨道间星间链的动态特性,特别是与星上跟瞄系统密切相关的俯仰角、方位角和链路长度变化,为卫星网络路由提供依据.对传统的卫星路由策略作了改进,利用卫星系统的冗余覆盖的特性,选择不同策略下的最优路径.针对用户不能忍受通信中断的情况,提出考虑消除中断的路由策略,进行服务质量的分析比较.同时也比较在消除中断的路由策略下,LEO同MEO网络差异之处.消除通信中断是以其它QoS性能下降为代价.     

浅析LEO卫星网络中的QoS路由问题

LEO卫星网络能够提供全球覆盖,为任何地点的用户提供适时应用服务。然而由于LEO的高速运动,LEO卫星网络的网络拓扑一直处于动态变化的过程中。文中首先分析了在这种动态变化的网络环境中QoS路由面临的新问题,接着提出了解决这些问题的几点考虑。     

一种保证QoS的组播网络设计

给出了一种利用建立一系列本地策略(优先级策略、收发数据速率调整策略、路由选择策略、组播管理策略等)的网络主机来分摊控制管理组播系统的设计，保证了组播系统拥有良好的服务质量。     

三网融合浅析

三网融合是指电信网、广播电视网和互联网的相互之间渗透、互相兼容、并逐步整合成为统一的信息网络通信平台。三网融合可以实现网络资源的共享,避免了一些低水平的重复建设,形成广泛的适应性、易维护、费用低廉的高速宽带的多媒体网络基础平台。     

Scheduling multimedia services in cloud computing environment

Currently, security is a critical factor for multimedia services running in the cloud computing environment. As an effective mechanism, trust can improve security level and mitigate attacks within cloud computing environments. Unfortunately, existing scheduling strategy for multimedia service in the cloud computing environment do not integrate trust mechanism when making scheduling decisions. In this paper, we propose a scheduling scheme for multimedia services in multi clouds. At first, a novel scheduling architecture is presented. Then, We build a trust model including both subjective trust and objective trust to evaluate the trust degree of multimedia service providers. By employing Bayesian theory, the subjective trust degree between multimedia service providers and users is obtained. According to the attributes of QoS, the objective trust degree of multimedia service providers is calculated. Finally, a scheduling algorithm integrating trust of entities is proposed by considering the deadline, cost and trust requirements of multimedia services. The scheduling algorithm heuristically hunts for reasonable resource allocations and satisfies the requirement of trust and meets deadlines for the multimedia services. Detailed simulated experiments demonstrate the effectiveness and feasibility of the proposed trust scheduling scheme.