一种高效的基于服务功能规约的服务选择方法

服务因其灵活的应用机制,逐渐成为软件开发过程中的主要载体.面对网络中涌现出的大量功能相同或相似而QoS(quality of service)不同的服务群体,如何快速、准确地定位到所需要的服务个体,仍是一项十分具有挑战性的工作.基于服务对功能的封装特性,提出一种基于服务功能规约的服务选择方法,将功能相关的抽象服务规约为一个粒度更大的服务级的抽象服务;然后,针对规约后的大粒度抽象服务完成服务发现和组合优化的过程.由于规约操作能够有效减少参与服务组合优化的抽象服务的个数以及相应的候选服务的个数,从而使算法的执行效率得到有效提升.实验结果表明:该算法与传统的启发式算法相比执行效率更高,并且对服务组合规模及候选服务规模表现出更好的扩展性.     

QoS感知的副本放置问题研究综述

副本技术是分布式存储中的重要技术.与传统副本放置问题不同,QoS感知的副本放置关注单个访问请求的服务质量需求满足.介绍了QoS感知的副本放置问题出现的背景,归纳了系统的抽象模型与问题的定义,并逐一介绍了当前几种较好的算法.通过自行设计和实现的副本放置模拟器,对现有算法进行了定性和定量分析,讨论了算法的优劣性,并指出进一步研究需要关注的问题.     

事件驱动的无线多媒体传感器网络QoS通信协议

提出一种事件驱动的无线多媒体传感网QoS感知通信(EDQC)协议。首先,当监测到事件发生时,在满足事件监测质量的基础上,启动最少的视频节点进行数据采集,以减少冗余数据的产生。其次,在数据传输阶段,计算由前进距离、队列长度和剩余能量构成的复合权值,并选择权值最大的下一跳节点进行数据转发,从而避开拥塞区域、延长网络生存周期。仿真结果表明,EDQC协议能够较好的适应视频监测需求,同时减少通信拥塞、均衡节点能耗。     

基于服务质量的LTE增值业务下行跨层调度算法

针对LTE系统如何实现不同增值业务用户速率的问题,提出一种优化型比例公平(PF)算法。该算法在用户签约速率不能实现时,考虑信道条件、付费等级和满意度,同时通过引入业务服务质量(QoS)特征函数合理调度付费用户,从而实现各付费等级对应的用户速率。在Matlab环境中进行仿真,其中优化型算法在满意度、有效吞吐量方面优于传统PF算法。与PF算法相比,优化型算法使付费用户间满意度均值相差约26%,有效吞吐量均值提升约17%。仿真结果表明,优化型算法在保证多业务服务质量的前提下,可以实现各付费用户的感知平均速率,保障不同付费用户满意度,并提高系统有效吞吐量。     

Cyber–physical systems technologies and application — Part II

The second part of the special issue presents more practical issues on cyber–physical systems technologies and application. We have selected five research papers whose topics are strongly related to this special issue. As continued from the part 1, we have selected 5 additional papers.     

Design and implementation of a QoS-aware MAC protocol for Wireless Multimedia Sensor Networks

Wireless Multimedia Sensor Networks (WMSNs) have entered the class of Wireless Sensor Networks (WSNs) to meet the multimedia requirements of new emerging applications, such as surveillance and telepresence. Combining the traditional scalar sensors used in WSN nodes with tiny cameras and microphones, WMSNs commonly carry heterogeneous traffic with different Quality of Service (QoS) requirements. In order to deliver heterogeneous traffic with different requirements in highly resource constrained sensor networks, QoS provisioning and service differentiation become unavoidable. In this paper first we discuss the QoS-provisioning in sensor networks and evaluate the efficiency of existing QoS-aware MAC protocols. As a result of this evaluation, next we design and implement a QoS-aware MAC protocol for WMSNs, Diff-MAC, which integrates different methods to meet the requirements of QoS provisioning to deliver heterogeneous traffic and provides a fair all-in-one QoS-aware MAC protocol. Diff-MAC aims to increase the utilization of the channel with effective service differentiation mechanisms while providing fair and fast delivery of the data. Performance evaluation results of Diff-MAC, obtained through extensive simulations, show significant improvements, in terms of latency, data delivery and energy efficiency, compared to two other existing protocols. Implementation of Diff-MAC on Imote2 platform also reveals that the protocol with moderate complexity can be easily implemented on the resource constrained motes.     

满足原子事务与QoS端对端约束的服务优化选择方法

提出了一种基于层次服务候选图(SCG)模型优化选择方法,该方法首先利用提出的构造规则和规约规则来构造SCG模型,以建模候选服务之间的事务约束关系,并且该模型关于事务约束的正确性得以证明;其次,提出一种基于广度优先搜索(BFS)的全局QoS感知近优选择算法,该算法基于每个任务的事务属性进行放松剪枝,以控制算法的搜索规模在多项式时间内完成。最后,以网络在线发布的实际Web服务QoS数据和随机产生数据为测试集做模拟实验,结果表明本文提出方法在全局QoS效用和选择成功率方面优于其他相关方法,同时实验通过实现事务约束自动机从实践上也验证了该方法的正确性。     

基于历史用户QoS感知的Web服务发现方法

目前的Web服务发现方法,由于没有充分利用用户情境信息,导致在服务发现时间和结果准确率方面存在不足。首先对包括当前用户在内的情境相似的用户进行了聚类,缩小了服务发现的范围;然后,在此基础上利用当前用户偏好信息及情境相似的历史用户感知到的候选服务的QoS数据,给出了一种基于历史用户QoS感知的Web服务发现方法,包括候选服务的QoS数据获取和综合权重计算;最后,结合实验并与其他Web服务发现方法进行比较,证明了该方法在服务发现结果的准确率和时间效率方面均有了一定的提升。     

A QoS-aware routing algorithm based on ant-cluster in wireless multimedia sensor networks

QoS-aware routing algorithm is important in wireless multimedia sensor networks. This paper formulates a generalized QoS-aware routing model on the basis of multiple routing metrics and priorities of packets. We first introduce a 2D plain-based routing algorithm IPACR which improves the standard ant colony algorithm by optimizing the initial distribution of artificial pheromone in order to accelerate the algorithm convergence rate. Then a clustering-based routing algorithm ICACR is presented which can be well applied in a large scale network. ICACR is a variation of IPACR because it can be suitable for clustering cases to satisfy the larger scale situations. Both the numerical algorithm performance analysis and simulation of IPACR and ICACR are given. The results show that ICACR outperforms IPACR in terms of both network lifetime and QoS-aware routing metrics in large scale wireless multimedia sensor networks. Moreover, the simulation based on the real video traces shows that by extending the multi-path to ICACR for different priorities of video frames better performance can be achieved.     

基于时序约束分解的QoS感知的Web服务组合

基于时序约束的QoS感知的Web服务组合(TC-QSC)问题是在考虑时序约束的基础上寻找满足QoS约束或效用最大化的Web服务组合问题,受到了越来越多的关注.本文提出了一种时序约束分解方法,把施加于整个或部分工作流的时序约束分解为施加于每个活动的局部时序约束,从而将TC-QSC问题转换为一般的QoS感知的Web服务组合(QSC)问题,并通过过滤不满足局部时序约束的候选服务,一定程度上减小原问题的规模.这种时序约束分解过程主要依赖于工作流及其涉及的活动,而与各活动的候选服务关联不大,复杂度较低.实验测试了该方法的效果与时间开销,验证了其对于局部优选算法的必要性.