网络服务质量评估体系研究

讨论了QoS中的一项关键技术，即网络服务质量评估技术。基于SLA的核心思想，提出一个QoS评估模型，从6个方面描述了评估体系模型的构成。根据内容提供商、网络运营商、其它服务提供商和用户所处位置的不同，定义了两种网络性能参数的采集方法。给出业务分层和SLA服务性能指标的对应关系。以SLA高层应用为例详细介绍了6个性能指标的计算方法。     

基于实时服务质量的测控网络实时消息分析研究

根据分布式测控网络系统实时通信的特点及实时性的内在要求，提出了实时服务质量的概念及指标体系，建立了抽象的实时服务质量数学函数，并用实时服务质量具体指标对实时消息进行约束。实时服务质量对测控网络实例的实时分析表明：实时服务质量概念及指标体系对分布式测控网络这一类实时系统的分析与实现具有指导意义。     

PROFIBUS通信性能测试与参数设置分析

PROFIBUS现场总线协议的实时性是评价其性能的关键因素,因此,如何研究和计算实时性能参数显得尤为重要. 针对这一问题,在对PROFIBUS总线存取协议深入分析的基础上,设计了基于PROFIBUS-DP通信性能测试平台. 通过测试平台分析和计算了包信息率、传输效率、网络平均利用率、网络吞吐量、传输延迟和令牌循环时间等实时性能参数,并给出了总线循环时间与主站个数及报文数量之间的关系之间的关系,从而定性定量分析了PROFIBUS-DP现场总线的实时性能.     

无线传感器网络适应QoS机制的网络模型

基于无线传感器网络服务质量(QoS)的特点，提出了一个独立于具体算法的、在点和边上都可加权的有向图网络模型，并用数学定义描述了QoS参数间的关系及服从的函数约束，使用该网络模型分析QoS路由的数学约束集并提出QoS路由选择策略。     

基于共享缓存的无线网络呼叫接纳控制算法

针对移动网络中新的增值数据业务的增加、性能指标多样化的现状，提出了一种具有共享缓存、支持可变比特率业务的接入网系统模型，给出了性能参数的计算方法、兼顾分组层性能参数(丢包率和平均时延)和连接层性能参数的CAC算法，数值计算结果表明了该方法的正确性。     

基于线性函数的QoS路由预计算算法

多度量的服务质量路由(QoSR)作为下一代互联网的一个重要难题，具有NPC的复杂度．作者设计了启发式算法(LFP)使用线性函数将两个度量转化成单一函数值，进而通过多个不同线性函数实现了与服务质量请求无关的QoSR预计算方式．文章分析了线性函数对算法性能的影响，给出了服务质量约束的可行区域和不可行区域的线性函数判定方法．实验结果表明，算法使用少量均匀分布的线性函数，即可产生具有较高路由性能的QoSR路由表，在可扩展性和路由性能等方面均明显优于现有算法。     

MANET能量与其他网络性能平衡路由协议

提出了一种网络性能平衡估价函数，该函数考虑了节点通信过程中的通信信息，包括节点已成功传送的数据包数、掉包数、已发送的控制包数、路由发起次数、路由总跳数以及节点的剩余能量。基于该函数，设计了一种基于能量和其他网络性能参数平衡的路由协议——BEOP，该协议通过在网络中选择平衡估价函数值小于给定阈值的节点作为路由节点，从而得到一条网络性能较优的传输路径。仿真结果表明，该协议能够很好地平衡网络性能，与DSR、MBCR协议相比，BEOP协议在网络平均时延、平均吞吐量、控制开销、丢包率、包成功发送率及网络生存时间等性能上都有较好的改善。     

径向基函数网络在数值计算中的应用

由经典的函数逼近理论衍生的很多数值算法有共同的缺点：计算量大、适应性差、对模型和数据要求高，在实际应用中受到限制。神经网络可以被用来计算复杂输入与输出结果之间的关系，故神经网络具有很强的函数逼近功能。该文给出了径向基函数网络（RBFNN）的结构及学习过程，重点阐述了RBFNN在函数逼近、求解非线性方程组以及散乱数据插值中的应用，结合MATLAB神经网络工具箱给出了数值实例，并与BP网络进行了比较。应用结果表明RBFNN是数值计算的一个有力工具，与传统方法比较具有编程简单、实用的特点，在工程和科学研究上若将其制成软件包则具有很好的使用价值。     

异构融合网络中服务质量控制仿真

针对当前网络服务质量控制方法中存在的用户满意度低和服务延迟长问题,提出基于蚁群算法的异构融合网络中服务质量控制方法。定义网络服务质量效用函数,结合质量参数层与使用者感知层关键质量参数定量评价网络服务质量,引入网络服务延迟约束条件,构建异构融合网络中服务质量控制目标函数。基于网络资源ID查询资源目前状态信息,初始化网络各资源点信息素,并计算任务分配概率值,更新局部信息素,直到任务队列中的任务均被分配至资源处理处为止。判断任务成功解决与否,假设任务没有被成功解决,则重新调度网络资源,并将任务重新排列在等待队列中。实时更新全局信息素和网络中各个节点可信度,以此综合评价此次资源调度,假设调度方案满足网络服务质量控制目标函数,则将该调度方案当作最优网络服务质量控制方案;反之,则不断更新当前解,直到得到最优网络服务质量控制方案。实验结果表明,该方法用户满意度高、服务延迟短。     

基于排队网络的多业务网络资源分析方法

随着下一代网络(NGN)的发展和新业务不断涌现,如何优化网络资源是提高业务服务质量(QoS)的重要措施之一.针对资源配置优化问题,采用排队网络理论提出一种多业务网络的资源分析方法,建立了排队服务模型,定义了流量分配方法,进行了模型求解与计算,给出了多种资源与服务质量之间的配置关系.通过仿真实验,验证了该方法的正确性.     

基于OAM性能监测的ATM QoS管理

监视网络性能参数的变化是实现ATM网络QoS管理的一个关键，但是ITU－T定义的OAM性能管理功能只简单地监视网络性能，产生报告信息，而不能对QoS的管理提供足够的支持，本文为此在讨论QoS和网络性能参数的基础上，设计了一个ATM网络的QoS管理模型，其中，对OAM性能管理功能进行了改进，一些满足QoS管理需求的ATM网络性能监测功能在OAM信元的保留字段中得以实现。     

无线多跳网QoS性能统计性边界的研究

为保证无线多跳网的服务质量（QoS）,需要求解其性能边界。基于统计型流量包络建立了无线多跳网的数据流传输模型,在此模型的基础上利用统计网络演算理论推导了无线多跳网单节点的时延统计性边界、端到端的时延统计性边界以及端到端数据积压统计性边界。仿真实验结果表明,不同数据流的测量值都在数值计算的边界范围之内,表明基于统计网络演算理论的无线多跳网QoS边界模型具有较好的性能。     

Tuning Parameters of the QoS-Aware Routing Protocol for Smart Grids Using Genetic Algorithm

Smart Grid (SG) incorporates various data communication networks to cover the complicated power systems in an intelligent and efficient way. This network utilizes the mutual flows of the data and electricity to facilitate the relations among the network components. One of the most attractive areas in the SG is the routing optimization, by which the data transmission is accompanied by Quality of Service (QoS) assurance. In this article, we tune the suggested parameters of the genetic-algorithm-inspired QoS-aware routing protocol, namely Genetic Algorithm Stable Optimization Multiconstrained Routing (GASOMCR) protocol. The QoS requirements are extracted to monitor the degree of user satisfaction of the services as well as ensure the QoS existence in the routing approach. Different sets of parameters, i.e., packet loss, path loss, effective throughput, network criticality, network availability, packet transmission delay, and connection outage probability are used to assess the QoS of the SG. These parameters are analyzed and the behavior of the network cost function is determined for each of these parameters. Appropriate parameterization of the proposed GA is very effective in the performance convergence of the network. The results obtained by GASOMCR protocol show that the performance improvement, which is obtained from minimizing the network cost function as well as having the trade-off among the various proposed parameters, is obviously achieved.     

Stochastic backlog and delay bounds of generic rate-based AIMD congestion control scheme in cognitive radio sensor networks

Performance guarantees for congestion control schemes in cognitive radio sensor networks (CRSNs) can be helpful in order to satisfy the quality of service (QoS) in different applications. Because of the high dynamicity of available bandwidth and network resources in CRSNs, it is more effective to use the stochastic guarantees. In this paper, the stochastic backlog and delay bounds of generic rate-based additive increase and multiplicative decrease (AIMD) congestion control scheme are modeled based on stochastic network calculus (SNC). Particularly, the probabilistic bounds are modeled through moment generating function (MGF)-based SNC with regard to the sending rate distribution of CR source sensors. The proposed stochastic bounds are verified through NS2-based simulations.     

Providing QoS with the Deficit Table Scheduler

A key component for networks with Quality of Service (QoS) support is the egress link scheduling algorithm. An ideal scheduling algorithm implemented in a high-performance network with QoS support should satisfy two main properties: good end-to-end delay and implementation simplicity. Table-based schedulers try to offer a simple implementation and good latency bounds. Some of the latest proposals of network technologies, like Advanced Switching and InfiniBand, include in their specifications one of these schedulers. However, these table-based schedulers do not work properly with variable packet sizes, as is usually the case in current network technologies. We have proposed a new table-based scheduler, which we have called Deficit Table (DTable) scheduler, that works properly with variable packet sizes. Moreover, we have proposed a methodology to configure this table-based scheduler in such a way that it permits us to decouple the bounding between the bandwidth and latency assignments. In this paper, we thoroughly review the provision of QoS with the DTable scheduler and our configuration methodology, and evaluate the performance of our proposals in a multimedia scenario. Simulation results show that our proposals are able to provide a similar latency performance than more complex scheduling algorithms. Moreover, we show the advantages of our decoupling configuration methodology over the usual ways of configuring this kind of table-based schedulers.     

A calculus for stochastic QoS analysis

The issue of Quality of Service (QoS) performance analysis in packet-switched networks has drawn a lot of attention in the networking community. There is a lot of work including an elegant theory under the name of network calculus, which focuses on analysis of deterministic worst case QoS performance bounds. In the meantime, researchers have studied stochastic QoS performance for specific schedulers. However, most previous works on deterministic QoS analysis or stochastic QoS analysis have only considered a server that provides deterministic service, i.e. deterministically bounded rate service. Few have considered the behavior of a stochastic server that provides input flows with variable rate service, for example wireless links. In this paper, we propose a stochastic network calculus to analyze the end-to-end stochastic QoS performance of a system with stochastically bounded input traffic over a series of deterministic and stochastic servers. We also prove that a server serving an aggregate of flows can be regarded as a stochastic server for individual flows within the aggregate. Based on this, the proposed framework is further applied to analyze per-flow stochastic QoS performance under aggregate scheduling.     

基于网络演算的簇树WSN性能上界分析

为保证WSN的服务质量(QoS),需精确求解其性能上界。对进入WSN节点的数据流进行漏桶管制,节点为数据流提供基于速率-延迟模型的服务保障,在已有簇状拓扑WSN性能模型研究基础上,利用确定性网络演算理论推导簇树WSN节点的有效带宽、缓冲区队列长度上界和数据流端到端延迟上界。     

多波长光传送网QoS管理技术研究

文章介绍了QoS管理的概念,以及和网络管理之间的关系,提出了一种光传送网QoS管理的框架。根据光传送网的特点以及可能的业务种类,定义了一组基本的光传送QoS参数,并讨论了光网QoS参数到网络性能参数的映射问题。     

基于马尔可夫链与服务质量的网络可用性

针对网络可用性在不同网络业务中的服务质量（QoS）存在差异,且与性能花费相互制约的问题,引入了马尔可夫链理论,在定义了基于业务开销最小的服务能力匹配度的基础上构建了基于马尔可夫链和QoS指标的网络可用性（MCQNA）评价模型。首先,从最能反映网络可用特征的QoS指标出发,兼顾性能开销,同时定义了代价函数,并且给出了状态转移矩阵;然后,通过平稳状态与网络可用性关系的分析,求解出平稳分布并作为QoS运行开销的动态权重,实现了以业务运行代价最小为特点的网络可用性评判。仿真结果表明,所提模型构建的遍历性转移矩阵存在平稳分布,对网络可用性评判是可行的。该模型能针对不同业务的QoS标准,且有效针对具体业务衡量网络的可用性。     

Specification,Mapping and Control for QoS Adaptation

In this paper we describe a fuzzy-control approach for quality of service (QoS) adaptation, needed in distributed multimedia applications. QoS adaptation is necessary (a) due to sudden variations in network resource availability, especially in the case of Internet, and (b) due to multiple applications requiring shared resource such as bandwidth. To solve the problem of QoS adaptation, several sub-problems need to be considered: (1) mapping of user perception and different combinations of application QoS values onto a uniform quality metric, (2) estimation, control and adjustment of application QoS parameters in case of network and other resource congestion, and (3) enforcement algorithm which reacts according to adapted QoS parameters. Our approach is to solve the QoS adaptation using the integration of (a) quality degree function, which maps the application QoS parameters into a metric, called quality degree, (b) fuzzy controller, which controls, estimates and adjusts the application QoS parameters according to resource availability, and (c) filter algorithms, which are the services to enforce the adapted QoS parameters. The quality degree function associates quality degree as the quality measure with different combinations of application QoS values. This function is influenced by the users perception of quality. The fuzzy control takes the results of the quality degree function, estimates the new quality degree and its corresponding quality level, predicts the new application QoS parameters, and adjusts them. The results of the adapted QoS parameters are then used by the filter algorithms to enforce the changes, proposed by the fuzzy controller, by allocating bandwidth to the application according to its QoS parameter values. We have implemented and applied the quality degree function, the fuzzy controller, and the filter algorithms to the video distribution system (VDS). The results of VDS over the local area network show that (1) the target system improves user perceived QoS at the receivers, and (2) the bandwidth utilization increases significantly when using our fuzzy-control approach for QoS adaptation.