Design and evaluation of a high throughput QoS-aware and congestion-aware router architecture for Network-on-Chip

This paper proposes a novel QoS-aware and congestion-aware Network-on-Chip architecture that not only enables quality-oriented network transmission and maintains a feasible implementation cost but also well balance traffic load inside the network to enhance overall throughput. By differentiating application traffic into different service classes, bandwidth allocation is managed accordingly to fulfill QoS requirements. Incorporating with congestion control scheme which consists of dynamic arbitration and adaptive routing path selection, high priority traffic is directed to less congested areas and is given preference to available resources. Simulation results show that average latency of high priority and overall traffic is improved dramatically for various traffic patterns. Cost evaluation results also show that the proposed router architecture requires negligible cost overhead but provides better performance for both advanced mesh NoC platforms.     

QoS Performance Bounds and Efficient Connection Admission Control for Heterogeneous Services in Wireless Cellular Networks

Quality-of-Service (QoS) performance and connection admission control (CAC) for heterogeneous services in wireless multiple access networks are investigated. The heterogeneous services include constant bit rate (CBR), variable bit rate (VBR) and available bit rate (ABR) services. Multiple access control is handled by a polling-based scheme with non-preemptive priority. Tight delay variation (jitter) bounds for CBR connections and delay bounds for VBR connections are derived. A CAC scheme based on the derived bounds is developed. The CAC makes use of user mobility information to reserve an appropriate amount of system resources for potential handoff connections to achieve low handoff connection dropping rate (HCDR). Simulation results show that the proposed CAC scheme can achieve both low HCDR and high resource utilization.     

QoS-oriented design of embedded systems with specification PEARL

Only recently have methodical tools adequate to design real-time systems been formally introduced in design methodologies. Naturally, they were present from the beginning, but due to the large diversity of embedded systems’ areas of deployment, specially dedicated formalisms have been developed and used. High-level language programming and integration of modeling formalisms into design methods eased the development of more complex real-time applications. With the emerging object-oriented programming languages and design methods, their integration into larger information systems has become more transparent. It was the UML methodology, however, which eventually merged also the design methods and concepts of real-time systems into a consistent whole. It took a large consortium and a long process to persuade industry of the benefits the new integral methodology can offer. On the other hand, there are some trade-offs, and there are some features not completely covered, yet. Here, a different, more straightforward approach to program and design (embedded) real-time systems is presented. Since it emerged from the real-time community, it includes most features relevant there. Independent of the UML profile for schedulability, performance and time specification, a profile was devised for use in PEARL-oriented UML design. The strengths of the mentioned language and design methods for QoS-oriented design of (embedded) real-time systems are emphasised throughout this article.     

并行网络控制系统服务质量管理

为解决网络控制系统因并行而导致的时延增大问题,协调并行控制效率与信息通信负荷,建立了网络控制系统并行化体系结构、质量衡量标准和服务质量管理模型.提出了基于控制器闲置时间的最大闲置时间最先(MvTF)的消息调度策略.以基于CAN总线的并行网络控制系统服务质量管理为例,建立了服务质量管理仿真模型,并将上述调度策略与单调速率调度策略进行了仿真比较.仿真结果表明,采用MVTF调度策略进行并行系统的服务质量管理能够有效提高网络控制系统的控制性能及网络利用率.     

QoS contract preservation through dynamic reconfiguration: A formal semantics approach

The increasing pervasiveness of computing services in everyday life, combined with the dynamic nature of their execution contexts, constitutes a major challenge in guaranteeing the expected quality of such services at runtime. Quality of Service (QoS) contracts have been proposed to specify expected quality levels (QoS levels) on different context conditions, with different enforcing mechanisms. In this paper we present a definition for QoS contracts as a high-level policy for governing the behavior of software systems that self-adapt at runtime in response to context changes. To realize this contract definition, we specify its formal semantics and implement it in a software framework able to execute and reconfigure software applications, in order to maintain fulfilled their associated QoS contracts. The contribution of this paper is threefold. First, we extend typed-attributed graph transformation systems and finite-state machines, and use them as denotations to specify the semantics of QoS contracts. Second, this semantics makes it possible to systematically exploit design patterns at runtime by dynamically deploying them in the managed software application. Third, our semantics guarantees self-adaptive properties such as reliability and robustness in the contract satisfaction. Finally, we evaluate the applicability of our semantics implementation by integrating and executing it in FraSCAti, a multi-scale component-based middleware, in three case studies.     

An adaptive medium access control protocol using m-ary tree algorithms for quality-of-service support in single-cell ad hoc networks

Concurrent with the rapid expansion of wireless networks is an increasing interest in providing Quality-of-Service (QoS) support to them. As a consequence, a number of medium access control protocols has been proposed which aims at providing service differentiation at the distributed wireless medium access layer. However, most of them provide only average performance assurances. We argue that average performance guarantees will be inadequate for a wide range of emerging multimedia applications and “per-flow” service assurances must be provided instead. Based on m-ary tree algorithms, we propose an adaptive and distributed medium access algorithm for single-cell ad hoc networks to provide “per-flow” service assurances to flows whose QoS requirement can be expressed as a delay requirement. Both analytical and simulation experiments are conducted to assess the performance of the proposed scheme.     

基于位置聚类和张量分解的Web服务推荐算法

基于服务质量（QoS）的Web服务推荐能在众多功能相似的Web服务中发现最能满足用户非功能需求的Web服务,但QoS属性值预测算法仍存在预测准确度不高和数据稀疏性的问题。针对以上问题,提出了一种基于位置聚类和分层张量分解的QoS预测算法ClustTD,该算法基于用户和服务的位置属性将用户和服务聚类成多个局部组,分别对局部组和全局的用户、服务和时间上下文进行张量建模和分解,将局部和全局张量分解的QoS预测值进行加权组合,同时考虑了局部和全局因素,获得最终QoS预测值。实验结果表明,该算法具有较高的QoS预测准确率和Web服务推荐质量,并能在一定程度上解决数据稀疏性问题。     

SIMULATED ANNEALING BASED POLYNOMIAL TIME QOS ROUTING ALGORITHM FOR MANETS

Multi-constrained Quality-of-Service （QoS） routing is a big challenge for Mobile Ad hoc Networks （MANETs） where the topology may change constantly. In this paper a novel QoS Routing Algorithm based on Simulated Annealing （SA_RA） is proposed. This algorithm first uses an energy function to translate multiple QoS weights into a single mixed metric and then seeks to find a feasible path by simulated annealing. The paper outlines simulated annealing algorithm and analyzes the problems met when we apply it to Qos Routing （QoSR） in MANETs. Theoretical analysis and experiment results demonstrate that the proposed method is an effective approximation algorithms showing better performance than the other pertinent algorithm in seeking the （approximate） optimal configuration within a period of polynomial time.     

Multimedia Support for Wireless W-CDMA with Dynamic Spreading

The emerging multimedia communication needs more support in operating systems in order to be successful over a wireless environment. The system needs to support a seamless integration (i.e., transparent application switching) of voice, audio and conventional data (e.g., e-mails, and ftp). It should also support multiple users with a guaranteed quality. In this paper, we investigate effective protocol design with dynamic spreading factors such that various QoS based on different traffic types can be provided. Increasing spreading factors can benefit the system because it will increase the desired signal strength linearly. The measured bit error rate can be reduced 75 times with a long spreading factor. By taking advantage of this benefit, we propose some middle-ware solutions to monitor the network load and switch the spreading factors dynamically based on the current load with multimedia traffic. These middle-ware solutions are implemented in mobile and base stations and experiments are performed to measure the actual system performance. The preliminary results indicate that our proposed system can always maintain a desired quality for all the voice connections. We further extend our protocol to guarantee a balanced support among different traffic types. While the voice communication is still guaranteed to be non-interrupted, the data traffic is proved to be served with reasonable response time by our proposed system.     

Edge Provisioning and Fairness in VPN-DiffServ Networks

Customers of Virtual Private Networks (VPNs) over Differentiated Services (DiffServ) infrastructure are most likely to demand not only security but also guaranteed Quality-of-Service (QoS) in pursuance of their desire to have leased-line-like services. However, expectedly they will be unable or unwilling to predict the load between VPN endpoints. This paper proposes that customers specify their requirements as a range of quantitative services in the Service Level Agreements (SLAs). To support such services Internet Service Providers (ISPs) would need an automated provisioning system that can logically partition the capacity at the edges to various classes (or groups) of VPN connections and manage them efficiently to allow resource sharing among the groups in a dynamic and fair manner. While with edge provisioning a certain amount of resources based on SLAs (traffic contract at edge) are allocated to VPN connections, we also need to provision the interior nodes of a transit network to meet the assurances offered at the boundaries of the network. We, therefore, propose a two-layered model to provision such VPN-DiffServ networks where the top layer is responsible for edge provisioning, and drives the lower layer in charge of interior resource provisioning with the help of a Bandwidth Broker (BB). Various algorithms with examples and analyses are presented to provision and allocate resources dynamically at the edges for VPN connections. We have developed a prototype BB performing the required provisioning and connection admission.