1245128
Enabling network-centric music performance in wide-area networks
NMP on the Internet is not only possible, its delay bounds can satisfy the tight requirements involved in human perception while generating high-end audio quality for musicians and listeners alike.
2045346
Real-time service provisioning for mobile and wireless networks
As mobile devices and wireless networks are becoming ubiquitous, the interest of users to deploy real-time applications, e.g. online gaming or Voice-over-IP in such environments is also increasing. Due to the difference between traditional and wireless networks, in particular in terms of available bandwidth and network structure, the concepts used for supporting real-time applications in both networks are different. This paper gives an overview of the key technical challenges that are fundamental and need to be solved in order to easily support real-time applications in wireless and mobile environments. In a first step, issues related to service provisioning in mobile networks are discussed. This is followed by a look at the Quality of Service supported by wireless networks and possible techniques for improving it. Finally, concepts for securing the communication between the users of real-time applications in wireless and mobile networks are presented. For each of these issues, we provide a detailed analysis and an overview of the state-of-the-art. Moreover, we illustrate the main points using distributed online games as an example.
7031166
Performance evaluation of DCCP: A focus on smoothness and TCP-friendliness
Recent years have seen dramatic increases of the use of multimedia applications on the Internet, which typically either lack congestion control or use proprietary congestion control mechanisms. This can easily cause congestion collapse or compatibility problems. Datagram Congestion Control Protocol (Dccp) fills the gap betweenUdp andTcp, featuring congestion control rather than reliability for packet-switched rich content delivery with high degree of flexibility. We present aDccp model designed and implemented withOpnet Modeler, and the experiments and evaluation focused on largely the smoothness of the data rates, and the fairness between concurrentDccp flows andTcp flows. We foundDccp-ccid3 demonstrates stable data rates under different scenarios, and the fairness betweenDccp andTcp is only achieved under certain conditions. We also validated that the throughput ofDccp-Ccid3 is proportional to the average packet size, and relatively fixed packet size is critical for the optimal operation ofDccp. Problems in the slow start phase and insufficient receiver buffer size were identified and we hereby proposed solutions on this.RésuméLe nombre d’applications multimédias sur l’internet a considérablement augmenté ces dernières années. Ces applications généralement ne gèrent pas les congestions ou bien utilisent des mécanismes de contrôle propriétaires. Il peut en résulter facilement des congestions graves ou des problèmes d’incompatibilité. Le protocoleDccp (Datagram Congestion Control Protocol) se positionne entreUdp etTcp puisqu ’il fournit, pour des paquets multimédias, un contrôle de congestion hautement flexible mais sans la fiabilité de délivrance. Cet article présente un modèleDccp conçu et implémenté avec le simulateurOpnet. Les expérimentations et les analyses portent principalement sur le lissage des débits et l’équité entre des fluxDccp etTcp concurrents. On montre queDccp-Ccid3 affiche des débits stables sous divers scénarios et que l’équité entreDccp etTcp n’est atteinte que sous certaines conditions. On valide également que le débit deDccp-Ccid3 est proportionnel à la taille moyenne des paquets et que le fait d’avoir des paquets de taille relativement constante est un facteur essentiel pour un fonctionnement optimal deDccp. Les problèmes pendant la phase de démarrage lent et ceux dus à une mémoire tampon insuffisante côté récepteur sont également analysés et résolus.
2181030
Manifold splines
Constructing splines whose parametric domain is an arbitrary manifold and effectively computing such splines in real-world applications are of fundamental importance in solid and shape modeling, geometric design, graphics, etc. This paper presents a general theoretical and computational framework, in which spline surfaces defined over planar domains can be systematically extended to manifold domains with arbitrary topology with or without boundaries. We study the affine structure of domain manifolds in depth and prove that the existence of manifold splines is equivalent to the existence of a manifold's affine atlas. Based on our theoretical breakthrough, we also develop a set of practical algorithms to generalize triangular B-spline surfaces from planar domains to manifold domains. We choose triangular B-splines mainly because of its generality and many of its attractive properties. As a result, our new spline surface defined over any manifold is a piecewise polynomial surface with high parametric continuity without the need for any patching and/or trimming operations. Through our experiments, we hope to demonstrate that our novel manifold splines are both powerful and efficient in modeling arbitrarily complicated geometry and representing continuously-varying physical quantities defined over shapes of arbitrary topology.
6987147
Optimal Component Composition for Scalable Stream Processing
Stream processing has become increasingly important with emergence of stream applications such as audio/video surveillance, stock price tracing, and sensor data analysis. A challenging problem is to provide optimal component composition in a distributed stream processing environment. The goal of optimal component composition is to achieve load balancing subject to multiple function, resource, and quality-of-service (QoS) constraints while composing stream applications. In this paper, we present an adaptive composition probing (ACP) approach to the problem. Different from previous work, ACP provides a new hybrid approach that combines distributed composition probing with coarse-grain global state management. Guided by the coarse-grain global state information, ACP selectively probes a subset of candidate components to discover an approximately optimal component composition. Further, ACP is self-tuning, which can adoptively adjust the number of probes to maintain a specified composition performance target (i.e., composition success rate) in a dynamic stream environment. While the optimal component composition problem is NP-hard, our ACP approach provides an adaptive polynomial approximation solution. We have conducted extensive simulation experiments to show the efficiency, scalability, and adaptability of the ACP approach by comparing with other alternative solutions
6538618
A Greedy Algorithm for Optimal Recombination
Let Σ be an alphabet and Σn denote the collection of all sequences of length n over Σ. For any s1 = ajaj+1 . . . an+s2 = b1b2 . . . bj bj+1 . . . bn ∈ Σn, a recombination of s1 and s2 at position j is defined as an operation that crosses s1 and s2 at position j and generates t1 = a1a2 . . . ajbj+1 . . . bn and t2 = b1b2 . . . bjaj+1 . . . an. Denote A and S two collections of sequences. In this paper, we discuss generating A from S by a series of recombinations in minimum number of steps. We present a greedy algorithm for finding the optimal recombination evolutionary history from S to any tree A of sequences when |S| = 2.
2093792
Visual QoS programming environment for ubiquitous multimedia services
The provision of distributed multimedia services is becoming mobile and ubiquitous. Different multimedia services require application-specific Quality of Service (QoS). In this paper, we present QoSTalk, a unified component-based programming environment that allows application developers to specify different application-specific QoS requirements easily. In QoSTalk, we adopt a hierarchical approach to model application configuration graphs for different distributed multimedia services. We design and implement the XML-based Hierarchical QoS Markup Language, called HQML, to describe the hierarchical configuration graph as well as other application-specific QoS requirements and policies. QoSTalk promotes the separation of concerns in developing QoS-aware ubiquitous multimedia applications and thus enables easy programming of QoS-aware applications, running on top of a unified QoS-aware middleware framework. We have prototyped the QoSTalk in Java and CORBA. Our case studies with several multimedia applications show that QoSTalk effectively fills the gap for application developers between the very general facilities provided by the QoS-aware middleware and different kinds of distributed multimedia applications.
5425849
QoS-assured service composition in managed service overlay networks
Many value-added and content delivery services are being offered via service level agreements (SLAs). These services can be interconnected to form a service overlay network (SON) over the Internet. Service composition in SON has emerged as a cost-effective approach to quickly creating new services. Previous research has addressed the reliability, adaptability, and compatibility issues for composed services. However little has been done to manage generic quality-of-service (QoS) provisioning for composed services, based on the SLA contracts of individual services. In this paper we present QUEST a QoS assUred composEable Service infrasTructure, to address the problem. QUEST framework provides: (1) initial service composition, which can compose a qualified service path under multiple QoS constraints (e.g., response time, availability). If multiple qualified service paths exist, QUEST chooses the best one according to the load balancing metric; and (2) dynamic service composition, which can dynamically recompose the service path to quickly recover from service outages and QoS violations. Different from the previous work, QUEST can simultaneously achieve QoS assurances and good load balancing in SON.