29466407
An adaptive transmission scheme for audio and video synchronization based on real-time transport protocol
Multimedia streams impose tight temporal constraints since different kinds of continuous multimedia streams have to be played synchronously. We devise in this paper an adaptive transmission scheme to ensure the continuous and synchronous playback of audio and video streams based on Real-time Transport Protocol. Realization of our adaptive scheme is composed of a series of operations in three stages, namely, (1) dynamic reordering mechanism, (2) decoding-recovery mechanism, and (3) adaptive synchronization mechanism. An empirical study is conducted to provide insights into our adaptive transmission scheme. As validated by our simulation results, the adaptive transmission mechanism is able to strike a good balance of both stable playback and the end-to-end delay reduction. Furthermore, we analyze the jitter resistance, the end-to-end delay, and the buffer size required in order to enhance the applicability of this scheme to more applications that require the transmission of multimedia data.
37840776
Design and implementation of a network application architecture for thin clients
This paper explores the issues and the techniques of enabling multimedia applications for the thin client computing. Our study on the network applications over thin clients is devoted to the universal plug-in architecture which supports multimedia applications over thin clients. With the proposed architecture, the universal plug-in technique is devised to shift jobs from thin clients to a supporting server, thus reducing the computing overhead required by the thin clients. In addition, this plug-in architecture is implemented and empirically evaluated It is shown by our experiments that the proposed architecture not only significantly enhances the multimedia capability of thin clients but also reduces the memory consumed by the clients for various applications, showing the very advantage of the universal plug-in architecture for thin clients of limited resources.
14887651
Adaptive recovery techniques for real-time audio streams
There are a number of packet-loss recovery techniques proposed for streaming audio applications. However, there are few works that are able to exploit the tradeoff between the recovery quality and the computational complexity. We develop a recovery method, called DSPWR (Double Sided Pitch Waveform Replication) which is able to tolerate a much higher packet loss rate. In essence, DSPWR is composed of several procedures devised to improve the quality of the reconstructed speech. It is noted that a more sophisticated recovery scheme that can tolerate a higher degree of packet loss in general requires a larger computational cost. In view of this, we evaluate the quality of the reconstructed speech under different packet loss rates for various receiver-based recovery methods, and compare the computational complexity among these methods. Under the acceptable speech quality whose MOS (Mean Opinion Score) is above 3.5, we develop an adaptive mechanism that can select the recovery method with the minimal complexity in accordance with different packet loss rates encountered. To conduct real experiments in the networks, we implement these recovery methods and evaluate the performance of DSPWR devised and the adaptive recovery techniques empirically. As validated by our experimental results, the adaptive mechanism is able to strike a compromise between the computational overhead and the quality of the speech desired.
18278456
On General Results for All-to-All Broadcast
All-to-all broadcast refers to the process by which every node broadcasts its certain piece of information to all other nodes in the system. In this paper, we develop all-to-all broadcast schemes by dealing with two classes of schemes. A prior scheme based on generation of minimal complete sets is first described, and then a new scheme based on propagation of experts is developed. The former always completes the broadcasting in the minimal number of steps and the latter is designed to minimize the number of messages. Performance of these two classes of schemes is comparatively analyzed. The all-to-all broadcast scheme desired can be derived by combining the advantages of these two classes of schemes.
20277412
Adaptive hypertext navigation based on user goals and context
Hypertext systems allow flexible access to topics of information, but this flexibility has disadvantages. Users often become lost or overwhelmed by choices. An adaptive hypertext system can overcome these disadvantages by recommending information to users based on their specific information needs and preferences. Simple associative matrices provide an effective way of capturing these user preferences. Because the matrices are easily updated, they support the kind of dynamic learning required in an adaptive system.HYPERFLEX, a prototype of an adaptive hypertext system that learns, is described. Informal studies with HYPERFLEX clarify the circumstances under which adaptive systems are likely to be useful, and suggest that HYPERFLEX can reduce time spent searching for information by up to 40%. Moreover, these benefits can be obtained with relatively little effort on the part of hypertext authors or users.The simple models underlying HYPERFLEX's performance may offer a general and useful alternative to more sophisticated modelling techniques. Conditions under which these models, and similar adaptation techniques, might be most useful are discussed.
117657252
Labeled Search Trees and Amortized Analysis: Improved Upper Bounds for NP-Hard Problems
A sequence of exact algorithms to solve the Vertex Cover and Maximum Independent Set problems have been proposed recently in the literature. All these algorithms appeal to a very conservative analysis that considers the size of the search tree, under a worst-case scenario, to derive an upper bound on the running time of the algorithm. In this paper we propose a different approach to analyze the size of the search tree. We use amortized analysis to show how simple algorithms, if analyzed properly, may perform much better than the upper bounds on their running time derived by considering only a worst-case scenario. This approach allows us to present a simple algorithm of running time O(1.194 k + n) for the parameterized Vertex Cover problem on degree-3 graphs, and a simple algorithm of running time O(1.1254 n ) for the Maximum Independent Set problem on degree-3 graphs. Both algorithms improve the previous best algorithms for the problems.
14690444
Fluid-flow analysis of TCP Westwood with RED
This paper concerns TCP Westwood (TCPW), a recently developed modification of TCP, in combination with RED queue management. We develop a fluid-flow model of TCPW with RED and use it to study both equilibrium and dynamic features. On the equilibrium side, we identify the scaling of window with loss-probability, and compare it to TCP NewReno. We also use the model to find the boundary of stability, beyond which we see large oscillations; we find that the stable region of TCPW is enhanced with respect to TCP NewReno. Furthermore we show preliminary evidence that oscillations, when they occur, have a limited impact on network throughput. Fairness and friendliness of TCPW is also analyzed and compared with NewReno. Our results show that TCPW is more fair than NewReno for flows with heterogenous round trip time. We also found that TCPW friendliness to NewReno is dependent on the difference between equilibrium queue size and the product of bandwidth and delay.
24126539
A Behavior-Based Classification and Retrieval Technique for Object-Oriented Specification Reuse
This paper presents a classification and retrieval technique for object-oriented specification reuse, based on the assumption that existing specifications exhibiting behaviors similar to that of the system under development are appropriate for reuse. Existing specifications are classified and retrieved according to the semantic networks abstracted from their behaviors. Since semantic networks attach semantic meanings to certain degrees of detail, our technique is rather precise. Primary behavior is used to classify specifications because it can be obtained in the early phases of system analysis. Therefore, our technique allows early reuse. Moreover, subspecifications and classes of existing specifications are classified independently so that they can be retrieved for reuse separately. Thus, our technique encourages reusing subspecifications as well as classes. Since a subspecification is composed of classes and their relationships, reusing it corresponds to reusing all those classes and relationships. A technique that reuses subspecifications as well as classes is thus expected to save more time than those that reuse only classes.
9759106
Design and analysis of low‐power access protocols for wireless and mobile ATM networks
This paper describes the design and analysis of a low‐power medium access control (MAC) protocol for wireless/mobile ATM networks. The protocol – denoted EC‐MAC (energy conserving medium access control) – is designed to support different traffic types with quality‐of‐service (QoS) provisions. The network is based on the infrastructure model where a base station (BS) serves all the mobiles currently in its cell. A reservation‐based approach is proposed, with appropriate scheduling of the requests from the mobiles. This strategy is utilized to accomplish the dual goals of reduced energy consumption and quality of service provision over wireless links. A priority round robin with dynamic reservation update and error compensation scheduling algorithm is used to schedule the transmission requests of the mobiles. Discrete‐event simulation has been used to study the performance of the protocol. A comparison of energy consumption of the EC‐MAC to a number of other protocols is provided. This comparison indicates the EC‐MAC has, in general, better energy consumption characteristics. Performance analysis of the proposed protocol with respect to different quality‐of‐service parameters using video, audio and data traffic models is provided.