Showing papers by "Jia Wang published in 1999"

A survey of web caching schemes for the Internet

Abstract: The World Wide Web can be considered as a large distributed information system that provides access to shared data objects. As one of the most popular applications currently running on the Internet, the World Wide Web is of an exponential growth in size, which results in network congestion and server overloading. Web caching has been recognized as one of the effective schemes to alleviate the service bottleneck and reduce the network traffic, thereby minimize the user access latency. In this paper, we first describe the elements of a Web caching system and its desirable properties. Then, we survey the state-of-art techniques which have been used in Web caching systems. Finally, we discuss the research frontier in Web caching.

Efficient and accurate Ethernet simulation

Abstract: The Internet is increasingly being called upon to provide different levels of service to different applications and users. A practical problem in doing so is that although Ethernet is one of the hops for nearby all communication in the Internet, it does not provide any QoS guarantees. A natural question, therefore, is the effect of offered load on Ethernet throughput and delay. In this paper, we present several techniques for accurately and efficiently modeling the behavior of a heavily loaded Ethernet link. We propose an efficient distributed simulation model, called Fast Ethernet Simulation, that empirically models an Ethernet link to quickly and accurately simulate it. By eliminating the implementation of the CSMA/CD protocol, our approach reduces computational complexity drastically while still maintaining desirable accuracy. Performance results show that our techniques not only add very little overhead (less than 5% in our tests) to the basic cost of simulating an Ethernet link, but also closely match real-world measurements. We also present efficient techniques for compressing cumulative distributions using hyperbolic curves and for monitoring the load on a heavily loaded link. Finally, we show applications to illustrate the potential usage of the Fast Ethernet Simulation.

Using genetic algorithms to determine nonnegative monotone set functions for information fusion in environments with random perturbation

Abstract: Due to some inherent interactions among diverse information sources, the classical weighted average method is not adequate for information fusion in many real problems. To describe the interactions, an intuitive and effective way is to use an appropriate nonadditive set function. Instead of the weighted average method, which is essentially the Lebesgue integral, we should thus use the Choquet integral or some other nonlinear integrals. To apply this alternative, more realistic approach to information fusion, we need to determine the nonadditive set function from given input-output data, viewing the nonlinear integral as a multi-input one-output system. In this paper, we employ an adaptive genetic algorithm to construct an approximate optimal nonnegative monotone set function from given input-output data in an environment with random perturbation. An example for diverse strengths of random perturbation is shown to demonstrate the efficiency of this algorithm.

Detecting Static Objects in Busy Scenes

Abstract: Detecting static objects in scenes containing signiicant number of moving objects has several applications in video surveillance. One example is the detection of suspicious packages which is left unattended in an airport terminal or railway station. This paper outlines an approach to automatically detect static objects from a video sequence of a busy scene. Our approach consists of two phase : foreground object extraction and object matching. In the rst phase, we nd the foreground objects in current video frame, using an image of a background as reference. In the object matching phase, we try to match the objects with objects that appears before in previous frames. Matching is done based on three parameter : shape and position, intensity and edge. Temporary occluded of objects is also handled. We built a system based on our approach. Preliminary experiments shows that our system are able to identify static objects in a busy scene in real time.

The Implication of Network Performance on Service Quality

Abstract: As the Internet infrastructure evolves to include Quality of Service (QoS), it is necessary to map application quality requi rements to network performance specifications in terms of delay and loss ra te. In this paper, we first propose a new testbed by using a combination of si mulation and emulation technics. Next, we use this testbed in studyin g the effect of network performance metrics on the perceptual quality of various applications to demonstrate the applicability of the testbed. We ex amine two typical applications on the basis the new testbed: the World Wide Weband the Internet Telephony. In our study of the World Wide Web, we derived a new TCP short connection model that computes the latency of Web r etrieval accurately and efficiently given only the packet delay and loss rate characteristics apriori. In the study of Internet telephony, we show that the packet delay variance is the dominant network characteristics which aff ect the perceptual quality. As a result, the service quality drops dramatically when the network offered load reaches80%. This can serve as a guideline for studies towards improving service quality of Internet telephony.

Image Disorientation Auto-Recovery

Abstract: Automatically detecting and correcting disoriented image frames in a content-related image sequence is a problem that must be addressed in many image and video applications. In this paper, we give a robust feature-based algorithm to efficiently detect and adjust the disorientation of images. Keyword image orientation, crop, Robert edge detection, line feature, Hough transformation.