10812167
A TCP-Friendly Stateless AQM Scheme for Fair Bandwidth Allocation
Queue management, bandwidth share, and congestion control are very important to both robustness and fairness of the Internet. In this article, we investigate the problem of providing a fair bandwidth allocation to those flows that share congested link in a router. A new TCP-friendly router-based AQM (active queue management) scheme, termed WARD, is proposed to approximate the fair queueing policy. WARD is a simple packet dropping algorithm with a random mechanism, and discriminates against the flows which transmit more packets than allowed. By doing this, it not only protects TCP connections from UDP flows, but also solves the problem of competing bandwidth among different TCP versions such as TCP Vegas and Reno. In addition, WARD works quite well for TCP flow isolation even with different round trip times. In other words, WARD improves the unfair bandwidth allocation properties. Furthermore, it is stateless and easy to implement, so WARD controls unresponsive or misbehaving flows with a minimum overhead
18724966
An Aided Congestion Avoidance Mechanism for TCP Vegas
TCP Vegas detects network congestion in the early stage and successfully prevents periodic packet loss that usually occurs in TCP Reno. It has been demonstrated that TCP Vegas achieves much higher performance than TCP Reno in many aspects. However, TCP Vegas cannot prevent unnecessary throughput degradation when congestion occurs in the backward path, it passes through multiple congested links, or it reroutes through a path with longer round-trip time (RTT). In this paper, we propose an aided congestion avoidance mechanism for TCP Vegas, called Aid-Vegas, which uses the relative one-way delay of each packet along the forward path to distinguish whether congestion occurs or not. Through the results of simulation, we demonstrate that Aid-Vegas can solve the problems of rerouting and backward congestion, enhance the fairness among the competitive connections, and improve the throughput when multiple congested links are encountered.
28992997
Creating reusable WebQuest objects with WebQuest authoring engine
WebQuest is a constructivist lesson format for Web-enabled inquiry-based learning. A WebQuest exists in form of a Web site that contains a collection of Web pages. In this paper, we define the "WebQuest Object" which is basically a learning object. We also present the WebQuest authoring engine which enables one to generate WebQuest objects without the knowledge in Web page construction and publishing. The WebQuest authoring engine also allows ones to edit the metadata of the WebQuest so as to facilitate the reuse of the WebQuest objects.
35179919
WebQuest Markup Language (WQML) for Sharable Inquiry-Based Learning
WebQuest is a model for constructivist inquiry-based learning in which the information used by learners is collected from the Web. A WebQuest exists in form of a Web site that contains a defined set of componential Web pages. In this paper, we specify the WebQuest Markup Language (WQML) for WebQuest construction. WQML enables WebQuests to be implemented as sharable courseware objects and thus to be interoperable with most learning management systems (LMS).
3198744
Dynamic frame skipping for high-performance transcoding
Transcoding is a process of converting a previously compressed video bitstream into a lower bit-rate bitstream. When some incoming frames are dropped for the frame-rate conversion in transcoding, the newly quantized DCT coefficients of prediction error need to be re-computed, which can create an undesirable complexity as well as introduce re-encoding error. We propose a new architecture for a frame-skipping transcoder to improve picture quality and to reduce complexity. It is observed that re-encoding error is reduced significantly when the strategy of direct summation of DCT coefficients and the error compensation feedback loop are employed. Furthermore, we propose a frame-rate control scheme which can dynamically adjust the number of skipped frames according to the incoming motion vectors and the re-encoding error due to transcoding such that the decoded sequence can have smooth motion as well as better transcoded pictures. Experimental results show that, as compared to the conventional transcoder, the new frame-skipping transcoder is more robust, produces smaller requantization errors, and has simple computational complexity.
7668661
Evaluation on security and privacy of Web-based learning systems
Web-based learning systems are becoming popular in the recent years. Many courses and lectures are now conducted online. Similar to other Web-based applications, security and privacy of Web-based learning systems should not be overlooked. We evaluate the security and privacy of general Web-based learning systems. We address the security and privacy requirements specific to them. Recommendations on design and implementation of a secure Web-based learning system are also presented. In particular, we have evaluated the security services of two popular Web-based learning tools.
6180081
New adaptive partial distortion search using clustered pixel matching error characteristic
The partial distortion search is a particularly attractive fast block-matching algorithm, because it introduces no prediction error as compared with the full-search algorithm. It reduces the number of necessary matching evaluations for every searching point to save computation. In the literature, many researches have tried to improve block-matching algorithms by making use of an assumption that pixels with larger gradient magnitudes have larger matching errors on average. Based on a simple analysis, we have found that on average, pixel matching errors with similar magnitudes tend to appear in clusters for natural video sequences. By using this clustering characteristic, we propose an adaptive partial distortion search algorithm which significantly improves the computational efficiency of the original PDS. This approach is much better than other pixel gradient based adaptive PDS algorithms. In addition, our proposed algorithm is suitable for motion estimation of both opaque and boundary macroblocks of an arbitrary shaped object in MPEG-4 coding.