Yeali S. Sun

Extending the TAM model to explore the factors that affect Intention to Use an Online Learning Community

An online learning community enables learners to access up-to-date information via the Internet anytime-anywhere because of the ubiquity of the World Wide Web (WWW). Students can also interact with one another during the learning process. Hence, researchers want to determine whether such interaction produces learning synergy in an online learning community. In this paper, we take the Technology Acceptance Model as a foundation and extend the external variables as well as the Perceived Variables as our model and propose a number of hypotheses. A total of 436 Taiwanese senior high school students participated in this research, and the online learning community focused on learning English. The research results show that all the hypotheses are supported, which indicates that the extended variables can effectively predict whether users will adopt an online learning community. Finally, we discuss the implications of our findings for the future development of online English learning communities.

PVA: A Self-Adaptive Personal View Agent

In this paper, we present PVA, an adaptive personal view information agent system for tracking, learning and managing user interests in Internet documents. PVA consists of three parts: a proxy, personal view constructor, and personal view maintainer. The proxy logs the users activities and extracts the users interests without user intervention. The personal view constructor mines user interests and maps them to a class hierarchy (i.e., personal view). The personal view maintainer synchronizes user interests and the personal view periodically. When user interests change, in PVA, not only the contents, but also the structure of the user profile are modified to adapt to the changes. In addition, PVA considers the aging problem of user interests. The experimental results show that modulating the structure of the user profile increases the accuracy of a personalization system.

Life cycle modeling of news events using aging theory

In this paper, an adaptive news event detection method is proposed. We consider a news event as a life form and propose an aging theory to model its life span. A news event becomes popular with a burst of news reports, and it fades away with time. We incorporate the proposed aging theory into the traditional single-pass clustering algorithm to model life spans of news events. Experiment results show that the proposed method has fairly good performance for both long-running and short-term events compared to other approaches.

Proportional delay differentiation service based on weighted fair queuing

Differentiation service (Diffserv) is regarded as one of the practical architectures to realize quality of service (QoS) on the Internet. Relative differentiated service, which achieves relative QoS differentiation between traffic classes, is a simple and easily-deployed service model. Based on the concept of relative differentiated service, Dovrolis et al. (ACM SIGMETRICS Performance Evaluation Review vol.27, no.1, pp.204-5, 1999; IEEE Network, September 1999; ACM SIGCOMM-99, September 1999) proposed a proportional differentiation service model which guarantees the ratios of service differences between classes. They claimed that weighted fair queuing (WFQ) is not suitable for implementing relative differentiation service and employed priority-based scheduling algorithms in their model. In this paper, we extend WFQ and apply it to proportional delay differentiation service. The extended WFQ algorithm adjusts the weighting of each class dynamically so that the delay differences between classes can be well controlled. Simulations show that the proposed methods can realize proportional delay differentiation service effectively and efficiently.

A Spectral Efficient and Fair User-Centric Spectrum Allocation Approach for Downlink Transmissions

Traditional spectrum allocation approaches assume that the intended users of BSs are treated equally, without consideration of their distances. Consequently, the efficiency of spectrum usage for downlink transmissions may suffer, because a BS may interfere with other BS transmissions; this would not happen if a proper transmission power is used. In this paper, we propose a user-centric spectrum allocation algorithm based on a physical interference model for downlink transmissions. In our approach, BSs set the power of an allocated spectrum band to ensure an effective transmission range for covering a group of intended users. A spectrum band is allocated to a BS if it can satisfy a group of users with the least amount of power possible (relative to other spectrum bands). Thus, after spectrum bands and transmission ranges are assigned, each BS owns several spectrum bands that can cover a group of users within varying transmission ranges. This approach leads to a higher rate of spectral reuse and improves system performance. In addition, the approach properly considers fairness issues among both users and BSs. Overall, simulation results show that our approach not only outperforms traditional BS-centric approaches by offering a 26% higher throughput in dense networks, but also provides fairer spectrum allocation.

PVA: a self-adaptive personal view agent system

In this paper, we present PVA, an adaptive personal view information agent system to track, learn and manage, users interests in Internet documents. When users interests change, PVA, in not only the contents, but also in the structure of user profile, is modified to adapt to the changes. Experimental results show that modulating the structure of user profile does increase the accuracy of personalization systems.

TCP Throughput Enhancement over Wireless Mesh Networks

TCP is the predominant technology used on the Internet to support upper layer applications with reliable data transfer and congestion control services. Furthermore, it is expected that traditional TCP applications (e.g., Internet access) will continue to constitute the major traffic component during the initial deployment of wireless mesh networks. However, TCP is known for its poor throughput performance in wireless multihop transmission environments. For this article, we conducted simulations to examine the impact of two channel interference problems, the hidden terminal and exposed terminal, on TCP transmissions over wireless mesh networks. We also propose a multichannel assignment algorithm for constructing a wireless mesh network that satisfies the spatial channel reuse property and eliminates the hidden terminal problem. The simulation results demonstrate the effectiveness of the proposed approach in improving the performance of TCP in wireless multihop networks.

A novel approach for enhancing student reading comprehension and assisting teacher assessment of literacy

For students of English as a Foreign Language (EFL), reading exercises are critical not only for developing strong reading comprehension, but also for developing listening, speaking, and writing skills. Prior research suggests that social, collaborative learning environments are best suited for improving language ability. However, opportunities for English learners to collaboratively practice reading comprehension are minimal, and due to resource constraints and a lack of accurate evaluation methods, English instructors rarely assess student literacy effectively. In response to these problems, we propose a Tag-based Collaborative reading learning System (TACO) that makes use of Web 2.0 Internet social tagging techniques to provide a collaborative environment for reading English. We test our systems ability to both improve reading comprehension and aid teachers in accurately assessing literacy by conducting a three-month trial with 56 participating Taiwanese high school students from February to May 2009. During this period, post-testing results show a significant improvement in reading scores among participants in our tag-based system, and survey feedback from teachers suggests an improved capacity for literacy assessment.

WF2Q-M: Worst-case fair weighted fair queueing with maximum rate control

While existing weighted fair scheduling schemes guarantee minimum bandwidths/resources for the classes/processes of a shared channel, the maximum rate control, which is critical to service providers, carriers, and network managers for resource management and business strategies in many applications, is generally enforced by employing traffic policing mechanisms. These approaches use either a concatenation of the rate controller and scheduler, or a policer in front of the scheduler. The concatenation method uses two sets of queues and a management apparatus that incurs overhead. The latter method may allow bursty traffic to pass through the controller, which violates the maximum rate constraint, or results in packet loss. In this paper, we present a new weighted fair scheduling scheme, WF^2Q-M, which can simultaneously support maximum rate control and minimum service rate guarantees. WF^2Q-M uses the virtual clock adjustment method to enforce maximum rate control and distribute the excess bandwidths of saturated sessions to other sessions without recalculating the virtual starting and finishing times of sessions. In terms of performance, we prove that WF^2Q-M is theoretically bounded by a corresponding fluid reference model. A procedural scheduling implementation of WF^2Q-M is proposed, and a proof of correctness is given. Finally, we present the results of extensive experiments to show that the performance of WF^2Q-M is just as claimed.

Seamless Handover for High-Speed Trains Using Femtocell-Based Multiple Egress Network Interfaces

High-speed rail systems are becoming increasingly popular among long-distance travelers. With the explosive growth in the number of mobile devices, the provision of high-quality telecommunication and Internet access services on high-speed trains is now a pressing problem. Network mobility (NEMO) has been proposed to enable a large number of mobile devices on a vehicle to access the Internet; however, several issues must be solved before it can be put into practice, e.g., frequent handovers, long handover latency, and poor quality of service. To resolve these problems, we propose an LTE femtocell-based network mobility scheme that uses multiple egress network interfaces to support seamless handover for high-speed rail systems called MEN-NEMO. The results of simulations show that the proposed MEN-NEMO scheme reduces the handover latency and transmission overhead of handover signaling substantially.