Abstract-Recently, a time synchronization algorithm called Pairwise Broadcast Synchronization (PBS) is proposed. With PBS, a sensor can be synchronized by overhearing synchronization packet exchange among its neighbouring sensors without sending out any packet itself. In an one-hop sensor network where every node is a neighbour of each other, a single PBS message exchange between two nodes would facilitate all nodes to synchronize. However, in a multi-hop sensor network, PBS message exchanges in several node pairs are needed in order to achieve network-wide synchronization. To reduce the number of message exchanges, these node pairs should be carefully chosen. In this paper, we investigate how to choose these "appropriate" sensors aiming at reducing the number of PBS message exchanges while allowing every node to synchronize. This selection problem is shown to be NP-complete, for which the greedy heuristic is a good polynomial-time approximation algorithm. Nevertheless, a centralized algorithm is not suitable for wireless sensor networks. Therefore, we develop a distributed heuristic algorithm allowing a sensor to determine how to synchronize itself based on its neighbourhood information only. The protocol is tested through extensive simulations. The simulation results reveal that the proposed protocol gives consistent performance under different conditions with its performance comparable to that of the centralized algorithm.

Curiosity is the best driving force for learning; keeping learners curious by engaging them via gaming has been regarded as a desirable approach to education. Virtual Interactive Student-Oriented Learning Environment (VISOLE) is a pedagogical approach to serious gaming that we have proposed. Based on the VISOLE pedagogy, we developed Farmtasia ® , a multiplayer online serious game based on a thematic topic, Agriculture, in the Hong Kong senior secondary geography education curriculum. Drawing on the notion of virtual mentoring, we aim to further enhance the design of the game by introducing a number of non-player characters (NPCs) to scaffold non-gamer students' learning in the gameplay process. This chapter reports a learning experiment in which we compared the pedagogical effectiveness of the revised version of the game with that of the original version, in terms of non-gamer students' knowledge acquisition. The results show that the experimental group students (who learned with the revised) significantly outperformed the control group students (who learned with the original), with a considerable effect size.

There were many successful Web-based learning systems boilt to enhance the effectiveness of institutional teaching over the past decade. Students were benefited in two major aspects: asking questions to their conne instructors, and downloading relevant course materials only when InterneVIntranet access is available. Recently, handheld devices integrated with the latest wireless technology are becoming popular. Thus, it is foreseeable that such learning facilities may move beyond the boundary offixed network connections one day. In this paper, we considered an interesting proposal to mobilize conventional Web-based learning systems with the integration of handbeld devices, and pioneered its prototype implementation in the University of Hong Kong. Besides getting encouraging students' feedbacks, we gained invaluable experience of combining frontier technologies such as the Conduits and Web server technology to solve the data synchronization problems of students' questions distributed among the 'local' databases of handheld devices and the centralized database server.

In the past few years, many new mobile technologies including the 3G, WiFi or mobileTV have created unprecedented learning opportunities on mobile devices. Furthermore, such technologies continuously fuel the rapid growth of new fields of research like the edutainment for educational entertainment. In a recent project awarded by the Hong Kong Wireless Development Center, we have developed a mobile quiz game system on 3G mobile phone networks in China, Hong Kong or other countries to facilitate learning anytime and anywhere.Our developed mobile quiz system is so generic that it can be readily extended to any wireless network. In this paper, we discuss about the design and possible uses of our quiz system in mobile learning, and also share the relevant experience in system development with the evaluation strategies carefully examined. After all, our work shed light on many interesting directions for future exploration.

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