Joe Chun-Hung Yuen

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In this paper, we propose a cache invalidation scheme called Invalidation by Absolute Validity Interval (IAVI) for mobile computing systems. In IAVI, we define an absolute validity interval (AVI), for each data item based on its dynamic property such as the update interval. A mobile client can verify the validity of a cached item by comparing the last(More)
In a mobile computing system, caching data items at the mobile clients is important to reduce the data access delay in a unreliable and low bandwidth mobile network. However, efficient methods must be used to ensure the coherence between the cached items and the data items at the database server. In this paper, by exploring the real-time properties of the(More)
In this paper, we study the data dissemination problem in time-constrained mobile computing systems (TCMCS) in which maximizing data currency (minimizing staleness) and meeting transaction deadlines are of equal importance as providing consistent data items to transactions. We first investigate what are the performance problems of the multi-version data(More)
Rapid advances in mobile communication technology have spawned many new mobile applications. A key element in many of these systems is the need to distribute real-time information from a database server to mobile clients. While data broadcast has been shown to be an efficient data dissemination technique, many issues such as selection of broadcast data and(More)
In this paper, we propose broadcast algorithms, based on the policies proposed in previous studies, to disseminate data items to time-constrained read-only transactions. In the proposed algorithms, the number of data items requested by a transaction will be considered explicitly in selecting the data items for broadcast. The purpose of the algorithms is to(More)
Although data broadcast has been shown to be an efficient data dissemination technique for mobile computing systems, many issues such as selection of broadcast data and caching strategies at the clients are still active research areas. In this paper, by examining the dynamic properties of the data items in mobile computing systems, we define the validity of(More)
In this paper, we propose an Adaptive Buffer Sensitive (ABS) protocol for scheduling the transmission of video streams over a mobile network. Two important considerations in the design of ABS are: (1) to minimize the impact of transient overloading and communication errors on video playback; and (2) to minimize the impact of a video playback by other video(More)
In this paper, we propose the Adaptive Buffer Sensitive (ABS) algorithm for scheduling the transmission of video packets from multiple video streams in a mobile multimedia system. Two important considerations in the design of the ABS are: (1) to maximize the mobile network bandwidth utilization and at the same time to minimize the impact of transient(More)