SangKeun Lee

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In a mobile ad hoc network, the mobility and resource constraints of mobile nodes may lead to network partitioning or performance degradation. Several data replication techniques have been proposed to minimize performance degradation. Most of them assume that all mobile nodes collaborate fully in terms of sharing their memory space. In reality, however,(More)
In this paper, we propose a cluster-based group key management scheme for wireless sensor networks(WSNs) that targets at reduce the communication overhead and storage cost of sensor nodes. In the proposed scheme, a group key is generated by the collaboration of cluster head and nodes within the cluster. Only cluster heads take responsible for reconstruct(More)
To facilitate XML query processing, several labeling schemes have been proposed, in which the ancestor-descendant and parent-child relationships in XML queries can be quickly determined without accessing the original XML file. However, all of these existing schemes have to relabel the existing nodes or recalculate certain values when order-sensitive updates(More)
In this paper, a simple approach to camera motion analysis is proposed to index videos compressed using MPEG (Moving Picture Experts Group) −1, 2 in faster than real time. Specifically, this paper presents a template-matching algorithm to classify basic camera operations. The proposed approach involves 1) the construction of motion vector fields(More)
Wireless data broadcast allows a large number of users to retrieve data simultaneously in mobile databases, resulting in an efficient way of using the scarce wireless bandwidth. However, the efficiency of data access methods is limited by an inherent property that data can only be accessed strictly sequentially by users. To properly cope with the inherent(More)
Web crawlers are essential to many Web applications, such as Web search engines, Web archives, and Web directories, which maintain Web pages in their local repositories. In this paper, we study the problem of crawl scheduling that biases crawl ordering toward important pages. We propose a set of crawling algorithms for effective and efficient crawl ordering(More)
Broadcasting in wireless mobile computing environments is an effective technique to disseminate information to a massive number of clients equipped with powerful, battery operated devices. To conserve the usage of energy, which is a scarce resource, the information to be broadcast must be organized so that the client can selectively tune in at the desired(More)