Soon J. Hyun

A dynamic context-conflict management scheme for group-aware ubiquitous computing environments

In this paper, we propose a context-conflict management scheme for group-aware ubiquitous computing environments that allows context-aware applications to serve multiple users without distracting and sacrificing each other. The proposed scheme can detect semantic conflicts without explicit descriptions of the conflicts between different applications. Conflicts are resolved by a dynamically generated adaptation policy based on the weight value of user preference on each service. Individual context-aware applications can be reused without modification since middleware components for the context-conflict management take charge of detecting and resolving conflicts. Thus, the complicated context-conflict situation becomes more transparent to application programmers.

OEFMON: An open evaluation framework for multimedia over networks

As various types of networks are proliferating with greater capacity, the demand for multimedia services, such as videoconferencing, VoIP, and IPTV, over underlying networks has been increasing. This demand has increased the need for an evaluation framework to analyze the quality of such multimedia services and network performances for the related research areas. This article proposes OEFMON, an open framework for evaluating the quality of multimedia transmissions over networks. OEFMON integrates a multimedia module and a network simulator. The major advantages of OEFMON compared to other existing work are support for any number of multimedia codecs, adaptive coding based on network feedback, on-the-fly observation of multimedia transmission, and easy extension for other tools. A couple of case studies are performed to demonstrate the applicability and usefulness of our framework.

MiRE: A Minimal Rule Engine for context-aware mobile devices

Context-aware services have been introduced into mobile devices, such as cellular phones. Context management and rule processing are the key research issues for the resource-limited devices to have context-aware capability. In this paper, we introduce a context-aware rule processing engine, called MiRE (minimal rule engine). The engine implements the minimum cores of the conventional rule processing facilities and some special policies to achieve resource-saving and light-weight inference engine suitable for resource-limited mobile devices. MiRE, as a part of context-aware middleware system, provides a flexible architecture to adopt various context-aware applications while rules and contexts are dynamically registered at run-time. It maintains the amount of context (i.e., facts) and rules to be optimal in order to save computing resources and processing time. Its design strategy allows MiRE to be conveniently equipped into resource-limited context-aware mobile devices. The performance evaluation carried out on a context-aware cellular phone shows the intended efficiency has been well achieved.

Temporal association algebra: a mathematical foundation for processing object-oriented temporal databases

This paper describes an object-oriented temporal association algebra (called TA-algebra) which is intended to serve as a formal foundation for supporting a pattern-based query specification and processing paradigm. Different from the traditional table-and-attribute-based paradigm, the pattern-based paradigm views the intension of an object-oriented temporal database as a network of object classes interconnected by different association types and its extension as a network of associated temporal object instances. Consistent with this view, queries can be specified in terms of patterns of temporal object associations or nonassociations (i.e., linear, tree and network structures of object classes/objects with logical AND and OR branches). TA-algebra provides a set of algebraic operators for processing these patterns and allows the direct and/or indirect associations and/or nonassociations among temporal object instances to be more explicitly represented and maintained during processing than the traditional tabular representation of temporary or final query results. TA-algebra operators are based on time-interval and valid-time semantics and they preserve the closure property. The algebra is capable of operating on heterogeneous as well as homogeneous patterns of object associations. Both homogeneous and heterogeneous patterns are decomposed into a set of primitive temporal pattern instances for uniform treatment. This paper formally defines the TA-algebra operators and their mathematical properties. The applications of these operators in query decomposition and processing are illustrated by examples.

A Distributed Middleware for a Smart Home with Autonomous Appliances

This paper presents a distributed smart home middleware where each appliance is able to learn user behavior and customize their actions by themselves as well as cooperate with other appliances through a more light-weight smart home gateway. As the key components, we present a knowledge base which describes common- and appliance-specific concepts in a smart home domain, and design libraries for smart appliances and a smart home gateway. We implement the proposed middleware on our testbed and conduct evaluations. The result shows that our scheme reduces the interaction time and the runtime memory allocation.

Performance analysis of H.264/AVC, H.264/SVC, and VP8 over IEEE 802.11 wireless networks

Although the latest video codecs such as H.264/AVC, H.264/SVC, and VP8 were developed with network-friendly features, provisioning the quality of video delivery over IEEE 802.11 wireless networks is still challenging because of error-prone medium and random access. This paper evaluates the quality of video delivery using those latest video codecs over IEEE 802.11. Our results show that reduction of coded video data, consideration of the queue size of each Access Category, and the mandatory implementation of error recovery features in H.264/SVC can help provide robust multimedia transmission over IEEE 802.11. In addition, the performance of the latest video codecs is compared via extensive simulation scenarios. Our comparison shows that VP8 achieves good video quality with the basic medium access control techniques of IEEE 802.11, whereas H.264/AVC and H.264/SVC benefit significantly from appropriate mapping schemes between encoded video fragments and IEEE 802.11e Access Categories.

An Overlay-Based Resource Monitoring Scheme for Social Applications in MANET

The popularity of Social Networking Service and the ubiquity of handheld devices improve chances of social interactions. Mobile social software emerges as a key part of this new trend. In order for users to enjoy this social experience, the resource state of member needs to be monitored so applications can adapt to dynamics of MANET and resource constraints on mobile devices. Previous work in resource monitoring for MANETs focuses on providing a general monitoring scheme. Therefore important group semantics, such as membership information, are not considered. This lack of consideration generates unnecessary traffic overhead and delay in responses. In this paper, we propose a resource monitoring scheme for group-based applications in MANETs. The proposed scheme is based on clusters of information that communicate each other using a group-based overlay. An evaluation shows that the proposed scheme shows shorter response time and smaller traffic overhead without accuracy degradation compared with previous work.

A Multimedia Digital Library System Based on MPEG-7 and XQuery

We designed and implemented a digital library system that supports content-based retrieval of multimedia objects based on MPEG-7 and XQuery. MPEG-7, a metadata standard for multimedia objects, can describe various features such as color histograms of images and content descriptors. As such, a multimedia digital library system built with MPEG-7 metadata can provide content-based search for multimedia objects. Since MPEG-7 is defined by XML schema, XQuery is a natural choice as a query language. By adopting the standards, MPEG-7 and XQuery, our system has benefited for interoperability. First, any MPEG-7 metadata instance can be accommodated into the system with no additional effort. Second, any system that can generate a query in XQuery can retrieve necessary information. Third, our system can be easily extended to support any XML documents. Currently we have developed a prototype system for retrieving images of Korean cultural heritage.

Prediction-based concurrency control for a large scale networked virtual environment supporting various navigation speeds

Shared sense of a virtual world is often enhanced by replicating the information at each users site since replication provides acceptable interactive performance, especially when users are geographically distributed over large networks like the Internet. However, multiple concurrent updates may lead to inconsistent views among replicas. Therefore concurrency control is a key factor to maintaining a consistent state among replicas. We proposed a scalable prediction-based scheme in which an ownership request is multicasted to only the users surrounding a target entity. In our previous work, we assumed that all the users navigate a virtual world with a single speed. It, however, is quite common in a networked virtual environment like a network game that users are allowed to change their navigation speed as they interact with a virtual world for adding more realism. This paper proposes an enhancement to support users with various speeds. The enhanced scheme allows as many Entity Radii as the number of different speed and allocates a separate queue for users of each speed. Each queue is examined in parallel to predict the next owner candidate and among the selected candidates is chosen the final candidate, which has a minimum predicted collision time. It contributes to the timely advanced transfer of ownership by using appropriate Entity Radius based on a users speed, fair granting of ownership by reducing the interference between users with different speed and latency, and high prediction accuracy by reducing the redundant ownership transfer.

A data acquisition architecture for healthcare services in mobile sensor networks

Mobile healthcare services have received growing attention due to the rapid technical advancement of sensor devices, sensor networks, and mobile data transmission. Healthcare monitoring services, in general, lack the needed sophistication for the acquisition of the huge amount of healthcare data generated from mobile users. The overhead of filtering out a large amount of unnecessary data that are not directly useful for the healthcare applications is unavoidable. In this paper, we propose a healthcare service architecture and introduce data acquisition software using a database querying facility as a solution to the problem. Our proposed service architecture with the data acquisition scheme effectively bridges the gap between the healthcare application domain and the acquisition of physical data.