Hyunmin Park

A novel mobility prediction algorithm based on user movement history in wireless networks

For an efficient resource reservation, mobility prediction has been reported as an effective means to decrease call dropping probability and to shorten handoff latency in wireless cellular networks. Several early-proposed handoff algorithms making use of a users movement history on a cell-by-cell basis work on the assumption that the users movement is restricted to the indoor locations such as an office or a building. These algorithms do not present a good performance in a micro-cell structure or a metropolis with complicated structure of roads. To overcome this drawback, we propose a new mobility prediction algorithm, which stores and uses the history of the users positions within the current cell to predict the next cell.

Simulation-based web service composition: framework and performance analysis

As Service Oriented Architecture is expected to grow in the future e-business, web services are believed to be the ideal platform to integrate various business artifacts disparate platforms and systems. QoS(Quality of Service) of web services in terms of performance, reliability, and availability becomes the key issue when web services model complex and mission-critical applications. In this paper, we propose a simulation-based framework that enables web services to be composed based on their QoS properties. The proposed framework iteratively analyzes the QoS of the composite web services with multiple perspectives until the QoS requirements are met to various service users and providers.

Generic methodologies for deadlock-free routing

This paper introduces a graph-partitioning generic methodology for developing deadlock-free wormhole routing in an arbitrary network. Further extension allows partial cyclic dependencies among virtual channels. A novel fully adaptive nonminimal deadlock-free routing algorithm has been developed for k-ary n-cube torus network. Since our technique is based on decomposing a network into several subdigraphs, it simplifies and generalizes the development of both static and adaptive deadlock-free routing algorithms for arbitrary network topologies. We show that our methodology can be applied to store-and-forward and virtual cut-through routings as well.

WICI: an efficient hybrid routing scheme for scalable and hierarchical networks

Many recent supercomputers employ either a cluster-based design or a highly scalable network. Clustering is built-in in a hierarchical system, while highly scalable networks like mesh or torus could be easily partitioned into modules to form several clusters. This paper first specifies a self-routing connection method in a recently introduced class of hierarchical topology called de Bruijn-Cube (dBCube) network, and presents a deadlock-free routing scheme using virtual channels. A new switching method called Wormhole Intracluster Cut-through Intercluster (WICI) routing is also introduced to improve the network performance fairly close to the virtual cut-through and to maintain the buffer cost as compared to prevalent routing schemes of wormhole. Usefulness of WICI routing has been demonstrated for the hierarchical network of dBCube and large networks like mesh and torus, and simulation results for WICI routing are compared with wormhole and virtual cut-through routings.

A Generic Design Methodology for Deadlock-Free Routing in Multicomputer Networks

This paper introduces a generic methodology for defining deadlock-free wormhole routing schemes in any arbitrary network. The basic strategy is to partition a graph into subdigraphs with no cyclic dependencies and selectively assign virtual channels. The usefulness of our scheme is shown for the n-dimensional hypercube, the n-dimensional mesh, and the k-ary n-cube torus by identifying subdigraph characteristics that ensure acyclic routing. Further generalization which allows partial cyclic dependencies without deadlock is achieved by our extended generic methodology. We also illustrate how to identify shortest fixed path and nonminimal adaptive routing schemes using minimum required channels.

Combining Hybrid Media Tools for Web-Based Education

In recent years, due to the improvement in network speed, it has become possible to deliver diverse multimedia applications in near real time, and remote education is an area that can most benefit from such developments. In this way, large numbers of people have the opportunity to learn anywhere and at any time. With remote education, the proper use of multimedia components is an essential factor for achieving higher learning efficiency. However, the main prevailing tools used for contents creation do not explicitly provide a detail-level interface for combining possible media components. Most importantly, an interface that can coordinate the synchronization between hybrid media is required. In this paper, we present two additional types of teaching media, namely slides and handwriting. Moreover, we present an encoder interface that can combine these media with the conventional video streaming format.

Efficient Deadlock-Free Wormhole Routing and Virtual-Channel Reduction in Shuffle-Based Networks

Many aspects of shuffle-based networks have recently been studied by numerous researchers. However, no attention has been paid to deadlock-free wormhole routing algorithms. In this paper, for a set of shuffle-based networks, we introduce a graph-partitioning technique that enables a deadlock-free routing algorithm with fewer virtual channels than the known algorithms. This is achieved for the de Bruijn digraphs which are shown to require a maximum ofm? ?(m? 1)/r? virtual channels per physical channel, wheremis the diameter andris the radix. Algorithms for the generalized de Bruijn graph, the de Bruijn Cube (dBCube) graph and the Shuffle?Exchange network are introduced, and virtual channel requirements are determined. The dBCube graph of size (r,Nb,n) requires a maximum ofm? ?(m? 1)/r? virtual channels for the outcluster channels, and a maximum ofm+ 1 ? ?m/r? virtual channels for the incluster channels in most cases, wherem= ?logrNb?,ris the radix of a generalized de Bruijn graph of sizeNb, andnrepresents the number of dimensions in a binary hypercube. We also show that a maximum ofm? ?(m? 1)/2? virtual channels are required in shuffle-exchange networks with 2mnodes.

W-CoSIM (Web-Based Hardware-Software CoSimulator) - A Design-Time Simulation Tool for Estimating the Performance of Online Multimedia Applications

Internet applications are increasingly being equipped with rich multimedia data. Most e-business development tools are quite good at authoring multimedia contents, however they lack explicit support for estimating the performance of the envisioned multimedia system at design time. W-CoSim (Web-based Hardware and Software Co-Simulator) is an EJB-based simulation tool used for validating the architecture and the performance of online multimedia systems at design time. WCoSim has four components: Modeler, Translator, Engine and Scenario. Users start from Modeler to describe systems architecture by means of a UML(Unified Modeling Language) deployment diagram, and then specify hardware & software performance parameters such as the size of audio and video data, execution delay and network topology. All information specified in the Modeler are sent to the Translator, and then automatically converted to Java code. Engine and Scenario are responsible to run the Java code and produce results in the form of text and graphs.

L-system Tree with Particle Attributes

In computer graphics, L-system is primarily used for the production of such natural shapes as flowers, trees, and grass. It is possible by iteratively applying the theory of multiple-reduction-copy-machine to an arbitrary initial shape. The purpose of this paper is to modify the shape of ordinary L-system trees so that more realistic trees can be generated. Instead of applying simple iterative function system of the L-system, we regard each branch of the trees as a living thing, and endow them with corresponding attributes. Such branch attributes as lifetime, growth speed, shape variation, attraction by environment are known to belong to the attributes of the particle system. We presented modeling methods as hypotheses for each of the attributes based on parameters, iud shown the resulting diverse tree shapes.