Taesoo Kwon

Design and implementation of a simulator based on a cross-layer protocol between MAC and PHY layers in a WiBro Compatible.IEEE 802.16e OFDMA system

In this article we propose cross-layer design frameworks for 802.16e OFDMA systems that are compatible with WiBro based on various kinds of cross-layer protocols for performance improvement: a cross-layer adaptation framework and a design example of primitives for cross-layer operation between its MAC and PHY layers. In addition, we provide a simulation framework for cross-layer analysis between the MAC and PHY layers in 802.16e systems. Through this cross-layer simulator, we show that average cell throughput can be improved by 25-60 percent by applying careful cross-layer adaptation schemes.

Fast handover scheme for real-time downlink services in IEEE 802.16e BWA system

IEEE 802.16 WirelessMAN aiming to broadband wireless access (BWA) is evolving to 4G mobile communication systems through the standardization of IEEE 802.16e supporting mobility on existing fixed WirelessMAN systems. Because IEEE 802.16e system is based on OFDM(A) technology, a mobile subscriber station (MSS) basically conducts hard handover operation when it moves to another base station (BS). Therefore, the MSS is not able to send or receive the data during handover process and these data should be delayed. As a result, real-time packet could be dropped by handover delay. In this paper, we propose an enhanced link-layer handover algorithm that an MSS can receive downlink data before synchronization with uplink during handover process. Our proposed scheme reduces data transmission delay and packet loss probability for real-time downlink service.

Motion modeling for on-line locomotion synthesis

In this paper, we propose an example-based approach to on-line locomotion synthesis. Our approach consists of two parts: motion analysis and motion synthesis. In the motion analysis part, an unlabeled motion sequence is first decomposed into motion segments, exploiting the behavior of the COM (center of mass) trajectory of the performer. Those motion segments are subsequently classified into groups of motion segments such that the same group of motion segments share an identical footstep pattern. Finally, we construct a hierarchical motion transition graph by representing these groups and their connectivity to other groups as nodes and edges, respectively. The coarse level of this graph models locomotive motions and their transitions, and the fine level mainly captures the cyclic nature of locomotive motions. In the motion synthesis part, given a stream of motion specifications in an on-line manner, the motion transition graph is traversed while blending the motion segments to synthesize a motion at a node, one by one, guided by the motion specifications. Our main contributions are the motion labeling scheme and a new motion model, embodied by the hierarchical motion transition graph, which together enable not only artifact-free motion blending but also seamless motion transition.

Group motion editing

Animating a crowd of characters is an important problem in computer graphics. The latest techniques enable highly realistic group motions to be produced in feature animation films and video games. However, interactive methods have not emerged yet for editing the existing group motion of multiple characters. We present an approach to editing group motion as a whole while maintaining its neighborhood formation and individual moving trajectories in the original animation as much as possible. The user can deform a group motion by pinning or dragging individuals. Multiple group motions can be stitched or merged to form a longer or larger group motion while avoiding collisions. These editing operations rely on a novel graph structure, in which vertices represent positions of individuals at specific frames and edges encode neighborhood formations and moving trajectories. We employ a shape-manipulation technique to minimize the distortion of relative arrangements among adjacent vertices while editing the graph structure. The usefulness and flexibility of our approach is demonstrated through examples in which the user creates and edits complex crowd animations interactively using a collection of group motion clips.

Spectral-Based Group Formation Control

Given a pair of keyframe formations for a group consisting of multiple individuals, we present a spectral‐based approach to smoothly transforming a source group formation into a target formation while respecting the clusters of the involved individuals. The proposed method provides an effective means for controlling the macroscopic spatiotemporal arrangement of individuals for applications such as expressive formations in mass performances and tactical formations in team sports. Our main idea is to formulate this problem as rotation interpolation of the eigenbases for the Laplacian matrices, each of which represents how the individuals are clustered in a given keyframe formation. A stream of time‐varying formations is controlled by editing the underlying adjacency relationships among individuals as well as their spatial positions at each keyframe, and interpolating the keyframe formations while producing plausible collective behaviors over a period of time. An interactive system of editing existing group behaviors in a hierarchical fashion has been implemented to provide flexible formation control of large crowds.

Control systems for human running using an inverted pendulum model and a reference motion capture sequence

Physical simulation is often proposed as a way to generate motion for interactive characters. A simulated character has the potential to adapt to changing terrain and disturbances in a realistic and robust manner. In this paper, we present a balancing control algorithm based on a simplified dynamic model, an inverted pendulum on a cart. The simplified model lacks the degrees of freedom found in a full human model, so we analyze a captured reference motion in a preprocessing step and use that information about human running patterns to supplement the balance algorithms provided by the inverted pendulum controller. At run-time, the controller plans a desired motion at every frame based on the current estimate of the pendulum state and a predicted pendulum trajectory. By tracking this time-varying trajectory, our controller creates a running character that dynamically balances, changes speed and makes turns. The initial controller can be optimized to further improve the motion quality with an objective function that minimizes the difference between a planned desired motion and a simulated motion. We demonstrate the power of this approach by generating running motions at a variety of speeds (3 m/s to 5m/s), following a curved path, and in the presence of disturbance forces and a skipping motion.

Two-Character Motion Analysis and Synthesis

In this paper, we deal with the problem of synthesizing novel motions of standing-up martial arts such as kickboxing, karate, and taekwondo performed by a pair of humanlike characters while reflecting their interactions. Adopting an example-based paradigm, we address three nontrivial issues embedded in this problem: motion modeling, interaction modeling, and motion synthesis. For the first issue, we present a semiautomatic motion-labeling scheme based on force-based motion segmentation and learning-based action classification. We also construct a pair of motion transition graphs, each of which represents an individual motion stream. For the second issue, we propose a scheme for capturing the interactions between two players. A dynamic Bayesian network is adopted to build a motion transition model on top of the coupled motion transition graph that is constructed from an example motion stream. For the last issue, we provide a scheme for synthesizing a novel sequence of coupled motions, guided by the motion transition model. Although the focus of the present work is on martial arts, we believe that the framework of the proposed approach can be conveyed to other two-player motions as well.

Locomotion control for many-muscle humanoids

We present a biped locomotion controller for humanoid models actuated by more than a hundred Hill-type muscles. The key component of the controller is our novel algorithm that can cope with step-based biped locomotion balancing and the coordination of many nonlinear Hill-type muscles simultaneously. Minimum effort muscle activations are calculated based on muscle contraction dynamics and online quadratic programming. Our controller can faithfully reproduce a variety of realistic biped gaits (e.g., normal walk, quick steps, and fast run) and adapt the gaits to varying conditions (e.g., muscle weakness, tightness, joint dislocation, and external pushes) and goals (e.g., pain reduction and efficiency maximization). We demonstrate the robustness and versatility of our controller with examples that can only be achieved using highly-detailed musculoskeletal models with many muscles.

Interactive manipulation of large-scale crowd animation

Editing large-scale crowd animation is a daunting task due to the lack of an efficient manipulation method. This paper presents a novel cage-based editing method for large-scale crowd animation. The cage encloses animated characters and supports convenient space/time manipulation methods that were unachievable with previous approaches. The proposed method is based on a combination of cage-based deformation and as-rigid-as-possible deformation with a set of constraints integrated into the system to produce desired results. Our system allows animators to edit existing crowd animations intuitively with real-time performance while maintaining complex interactions between individual characters. Our examples demonstrate how our cage-based user interfaces mitigate the time and effort for the user to manipulate large crowd animation.

Complete Genome Sequence of Klebsiella pneumoniae subsp. pneumoniae KP617, Coproducing OXA-232 and NDM-1 Carbapenemases, Isolated in South Korea

ABSTRACT The prevalence of Klebsiella pneumoniae coproducing carbapenemase metallo-β-lactamase 1 (NDM-1) and OXA-48 has been increasing globally since 2013. The complete genome of KP617 was sequenced and assembled into a circular chromosome and two plasmids. This sequence provides the genetic background for understanding the evolution of carbapenemase genes in K. pneumoniae KP617.