Cheol-Hoon Lee

Optimal task assignment in homogeneous networks

This paper considers the problem of assigning the tasks of a distributed application to the processors of a distributed system such that the sum of execution and communication costs is minimized. Previous work has shown this problem to be tractable for a system of two processors or a linear array of N processors, and for distributed programs of serial parallel structures. Here we focus on the assignment problem on a homogeneous network, which is composed of N functionally-identical processors, each with its own memory. Some processors in the network may have unique resources, such as data files or certain peripheral devices. Certain tasks may have to use these unique resources; they are called attached tasks. The tasks of a distributed program should therefore be assigned so as to make use of specific resources located at certain processors in the network while minimizing the amount of interprocessor communication. The assignment problem in such a homogeneous network is known to be NP-hard even for N=3, thus making it intractable for a network with a medium to large number of processors. We therefore focus on task assignment in general array networks, such as linear arrays, meshes, hypercubes, and trees. We first develop a modeling technique that transforms the assignment problem in an array or tree into a minimum-cut maximum-flow problem. The assignment problem is then solved for a general array or tree network in polynomial time.

On-line dynamic voltage scaling for hard real-time systems using the EDF algorithm

Recently, there has been a rapid and wide spread of non-traditional computing platforms, especially mobile and portable computing devices. As applications become sophisticated and computation power increases, the most serious limitation on these devices is the available battery life. Dynamic voltage scaling (DVS) has been a key technique to exploit the hardware characteristics of processors to reduce energy dissipation by lowering the supply voltage and operating frequency. This paper presents a novel on-line DVS algorithm called OLDVS that, when coupled with the underlying OS task management mechanism and real-time scheduler, can make significant energy savings, while preserving timeliness guarantees made by the underlying real-time scheduling algorithm. While most existing DVS algorithms are confined to periodic tasks only, OLDVS does not assume task periodicity, nor does it require any a priori information on the task set to be scheduled. OLDVS requires only O(1) computation on each task context switch, thus making it fairly easy to be incorporated into a real-time operating system. The OLDVS algorithm considers a general task model which is very difficult, if not impossible, for the existing DVS algorithms to handle. Our simulation results show that OLDVS achieves great energy savings and outperforms the existing DVS algorithms when the ratio of the computation requirement of aperiodic tasks to the total computation requirement is higher than 40%. The performance advantage becomes much larger as the ratio increases.

Actual remote control: a universal remote control using hand motions on a virtual menu

Consumer electronic devices are becoming more complex and diverse. In order to provide users with an easy and convenient way of controlling various consumer electronics, it is necessary to use a universal way to control various devices. This requires using a user-friendly and intuitive interface. We introduce a wristwatch-type of remote that offers a unified way to control various devices. Total of seven gestures that are based on hand motions are defined. These seven gestures are suitable to the wearable wristwatch-type device. For a variety of systems, these gestures can be used in the same way. Gestures are not designed and analyzed in a discrete manner; instead, they are designed in continuous hand motions and analyzed in gesture commands. Also, a method of modeling a virtual menu from the menu on a consumer electronic device is introduced. With the virtual menu, the user is able to control various devices by using gestures. The virtual menu has to reflect hand motion characteristics and represents functions of electronic appliances. The virtual menu is implemented in XML to represent the basic menu construction and its properties. In order to use virtual menu, we introduce how a users hand motions can be used in a fast and effective way. Finally we compare our wearable remote control to the conventional remote control through user tests in terms of user convenience and efficiency.

Design and implementation of integrated security engine for secure networking

Conventional security systems provide the functions like intrusion detection, intrusion prevention and VPN individually, leading to management inconvenience and high cost. To solve these problems, attention has been paid on the integrated security engine integrating and providing intrusion detection, intrusion prevention and VPN. This paper introduces a security framework that allows secure networking by mounting integrated security engine to the network nodes like router or switch. Also, this paper introduces the structure of integrated security engine for router which provides and integrates intrusion detection and intrusion prevention, and describes core functions and algorithms implemented for the functions. Finally, this paper explains the efficiency of integrated security engine by comparing security network structure based on the network node equipped with integrated security engine, and security network structure composed of conventional individual systems.

Development of a single 3-axis accelerometer sensor based wearable gesture recognition band

A daily-wear wearable system is one of the most convenient mediums in practical application scenario of transferring various information data or services between two users as well as between a user and a device. To implement this service scenario, we chose to develop a wearable forearm mounted accelerometer based input system. A set of gesture commands was defined by analyzing intuitive forearm movements. A hardware system and software recognition engine that utilizes the accelerometer sensor data to recognize the gesture commands were implemented and tested. This paper describes the development techniques of a wearable gesture recognition system. It also includes discussions of software and hardware design and how variations in these affected gesture recognition rate by analyzing experimental results from the actual implementations.

Energy-saving set-top box enhancement in BitTorrent networks

BitTorrent is a leading P2P network system for downloading contents. This trend moves the energy use out of the data center and into the homes of content consumers who are also then content distributors. BitTorrent clients must be fully powered-on at all times so that they are part of the swarm. Energy saving mode of the BitTorrent protocol is a critical issue, whether the goal is to reduce energy consumption of consumers or make your data centers room green. In this paper, we explore how the BitTorrent protocol can be changed so that BitTorrent-based IPTV set-top box can hibernate.

On-Line Dynamic Voltage Scaling on Processor with Discrete Frequency and Voltage Levels

The processors supporting the dynamic voltage scaling, called by DVS, have a feature that practically operates with discrete frequency and voltage levels. Almost of DVS algorithms select the smallest frequency level greater than the computed ideal level. Thus the system wastes a computational resource due to under-utilization. In this paper, we present an approach that the task executes its job under two adjacent discrete frequency levels, if possible, instead of the scaling factor computed by on-line dynamic voltage scaling(OLDVS) under the ideal level. This approach combines discrete DVS feature with OLDVS. So, each task can divide the given time budgets into two parts. Then the task executes its job at the lower frequency/voltage level in the first part. If the task does not complete until the end of the first part, then the scheduler increases the frequency to complete the remaining computation load with the remaining time budgets. Therefore, it can achieve more energy savings than the original OLDVS while simultaneously preserving timeliness guarantees made by real-time scheduling. Simulation results show that OLDVS provides up to 20% of additional energy savings for Intel PXA250[18] which has four discrete frequency/voltage levels.

A low-power real-time operating system for ARC (actual remote control) wearable device

In recent years, consumer electronic devices have been expanding their application domains from traditional consumer electronic devices such as cellular phones, PDAs(Personal Digital Assistants), PMPs(Portable Multimedia Players), Navigation, to Next Generation Personal Computers(NGPCs) such as eating consumer electronic devices, implanted consumer electronic devices, wearable consumer electronic devices. A wearable consumer electronic device is a computer that is subsumed into the personal space of the user, controlled by the user, and is always on and always accessible. Therefore, among the most salient aspect of wearable consumer electronic devices should be small form factor and long battery lifetime. In this paper, we propose a novel low-power real-time operating system (RTOS) specialized for the ARC(Actual Remote Control). An ARC is a wearable wristwatch-type remote controller; it also can serve as a universal remote control for various consumer electronic devices. The proposed RTOS has about 9KB footprints and is equipped with low-power techniques composed of the dynamic power management and the device power management. Experimental results with wearable application show that we can save energy up to 47 % using the proposed low-power techniques.

Live Book: A mixed reality book using a projection system

In this paper, we propose a mixed reality book service, called Live Book, which provides new user experience by directly augmenting digital contents on a printed book using a small projector. For this service, a stand-type system was developed, which recognizes each page of the printed book and then automatically projects digital contents corresponding to that page. Main feature of the Live Book is its ability to allow user to interact with the system using a bare finger.

A Development of Software Component Framework for Robotic Services

Robot software components, which can be accessed through their interface, are reusable and replaceable software modules used in composing robotic services. Using robot software components in developing a robot, developers can expect shortening of developing times, reduction of maintenance cost and improvement of program reusability, because interoperability among components is guaranteed. We have developed a component framework assisting robot developers to make robot application with ease. The component framework consists of a specification of component model, a component authoring tool, a component composer, and a component container. In this paper, we will not only show the developed component framework, but also demonstrate its usability by applying to commercial robots.