• The Journal of the Institute of Internet, Broadcasting and Communication
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• v.8 no.4
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• pp.35-42
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• 2008

Since Bianchi's 2-D Markov Chain Model considers collision problem only in ideal channel condition, it does not reflect real channel impaired by fading, interference, and noise. Distributed Coordination Function(DCF) doubles its contention window(CW) when transmission fails regardless of collision or transmission error. Increase of CW caused by transmission error degrade throughput and increase the delay. In this paper, we present quantitative analysis of the impact of the parameters such as contention window size(CW), transmission probability for a given time slot(${\Im}$), transmission failure probability($p_f$), on the system performance and provide a method how to decrease the initial CW to achieve equivalent performance.

• The Journal of Information Systems
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• v.6 no.2
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• pp.85-105
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• 1997

The objective of this research is to construct and build a software platform to enable collaboration among enterprise headquarters, product designers, software engineers, manufacturing plants, and suppliers which are locate at different remote locations via internet. In specific, agent technology is adopted as a software vehicle to automate demand and supply process in the internet environment. Agents are programs that act on behalf of their human users to perform laborious tasks such as information locating, accessing, filtering, integrating, adapting and resolving inconsistencies. Global competion is forcing the present day industry to produce high quality product more fast and inexpensively. In Korea, most labor-intensive industries have moved to China and other Asian countries for cost reduction. The need for fast information exchange has increased among the remote locations for the cooperation and coordination. In this research, a virtual global purchasing and ordering system will be constructured that distributes production schedule among remote places, acts as a bridge between the headquarters and manufacturing plants, distributes tasks and collates different solutions between demand and supply using agent. The external communication protocol takes HTML format, internal message handling requires SGML for document exchange, and KQML for agent implementation. The expected benefits will be : reduced cost of real-time information exchange, realization of global manufacturing environment, the maximum utilization of internet for the enterprise data exchange.

• Electronics and Telecommunications Trends
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• v.13 no.6 s.54
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• pp.83-93
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• 1998

Best effort 서비스 품질만 지원하는 현재의 인터넷에 음성, 오디오 그리고 영상 통신 응용 서비스와 같은 새로운 멀티미디어 응용 서비스를 사용하려는 요구가 확대됨에 따라서 멀티미디어 서비스를 제공할 수 있는 인터넷의 필요성이 증대하고 있다. 또한 이러한 멀티미디어 서비스를 제공하기 위하여 서비스 품질(QoS)을 보장할 수 있는 통신 방식과 대량의 트래픽을 효과적으로 전달할 수 있는 메커니즘이 필요하게 되었다. 비동기 전송방식(ATM)은 이러한 멀티미디어 서비스를 인터넷에서 제공할 수 있는 최적의 통신 방식으로 고려되고 있는데, 이것은 ATM의 장점인 고속의 스위칭 기술과 논리적으로 VPI/VCI를 다중화 하는 기법, 그리고 유연한 서비스 품질 관리가 가능하기 때문이다. 본 고에서는 ATM 망에서 인터넷 서비스를 지원하기 위하여 결성된 ITU-T SG11의 Coordination 그룹인 Signalling Support of Internet-Based Applications(SoI) 회의 결과를 중심으로 하며 SoI의 표준화 연구 목표, B-ISDN 신호 프로토콜을 이용한 Long-lived 세션과 QoS에 민감한 세션의 인터넷 트래픽에 대한 ATM 연결 설정 절차 및 인터넷 세션 정보의 전달 방법 그리고 인터넷 서비스를 위한 멀티캐스팅 방법에 대하여 기술한다. 본 고의 목적은 인터넷 서비스 및 프로토콜을 지원하기 위하여 확장이 필요한 B-ISDN 신호 프로토콜의 기능을 명확히 기술하기 위한 것이다.

• The Journal of the Korea institute of electronic communication sciences
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• v.5 no.1
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• pp.44-50
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• 2010

Wireless sensor network is consist of multiple sensor nodes and performs a shared tasks through the coordination of sensor nodes. Traffic in WSN is categorized as periodical monitoring traffic, event-driven traffic and query-based traffic. Periodic traffic takes significant proportion of the whole traffic processing because multiple sensor nodes generate traffic in a steady interval although the generation frequency of periodic traffic is low. In this paper, we propose a traffic control algorithm of network protocol for periodic traffic in terms of energy efficiency and conduct performance analysis of the algorithm.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2007.10a
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• pp.91-94
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• 2007

In the IEEE 802.11 Wireless Local Area Networks (WLANs), network nodes experiencing collisions on the shared channel need to backoff for a random period of time, which is uniformly selected from the Contention Window (CW). This contention window is dynamically controlled by the Binary Exponential Backoff (BEB) algorithm. The BEB scheme suffers from a fairness problem and low throughput under high traffic load. In this paper, I propose a new backoff algorithm for use with the IEEE 802.11 Distributed Coordination Function.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.11 no.8
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• pp.1612-1618
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• 2007

Requirement of coordination among heterogeneous devices is significantly increasing to meet the challenges presented by the evolvement of the ubiquitous computing environment. The web services technology is receiving much attention as a promising solution to support the inter-operability between such heterogeneous devices by means of well-defined protocol. Recenlty, ECA(Event-Condition-Action) rule-based framework for coordinating devices is proposed, which is called WS-ECA(Web Services-ECA) framework In this paper we propose a specific design and an implementation methodology for WS-ECA framework.

• The Journal of Korean Academy of Sensory Integration
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• v.15 no.2
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• pp.35-45
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• 2017

Objective : The purpose of this study is to investigate the effect of modified Interactive Metronome (IM) program which is applicable to clinical practice based on the IM protocol on the behavioral symptoms, timing and motor function of children with Attention Deficit Hyperactivity Disorder (ADHD). Method : This study used one-group pretest-posttest research design. 13 ADHD children aged 7-12 years in Busan were participated in this study. The participants were underwent 24 sessions of 30 minutes intervention, 3 times a week. Evaluations were performed before- and after the intervention. Measurements used in this study were Korean-ADHD Rating Scale for behavior symptom, Long Form Assessment (LFA) for the timing, and second version of Bruininks-Oseretsky Test of Motor Proficiency (BOT-2) for the motor function. Results : There was a significant improvement in hyperactivity / impulsivity among the behavioral symptoms, and there was a statistically significant improvement in timing, hand coordination, and body coordination. Conclusion : Modified IM program for clinical application has significant effect on improving behavioral symptoms, timing and motor function of children with ADHD.

• Journal of KIISE:Information Networking
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• v.31 no.5
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• pp.532-543
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• 2004

Mobile Ad hoc NETworks (MANET) consist of mobile nodes which are usually powered by battery Approaches for minimizing power consumption have been proposed for all network layers and devices. IEEE 802.11 DCF (Distributed Coordination Function), a well-known medium access control protocol for MANETS, also defines a power save mode operation. The nodes in power save mode periodically repeat the awake state and the doze state in synchronized fashion. When all nodes are in the awake state, the exchange the announcements for the subsequent message transmission with neighbors. The nodes that send or receive the announcements stay awake for data transmission, and others go into the dole state. The previous works for enhancing the power save mode operation have focused on shortening the duration of the awake state. We observed that the longer sleeping period results in seriously long delivery latency and the consequent unnecessary power consumption as well, because the packets can move forward only one hop for a fixed interval. In this paper, we propose an improved protocol for the power save mode of IEEE 802.11 DCF, which allows the flooding packets to be forwarded several hops in a transmission period. Our approach does not reduce the duration of compulsory awake period, but maximizes its utilization. Each node propagates the announcements for next flooding to nodes of several hops away, thus the packets can travel multiple hops during one interval. Simulation results of comparison between our scheme and the standard show a reduction in flooding delay maximum 80%, and the unicasting latency with accompanying flooding flows near 50%, with slight increase of energy consumption.

• 제어로봇시스템학회:학술대회논문집
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• 2005.06a
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• pp.1938-1943
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• 2005

Network human-robot interface is an important research topic. In home application, users access the robotic system directly via voice, gestures or through the network. Users explore a system by using the services provided by this system and to some extend users are enable to participate in a service as partners. A service may be provided by a robot, a group of robots or robots and other network connected systems (distributed sensors, information systems, etc). All these services are done in the network environment, where uncertainty such as the unstable network connection, the availability of the partners in a service, exists. Moreover, these services are controlled by several users, accessing at different time by different methods. Our research aimed at solving this problem to provide a high available level, flexible coordination system. In this paper, a multi-agent framework is proposed. This framework is validated by using our new concept of slave agents, a responsive multi-agent environment, a virtual directory facilitator (VDF), and a task allocation system using contract net protocol. Our system uses a mixed model between distributed and centralized model. It uses a centralized agent management system (AMS) to control the overall system. However, the partners and users may be distributed agents connected to the center through agent communication or centralized at the AMS container using the slave agents to represent the physical agents. The system is able to determine the task allocation for a group of robot working as a team to provide a service. A number of experiments have been conducted successfully in our lab environment using Issac robot, a PDA for user agent and a wireless network system, operated under our multi agent framework control. The experiments show that this framework works well and provides some advantages to existing systems.

• Information Systems Review
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• v.8 no.2
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• pp.103-117
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• 2006

As the interest in the combinatorial auction has increased, diverse combinatorial auction market types have been proposed. Although there have been several studies on the combinatorial auction design, the studies covered some factors or partial dimensions of combinatorial auction design. Given the potential practical value of combinatorial auctions, it is necessary to approach it with an integrated and systematic design methodology for supporting a comprehensive range of combinatorial auction models. Thus, we present a systematic framework for combinatorial auction design methodology. In particular, we classified the combinatorial auction architecture types, process types, and mechanism types. This framework characterizes the different combinatorial auction models, and lead to a useful taxonomy of the combinatorial auction design factors and taxonomy of the market types by coordination among the design factors. In addition, we illustrate an n-bilateral combinatorial auction market, derived from our design methodology, to show the viability of our study.