• Journal of KIISE:Software and Applications
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• v.37 no.11
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• pp.812-825
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• 2010

Service-Oriented Computing (SOC) is a reuse paradigm for developing business processes by dynamic service composition. Service consumers subscribe services deployed by service providers only through service interfaces. Therefore, services on server-side are perceived as black box to service consumers. Due to this nature of services, service consumers have limited knowledge on the quality of services. This limits utilizing of services in critical domains hard. Therefore, there is an increasing demand for effective methods for monitoring services. Current monitoring techniques generally depend on specific vendor's middleware without direct access to services due to the technical hardship of monitoring. However, these approaches have limitations including low data comprehensibility and data accuracy. And, this results in a demand for effective service monitoring framework. In this paper, we propose a framework for efficiently monitoring services. We first define requirements for designing monitoring framework. Based on the requirements, we propose architecture for monitoring framework and define generic patterns for efficiently acquiring monitored data from services. We present the detailed design of monitoring framework and its implementation. We finally implement a prototype of the monitor, and present the functionality of the framework as well as the results of experiments to verify efficiency of patterns for transmitting monitoring data.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.26 no.6B
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• pp.709-716
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• 2001

반복 복호 알고리듬에 의해 복호화된 터보 코드는 가산성 백색 가우시안 잡음(AWGN) 채널 환경에서 이론적으로 Shannon의 한계에 근접한 뛰어난 코딩 이득을 나타내는 것으로 보여지고 있다. 그러나, 터보 코드의 성능은 터보 부호화기에서 프레임의 크기 즉, 인터리버의 크기에 의존한다. IMT-2000과 같은 이동 통신 채널 환경에서 음성을 전송하는 경우에는 터보 코드의 프레임 크기는 매우 작다. 그리고, 그것은 터보 코드의 성능을 떨어뜨리는 직접적인 원인이 된다. 본 논문에서는 차세대 이동 통신 시스템에서 프레임 크기가 작은 음성 프레임을 이용하여 터보 코드의 성능을 검증하며, 작은 프레임 크기에 알맞은 3개의 직렬 MAP(Maximum A Posteriori probability) 복호기를 이용한 반복 복호의 터보 코드를 제안하고 부호율 1/3, 구속장의 길이 3 또는 4, 프레임 크기 24, 192 비트에 대하여 컴퓨터 모의실험을 통해 터보 코드의 성능을 분석한다.

• Proceedings of the Korean Information Science Society Conference
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• 2002.10e
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• pp.289-291
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• 2002

100Mbps의 전송속도를 만족하는 TDMA 방식의 전송 방식의 MAC을 연구중이다. 현재까지 진행된 MAC에 대한 간단한 소개와 또 MAC 프레임의 구조를 설명하고 이를 개발하기 위하여 11Mbps급의 IEEE 802 11b 모뎀을 활용한 방법에 대하여 설명한다.

• Proceedings of the KAIS Fall Conference
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• 2004.11a
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• pp.192-194
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• 2004

본 논문에서는 CPDLC 통합정보 전송환경에서 보안서비스를 제공하기 위해 사용되는 키교환 매커니즘에 대해 살펴보았고, 키 핸드쉐이크를 위해 요구되는 전송되는 프레임 구조 및 소요시간을 분석하였다.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.13 no.8
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• pp.1505-1512
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• 2009

This paper propose a new frame level rate control algorithm for improving video quality and decreasing quality variation of an entire video sequence in a very low bit rate environment. In the proposed scheme, the allocated bits to a GOP are distributed to each frame properly according to the frame characteristics as well as the buffer status and the channel bandwidth. The H.264 standard uses various coding modes and optimization methods to improve the compression performance, which makes it difficult to control the generated traffic accurately. In this paper, proper prediction models for low bit rate environments are lust proposed, and a target distortion is determined using the models. According to the target distortion, the bit budget is allocated to each frame. It is shown by experimental results that the new algorithm can generate the PSNR performance better than that of the existing rate control algorithm.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.34 no.11B
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• pp.1142-1150
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• 2009

In this paper, we propose an novel bandwidth scheduling algorithm for the MAC protocol employed by the Data Over Cable Service Interface Specifications (DOCSIS) 3.0 compliant cable networks. The proposed algorithm statistically improves the chances of request piggybacking to minimize the access delay. It utilizes the piggyback request feature of the segment packets that has been newly specified in DCOSIS 3.0. In DOCSIS 3.0, a bandwidth request can be granted to several upstream channels within an upstream bonding group. The grant on each individual channel is treated as a segment packet. We find the optimal segment placement to minimize the access delay in the proposed algorithm. We also use a self-similar traffic model for simulation and analysis to evaluate the performance of the proposed algorithm.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.28 no.5C
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• pp.476-485
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• 2003

This paper proposers a preprocessing approach to improving the quality of the music produced by the EVRC(enhanced variable rate codec) which is one of the CDMA(Code Division Multiple Access) voice codecs. Since the EVRC is optimized only for speech signals, it can deteriorate the quality of the music passed through it. One of the problems with the EVRC-coded music is time-clipping, which usually occurs when subsequent frames are encoded at Rate l/8. Since the EVRC determines the bit rate for an input frame based on the long-term prediction gain, we increase the long-term prediction gain in order for the most of the frames to be encoded at Rate 1 or Rate 1/2. Experimental results show that the approach works well on music signals and the number of time-clipped frames is considerably reduced.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.36 no.11A
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• pp.903-911
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• 2011

In this paper we proposed an energy adaptive data aggregation and transmission mechanism to solve the problem of energy limitation in wireless sensor networks (WSNs). Hierarchical structure methods are wildly used in WSNs to improve the energy efficiency. LEACH and TEEN protocols are the typical techniques. In these methods, all nodes, including nodes who have sensed data to transmit and nodes who haven't, are set frame timeslots in every round. MNs (member nodes) without sensed data keep active all the time, too. These strategies caused energy waste. Furthermore, if data collection in MNs is same to the previous transmission, it increases energy consumption. Most hierarchical structure protocols are developed based on LEACH. To solve the above problems, this paper proposed a method in which only MNs with sensed data can obtain allocated frame to transmit data. Moreover, if the MNs have same sensed data with previous, MNs turn to sleep mode. By this way redundant data transmission is avoided and aggregation in CH is lightened, too.

• Journal of IKEEE
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• v.13 no.3
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• pp.7-17
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• 2009

WiMedia UWB technology is a fully distributed data communication technology developed for the application demanding a high data transmission rate in the wireless PAN area. In general, devices can send data either by reserving time slots or by using prioritized CSMA/CA. If the PCA protocol of prioritized CSMA/CA is used, they are suffered congestion as the number of devices increases. In this paper, we propose a Deterministic Access Protocol(DAP) in WiMedia WPANs. A DAP is a method to transmit data in the non-reserved DRP period without competition as each device informs the beacon order information in the beacon period and the queue information. In addition, the problem that the devices with a lower beacon slot number have more transmission opportunities is addressed by introducing the reference point. Simulation results are given to demonstrate that a DAP can improve the throughput and reduce the packet loss rate.

• Journal of the Institute of Electronics Engineers of Korea CI
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• v.45 no.6
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• pp.18-26
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• 2008

In this paper, dynamic GTS scheduling method based on IEEE 802.15.4 is proposed for wireless control system considering reliability and real-time property. The proposed methods can guarantee a transmission of real-time periodic and sporadic data within the limited time frame in factory environment. The superframe of IEEE 802.15.4 is used for the dynamic transmission method of real-time mixed traffic (periodic data, sporadic data, and non real-time message). By separating CFP and CAP properly, the periodic, sporadic, and non real-time messages are transmitted effectively and guarantee real-time transmission within a deadline. The simulation results show the improvement of real-time performance of periodic and sporadic data at the same time.