• Journal of KIISE:Computer Systems and Theory
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• v.34 no.5_6
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• pp.249-256
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• 2007

GPS(generalized processor sharing) is a fair scheduling scheme that guarantees fair distribution of resources in an instantaneous manner, while virtual clock pursues fairness in the sense of long-term. In this paper, we notice that the degree of memorylessness is the key difference of the two schemes, and propose a unified scheduling model that covers the whole spectrum of history-sensitiveness. In this model, each application's resource right is represented in a value called deposit, which is accumulated at a predefined rate and is consumed for services. The unused deposit, representing non-usage history, gives the application more opportunity to be scheduled, hence relatively enhancing its response time. Decay of the deposit means partial erase of the history and, by adjusting the decaying rate, the degree of history-sensitiveness is controlled. In the spectrum, the memoryless end corresponds GPS and the other end with full history corresponds virtual clock. And there exists a tradeoff between average delay and long-term fairness. We examine the properties of the model by analysis and simulation.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.35 no.2A
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• pp.95-104
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• 2010

In wireless communication system, a variety of retransmission algorithms are used in order to improve the quality of service of users. But the system may be inefficient because retransmission algorithms operate independently with other layers. Also, the quality of service can be degraded due to the unnecessary retransmission of packets. To solve these problems, the study on the cross-layer retransmission schemes have been widely performed. However, in order to apply cross-layer retransmission schemes to wireless communication system, whether the performance of cross-layer retransmission schemes meets QoS requirements of each service class has to be verified. Thus, this paper proposes the mathematical model for analyzing the performance of the cross-layer retransmission schemes and derives both the suitable retransmission scheme and the optimal retransmission parameter on each service class. The proposed mathematical model selects the MCS level based on channel state information and The performance analysis is comparatively easy in case that HARQ, ARQ, and AMC schemes are combined. The proposed mathematical model also enables the analysis of the packet transmission delay. To utilize the analytical model, this paper derives the suitable retransmission scheme and the optimal retransmission parameter for delay sensitive services in WiMAX system. Also, the proposed analytical model can be used to analyze the performance of wireless communication system such as LTE and WLAN.

• Korean Journal of Social Welfare Studies
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• v.47 no.1
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• pp.151-178
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• 2016

The primary goal of the current study was to investigate the longitudinal relationship between household income, main caregiver depression, and youth aggression from the interactionist perspective. The data were derived by combining the 2006, 2009 and 2012 survey waves from the Korean Welfare Panel Study. This data set covered the full span of adolescence from elementary to high school. The study utilized 561 families as the final sample and conducted autoregressive cross-lagged analysis. As a result, the early income status, main caregiver depression and youth aggression were likely maintained over time. Second, the results provided support for a reciprocal relationship between income and main caregiver depression. On the other hand, the reciprocal relationship between main caregiver depression and youth aggression was not found in the current study. Finally, the mediating effect of main caregiver depression between income and youth aggression was not found in the present study. In conclusion, the results of this study support the interactionist model in that the association between family income and main caregiver depression involves reciprocity and mutual influence across time. These findings have major implications for policy and interventions in regards to low-income families.

• The Journal of Information Technology
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• v.4 no.3
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• pp.87-100
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• 2001

IETF has proposed integrated services model(Int-Serv) and differentiated service(Diff-Serv) to supply IP QoS in Internet[1][2]. Int-Serv model uses state information of each IP flow, so satisfies QoS according to traffic characteristics, but increases the amount of flow state information with increasing flow number. Diff-Serv uses PHP(Per Hop Behaviour) and there are well-defined classes to provide differentiated traffics with different services according to delay and loss sensitivity. Diff-Serv model can provide diverse services in Internet because of having no the state and signal information of each flow. As MPLS uses the packet forwarding technology based on label, it implements the forwarding engine of high performance easily. The MPLS can set up the path having different and variable bandwidth and assign each path to particular CoS (Class of Service). Therefore it is possible to support the Diff-Serv model of well- defined classes that can provide the differentiated traffic with different services according to delay and loss sensitivity in IP QoS models of IETF. In this paper we propose a scheme that can accommodate Diff-Serv model to provide QoS. The system performance has been estimated by scheduling plan according to traffic classes.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.13 no.12
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• pp.6027-6033
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• 2012

In this paper, we proposed to model identification in frequency domain using relay feedback and Design of internal model controller(IMC) with Cascade controller. The parameters of controller in the inner loop are determined to minimize the integral of time multiplied by the absolute value of error (ITAE) value of performance Index. The controller of outer loop and parameters of IMC-PID controller can be obtain using identified model. The model identification is considered that it is the transient response and the steady-state response through the use of nyquist curve. Simulation examples are given to show the better performance of the proposed method than conventional methods.

• Journal of the Institute of Electronics Engineers of Korea SC
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• v.44 no.5
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• pp.1-10
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• 2007

In this paper, we proposed development of improved model reduction and design of common controller using reduction model. The Algorithm of improved model reduction considered the transient response and the steady-state response in response curve. The generalized controller is designed not only to ensure specified phase margin and iso-damping property also optimized smith-predictor controller about real model using reduction model. Simulation examples are given to show the better performance of the proposed method than convention methods.

• Proceedings of the Korea Information Processing Society Conference
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• 2006.05a
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• pp.905-908
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• 2006

MIPv6 는 MN(Mobile Node)가 자신의 홈 네트워크를 벗어나 외부 네트워크로 이동하여도 다른 노드들과 끊김 없이 지속적인 통신을 할 수 있게 해주는 인터넷 프로토콜이다. MN 은 외부네트워크로 이동 후 HA(Home Agent) 및 CN(Correspondent Node)로 핸드오버(Handover) 동작의 수행하며 이로 인한 지연이 발생하게 된다. 이러한 지연을 줄이기 위한 대책으로 Fast 핸드오버가 등장하였다. Fast 핸드오버 과정에서 MN 은 이동하려는 서브넷의 라우터(New Access Router: NAR)로의 전환을 위하여 현재 연결된 AR 과 미리 정보를 주고 받게 되고, 이동이 발생한 후에 NAR 과의 핸드오버 지연시간이 감소하게 된다. 반면 공격자가 flooding 을 통해 MN 에게 DoS(Denial of Service) 공격을 가하여 MN 을 다운시킨 후, MN 으로 위장하여 데이터를 가로채는 취약점이 존재한다. 본 논문에서는 위의 취약점을 보완하기 위하여 핸드오버 과정에서 주고받는 메세지에 대한 기밀성 및 노드 인증을 제공하는 ID 기반 암호시스템에 기반한 안전한 Fast 핸드오버 방식을 제안한다. 제안하는 모델은 메시지의 암호화와 노드 인증을 통해 무결성 및 기밀성을 보장하고 Traditional PKI 시스템에 비해 공개키 인증시간을 단축하는 이점을 가질 것으로 기대된다.

• Journal of the Institute of Electronics Engineers of Korea TC
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• v.43 no.2 s.344
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• pp.16-21
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• 2006

Internet Engineering Task Force(IETF) proposed the Hierarchical Mobile IPv6(HMIPv6) to support mobility efficiently. The HMIPv6 was developed to reduce the signaling overhead and delay concerned with Binding Update in Mobile IPv6. However, the HMIPv6 still need a further enhancement for supporting the real-time application because HMIPv6 only concerns with the latency resulted within a MAP For providing seemless handoff we propose a scheme that can reduce latency when Mobile Node changes a MAP. Also we compare the HMIPv6 with the proposed scheme through a analysis model.

• Proceedings of the Korean Information Science Society Conference
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• 2011.06b
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• pp.409-412
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• 2011

본 논문에서는 Xen-ARM 기반의 가상화 환경에서 실시간 게스트 운영체제의 I/O를 지원하기 위한 방법을 제안한다. Xen-ARM 하이퍼바이저는 서버 환경에서 주로 사용되는 Xen 가상화 기법을 모바일 구조인 ARM에서 구현한 것으로, 분할 드라이버 모델과 크레딧 스케줄러를 지원한다. 하지만, 이러한 두 가지 특성은 I/O 처리 지연의 주요 원인이 된다. 특히, 장치 드라이버와 사용자 태스크의 실행 중에 하이퍼바이저의 도메인 간 스위칭이 필요하므로, 특정 시간으로 I/O 처리 지연을 제한하기 대단히 어렵다. 본 논문에서는 게스트 운영체제의 수정을 통해 I/O 처리 지연을 제한하는 기법을 제안한다. 게스트 운영체제는 현재 실행되는 태스크의 특성을 Xen-ARM 하이퍼바이저에게 간접적으로 전달하여, 전체 시스템의 모든 태스크에 대하여 우선순위를 부여하며, 하이퍼바이저의 스케줄러에서 인터럽트 처리를 위해 가장 응급한 태스크 실행을 스케줄링 할 수 있도록 한다. 제안하는 기법은 실험을 통해, I/O를 처리하는 도메인의 1ms 이상의 처리시간이 84%에서 99%까지 줄어들 수 있음을 보인다.

• Journal of Broadcast Engineering
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• v.12 no.1 s.34
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• pp.28-40
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• 2007

In this paper, we proposes an idea for improved sound characteristic which decreasing a problem in previous reverberation algorism structure. To later reflection sound, proposed new reverberation structure, using a lopped and nested all-pass delay line, and it is designed to improve an natural concert hall sound. In addition, In order to have best imaginary sound effect, we extracted the factors by controlling each delay line's delay time, and we realized a proposed new algorithm by using general-purpose DSP. Through several experimental cases, we observed better effect on improvement of linear flatten and reverberation density and decreasing about colorlessness and non-linear sound at previous proposed model about impulse input.