• KIPS Transactions on Computer and Communication Systems
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• v.3 no.7
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• pp.231-240
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• 2014

Video transcoding techniques provide an efficient mechanism to make a video content adaptive to the capabilities of a variety of clients. However, it is hard to provide an appropriate quality-of-service(QoS) to the clients owing to heavy workload on transcoding operations. In light of this fact, this paper presents the dual transcoding method in order to guarantee QoS in streaming services by maximizing resource usage in a transcoding server equipped with both CPU and GPU computing units. The CPU and GPU computing units have different architectural features. The proposed method speculates workload of incoming transcoding requests and then schedules the requests either to the CPU or GPU accordingly. From performance evaluation, the proposed dual transcoding method achieved a speedup of 1.84 compared with traditional transcoding approach.

• 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.

• 전자공학회논문지 IE
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• v.45 no.1
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• pp.58-64
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• 2008

This Paper provides perceptual metrics for video quality based on properties of human visual system, and audio quality based on human audition. All metrics work without reference signals, allowing non-intrusive, in-service measurements. A simple and easy-to-learn user interface displays the metrics and saves them in popular file formats like CSV. In this paper, proposed method was able to various and corrective measurement for the multimedia service video quality. As that it was able to application to set up service guide line and the methode of measurement and system for the set up standardization of the high quality video service.

• PNF and Movement
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• v.16 no.2
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• pp.275-286
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• 2018

Purpose: This study aimed to investigate the effect of an intensive rehabilitation program on the pain, range of motion (ROM), muscle strength, function, quality of life (QoL), and depression of patients with traumatic rotator cuff injury caused by an industrial accident. Methods: Seventeen patients with traumatic rotator cuff injury caused by an industrial accident participated in this study. The 12-week treatment included 30 min of manual therapy and 30 min of exercise therapy twice a day, five times a week. The outcomes were measured for evaluating the pain, ROM, muscle strength, function, QoL, and depression before the commencement of the program and after 4, 8, and 12 weeks. Results: According to the time of applying the intensive rehabilitation program, the pain (p<0.01), ROM (p<0.01), muscle strength (p<0.01), function (p<0.01), and depression (p<0.05) significantly improved with time. However, QoL was not statistically significant. Conclusion: This study confirmed the excellent effect of an intensive rehabilitation program on the pain, ROM, muscle strength, function, and depression of patients with traumatic rotator cuff injury caused by an industrial accident. However, this study was limited by the absence of a control group. This pilot study highlights the need for more extensive research with a larger sample.

• TTA Journal
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• s.66
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• pp.80-95
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• 1999

최근 인터넷 트래픽이 급증함에 따라 IP 패킷 전달의 중추를 담당하는 코아망(또는, 백본망)이 새롭게 만족시켜야 할 요구사항 들이 대두되었다. 이에는 고속 패킷 전달과 QoS(Quality of Service)의 보장이라는 이미 잘 알려진 대표적 두 요구사항 외에, Scalability(확장성), 새로운 라우팅 기능 및 트래픽 엔지니어링 등의 요구사항이 포함된다. 본고에서는 이와 같은 인터넷 백본망의 새로운 요구사항을 먼저 살펴보고, 최근 IETF[1]를 중심으로 활발히 표준화 되고 있는 IP 패킷 전달 프로토콜 들의 간략한 개요와 이들의 백본망 요구사항 충족도를 분석한다. 본 고의 분석 대상 프로토콜은 세가지 대표적인 ATM 기반 프로토콜과 Multiprotocol Label Switching 그리고 Differentiated Services이다. 끝으로, 향후 코아망 프로토콜의 발전 전망을 간략히 기술한다.

• KSII Transactions on Internet and Information Systems (TIIS)
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• v.10 no.5
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• pp.2015-2028
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• 2016

In this paper, we propose a sum transmission rate maximization based cooperative spectrum sharing protocol with quality-of-service (QoS) support for both of the primary and secondary systems, which exploits the situation when the primary system experiences a weak channel. The secondary transmitter ST_b which provides the best performance for the primary and secondary systems is selected to forward the primary signal. Specifically, ST_b helps the primary system achieve the target rate by using a fraction of its power to forward the primary signal. As a reward, it can gain spectrum access by using the remaining power to transmit its own signal. We study the secondary user selection and optimal power allocation such that the sum transmission rate of primary and secondary systems is maximized, while the QoS of both primary and secondary systems can be guaranteed. Simulation results demonstrate the efficiency of the proposed spectrum sharing protocol and its benefit to both primary and secondary systems.

• IE interfaces
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• v.22 no.1
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• pp.95-103
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• 2009

During the past few years, design of experiments (DOE) has been gaining acceptance in the telecommunications research community as a mean for designing and analyzing experiments economically and efficiently. In addition, the need for introducing a systematic robust design methodology (i.e., one of the most popular DOE methodologies) to network simulations has been increasing. In this paper, we present an architecture of voice over IP (VoIP) application and the E-Model for calculating the perceived quality of service (QoS). Then, we apply the Taguchi robust design methodology to optimize the perceived QoS of VoIP application, and describe the detailed step-by-step procedures. We have used ns-2 simulator to collect experimental data in which the SN ratio, a robustness measure, is analyzed to determine an optimal design condition. The analysis shows that "initial delay time in playout buffer" is a major control factor for ensuring robust behaviors of the perceived QoS of VoIP. Finally, we verify the proposed optimal design condition using a confirmation experiment.

• Journal of Communications and Networks
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• v.4 no.3
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• pp.230-245
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• 2002

Usually the network-throughput maximization problem for constant-bit-rate (CBR) circuit-switched traffic is posed for a fixed offered load profile. Then choices of routes and of admission control policies are sought to achieve maximum throughput (usually under QoS constraints). However, similarly to the notion of channel “capacity,” it is also of interest to determine the “network capacity;” i.e., for a given network we would like to know the maximum throughput it can deliver (again subject to specified QoS constraints) if the appropriate traffic load is supplied. Thus, in addition to determining routes and admission controls, we would like to specify the vector of offered loads between each source/destination pair that “achieves capacity.” Since the combined problem of choosing all three parameters (i.e., offered load, admission control, and routing) is too complex to address, we consider here only the optimal determination of offered load for given routing and admission control policies. We provide an off-line algorithm, which is based on Lagrangian techniques that perform robustly in this rigorously formulated nonlinear optimization problem with nonlinear constraints. We demonstrate that significant improvement is obtained, as compared with simple uniform loading schemes, and that fairness mechanisms can be incorporated with little loss in overall throughput.

• Proceedings of the KIEE Conference
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• 2001.07d
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• pp.1990-1992
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• 2001

In this paper, a NeuroFuzzy controller (NFC) with enhanced packet reservation multiple access (PRMA) protocol for QoS-guaranteed multimedia communication systems is proposed. The enhanced PRMA protocol adopts mini-slot technique for reducing contention cost, and these minislot are futher partitioned into multiple MAC regions for access requests coming from users with their respective QoS (quality-of-service) requirements. And NFC is designed to properly determine the MAC regions and access probability for enhancing the PRMA efficiency under QoS constraint. It mainly contains voice traffic estimator including the slot information estimator with recurrent neural networks (RNNs) using real-time recurrent learning (RTRL), and fuzzy logic controller with Mandani- and Sugeno-type of fuzzy rules. Simulation results show that the enhanced PRMA protocol with NFC can guarantee QoS requirements for all traffic loads and further achieves higher system utilization and less non real-time packet delay, compared to previously studied PRMA, IPRMA, SIR, HAR, and F2RAC.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 1999.11a
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• pp.401-405
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• 1999

본 논문은 실시간성 서비스인 버스트 트래픽을 갖는 ATM(Asynchronous Transfer Mode)망에서 실시간 연결 수락 제어를 위한 종단간의 지연보장을 알고리즘을 이용하여 실시간 서비스 트래픽 서비스 품질의 성능에 대해 분석하였다. 셀 손실 확률은 QoS(Quality of Service)의 기준이 되므로 제안된 실시간 알고리즘은 일정한 버퍼 메모리 크기와 연결 요청에 대한 수락 여부 즉, 연결 수락 여부의 결정을 위한 하나의 큐잉 서비스를 필요로 한다. 이러한 트래픽 소스 각 타입에 대한 초과된 셀에 대한 셀 손실 확률은 트래픽 소스 타입 전체에 하나만 존재하더라도 요구를 충족시킬 수 없으므로, 본 논문에서 제안된 버스트 트래픽 특성에 따라 지연보장 알고리즘을 이용한 큐 서비스 방식은 기존의 종단간 지연 보장 알고리즘들에서 사용하던 씬 정렬을 이용하지 않고 몇 개의 FIFO 큐로 구성된 라운드로빈 큐를 이용하여 복잡성을 크게 감소시켰으며 실시간 서비스와 비실시간 서비스의 서비스방식을 효과적으로 결합하여 다양한 QoS를 보장해야 하는 ATM망에 효과적으로 적용할 수 있고 제안된 알고리즘에 산출되는 각각의 셀 손실 확률에 충분한 상한선을 제공하는 전형적인 매개변수를 사용하여 성능을 분석한다.