• The Journal of Korean Institute of Communications and Information Sciences
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• v.30 no.12B
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• pp.811-817
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• 2005

Efficient bandwidth management is necessary in order to provide high quality service to users in a multimedia wireless/mobile network. In this paper, I propose an on-line load balancing algorithm with preemption. This technique is able to balance the traffic load among cells accommodating heterogeneous multimedia services while ensuring efficient bandwidth utilization. The most important features of my algorithm are its adaptability, flexibility and responsiveness to current network conditions. In addition, my online scheme to control bandwidth adaptively is a cell-oriented approach. This approach has low complexity making it practical for real cellular networks. Simulation results indicate the superior performance of my algorithm.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.27 no.4C
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• pp.308-315
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• 2002

Guaranteed frame rate (GFR) service has been defied to provide minimum cell rate (MCR) guarantees for virtual connections (VCs) carrying Internet traffic in ATM networks and allow them to fairly share residual bandwidth. The simplest switch implementation mechanism to support the GFR service in ATM networks consists of the frame-based generic cell rate algorithm (F-GCRA) frame classifier and the early packet discard (EPD)-like buffer acceptance algorithm in a single FIFO buffer. This mechanism is simple, but has foiled to guarantee the same bandwidth as an MCR to a VC that has reserved a relatively large MCR. This paper applies the packet spacing scheme to TCP traffic to alleviate its burstness, so as to guarantee a larger MCR to a VC. In addition, the random early detection (RED) scheme is added to the buffer acceptance algorithm in order to improve fairness in use of residual bandwidth. Simulation results show that the applied two schemes improve a quality of service (QoS) in the GFR service for the TCP traffic.

• The KIPS Transactions:PartB
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• v.15B no.5
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• pp.413-420
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• 2008

Network bandwidth is one of the major factors that impact the cost of a video service. In this paper we propose approaches to reducing the bandwidth requirement for transporting MPEG-4 video traffic over wireless LANs while guaranteeing a required level of quality of service(QoS). To support high quality video playbacks, video frames must be transported to the client prior to their playback times. A real-time transmission scheduling is used for this purpose, which transmits each frame assigned with a priority according to its importance. It addresses the challenge for a scheduling algorithm that efficiently handles the changing workloads of MPEG-4 video traffic. The goal of our research is to maximize the number of frames that are transported within their deadlines while minimizing the tardiness of frames that missed their deadlines. The performance of the proposed method is compared with that of similar service mechanisms through extensive simulation experiments.

• The Journal of the Korea Contents Association
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• v.2 no.1
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• pp.104-112
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• 2002

Dynamic Handoff Control Scheme (DHCS), which is propose d in this paper, suggests the method to request handoff at the optimal time. To accomplish this, DHCS measures the speed of the mobile station and sets the pilot strength for handoff request. When the pilot strength of the current base station is bigg or than the pilot strength for handoff request, which means the pilot strength of the current base station is big enough so the possibility of the call to be disconnected is low, DHCS doesn't request for the handoff even though the pilot strength of the adjacent base station is bigger than the pilot strength of the curent base station. DHCS guarantees the QoS (Quality of Service) by processing the handoff calls prior to new calls at the base station and providing continuous service for the mobile station by setting the priorities for the calls according to the queue waiting time transmitted from the mobile stations.

• Journal of KIISE:Information Networking
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• v.28 no.4
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• pp.540-549
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• 2001

Internet telephony service is very cheap and very easy to introduce the value-added service than the POTS, but is difficult to the QoS of telephone service. The existing Internet typically offers 'best effort' services only, which do not make any commitment about delay, packet loss and jitter. This paper compensates the low quality of the speech for packet loss or delay using SOLA algorithm in Internet phone. SOLA algorithm is a popular technique for Time Scale Modification of speech and audio signal. In the proposed algorithm, the receiver expands the received packet under resonable threshold, and hence compensates the QoS of speech. From the simulation, this algorithm can conceals packet loss considerably, and is also improved the quality of the speech.

• KIPS Transactions on Computer and Communication Systems
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• v.4 no.11
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• pp.369-382
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• 2015

Energy aware server clusters aim to reduce power consumption at maximum while keeping QoS(quality of service) compared to energy non-aware server clusters. They adjust the power mode of each server in a fixed or variable time interval to activate only the minimum number of servers needed to handle current user requests. Previous studies on energy aware server cluster put efforts to reduce power consumption or heat dissipation, but they do not consider energy efficiency well. In this paper, we propose an energy efficient cluster management method to improve not only performance per watt but also QoS of the existing server power mode control method based on autonomous learning. Our proposed method is to adjust server power mode based on a hybrid approach of autonomous learning method with multi level thresholds and power consumption prediction method. Autonomous learning method with multi level thresholds is applied under normal load situation whereas power consumption prediction method is applied under abnormal load situation. The decision on whether current load is normal or abnormal depends on the ratio of the number of current user requests over the average number of user requests during recent past few minutes. Also, a dynamic shutdown method is additionally applied to shorten the time delay to make servers off. We performed experiments with a cluster of 16 servers using three different kinds of load patterns. The multi-threshold based learning method with prediction and dynamic shutdown shows the best result in terms of normalized QoS and performance per watt (valid responses). For banking load pattern, real load pattern, and virtual load pattern, the numbers of good response per watt in the proposed method increase by 1.66%, 2.9% and 3.84%, respectively, whereas QoS in the proposed method increase by 0.45%, 1.33% and 8.82%, respectively, compared to those in the existing autonomous learning method with single level threshold.

• Proceedings of the Korean Information Science Society Conference
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• 2002.04a
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• pp.265-267
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• 2002

인터넷에서 멀티미디어 응용들이 증가함에 따라 서비스 품질(QoS: Quality of Service)을 보장해 줄 수 있는 여러 가지 방안이 제안되어 왔는데, 일반적으로 이들 방안은 확장성과 종단간 QoS 보장 간에 상호 모순이 발생하는 경향을 가지고 있다. 본 논문에서는 이와 같은 상호 모순을 피할 수 있는 QoS 지원 방안으로서 DQSP(Dynamic QoS Support Protocol)를 제안한다. DQSP는 도메인 내에서의 자원 예약과 연결 수락 제어 메커니즘을 정의한다. DQSP는 링크 자원을 각 에지 라우터로부터의 트래픽 클래스별로 동적으로 할당하고 에지 라이투가 자신에게 할당된 링크 자원에 관한 정보를 유지하도록 한다. DQSP는 목적지로의 연결 수락 제어를 위한 QoS 신호 프로토콜이 필요 없이 에지 라우터에서 매 사용자 플로우별로 직접적으로 연결 수락 결정을 내리므로 확장성 문제 및 코어 라우터의 복잡한 기능 요구 사항 문제를 해결한다. 또한 UQSP는 에지 라우터가 트래픽 부하에 따라 자신에게 할당되어 있는 자원을 반납하거나 추가적인 자원을 제공받을 수 있도록 해 자원 오버 프로비져닝으로 인해 발생할 수 있는 비효율적인 자원 활용 문제를 해결한다. 또한 DQSP는 경로 재계산을 수행하여 라우팅을 조정해 나감으로써 효율적일 네트워크 자원 활용이 가능하다. 시뮬레이션을 통하여 DQSP와 기존의 자원 할당 및 공유 방식들을 비교한 결과 DQSP가 시그널링과 상태 정보 유지를 위한 오버헤드 면에서 기존의 종단간 QoS 보장을 제공하는 구조인 IntServ에서와 같은 확장성 문제를 발생시키지 않으면서도 효율적으로 네트워크 자원을 활용할 수 있음을 확인할 수 있었다.재 상용화 되어있는 Bellcore 의 S/KEY 시스템과의 비교를 수행하였다. 분석에서는 제품의 효율성뿐만 아니라 보안성을 중요하게 생각하였으며, 앞으로 보안 관련 소프트웨어 개발에 사용될 수 있는 도구들이 가이드 라인에 대한 정보를 제공한다.용할 수 있는지 세부 설계를 제시한다.다.으로서 hemicellulose구조가 polyuronic acid의 형태인 것으로 사료된다. 추출획분의 구성단당은 여러 곡물연구의 보고와 유사하게 glucose, arabinose, xylose 함량이 대체로 높게 나타났다. 점미가 수가용성분에서 goucose대비 용출함량이 고르게 나타나는 경향을 보였고 흑미는 알칼리가용분에서 glucose가 상당량(0.68%) 포함되고 있음을 보여주었고 arabinose(0.68%), xylose(0.05%)도 다른 종류에 비해서 다량 함유한 것으로 나타났다. 흑미는 총식이섬유 함량이 높고 pectic substances, hemicellulose, uronic acid 함량이 높아서 콜레스테롤 저하 등의 효과가 기대되며 고섬유식품으로서 조리 특성 연구가 필요한 것으로 사료된다.리하였다. 얻어진 소견(所見)은 다음과 같았다. 1. 모년령(母年齡), 임신회수(姙娠回數), 임신기간(姙娠其間), 출산시체중등(出産時體重等)의 제요인(諸要因)은 주산기사망(周産基死亡)에 대(對)하여 통계적(統計的)으로 유의(有意)한 영향을 미치고 있어 $25{\sim}29$세(歲)의 연령군에서, 2번째 임신과 2번째의 출산에서 그리고 만삭의 임신 기간에, 출산시체중(出産時體重) $3.50{\sim}3.99kg$사이의 아이에서 그 주산기사망률(周産基死亡率)이 각각

• Journal of Korea Multimedia Society
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• v.1 no.1
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• pp.98-108
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• 1998

In the multimedia tele-medical system the medical informations are stored and managed in multimedia database. Also, multimedia DBMS is essential in order to manage large scale medical informations, and the remote access function is necessary for the distributed processing at all around the hospital. For the multimedia tele-medical information that is composed of image/picture, data, video, and audio, a high-speed telecommunication network is necessary that can provide separated connections for each medical information type with different QoS. The commercial DBMSs are based on the TCP/IP socket API(Application Programming Interface) that does not provide multiple QoS. Also, each commercial DBMS has its own API that is incompatible with other DBMS. In this paper, we propose a multimedia DBMS agent for the remote access of the multimedia database in the tele-medical system. The proposed multimedia DBMS agent is based on the ATM API that can provide high-speed data transfer capability and multiple QoS connections. Also, the proposed multimedia DBMS agent is independent of the commercial DBMS. We explain the functional architecture of the multimedia DBMS agent, implementation technology on the ATM network environment, and the result of performance analysis.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.12 no.7
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• pp.3176-3183
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• 2011

Traffic and congestion control in the wireless sensor network is an important parameter that decides the throughput and QoS (Quality of Service). This paper proposes a transmission rate priority-based traffic control scheme to serve digital contents streaming in wireless sensor networks. In this paper, priority for transmission rate decides on the real-time traffic and non-real-time with burst time and length. This transmission rate-based priority creates low latency and high reliability so that traffic can be efficiently controlled when needed. Traffic control in this paper performs the service differentiation via traffic detection process, traffic notification process and traffic adjustment. The simulation results show that the proposed scheme achieves improved performance in delay rate, packet loss rate and throughput compared with those of other existing CCF and WCA.

• KSII Transactions on Internet and Information Systems (TIIS)
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• v.9 no.5
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• pp.1569-1586
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• 2015

This paper considers the optimal cell association and resource allocation for load balancing in a heterogeneous cellular network subject to user's quality-of-service (QoS) constraints. We adopt the proportional fairness (PF) utility maximization formulation which also accommodates the QoS constraints in terms of minimum rate requirements. With equal resource allocation this joint optimization problem is either infeasible or requires relaxation that yields a solution which is difficult to implement. Nevertheless, we show that this joint optimization problem can be effectively solved without any priori assumption on resource allocation and yields a cell association scheme which enforces single BS association for each user. We re-formulated the joint optimization problem as a network-wide resource allocation problem with cardinality constraints. A reweighted heuristic l₁-norm regularization method is used to obtain a sparse solution to the re-formulated problem. The cell association scheme is then derived from the sparsity pattern of the solution, which guarantees a single BS association for each user. Compared with the previously proposed method based on equal resource allocation, the proposed framework results in a feasible cell association scheme and yields a robust solution on resource allocation that satisfies the QoS constraints. Our simulations illustrate the impact of user's minimum rate requirements on cell association and demonstrate that the proposed approach achieves load balancing and enforces single BS association for users.