• The Journal of Korean Institute of Communications and Information Sciences
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• v.31 no.7A
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• pp.717-724
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• 2006

In order to maximize the throughput and provide the fairness between users in MIMO-OFDM system, FATM(fairness-aware throughput maximization) scheduling algorithm was proposed. In this paper, a QoS-aware scheduling algorithms for MINO-OFDM system are proposed, each of which is based on FATM. These scheduling algorithms aim to satisfy the different service requirements of various service classes. Three proposed QoS scheduling algorithms called SPQ (Strict Priority Queueing), DCBQ (Delay Constraint Based Queuing), HDCBQ (Hybrid Delay Constraint Based Queuing) are compared through computer simulations. It is shown that HDCBQ algorithm outperforms other algorithms in satisfying different requirements of various service classes.

• Journal of Korea Society of Industrial Information Systems
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• v.8 no.3
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• pp.19-31
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• 2003

For the implementation of large scale GRID systems, the performance scalability in resource scheduling is clearly to be addressed. In this research, we analyzed existing scheduling frameworks from the viewpoint of the performance and propose a novel resource scheduling framework called resource parameter based scheduling. Proposed scheduling framework consists of three components. The first is the resource parameter graph that expresses resource information via inter-resource relation and the composition base on the hierarchical structure. The second component is the resource parameter tree to be used for the implementation of the memory-based index of resource information. The third component is the resource information repository which mostly consists of static data to be used for the general resource information services. This paper presents the details of the framework.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.13 no.6
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• pp.1065-1071
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• 2009

Satellite application services can be divided into realtime services like voice communications and non-real time services like traditional data communications. To support both types of services on the same On-Board Switching(OBS), a scheduler which depends on their service classes is required. A fixed priority scheduling policy has a starvation problem. In this paper we propose a scheduling scheme based on premium and age. Premium is a fixed value which is given to a certain class of services. Age is another parameter of the scheduling policy and it will be increased by one for every scheduling cycle. The scheme we propose chooses a packet which has the largest sum of its age and premium. Simulation results indicate that the proposed approach shows better performance in both average cell delay and std-dev of cell delay for the lower class of service. There is no staying in infinite starvation state.

• Proceedings of the Korean Information Science Society Conference
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• 2006.06d
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• pp.313-315
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• 2006

유비쿼터스 환경 하에서 사용자가 원하는 정보나 서비스를 실시간으로 제공하는 프로그램을 효과적으로 제공하기 위해서는 에이전트와 같이 자율적 수행 능력을 갖는 시스템과 다중 에이전트들간의 실시간 스케줄링 기능을 미들웨어 단계에서 효과적으로 지원하는 기능이 필수적이다. 본 논문에서는 분산객체 미들웨어에 에이전트 서비스 계층을 제공하고, 이러한 계층에 다중 에이전트를 기반으로 한 실시간 스케줄링 서비스를 지원할 수 있는 구조를 제시한다.

• Proceedings of the Korean Information Science Society Conference
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• 1998.10a
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• pp.104-106
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• 1998

멀티미디어 응용은 시간 제약 조건을 가지며, 이를 만족시키는 실시간 스케줄러는 멀티미디어를 지원하는 운영체제의 필수적인 요소이다. 본 논문에서 제안하는 실시간 스케줄링 기법은 시간 제약 조건의 명세를 이용하여 멀티미디어 응용들의 수행시간과 지연 시간 변동폭의 상한을 보장한다. 응용은 그 주기와 수행시간을 명세하며, 스케줄러는 수행률에 기반하여 응용들을 스케쥴한다. 또한 본 논문에서는 제안된 스케줄링 기법을 RT-MACH[6] 운영체제 상에서 구현하여 실제로 수행시간과 지연시간 변동폭의 상한이 보장됨을 보인다.

• Proceedings of the Korean Information Science Society Conference
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• 2003.10a
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• pp.424-426
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• 2003

웹 서비스의 사용이 급격히 증가함에 따라 사용자의 웹 서비스 005(Quality of Services)에 대란 관심도 높아지고 있다. 본 논문에서는 QoS 요소들 중 응답 시간(Response time) 향상에 대한 스케줄링 기법을 제안하여, 서비스의 질을 향상시키고자 한다. 구체적으로는 기존의 그리드 시스템에 사용되고 있는 단일 배치 스케줄링 기법을 기본으로 한 다중 배치 스케줄링을 연구하였으며, 이를 통해 그리드 기반 웹 서비스의 응답 시간 성능이 개선됨을 확인하였다.

• KIISE Transactions on Computing Practices
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• v.22 no.7
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• pp.310-314
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• 2016

Currently, several research studies are looking to improve the quality of DASH (Dynamic Adaptive Streaming over HTTP) based live streaming services. However, conventional DASH based streaming schemes cannot provide seamless playback while maintaining the low buffering and it adversely affects the QoE (Quality of Experience). To address this problem, we propose the QoE driven segment scheduling scheme. The proposed scheme adaptively schedules the segment request message according to the time and variation of segment fetching. Simulation results indicate that the proposed scheme improves the QoE of live streaming service by maintaining the low buffering delay and reducing the buffer underflow events.

• Proceedings of the Korea Information Processing Society Conference
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• 2015.10a
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• pp.223-226
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• 2015

최근 클라우드를 지원하는 Xen 가상화 환경에서 HPC를 구현하는 서비스의 수가 증가하고 있다. 따라서 SMP기반의 병렬컴퓨팅 구현을 위한 표준 라이브러리인 OpenMP 연산효율의 중요성이 높아지고 있다. 본 논문에서는 Xen 가상화 기반 OpenMP 환경에서 CPU Pinning 적용 여부에 따라 다양한 태스크 스케줄링의 성능 변화를 측정하기 위한 실험을 수행하였다. 실험결과, CPU Pinning을 적용했을 시정적 스케줄링은 3.7%, 동적 스케줄링은 3.4%, 태스크 지시자 스케줄링은 3.8%의 성능 향상을 보였다. 이러한 결과는 Xen 가상화 환경에서 효율적인 병렬 컴퓨팅 기법 설계를 위한 방향을 제시한다.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.36 no.11A
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• pp.861-869
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• 2011

In this paper, we propose coordinated scheduling and beamforming based on limited feedback to overcome the effects of inter-cell interference in multi-cell environment. The goal of this study is to improve a performance of cell-edge area significantly affected by the inter-cell interference and also to guarantee a performance of the entire system. Existing coordinated scheduling and beamforming based on the perfect channel state information generates an overhead for the channel state information feedback and exchange at the users and base stations, respectively. In this study, first we propose a novel codebook to obtain a null space of an interference channel efficiently which can be used to reduce the inter-cell interference. Using the proposed codebook, we propose coordinated scheduling and beamforming to improve the performance of cell-edge area and the entire system. Through the proportional fair scheduling, the performance of the proposed technique is shown as improvement of channel capacity for users located cell-edge area and entire system.

• Journal of KIISE:Information Networking
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• v.41 no.4
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• pp.192-201
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• 2014

User scheduling boosts the Multi-User Multi-Input Multi-Output (MU-MIMO) gain by selecting an optimal set of users to increase the 802.11 Wi-Fi system capacities. Many kinds of user scheduling algorithms, however, fail to realize the advantages of MU-MIMO due to formidable Channel State Information (CSI) overhead. In this paper, we propose a user scheduling method considering such CSI exchange overhead and its MAC protocol, called ACE (Active CSI Exchange based User Scheduling for MU-MIMO Transmission). Unlike most proposals, where user scheduling is performed after an Access Point (AP) receives CSI from all users, ACE determines the best user set during the CSI exchange phase. In particular, the AP broadcasts a channel hint about previously scheduled users, and the remaining users actively send CSI reports according to their Effective Channel Gains (ECGs) calculated from the hint. Through trace-driven MATLAB simulations, we prove that the proposed scheme improves the throughput gain significantly.