• 산업융합연구
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• 제1권2호
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• pp.69-79
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• 2003

In order to solve scheduling, many techniques including optimization and heuristics methods have been proposed. However, these conventional approaches are usually inadequate to obtain a satisfactory solution because of a NP-Complete which requires extensive computation effort. The aim of this paper is to develop an expert system for job shop scheduling using an AI technique. Through this system, the user can choose one of several performances. If one performance is chosen, then the system solves a scheduling in order to satisfy that performance. Then, this system decides urgent job. This system can utilize production resources efficiently and minimize work-in-process inventories and tardy jobs.

• KSII Transactions on Internet and Information Systems (TIIS)
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• 제5권6호
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• pp.1101-1112
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• 2011

The Multiuser Eigenmode Transmission (MET) has generated significant interests in literature due to its optimal performance in linear precoding systems. The MET can simultaneously transmit several spatial multiplexing eigenmodes to multiple users which significantly enhance the system performance. The maximum number of users that can be served simultaneously is limited due to the constraints on the number antennas, and thus an appropriate user selection is critical to the MET system. Various algorithms have been developed in previous works such as the enumerative search algorithm. However, the high complexities of these algorithms impede their applications in practice. In this paper, motivated by the necessity of an efficient and effective user selection algorithm, a low complexity recursive user selection algorithm is proposed for the MET system. In addition, the fairness of the MET system is improved by using the combination of the proposed user selection algorithm and the adaptive Proportional Fair Scheduling (PFS) algorithm. Extensive simulations are implemented to verify the efficiency and effectiveness of the proposed algorithm.

• Journal of Multimedia Information System
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• 제2권1호
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• pp.143-152
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• 2015

Multimedia services in the cloud have become a popular trend in the big data environment. However, how to efficiently schedule a large number of multimedia services in the cloud is still an open and challengeable problem. Current cloud-based scheduling algorithms exist the following problems: 1) the content of the multimedia is ignored, and 2) the cloud platform is a known parameter, which makes current solutions are difficult to utilize practically. To resolve the above issues completely, in this work, we propose a novel distributed multimedia scheduling to satisfy the objectives: 1) Develop a general cloud-based multimedia scheduling model which is able to apply to different multimedia applications and service platforms; 2) Design a distributed scheduling algorithm in which each user makes a decision based on its local information without knowing the others' information; 3) The computational complexity of the proposed scheduling algorithm is low and it is asymptotically optimal in any case. Numerous simulations have demonstrated that the proposed scheduling can work well in all the cloud service environments.

• 한국경영과학회:학술대회논문집
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• 한국경영과학회 2006년도 추계학술대회
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• pp.201-204
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• 2006

In this paper, we propose efficient scheduling strategy for Multi-user MIMO systems that find advantageous trade off solution between multiuser diversity and spatial diversity, spatial multiplexing technique. Specifically, we suggest P-SFS(Pseudo-SNR Fair scheduling) algorithm that consider throughput and fairness problem. also we propose channel aware Antenna deployment that decide how to use assigned multiple antennas by the information of each user's channel condition.

• 전자공학회논문지
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• 제52권6호
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• pp.3-9
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• 2015

본 논문에서는 짧은 지연시간을 요구하는 CDMA 시스템 환경에서 전송률 스케줄링과 전력량 할당 문제를 연구한다. 구체적으로, 본 논문은 각각의 단말이 짧은 구간 동안의 평균 전송률을 유지하는 동시에 에너지 효율적인 스케줄링 방안을 제안한다. 다중 코드를 적용한 CDMA 시스템을 고려하며, 각각의 코드는 가상의 사용자로 해석할 수 있다. 논문의 최종 목적은 전송률 과정에서 소모하는 에너지가 최소화되도록 각각의 시간슬럿에 가상의 사용자를 스케줄링하는 방안을 제안하는 것이다. 주목할만한 점은, 본 논문에서 고려하는 전송률 최적화 문제가 최단 경로 알고리즘으로 해결 가능하다는 점이다. 마지막으로, 본 논문이 제안하는 에너지 최적화 스케줄링 방안을 TDMA 형식의 스케줄링 방안과 성능 비교 분석한다.

• Journal of Communications and Networks
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• 제12권4호
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• pp.346-357
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• 2010

Opportunistic scheduling provides the capability of resource management in wireless networks by taking advantage of multiuser diversity and by allowing delay variation in delivering data packets. It generally aims to maximize system throughput or guarantee fairness and quality of service (QoS) requirements. In this paper, we develop an extended proportional fair (PF) scheduling policy that can statistically guarantee three kinds of QoS. The scheduling policy is derived by solving the optimization problems in an ideal system according to QoS constraints. We prove that the practical version of the scheduling policy is optimal in opportunistic scheduling systems. As each scheduling policy has some parameters, we also consider practical parameter adaptation algorithms that require low implementation complexity and show their convergences mathematically. Through simulations, we confirm that our proposed schedulers show good fairness performance in addition to guaranteeing each user's QoS requirements.

• 제어로봇시스템학회논문지
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• 제4권5호
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• pp.651-657
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• 1998

In this study, an intelligent scheduling with hybrid architecture, which integrates expert system and neural network, is proposed. Neural network is trained with the data acquired from simulation model of FMC to obtain the knowledge about the relationship between the state of the FMC and its best dispatching rule. Expert system controls the scheduling of FMC by integrating the output of neural network, the states of FMS, and user input. By applying the hybrid system to a scheduling problem, the human knowledge on scheduling and the generation of non-logical knowledge by machine teaming, can be processed in one scheduler. The computer simulation shows that comparing with MST(Minimum Slack Time), there is a little increment in tardness, 5% growth in flow time. And at breakdown, tardness is not increased by expert system comparing with EDD(Earliest Due Date).

• KSII Transactions on Internet and Information Systems (TIIS)
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• 제8권6호
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• pp.1848-1868
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• 2014

Multiple-in multiple-out (MIMO) in long-term evolution (LTE) is an essential factor in achieving high speed data rates and spectral efficiency. The unexpected growth in data rate demand has pushed researchers to extend the benefits of multi-user MIMO. The multi-user MIMO system can take full advantage of channel conditions by employing efficient adjustment techniques for scheduling, and by assigning different modulation and coding rates. However, one of the critical issues affecting this feature is the appropriate estimation of channel quality indicator (CQI) to manage the allocated resources to users. Therefore, an accurate CQI estimation scheme is required for the multi-user MIMO transmission to obtain significant improvements on spectral efficiency. This paper presents overviews of multi-user MIMO in LTE/LTE-advanced systems. The link adaptation, scheduling process, and different factors that affect the reliability of CQI measurements are discussed. State-of-the-art schemes for the post-processing CQI estimation, and the comparisons of various CQI estimation schemes to support multi-user MIMO are also addressed.

• 디지털산업정보학회논문지
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• 제11권3호
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• pp.63-68
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• 2015

We consider a cell edge environment. In cell edge, a user interfered by signal which is generated by a base stations not including the user. In cell edge environment, that is, there are inter cell interference (ICI) as well as multi user interference (MUI). Coordinated multi-point transmission (CoMP) is a technique which mitigates ICI between base stations. In CoMP, therefore, base stations can coordinate with each other by sharing user state information (CSI) in order to mitigate ICI. To improve sum rate performance in CoMP, each base station should generate optimal user group and transmit data to users selected in the optimal user group. In this paper, we propose a user selection algorithm in CoMP. The proposed method use signal to interference plus noise ratio (SINR) as criterion of selecting users. Because base station can't measure accurate SINR of users, in this paper, we estimate SINR equation considering ICI as well as MUI. Also, we propose a user selection algorithm based on the estimated SINR. Through MATAL simulation, we verify that the proposed method improves the system sum rate by an average of 1.5 ~ 3 bps/Hz compared to the conventional method.

• 대한전자공학회논문지TC
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• 제49권2호
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• pp.9-16
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• 2012

본 논문에서는 Device-to-Device (D2D) 통신 시스템이 셀룰러 단말기들과 하향 링크의 주파수 자원을 공유할 때 D2D 통신으로 인한 간섭을 완화하기 위한 빔 형성 및 스케줄링 기법을 제안한다. 유니터리 행렬을 이용한 빔 형성 기법과 양자화된 채널 상태 정보의 되먹임 방식을 사용하는 셀룰러 기지국이 D2D 수신 단말기에 미치는 간섭이 최소화되도록 전송 가중치 행렬과 셀룰러 단말기를 선택한다. 기지국으로부터 D2D 수신 단말기에 미치는 간섭을 줄여 D2D 송신 단말기의 전송 전력을 줄임으로써 D2D 통신이 셀룰러 단말기에 미치는 간섭을 최소화한다. 이때 가중치 행렬의 선택을 제한함으로써 발생하는 셀룰러 단말기들의 총 전송률의 저하를 개선하기 위하여 각 코드 벡터가 1개 이상의 유니터리 행렬에 포함되도록 코드북을 구성한다. 모의실험을 통해 제안하는 방식이 D2D 통신으로 인한 간섭을 완화시킬 뿐만 아니라 개선된 코드북을 사용함으로써 셀룰러 단말기의 총 전송률도 향상시킬 수 있음을 보인다.