• KSII Transactions on Internet and Information Systems (TIIS)
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• 제13권9호
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• pp.4429-4445
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• 2019

As low-power and low-rate WSNs are being widely used for industrial applications, the scheduling of such applications becomes a critical issue to guarantee meeting the stringent requirements of determinism and tight latencies. This paper studies the link scheduling problem for real-time industrial applications in time-slotted channel hopping (TSCH) networks. We propose a heuristic algorithm for centralized link scheduling referred to as path-collision aware least laxity first (PC-LLF) algorithm, which dynamically prioritizes the packets based on the laxity time to the end-to-end deadlines and the amount of collisions that messages might deal with along their designated paths to the destination device. We propose schedulability analysis of real-time applications scheduled under our prioritization approach over TSCH networks, based on the literature on real-time schedulability analysis of multiprocessors and distributed systems. We show that our methodology provides an improved schedulability condition with respect to the existing approaches. Performance evaluation studies quantify to quantify the performance of our proposed approach under a variety of scenarios.

• 한국통신학회논문지
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• 제35권2A호
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• pp.134-141
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• 2010

본 논문에서는 지향성 안테나를 사용하는 IEEE 802.16 기반 무선 메쉬 네트워크(wireless mesh networks)의 성능 향상을 위한 스케줄링 알고리즘을 제안한다. 성능은 사용자 수에 따른 시스템의 수율과 각 노드 간의 지연으로 나타낸다. 분석 결과를 통해 제안된 알고리즘이 메쉬 네트워크 시스템의 지연을 줄여 시스템의 성능을 향상시킬 수 있음을 보인다. 본 논문의 결과는 향후 메쉬 네트워크, 멀티 홉 중계기 등의 다중 홉 시스템에서 각 SS(subscribe station)들의 공정성을 고려한 지향성 안테나 도입 시에 참고할 만한 가이드라인을 제시할 수 있을 것이다.

• 한국정밀공학회:학술대회논문집
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• 한국정밀공학회 1994년도 추계학술대회 논문집
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• pp.701-706
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• 1994

Holonic manufacturing system is a new approachto the organization and architecture of decentralized, autonomous and cooperative manufacturing system. The new paradigm combines the concepts of hierarchical systems and the integration of autonomous elements in distributed system. Today's scheduling and control techniques are mostly based on a centralized structure. Only little work has been done on scheduling and control of decentralized, autonomous and cooperative manufacturing system. This paper proposes a new approach IPM(Interactive Prediction Method) for scheduling and control of holonic manufacturing system.

• 전기학회논문지
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• 제56권12호
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• pp.2262-2264
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• 2007

In this paper, we propose a distributed opportunistic scheduling scheme for wireless LAN network. Proportional fair scheduling is one of the opportunistic scheduling schemes and used for centralized networks, whereas we design distributed proportional fair scheduling (DPFS). In the proposed DPFS scheme, each receiver estimates channel condition and calculates independently its own priority with probabilistic manner, which can reduce excessive probing overhead required to gather the channel conditions of all receivers. We evaluate the proposed DPFS using extensive simulation and simulation results show that DPFS obtains up to 23% higher throughput than conventional scheduling schemes and has a flexibility to control the fairness and throughput by controlling the system parameter.

• KSII Transactions on Internet and Information Systems (TIIS)
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• 제11권2호
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• pp.650-669
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• 2017

Coordinated multiple points transmission and reception (CoMP) technology is used to mitigate the inter-cell interference, and increase cell average user normalized throughput and cell edge user normalized throughput. There are two kinds of radio resource schedule strategies in LTE-A/5G CoMP system, and they are called centralized scheduling strategy and distributed scheduling strategy. The regional centralized scheduling cannot solve interference of inter-region, and the distributed scheduling leads to worse efficiency in the utilize of resources. In this paper, a novel distributed scheduling scheme named 9-Cell alternate authorization (9-CAA) is proposed. In our scheme, time-domain resources are divided orthogonally by coloring theory for inter-region cooperation in 9-Cell scenario [6]. Then, we provide a formula based on 0-1 integer programming to get chromatic number in 9-CAA. Moreover, a feasible optimal chromatic number search algorithm named CNS-9CAA is proposed. In addition, this scheme is expanded to 3-Cell scenario, and name it 3-Cell alternate authorization (3-CAA). At last, simulation results indicate that 9/3-CAA scheme exceed All CU CoMP, 9/3C CU CoMP and DLC resource scheduling scheme in cell average user normalized throughput. Especially, compared with the non-CoMP scheme as a benchmark, the 9-CAA and 3-CAA have improved the edge user normalized throughput by 17.2% and 13.0% respectively.

• Journal of Electrical Engineering and Technology
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• 제11권4호
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• pp.810-819
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• 2016

Uncoordinated charging of large-scale electric vehicles (EVs) will have a negative impact on the secure and economic operation of the power system, especially at the distribution level. Given that the charging load of EVs can be controlled to some extent, research on the optimal charging control of EVs has been extensively carried out. In this paper, two possible smart charging scenarios in China are studied: centralized optimal charging operated by an aggregator and decentralized optimal charging managed by individual users. Under the assumption that the aggregators and individual users only concern the economic benefits, new load peaks will arise under time of use (TOU) pricing which is extensively employed in China. To solve this problem, a simple incentive mechanism is proposed for centralized optimal charging while a rolling-update pricing scheme is devised for decentralized optimal charging. The original optimal charging models are modified to account for the developed schemes. Simulated tests corroborate the efficacy of optimal scheduling for charging EVs in various scenarios.

• 대한전자공학회논문지TC
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• 제38권12호
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• pp.58-66
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• 2001

입력큐방식의 교환기는 간결하며 고속교환을 위한 효과적인 교환방법이나 입력 측의 큐에서 발생하는 HOL-블로킹(HOL-Blocking)은 패킷들의 대기시간을 크게 증가시켜 전체 시스템의 효율을 58%로 제한한다. 이를 해결하는 방법은 별도의 스케줄러(scheduler, contention controller)를 두어 블로킹의 방지 및 높은 처리율을 얻고 있다. 대부분의 스케줄러의 구현은 중앙집중방식으로 구현되는데 이는 다양한 교환기의 구성을 어렵게 한다. 본 논문에서는 입력포트별로 간단하면서 분산된 형태의 스케줄러를 소개하고 모의실험을 통하여 성능을 검증한다.

• 한국통신학회논문지
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• 제24권7B호
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• pp.1229-1238
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• 1999

무선 ATM의 매체 접근 제어 프로토콜에서의 통계적 다중화를 실현하기 위해서는 중앙의 무선 ATM 액세스점(Wireless ATM Access Point)에 의해 동적 슬롯 할당을 수행할 수 있는 스케쥴링 기능이 제공되어야 한다. 그러므로 AP에서는 이동국으로부터 전송된 동적 파라미터(Dynamic Parameter)를 이용해 중앙 집중식 스케쥴링 기법을 적용하는 동적 대역 할당 매체 접근 제어 프로토콜이 요구된다. 본 논문에서는 묵시적인 방법에 의한 간접적인 동적 파라미터의 전송을 통해 동적 슬롯 할당이 가능한 새로운 스케쥴링 알고리즘을 제안한다. 제안된 방식을 알고리즘의 적시성과 정확성 측면에서 우수한 성능을 보이는 것을 확인함으로써 동적 파라미터에 전적으로 의존하지 않고 효율적인 스케쥴링이 수행될 수 있음을 보였다.

• 시스템엔지니어링학술지
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• 제10권2호
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• pp.43-50
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• 2014

The Centralized Traffic Control(CTC) System of Urban Railway is an element(subsystem) of the Urban Railway system to aim safety operation and efficient management of rolling stock in accordance with a train scheduling program in train operation ways. That's why the CTC System must be developed considering systematic and safety-guaranteed methods such as RAMS(Reliability, Availability, Maintainability, and Safety) refereed to IEC standards. The CTC System is consists of rolling stock, signaling, power supply, communication, and mechanical equipment and preforms control and remote monitoring functions. The technical activities considering safety process are very important at such an early stage of development in a railway project. This paper introduces RAMS activities and an independent safety assessment by $3^{rd}$ Party focused on a safety applied to a development of the CTC system of Urban Railway and proposes the experiences as well practices.

• 대한전기학회논문지:시스템및제어부문D
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• 제52권6호
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• pp.365-371
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• 2003

Input queued switch is useful for high bandwidth switches and routers because of lower complexity and fewer circuits than output queued. The input queued switch, however, suffers the HOL-Blocking, which limits its throughput to 58%. To overcome HOL-Blocking problem, many input-queued switch controlled by a scheduling algorithm. Most scheduling algorithms are implemented based on a centralized scheduler which restrict the design of the switch architecture. In this paper, we propose a simple scheduler called Pipelined Round Robin (PRR) which is intrinsically distributed by each input port. We presents to show the effectiveness of the proposed scheduler.