• ETRI Journal
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• v.33 no.5
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• pp.689-694
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• 2011

In this paper, we study scheduling schemes for two-user two-way wireless relaying systems. Two transmission modes are considered: point-to-point direct transmission and two-way amplify-and-forward relaying. An optimal scheduling scheme that opportunistically selects the best transmission mode for each user is proposed to minimize the sum bit error rate (BER). The performance lower bound of the optimal scheduling scheme is analyzed, and closed-form expression of the lower-bound BER is derived. However, for optimal scheduling, the scheduler requires the knowledge of channel state information (CSI) of all links. To reduce the feedback information of CSI, we also propose a suboptimal scheduling scheme that selects the transmission mode using only the CSI of two direct links. Simulation results show that there are 4 dB to 8 dB gains for the proposed optimal and suboptimal schemes over the fixed direct transmission and fixed two-way relayed transmission scheme. The performance gap between the optimal and suboptimal scheduling schemes is small, which implies a good trade-off between implementation complexity and system performance.

• The Journal of The Korea Institute of Intelligent Transport Systems
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• v.8 no.1
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• pp.1-8
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• 2009

This paper aims mainly to reinterpretate Optimal Bus Scheduling Model by applying System Dynamics Perspective. Traditionally, the study regarding Optimal Bus Scheduling Model stems on the linear relationshp. However, this paper attempted to convert linear relationship based Optimal Bus Scheduling Model to causal loop perspective based Model. In result, the paper present Casual Loop Diagram for Optimal Bus Scheduling Model. Furthermore, the paper also ran a simulation based on Stock & Flow Diagram for Optimal Bus Scheduling Model. The outcome was not much different from the linear relationship based Model due to the similarity of the equation applied on two models.

• Journal of Electrical Engineering and Technology
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• v.13 no.5
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• pp.1864-1873
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• 2018

Energy shifting is an innovative method used to obtain the highest profit from the operation of energy storage systems (ESS) by controlling the charge and discharge schedules according to the electricity prices in a given period. Therefore, in this study, we propose an optimal charge and discharge scheduling method that performs energy shift operations derived from an ESS efficiency model. The efficiency model reflects the construction of power conversion systems (PCSs) and lithium battery systems (LBSs) according to the rated discharge time of a MWh-scale ESS. The PCS model was based on measurement data from a real system, whereas for the LBS, we used a circuit model that is appropriate for the MWh scale. In addition, this paper presents the application of a genetic algorithm to obtain the optimal charge and discharge schedules. This development represents a novel evolutionary computation method and aims to find an optimal solution that does not modify the total energy volume for the scheduling process. This optimal charge and discharge scheduling method was verified by various case studies, while the model was used to realize a higher profit than that realized using other scheduling methods.

• The Journal of The Korea Institute of Intelligent Transport Systems
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• v.6 no.3
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• pp.12-23
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• 2007

The purpose of this studγ if to understand problem of present bus scheduling system and to develop optimal bus scheduling model which improve bus passenger's degree of satisfaction(DOS) and bus company's operation efficiency at the same time. This study developed optimal bus scheduling model, which reflected bus passenger's degree of satisfaction(DOS), applied to existing model that summery of bus operation cost($C_o$), passenger queuing time cost($C_{pw}$) and passenger travel time cost($C_{pl}$). And optimal bus scheduling model which developed in this study is optimized that using LINGO program based on linear program. Also by using the general case in Busan, compare total cost of present bus scheduling system and existing scheduling model with total cost of optimal bus scheduling model which reflected bus passenger's degree of satisfaction(DOS).

• The Journal of Information Systems
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• v.28 no.4
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• pp.175-197
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• 2019

Purpose This study develops a heuristic algorithm to solve the time-resource tradeoffs in project scheduling problems with a real basis. Design/methodology/approach Resource constrained project scheduling problem with time-resource tradeoff is well-known as one of the NP-hard problems. Previous researchers have proposed heuristic that minimize Makespan of project scheduling by deriving optimal combinations from finite combinations of time and resource. We studied to solve project scheduling problems by deriving optimal values from infinite combinations. Findings We developed heuristic algorithm named Push Algorithm that derives optimal combinations from infinite combinations of time and resources. Developed heuristic algorithm based on simulated annealing shows better improved results than genetic algorithm and further research suggestion was discussed as a project scheduling problem with multiple resources of real numbers.

• Journal of Institute of Control, Robotics and Systems
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• v.9 no.12
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• pp.969-976
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• 2003

A remote control strategy for vehicles in Intelligent Vehicle Highway System (IVHS) is considered. An optimal scheduling of a limited communication channel is proposed for lead vehicle control in a platoon. The optimal scheduling problem is to find the optimal communication sequence that minimizes the cost obtained inherently by an optimal control without the communication constraint. In this paper, the PID control law which guarantees the string stability is used for the lead vehicle control. The fact that the PID control law is equivalent to the approximately linear quadratic tracker allows to obtain the performance measure to find an optimal sequence. Simulations are conducted with five maneuvering platoons to evaluate the optimality of the obtained sequence.

• The Journal of the Institute of Internet, Broadcasting and Communication
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• v.11 no.1
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• pp.165-170
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• 2011

The Pfair scheduling algorithm, which is an optimal algorithm in the hard real-time multiprocessor environments, is based on the fixed quantum size. Recently, several methods that can determine the optimal quantum dynamically are developed in the mode change environments. These methods are based on the reach function and in many cases, we have to do the sequential search to find the optimal quantum. In this paper, we propose a new scheduling method, based on the improved reach function, that can determine the optimal quantum more quickly.

• The Transactions of the Korean Institute of Electrical Engineers A
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• v.54 no.12
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• pp.597-602
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• 2005

The introduction of competition in electricity market emphasizes the importance of sufficient transmission capacities to guarantee various electricity transactions. Therefore, when dispatch scheduling, transmission security constraints should be considered for the economic and stable electric power system operation. In this paper, we propose an optimal dispatch scheduling algorithm incorporating transmission security constraints. For solving these constraints, the dispatch scheduling problem is decomposed into a master problem to calculate a general optimal power flow (OPF) without transmission security constraints and several subproblems to inspect the feasibility of OPF solution under various transmission line contingencies. If a dispatch schedule given by the master problem violates transmission security constraints, then an additional constraint is imposed to the master problem. Through these iteration processes between the master problem and subproblems, an optimal dispatch schedule reflecting the post-contingency rescheduling is derived. Moreover, since interruptible loads can positively participate as generators in the competitive electricity market, we consider these interruptible loads active control variables. Numerical example demonstrates efficiency of the proposed algorithm.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.56 no.10
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• pp.1721-1730
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• 2007

SThis paper proposes a new dispatch scheduling algorithm in interconnected regional system operations. The dispatch scheduling formulated as mixed integer non-linear programming (MINLP) problem can efficiently be computed by generalized Benders decomposition (GBD) algorithm. GBD guarantees adequate computation speed and solution convergency since it decomposes a primal problem into a master problem and subproblems for simplicity. In addition, the inter-temporal optimal power flow (OPF) subproblem of the dispatch scheduling problem is comprised of various variables and constraints considering time-continuity and it makes the inter-temporal OPF complex due to increased dimensions of the optimization problem. In this paper, regional decomposition technique based on auxiliary problem principle (APP) algorithm is introduced to obtain efficient inter-temporal OPF solution through the parallel implementation. In addition, it can find the most economic dispatch schedule incorporating power transaction without private information open. Therefore, it can be expanded as an efficient dispatch scheduling model for interconnected system operation.

• IEMEK Journal of Embedded Systems and Applications
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• v.6 no.1
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• pp.41-47
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• 2011

The Pfair scheduling algorithm, which is an optimal scheduling algorithm in the hard real-time multiprocessor environments, propose the necessary and sufficient condition for the schedulability and is based on the fixed quantum size. Recently, several methods that determine the optimal quantum size dynamically were proposed in the mode change environments. But these methods considered only the case in which the period of a task is increased or decreased. In this paper, we also consider the case in which the execution time of a task is increased or decreased, and propose new methods that determine the optimal quantum size dynamically.