• Korean Journal of Construction Engineering and Management
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• v.12 no.1
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• pp.23-32
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• 2011

Domestic leading construction companies has been establishing and performing TACT scheduling method, similar to linear scheduling model such as line of balance and repetitive schedule, and etc. in which repetitive construction works are involved like high-rise building. Linear scheduling model has been researched as a visual scheduling method presenting the work space and time information. Likewise scheduling constraints of CPM network such as finish-to-finish, start-to-start, finish-to-start, start-to-start, linear scheduling model also has the relationships constraints, namely boundary conditions, between activities. It is especially necessary to define the boundary conditions of the activities' relationships in order to apply the linear scheduling model to be compatible with the network schedule. Therefore, this research considers the boundary conditions between activities for establishing the linear scheduling model. This paper also applies the proposed boundary conditions to TACT schedule and then deduces the main considerations in order to establish and perform TACT schedule.

• Journal of Institute of Control, Robotics and Systems
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• v.8 no.6
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• pp.506-513
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• 2002

Distributed control systems(DCS) using fieldbus such as CAN have been applied to process systems but it is very difficult to design the DCS while guaranteeing the given end-to-end constraints such as precedence constraints, time constraints, and periods and priorities of tasks and messages. This paper presents a scheduling method to guarantee the given end-to-end constraints. The presented scheduling method is the integrated one considering both tasks executed in each node and messages transmitted via the network and is designed to be applied to a general DCS that has multiple loops with several types of constraints, where each loop consists of sensor nodes with multiple sensors, actuator nodes with multiple actuators and controller nodes with multiple tasks. An assignment method of the optimal period of each loop and a heuristic assignment rule of each message's priority are proposed and the integrated scheduling method is developed based on them.

• Journal of information and communication convergence engineering
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• v.16 no.2
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• pp.84-92
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• 2018

For large wireless sensor networks running on battery power, the time synchronization of all sensor nodes is becoming a crucial task for waking up sensor nodes with exact timing and controlling transmission and reception timing. However, as network size increases, this synchronization process tends to require long processing time consume significant power. Furthermore, a naïve synchronization scheduler may leave some nodes unsynchronized. This paper proposes a power-efficient scheduling algorithm for time synchronization utilizing the notion of density, which is defined by the number of neighboring nodes within wireless range. The proposed scheduling algorithm elects a sequence of minimal reference nodes that can complete the synchronization with the smallest possible number of hops and lowest possible power consumption. Additionally, it ensures coverage of all sensor nodes utilizing a two-pass synchronization scheduling process. We implemented the proposed synchronization algorithm in a network simulator. Extensive simulation results demonstrate that the proposed algorithm can reduce the power consumption required for the periodic synchronization process by up to 40% for large sensor networks compared to a simplistic multi-hop synchronization method.

• 제어로봇시스템학회:학술대회논문집
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• 2003.10a
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• pp.2198-2202
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• 2003

The data transmission of MVB(Multifunction Vehicle Bus) of TCN(Train Network Communication) is divided into the periodic transmission phase and the sporadic transmission phase. TCN standard defines the event-polling method for the message transfer in the sporadic phase. However, since the event-polling method does not use pre-scheduling to the priority of the messages to be transmitted, it is inefficient for the real-time systems. To schedule message transmission, a master node should know the priority of message to be transmitted by a slave node prior to the scheduling the sporadic phase, but the existing TCN standard does not support any protocol for this. This paper proposes the slave frame bit-stuffing algorithm, with which a master node gets the necessary information for transmission scheduling and includes the simulation results of the event-polling method and the proposed algorithm.

• Journal of Institute of Control, Robotics and Systems
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• v.10 no.4
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• pp.377-384
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• 2004

Nowadays, control systems consist of smart sensors, smart actuators, and controllers connected via fieldbus. Some devices such as motors in plant environments generate high degrees of EMI or noise. This noise may cause communication errors and make the successful transmission of data longer. Therefore, the noise condition has to be considered at the design of a reliable control system based on a network. This paper presents a scheduling method of task and message to guarantee the given end-to-end constraints under noise environments. A noise model with multi-sources of noise is used, and the analysis method of message's response time is presented when the noise model is applied to CAN (Controller Area Network). Two kinds of noise models are applied to an example system, and the effect to each control loop s end-to-end response time is analyzed. We believe that the proposed method help system designers design the control system guaranteeing its requirements under noise environment.

• ETRI Journal
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• v.39 no.1
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• pp.13-20
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• 2017

A method is proposed for scheduling sensor accesses to the shared network in a networked control system. The proposed method determines the access order in which the sensors are granted medium access through minimization of the state estimation error covariance. Solving the problem by evaluating the error covariance for each possible ordered set of sensors is not practical for large systems. Therefore, a convex optimization problem is proposed, which yields approximate yet acceptable results. A state estimator is designed for the augmented system resulting from the incorporation of the optimally chosen communication sequence in the plant dynamics. A car suspension system simulation is conducted to test the proposed method. The results show promising improvement in the state estimation performance by reducing the estimation error norm compared to round-robin scheduling.

• ETRI Journal
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• v.36 no.6
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• pp.960-967
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• 2014

In this paper, an analytical framework is proposed for the optimization of network performance through joint congestion control, channel allocation, rate allocation, power control, scheduling, and routing with the consideration of fairness in multi-channel wireless multihop networks. More specifically, the framework models the network by a generalized network utility maximization (NUM) problem under an elastic link data rate and power constraints. Using the dual decomposition technique, the NUM problem is decomposed into four subproblems - flow control; next-hop routing; rate allocation and scheduling; power control; and channel allocation - and finally solved by a low-complexity distributed method. Simulation results show that the proposed distributed algorithm significantly improves the network throughput and energy efficiency compared with previous algorithms.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2001.10a
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• pp.113-116
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• 2001

In this paper, a new multicasting scheduling is proposed for WDM single-hop broadcast network. The main idea of traditional multicast scheduling algorithms is partitioning the multicast group into several subgroups to reduce the delay time after receiving previous message. Those partitioning algorithms are grouping method of receivers already tuned to transmitters wavelength. However, multicast scheduling shows better performance by considering the previous status of receivers. Thus, in this paper, a new subgrouping method is proposed to minimize delay through collecting the current status of receivers. This method is operated by using the tunable transceiver in WDM single hop broadcasting network and uses fixed control channel for collecting the status of receivers. In addition, we analyzed the performance of proposed method through the computer simulation and then compared with existing multicast scheduling algorithm.

• IE interfaces
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• v.23 no.2
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• pp.193-202
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• 2010

The quality of service(QoS) model should be presented with the optimal network design to effectively provide the multimedia data services between users and converged services with mobile or TV in the next-generation Internet. In specific, the method to provide differentiated services for each user is needed in the given Internet node to offer the previously negotiated QoS with the user. In this paper, the performance of the QoS enabling technologies in the differentiated services(DiffServ) network domain is analyzed. The QoS offering model and QoS metrics are presented to analyze the performance of the major scheduling algorithms. Under the real network topology and virtual service scenarios in the university, the NS-2 network simulation based on the discrete-event is performed. The results show that the ratio-based scheduling method is more effective rather than the bandwidth-assignment method.

• Journal of the Korea Institute of Building Construction
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• v.10 no.4
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• pp.31-39
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• 2010

As the linear scheduling method has been used since the Empire State Building linear schedule in 1929, it is being applied in various fields, such as construction and manufacturing. When addressing concurrent critical paths occurring in a linear construction schedule, empirical researches have stressed resource management, which should be applied for optimizing workflow, ensuring flexible work productivity and continuous resource allocation. However, work relationships have been usually overlooked in making the linear schedule from an existing network schedule. Therefore, this research analyzes the previous researches related to the linear scheduling model, and then proposes a method that can be applied for adopting the relationships of a network schedule to the linear schedule. To this end, this research considers the work relationships occurring in changing a network schedule into a linear schedule, and then confirms the activities movement phenomenon of linear schedule due to workspace change, such as physical floors change. As a result, this research can be used as a basic research in order to develop a system generating a linear schedule from a network schedule.