• Journal of the Korea Institute of Information and Communication Engineering
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• v.5 no.2
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• pp.257-262
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• 2001

A new WDM-based protocol for scheduling a variable-length message is proposed in this paper Two control channels, reservation slot and control slot, are used to coordinate transmission and diminish the collisions of packet to minimize the across delay. When an idle control slot is available, control packet is transmitted on that slot and message is transferred. And the node continues to transmit its control packet through the corresponding slot every cycle, until the message is completely transmitted. If any control slot is not available, the node schedules the transmission time of message in earliest available time using reservation slots. The proposed scheduling algorithm shows better performance and lower access delay.

• Journal of KIISE:Computer Systems and Theory
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• v.33 no.9
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• pp.684-690
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• 2006

This paper proposes a message transmission model for hard real-time communications of periodic messages on a switched Ethernet and also proposes an algorithm to schedule the messages to be transmitted within their deadlines. The proposed scheduling algorithm is a distributed one and is peformed by the source and the destination nodes without the modification of the operational features of the standard Ethernet switch. When a new periodic message needs to be transmitted, it is first checked whether it can be scheduled on both the transmission and the reception links without affecting the already-scheduled messages, and a feasible schedule is made for the new message if it is schedulable. The proposed scheduling algorithm guarantees the transmission of periodic messages within their deadline and allows flexible message transmission on a hard real-time switched Ethernet through the dynamic addition of new periodic messages during run-time.

• The Transactions of the Korean Institute of Electrical Engineers D
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• v.51 no.7
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• pp.294-301
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• 2002

A new dynamic scheduling algorithm is proposed for CAN-based real-time system in this paper. The proposed algorithm is extended from an existing EDS(Earliest Deadline Scheduling) approach having a solution to the priority inversion. Using the proposed algorithm, the available bandwidth of network media can be checked dynamically, and consequently arbitration delay causing the miss of deadline can be avoided. Also, non-real time messages can be processed with their bandwidth allocation. Full network utilization and real-time transmission feasibility can be achieved through the algorithm. To evaluate the performance of algorithm, two simulation tests are performed. The first one is transmission data measurement per minute for periodic messages and the second one is feasibility in the system with both periodic messages and non-real time message.

• 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.

• The Transactions of the Korean Institute of Electrical Engineers D
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• v.53 no.10
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• pp.720-726
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• 2004

The data transmission over MVB(Multifunction Vehicle Bus) of TCN(Train Communication Network) is divided into the periodic transmission phase and the sporadic transmission phase. TCN standard recommends the event-polling method as the message transfer in the sporadic phase. However, since the event-polling method does not use pre-scheduling to the priority of the messages, 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 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 scheduling and includes the simulation results of the event-polling method and the proposed algorithm.

• Journal of the Korea Society of Computer and Information
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• v.13 no.1
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• pp.29-35
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• 2008

For efficient message passing of Parallel programs, it is required to schedule the involved two processes at the same time which are executed on different nodes, that is called 'co-scheduling' However, each node of cluster systems is built on top of general purpose multitasking OS. which autonomously manages local Processes. Thus it is not so easy to co-schedule two (or more) processes in such computing environment. Our work proposes a co-scheduling scheme for MPI-based parallel programs which exploits message exchange information between two parties. We implement the scheme on Linux cluster which requires slight kernel hacking and MPI library modification. The experiment with NPB parallel suite shows that our scheme results in 33-56% reduction in the execution time compared to the typical scheduling case. and especially better Performance in more communication-bound applications.

• The Transactions of the Korean Institute of Power Electronics
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• v.6 no.4
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• pp.369-375
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• 2001

This paper proposes a dual real-time scheduling design under real-time constraints kernel environments. In this paper, we have designed both the real-time kernel and the general kernel that have their different properties to satisfy these properties, that is, interrupt latency, scheduling precision, and message passing. In real-time tasks, interrupt processing should be run. In general kernel, non real-time tasks or general tasks are run. Also, when tasks conflict, it executed the mixed priority scheduling that non real-time kernel executed static scheduling and real-time kernel executed dynamic priority transformation scheduling, that is, least-laxity-first/minimization preemption scheduling. We have compared the results of this study for performance of the proposal real-time kernel with both RT Linux 0.5a and QNX 4.23A, that is, of interrupt latency scheduling precision and message passing.

• 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.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2000.11a
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• pp.717-720
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• 2000

Event-driven communication protocols such as CAN(Controller Area Network) have inherent packet delays due to the contention process for the use of network medium. These delays are stochastic in nature because most packets arrive at random time instants. The stochastic property of the delay adversely influences the control system's performance in terms of stability, responsiveness and steady-state error. Another problem for safety-critical application such as brake-by-wire systems is the reliability of the communication modules that can fail abruptly. This paper deals with two methods to overcome the above problems : (i) scheduling method that can maintain packet delays under some acceptable level, and (ii) redundancy management of communication modules that prescribes dual-redundancy modules' behavior when one of them fails.

• The Journal of Korea Institute of Information, Electronics, and Communication Technology
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• v.9 no.6
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• pp.584-590
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• 2016

This paper proposed "Priority Scheduling and MultiPath Routing Protocol (RRPS) for preventing communication disruption in the urban environment" to minimize the disconnection or disruption of V2I and V2V communication in the urban environment where communication is frequently disconnected according to density. The flow of the RRPS is explained as follows. RSU Request Priority Scheduling (RRPS) is used to apply the priority of the request message prior to reaching the end line by using the Start Line and End Line, which are the management areas of the RSU). This paper also proposed MPRP (Multi Path Routing Protocol) design to set up the multipath to the destination. As a result, the proposed RRPS improves the processing efficiency of V2I by applying priority scheduling to the message of the vehicle requesting the information in the RSU, and can prevent the communication disconnection. Thereby, it is improved the transmission success probability.