• Journal of Power Electronics
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• v.13 no.2
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• pp.313-321
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• 2013

This paper describes the operation analysis results of a communication-based DC micro-grid using a hardware simulator developed in the lab. The developed hardware simulator is composed of distributed generation devices such as wind power, photovoltaic power and fuel cells, and energy storage devices such as super-capacitors and batteries. Whole system monitoring and control was implemented using a personal computer. The power management scheme was implemented in a main controller based on a TMS320F28335 chip. The main controller is connected with the local controller in each of the distributed generator and energy storage devices through the communication link based on a CAN or an IEC61850. The operation analysis results using the developed hardware simulator confirm the ability of the DC micro-grid to supply the electric power to end users.

• Proceedings of the Korea Contents Association Conference
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• 2007.11a
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• pp.130-134
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• 2007

DCF(Distributed Coordination Function) of IEEE 802.11 WLAN(Wireless Local Area Network) MAC Layer apply to CSMA/CA(Carrier Sense Multiple Access with Collision Avoidance) for solution of collision when the station try to access at the same time. But DCF happens falling performance as increasing a number of stations. In this paper, we suggest algorithm that improved performance in congestion. And we compare DCF, DCF+ and proposed algorithm respect to saturation throughput, delay, collision rate and drop rate using NS2(Network Simulator 2) simulation tool.

• Journal of the Semiconductor & Display Technology
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• v.22 no.3
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• pp.112-118
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• 2023

As technology advances, the need for enhanced preparedness against cyber-attacks becomes an increasingly critical problem. Therefore, it is imperative to consider various circumstances and to prepare for cyber-attack strategic technology. This paper proposes a method to solve network security problems by applying reinforcement learning to cyber-security. In general, traditional static cyber-security methods have difficulty effectively responding to modern dynamic attack patterns. To address this, we implement cyber-attack scenarios such as 'Tiny Alpha' and 'Small Alpha' and evaluate the performance of various reinforcement learning methods using Network Attack Simulator, which is a cyber-attack simulation environment based on the gymnasium (formerly Open AI gym) interface. In addition, we experimented with different RL algorithms such as value-based methods (Q-Learning, Deep-Q-Network, and Double Deep-Q-Network) and policy-based methods (Actor-Critic). As a result, we observed that value-based methods with discrete action spaces consistently outperformed policy-based methods with continuous action spaces, demonstrating a performance difference ranging from a minimum of 20.9% to a maximum of 53.2%. This result shows that the scheme not only suggests opportunities for enhancing cybersecurity strategies, but also indicates potential applications in cyber-security education and system validation across a large number of domains such as military, government, and corporate sectors.

• 제어로봇시스템학회:학술대회논문집
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• 2005.06a
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• pp.362-367
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• 2005

Control network adopted in the national power-plant or manufactory are mostly vendor-dependent products, which have their own special specification, components and individual communication methods. These systems not only raise installation cost, but also bring many difficulties to maintenance and extension. To overcome these problems, this paper introduces a development and application case of a new "PC/Ethernet-based fieldbus" architecture and protocol to be used in mid-level fieldbus. The designed system has a basic idea of "3 Layers fieldbus over Standard-LAN" and implemented on PCs. PC gives user friendly environment. By using an open standard Ethernet in layer 1,2, the system has low cost, wide communication bandwidth and high compatibility. Layer 3 protocol designed for large realtime data communication makes user bypass TCP/IP layer and gives user direct access to the Ethernet. This new protocol eliminates potential collision of Ethernet, and transmits large periodic/non-periodic control data by using long-frame/wide-bandwidth of Ethernet effectively, and offers simple API-Services to the upper layer. Since the system have installed in H-power plant simulator and U-nuclear power plant simulator in Korea, it have been proved to be efficient and stable without any trouble in realtime communication service for full-scope plant simulator that has a lot of control elements.

• The Journal of the Korea institute of electronic communication sciences
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• v.5 no.3
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• pp.275-280
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• 2010

In this paper, VoIP(Voice over Internet Protocol) transmission performance for MANET(Mobile Ad-hoc Networks) is improved and analyzed with packet aggregation scheme which is aggregating some of short length packets to one large packet and sending to networks. VoIP simulator based on NS(Network Simulator)-2 is implemented and used to measure performance of VoIP traffic transmission. In this simulation, VoIP traffics are generated with parameters of some codes such as G.711, G.729A, GSM.AMR and iBLC. MOS(Mean Opinion Score), end-to-end network delay, packet loss rate and transmission bandwidth are measured. Performance improvements of 98% for MOS, 6.4times for end-to-end network delay, 32times for packet loss rate is shown as simulation results. On the other hand, transmission bandwidth is increased about maximum 10%. Finally, VoIP implementation guide for the performance with packet aggregation is suggested.

• International Journal of Internet, Broadcasting and Communication
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• v.12 no.3
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• pp.9-17
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• 2020

In this paper, as part of the research for the infrastructure of very high flexible and reconfigurable data center using very high speed crossbar switches, we developed a simulator that can model two and three dimensional connection structure of switches with an efficient control algorithm using software defined network and verified the functions and analyzed the performance accordingly. The simulator consists of a control module and a switch module that was coded using Python language based on the Mininet and Ryu Openflow frameworks. The control module dynamically controls the operation of switching cells using a shortest multipath algorithm to calculate efficient paths adaptively between configurable computing resources. Performance analysis by using the simulator shows that the three-dimensional switch architecture can accommodate more hosts per port and has about 1.5 times more successful 1:n connections per port with the same number of switches than the two-dimensional architecture. Also simulation results show that connection length in a 3-dimensional way is shorter than that of 2-dimensional way and the unused switch ratio in a 3-dimensional case is lower than that of 2-dimensional cases.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.28 no.11B
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• pp.1031-1037
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• 2003

A new scheduling scheme, which uses channel quality information of each flow in Bluetooth system of ad-hoc network for effective bandwidth assignment, has been proposed in this paper. By an effective bandwidth assignment, QoS (Quality of Service) could have been ensured in case of asymmetric data traffic, mixed data transmission, and congested data transmission in a specific channel. The scheduling algorithm determines channel weights using partial channel information of flows. Case studies conducted by NS-2 (Network Simulator 2) and Bluehoc simulator has been presented to show the effectiveness of the proposed scheduling scheme.

• Journal of the Korea Computer Industry Society
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• v.2 no.12
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• pp.1505-1516
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• 2001

The goal of Medical multimedia server is to develop computer hardware and software which would enable electronic access, storage, transmission, and display of patient data and images. Since the current network only provides so called "best-effort" services, it is impossible to satisfy QoS guarantee that is required for real time application services for emergency room, operating room etc. Accordingly, world-wide research is being made for a variety of services to provide QoS. he goal of DiffServ is to offer scalable differentiated service in Internet which are made possible by traffic classification and conditioning only performed at an edge(or a boundary) node. In case DiffServ was deployed in the Medical multimedia network, it is difficult to estimate how the QoS mechanism would affect totally the network performance. Therefore, we need to verify by simulation the design of algorithm which provide a variety of differentiated services. In QoS for Medical multimedia network, a simulator is designed and implemented using OPNET to investigate the performance of DiffServ QoS support mechanism. The developed DiffServ simulator may generate packets according to random, and bursty traffic models in order to incorporate diverse traffic conditions in the Medical multimedia network environment. Based on our simulation results, we confirmed that service differentiation is possible by using the EF(Expedited Forwarding) class in DiffServ networks.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.9 no.6
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• pp.1189-1194
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• 2005

An Ad-hoc network which do not use wired and base station system is composed the group of mobile and wireless nodes. That is various type of restriction. The biggest restriction is depend on the confined energy of battery. The network is devide more than two, if one of nodes consumed all energy that node can no longer participate to network. In recent years, the many number of studies research not only energy saving but also the networks lifetime extension which is to solve this problem. In this paper, we examine a AODV routing protocol which is modified to improve networks lifetime in mobile ad-hoc network. The one of improvement for AODV protocol is maximize the networks lifetime as apply Energy Mean Value algorithm which considerate node energy. We show the effectiveness for modified AODV(New-AODV) compared with AODV using NS-2(Network Simulator 2) the various performance metrics.

• The Journal of the Korea Contents Association
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• v.18 no.11
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• pp.655-664
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• 2018

Retina transforms the external light into electrical signal that stimulates visual cortex of the brain. Electrical modeling of the retina is useful to understand its structure and action that is a prerequisite to implement the retina as a hardware device. This paper introduces a 2-D electrical network model of vertebrate's retina considering signal pathway of retinal cells and synapses. We implemented a simulator of the retina based on the electrical network model to analyze its operation under various circumstances. Compared to the prior studies, It might contribute designing of artificial retina device in terms of that this study specifically observed input and output reactions of each cell and synapse node under various light intensity on the retina.