• Journal of the Korea Society of Computer and Information
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• v.11 no.1 s.39
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• pp.167-176
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• 2006

In this paper, a home network access agent, which controls and monitors networked appliances at home using various terminals regardless of user's location, is designed and implemented. The proposed access agent integrates wire and wireless network on a home gateway (or home server) and is accessed with consistent messages using various terminals such as a web terminal, a PDA and a cellular phone. Also, in order to verify the operation and availability of the agent, a user interface for the various terminals is designed and a home network testbed which is accessed and controlled by the terminals is implemented.

• Information and Communications Magazine
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• v.33 no.5
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• pp.3-11
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• 2016

자연계에서 존재하는 다양한 생명체는 자신들의 생존과 종의 번성을 위해 효율적인 행동 규칙을 만들어 진화해 왔다. 이러한 생명체의 다양한 생존원리로부터 착안을 하여 자연계가 아닌 다른 환경에서 적용이 가능하도록 알고리즘을 만들어 적용시키는 것을 생체모방 알고리즘이라 한다. 자연계의 환경자체가 불확실한 변화가 다양하게 포함되고 있으며, 제한된 자원 환경을 어떻게 효율적으로 활용하는가의 문제가 걸려 있음으로 인하여 이러한 생체모방 알고리즘은 적용환경의 변환에 빠른 적응력을 제공할 수 있고, 자원 제약형 환경에서 안정적으로 확장성과 적응성을 제공할 수 있어서 상호 운용성 측면에서 많은 이득을 줄 수 있다. 이와 같은 생체모방 알고리즘을 네트워크의 관점에서 적용시켜 보면, 전자의 경우에는 자율적인 네트워크 구성을 용이하게 제공할 수 있음을 나타내고, 후자의 경우에는 IoT 환경과 같은 자원 제약형 환경에서의 상호 운용성을 제공할 수 있다. 이렇듯이 생체모방 알고리즘을 네트워크에 접목시켜 연구하는 것은 최근의 네트워크 분야의 연구 이슈와 상호 보완적으로 작용하여 시너지 효과를 제공할 수 있다. 자연계의 군집 현상 및 동기화 현상을 네트워크 환경에서 적용하여 사용할 수 있는 생체모방 알고리즘 기술은 다양하게 존재하고 있으며 이를 활용하는 연구를 통해 SDN(Software Defined Networking)에서의 자율제어 네트워크 구성에 접목하거나 IoT 환경과 같은 자원 제약형 환경에서의 보다 효율적인 상호 연결성을 제공하는 방향으로 발전할 수 있다. 이러한 생체모방 자율제어 네트워크 환경 구현을 위해 기존의 OpenFlow 환경과 새로이 부각되는 P4: Programming Protocol-Independent Packet Processors 기술에 대해서 정리하여 향후 생체모방 자율제어 네트워크 구현 방안을 제시하고자 한다.

• Journal of the Institute of Electronics Engineers of Korea TC
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• v.47 no.12
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• pp.90-96
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• 2010

IT environment is rapidly changed, thus security threats such as worms and viruses have increased. Especially company's internal network requires to be inherently protected against these threats. In this respect, NAC(Network Access Control) has attracted attention as new network security techniques. The NAC implements the endpoint access decision based on the collected endpoint security status information and platform measurement information. In this paper, we describe the design and implementation of unauthorized NAC which protect against such as a worm, virus, malware-infected PC, and mobile device to connect to company's internal networks.

• The KIPS Transactions:PartC
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• v.11C no.4
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• pp.429-438
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• 2004

This Paper Presents the control structure for incoming traffic from arbitrary node to Provide admission control in policy-based W network management structure using fuzzy logic control approach. The proposed control structure uses scheme for deciding network resource allocation depending on requirements predefined-policies and network states. The proposed scheme enhances policy adapting methods of existing binary methods, and can use resource of network more effectively to provide adaptive admission control, according to the unpredictable network states for predefined QoS policies. Simulation results show that the proposed controller improves the ratio of packet rejection up to 26%, because it Performs the soft adaption based on the network states instead of accept/reject action in conventional CAC(Connection Admission Controller).

• The Journal of Korean Institute of Communications and Information Sciences
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• v.36 no.5A
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• pp.473-484
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• 2011

In this paper, we analyze and propose the Joint Call Admission Control(JCAC) scheme to combine network selection scheme and radio resource reservation based Call Admission Control(CAC) in LTE-WLAN heterogeneous networks. First, We propose the JCAC system that uses network decision rate to select a network for terminal and radio resource reservation scheme in overlaying LTE-WLAN network environment. And we analyze the performance of a proposed system using markov chain model. The performance is presented in terms of the new call blocking probability, handoff call dropping probability, and channel utilization of each network. As a performance result of the our research, the system using JCAC is better than the system using non-JCAC. We found a suitable resource reservation rate that is 10% in the system using JCAC. Our work may be useful as a guideline of resource reservation rate to introduce JCAC system using resource reservation scheme in overlaying LTE-WLAN network environment.

• Journal of Digital Convergence
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• v.15 no.6
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• pp.219-227
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• 2017

Network access control should be able to effectively block security threats to the IT infrastructure, such as unauthorized access of unauthorized users and terminals, and illegal access of employees to internal servers. From this perspective, it is necessary to build metrics based on relevant standards to ensure that security is being met. Therefore, it is necessary to organize the method for security evaluation of NAC according to the related standards. Therefore, this study builds a model that combines the security evaluation part of ISO / IEC 15408 (CC: Common Criteria) and ISO 25000 series to develop security metric of network access control system. For this purpose, we analyzed the quality requirements of the network access control system and developed the convergence evaluation metric for security of the two international standards. It can be applied to standardization of evaluation method for network access control system in the future by constructing evaluation model of security quality level of network access control system.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.11 no.1
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• pp.119-124
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• 2010

The MAC layer in ad-hoc network which makes network of nodes without infrastructure for a time has became an issue to reduce delay, allocate fairly bandwidth, control TX/RX power and improve throughput. Specially, the problem to reduce power consumption in ad-hoc network is very important part as ad-hoc devices use the limited battery. For solution of the problem, many power control algorithms, such as distribute power control, PCM (Power Control MAC) and F-PCF (Fragmentation based PCM), are proposed to limit power consumption until now. Although the algorithms are designed to minimize power consumption, the latency communication zone is generated by power control of RX/TX nodes. However the algorithms don't suitably reuse the space. In this paper proposes the algorithm to improve data throughput through Spatial Reuse based on a power control method.

• Journal of KIISE:Information Networking
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• v.29 no.3
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• pp.277-285
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• 2002

This paper proposes and analyzes an error control scheme for the transmission control based real-time communication, such as FDDI, TDMA, and wireless LAN, which delivers the message according to the round robin fashion after the off-line bandwidth allocation. Taking into account the time constraint of each message, the proposed error control scheme makes the receiver transmit the error report via asynchronous traffic while the sender resend the requested message via overallocated access time which is inevitably introduced by the bandwidth allocation procedure for hard real -time guarantee. The error control procedure does not interfere other real -time message transmissions. In addition, as each frame contains the size of the message it belongs, the receiver can recognize the end of completion of message transmission. This enables earlier error report to the receiver so that the sender can cope with more network errors. The analysis results along with simulation performed via SMPL show that the proposed scheme is able to enhance the deadline meet ratio of messages by overcoming the network errors. Using the proposed error control scheme, the hard real -time network can be built at cost lower than, but performance comparable to the expensive dual link network.

• Proceedings of the Korean Information Science Society Conference
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• 2004.10c
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• pp.181-183
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• 2004

본 논문은 TCP에서 사용되는 혼잡 제어 방식의 문제점인 전송 시간에 대한 전송률 편중 현상을 완화시키기 위한 비례 증가 혼잡 제어 방식을 제안한다. TCP는 네트워크의 혼잡 상황을 제어하기 위하여 ACK 기반의 혼잡 윈도우 조정 방식을 사용한다. 그러나 기존 TCP에서 사용되는 혼잡 제어 방식은 그 자체적으로 네트워크의 혼잡 상황을 유도하며, 전송 시간이 다른 두 개의 TCP 연결이 하나의 병목 지점을 공유할 경우, 전송 시간의 차이에 따라 전송률의 편중 현상이 나타난다. 본 논문에서는 이러한 네트워크 혼잡 상황 유발과 전송 시간의 차이에 따른 전송률 편중 현상을 완화시키기 위한 송신자 기반의 네트워크 대역폭 측정 방법 및 비례 증가 혼잡 제어 알고리즘을 제안하며, 구현 및 실험을 통해 기존 TCP의 문제점을 해결할 수 있음을 보인다.

• Proceedings of the KAIS Fall Conference
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• 2010.11a
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• pp.54-57
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• 2010

본 논문에서는 태양광, 풍력, 연료전지등과 같은 신에너지전원의 단지를 효율적으로 유지관리하기 위하여 유 무선 네트워크를 이용한 원격감시 제어장치를 제작하였다. 이 감시제어장치는 모의 배전계통장치와 유무선통신장치(AutoBase 포함)를 이용한 감시제어장치, 모의 태양광전원장치로 구성하였다. 여기서 감시제어장치는 태양광전원에서 실시간으로 출력되는 전압, 전류데이터를 무선네트워크로 전송하여, HMI 프로그램인 Autobase로 실시간 모니터링할 수 있는 감시장치 부분과 원격지점에서 태양광 전원을 On/Off 하기 위한 제어장치 부분으로 구성된다. 본 논문에서 제작한 장치를 이용하여, 신에너지전원 단지의 유지보수를 위한 무선네트워크의 기술적인 대안을 마련하고, 스마트그리드 구축에 기여할 수 있음을 확인하였다.