• Journal of Korea Society of Digital Industry and Information Management
• /
• v.6 no.4
• /
• pp.75-81
• /
• 2010

Due to the increasing use of smart phones, using Wifi, Wibro of mobile devices spread. Accordingly, Need of using peer-to-peer file sharing between mobile devices is growing. However, common Peer-to-Peer(P2P) system is too complex and is not suitable to be applied to mobile devices. Thus, the need of research has shown to improve way in a mobile environment that has a constraints as mobility and the scope of communication. Among them, there is a Chord as contents look up algorithm. Chord is the issue. Chord as the DHT-based P2P protocol shares files, index-key and distributed key across the network. However, exist Chord doesn't consider the mobility. So, It has a lot of problems in the mobile environment. Thus, in this paper, I will try to explore an appropriate way of Chord in a mobile environment.

• Proceedings of the Korean Information Science Society Conference
• /
• 2007.10d
• /
• pp.376-380
• /
• 2007

본 논문은 산업용으로 널리 사용되고 있는 DNP3.0(Distributed Network Protocol)과 국가 긴급 재난망으로 사용되고 있는 TETRA(Terrestrial Trunked Radio)간의 소프트웨어 및 하드웨어 인터페이스를 정의하였다. 전재 사용중인 DNP3.0의 전송 방식의 문제점을 살펴보고, 이에 대한 해결방안으로써 TETRA를 제안함으로써 좀 더 안정적인 데이터의 전송과 TETRA 망의 이용 극대화를 이룰 수 있다.

• Journal of Korea Society of Digital Industry and Information Management
• /
• v.14 no.1
• /
• pp.15-25
• /
• 2018

ISO/IEC 15118 is a standard for communications and services for electric vehicle charging infrastructure. Although this standard deals only with data communication between an electric vehicle and a charge station, communication with the outside is essential for establishing an authentication system for vehicle certification and V2G service for electric power transmission. In this study, it was designed to verify the information of electric car charging infrastructure in electric power system through communication link between ISO/IEC 15118 electric vehicle model and IEC 61850 standard MMS protocol. This is demonstrated in the field so that the electric vehicle communication data is linked with the micro grid management system. This could be used as an element technology in other distributed power sources as well as electric cars in the future.

• Electronics and Telecommunications Trends
• /
• v.31 no.1
• /
• pp.14-24
• /
• 2016

최근 ITU-R의 5G 서비스 및 성능 요구사항의 기준을 시작으로 각 표준화 단체 및 국가에서는 2020년을 목표로 5G에 대한 연구가 활발히 이루어지고 있다. 이 논문은 5G 서비스 및 기술적인 요구사항을 충족시킬 수 있는 네트워크 구조의 동향에 대해 살펴보고, 특히 5G 네트워크를 위한 이동성 관리 기술동향을 소개한다. 또한, 기존 4G 네트워크의 중앙집중형 이동성 관리 기술이 5G 서비스를 제공하는 데에 어떤 단점이 있을지에 관해 기술한 다음, 분산형, 평면형 이동성 관리 기술로 대표적인 Locator-Identifier Separation Protocol(LISP)과 Distributed Mobility Management(DMM) 기술을 소개하여, 각 이동성 관리 기술의 특징 및 장단점을 비교한다. 마지막으로, 5G에서의 이동성 관리 기술 요구사항을 도출하여, LISP과 DMM의 적용 가능성을 분석하여 최적의 5G 이동성 관리 기술을 도출하는 데 도움을 주고자 한다.

• Review of KIISC
• /
• v.24 no.3
• /
• pp.44-53
• /
• 2014

최근 전력 제어시스템의 자동화 효율(Automation Efficiency)과 상호운용성(Interoperability)을 높이기 위해 공개된 표준 프로토콜과 상용 시스템을 사용하게 되었고 외부망과의 연결 필요성이 증가됨에 따라 SCADA 시스템에 대한 공격 위협성이 증가하고 있다. 그러나 전력 제어시스템의 중앙제어장치(Master)와 현장 운영장치(Outstation) 간 데이터를 교환하기 위한 통신 규격인 DNP(Distributed Network Protocol) 프로토콜은 보안을 고려하지 않고 개발되어 통신규격 자체에 보안 취약점을 가지고 있었고, 제어시스템에 대한 사이버 위협 요소도 크게 증가하고 있다. 정보통신 기술의 발전과 개방형 망이 갖는 장점을 취하기 위하여 DNP3 프로토콜은 TCP/IP 네트워크를 지원하게 되었고, TCP/IP 네트워크가 가지고 있는 기존의 보안 취약점(Vulnerability)이 전력 제어시스템 및 통신망에 그대로 이전되고 있어 중앙제어장치와 현장운영장치 간에 DNP3 표준에서 제시한 사항 외에 추가적인 보안 메커니즘이 요구된다. 본 논문에서는 SCADA 시스템이 보안성을 갖고 안전하게 운용되기 위한 IEEE DNP3 표준과 ISO/IEC TC57 WG15에서 권고하고 있는 IEC 62351 표준의 인증 및 암호화 메커니즘을 소개한다.

• Journal of information and communication convergence engineering
• /
• v.5 no.3
• /
• pp.205-208
• /
• 2007

The IEEE 802.11 is a MAC protocol which has been standardized by IEEE for Wireless Local Area Networks (WLANs). In the IEEE 802.11 WLANs, network nodes experiencing collisions on the shared channel need to backoff for a random period of time, which is uniformly selected from the Contention Window (CW). This contention window is dynamically controlled by the Binary Exponential Backoff (BEB) algorithm. However, the BEB scheme suffers from a fairness problem; some nodes can achieve significantly larger throughput than others. This paper proposes a new backoff algorithm for the IEEE 802.11 DCF scheme. This algorithm uses the hop count for considering fairness. It causes flows with high hop count to generate short backoff interval than those with low hop count, thus getting high priority. Therefore, when a collision occurs, the modified IEEE 802.11 DCF assigns higher priority to flow to be close to a destination.

• Proceedings of the KIEE Conference
• /
• 2000.07d
• /
• pp.2542-2544
• /
• 2000

In this paper, CAN(Controller Area Network)is used to solve the wire harness problem in the outside mirror of automobile which has a lot of functions in narrow space. If the number of wires is reduced, it has benefits of lower product cost and maintenance. CAN was originally developed by the German company Robert Bosch for use in the car industry to provide a cost-effective communications bus for in car electronics and as alternative to expensive and cumbersome wiring looms. CAN controller is a serial communication protocol which efficiently supports distributed real-time control with a very high level of security. The communication between master CAN controller and slave CAN controller is realized and controller's performance is tested by experiment.

• Journal of Communications and Networks
• /
• v.15 no.6
• /
• pp.606-613
• /
• 2013

This paper proposes a complete solution of a contention-based medium access control in wireless local networks to provide station level quality of service guarantees in both downstream and upstream directions. The solution, based on the mature distributed coordination function protocol, includes a new fixed contention window backoff scheme, a tuning procedure to derive the optimal parameters, a super mode to mitigate the downstream bottleneck at the access point, and a simple admission control algorithm. The proposed system guarantees that the probability of the delay bound violation is below a predefined threshold. In addition, high channel utilization can be achieved at the same time. The numerical results show that the system has advantages over the traditional binary exponential backoff scheme, including efficiency and easy configuration.

• International Journal of Internet, Broadcasting and Communication
• /
• v.15 no.3
• /
• pp.43-51
• /
• 2023

Slotted ALOHA (S-ALOHA) is a classical medium access control protocol widely used in multiple access communication networks, supporting distributed random access without the need for a central controller. Although stability and delay have been extensively studied in existing works, most of these studies have assumed ideal channel conditions or independent fading, and the impact of time-correlated wireless channels has been less addressed. In this paper, we investigate the queueing delay performance in S-ALOHA networks under time-correlated channel conditions by utilizing a Gilbert-Elliott model. Through simulation studies, we demonstrate how temporal correlation in the wireless channel affects the queueing delay performance. We find that stronger temporal correlation leads to increased variability in queue length, a larger probability of having queue overflows, and higher congestion levels in the S-ALOHA network. Consequently, there is an increase in the average queueing delay, even under a light traffic load. With these findings, we provide valuable insights into the queueing delay performance of S-ALOHA networks, supplementing the existing understanding of delay in S-ALOHA networks.

• Annual Conference of KIPS
• /
• 2011.11a
• /
• pp.126-129
• /
• 2011

대용량 데이터의 분산/병렬 가시화를 위해서는 가시화 클라이언트와 서버 사이의 프로토콜이 필요하다. 기존 가시화 도구들은 개발 도구에 특화된 프로토콜을 사용하고 있으며, 이 때문에 클라이언트와 서버는 매우 tightly-coupled 되어 있다. 본 논문에서는 응용에 독립적인 분산/병렬 가시화를 위한 가시화 프로토콜을 설계하고 구현한다. 또한, 시변환 데이터의 효율적 가시화를 위해 animation을 구현할 수 있는 프리미티브를 설계하고 status machine으로 병렬 전송된 데이터들 간의 동기화를 구현한다. 이러한 응용 독립적 가시화 프로토콜을 도입함으로써 가시화는 병렬 분산 가시화를 수행하는 그리드의 서비스나 슈퍼컴퓨팅의 서비스로 확장될 수 있을 것이다.