• 디지털산업정보학회논문지
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• 제5권2호
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• pp.141-156
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• 2009

As the TCP is the protocol designed for the wired network that packet loss probability is very low, because TCP transmitter takes it for granted that the packet loss by the wireless network characteristics is occurred by the network congestion and lowers the transmitter's transmission rate, the performance is degraded. The Snoop Protocol was designed for the wired network by putting the Snoop agent module on the BS(Base Station) that connect the wire network to the wireless network to complement the TCP problem. The Snoop agent cash the packets being transferred to the wireless terminal and recover the loss by resending locally for the error occurred in the wireless link. The Snoop agent blocks the unnecessary congestion control by preventing the dupack (duplicate acknowledgement)for the retransmitted packet from sending to the sender and hiding the loss in the wireless link from the sender. We evaluated the performance in the wired/wireless network and in various TCP versions using the TCP designed for the wired network and the Snoop designed for the wireless network and evaluated the performance of the wired/wireless hybrid network in the wireless link environment that the continuous packet loss occur.

• Journal of Communications and Networks
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• 제11권6호
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• pp.634-644
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• 2009

A diversity of wireless networks, with rapidly evolving wireless technology, are currently in service. Due to their innate physical layer vulnerability, wireless networks require enhanced security components. WLAN, WiBro, and UMTS have defined proper security components that meet standard security requirements. Extensive research has been conducted to enhance the security of individual wireless platforms, and we now have meaningful results at hand. However, with the advent of ubiquitous service, new horizontal platform service models with vertical crosslayer security are expected to be proposed. Research on synchronized security service and interoperability in a heterogeneous environment must be conducted. In heterogeneous environments, to design the balanced security components, quantitative evaluation model of security policy in wireless networks is required. To design appropriate evaluation method of security policies in heterogeneous wireless networks, we formalize the security properties in wireless networks. As the benefit of security protocols is indicated by the quality of protection (QoP), we improve the QoP model and evaluate hybrid security policy in heterogeneous wireless networks by applying to the QoP model. Deriving relative indicators from the positive impact of security points, and using these indicators to quantify a total reward function, this paper will help to assure the appropriate benchmark for combined security components in wireless networks.

• 전력전자학회논문지
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• 제27권3호
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• pp.228-236
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• 2022

The charging methods of electric vehicles are divided into wired charging and wireless charging. Restrictions on the use of charging infrastructure for wireless charging vehicles currently exist because most charging infrastructure uses the wired charging method. Thus, wired and wireless integrated charging system has been studied. In this system, a wireless charging system especially requires a control method for high-efficiency operation in consideration of a change in a coupling coefficient. Therefore, this paper introduces two control methods for the high-efficiency operation of wireless charging that can be applied to wired and wireless integrated charging systems. In addition, loss analysis is performed through PSIM simulation to select a more advantageous method for high-efficiency operation among the two control methods. To verify the simulation-based loss analysis result, the two control methods are applied to the actual wireless charging system, and the efficiency is compared through the experiments Based on the experimental results, a control method suitable for high-efficiency operation of the wireless charging method is selected.

• Journal of Information Processing Systems
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• 제16권5호
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• pp.1158-1168
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• 2020

The distance vector-hop wireless sensor node location method is one of typical range-free location methods. In distance vector-hop location method, if a wireless node A can directly communicate with wireless sensor network nodes B and C at its communication range, the hop count from wireless sensor nodes A to B is considered to be the same as that form wireless sensor nodes A to C. However, the real distance between wireless sensor nodes A and B may be dissimilar to that between wireless sensor nodes A and C. Therefore, there may be a discrepancy between the real distance and the estimated hop count distance, and this will affect wireless sensor node location error of distance vector-hop method. To overcome this problem, it proposes a wireless sensor network node location method by modifying the method of distance estimation in the distance vector-hop method. Firstly, we set three different communication powers for each node. Different hop counts correspond to different communication powers; and so this makes the corresponding relationship between the real distance and hop count more accurate, and also reduces the distance error between the real and estimated distance in wireless sensor network. Secondly, distance difference between the estimated distance between wireless sensor network anchor nodes and their corresponding real distance is computed. The average value of distance errors that is computed in the second step is used to modify the estimated distance from the wireless sensor network anchor node to the unknown sensor node. The improved node location method has smaller node location error than the distance vector-hop algorithm and other improved location methods, which is proved by simulations.

• 정보처리학회논문지C
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• 제18C권4호
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• pp.265-278
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• 2011

이 논문의 목적은 시뮬레이션 소프트웨어인 OPNET Modeler Wireless Suite를 이용하여 WiFi (IEEE 802.11g)와 WiMAX (IEEE 802.16e)를 가상 무선망으로 모델링 후 종단간 패킷 통계를 시뮬레이션하여 그 특성을 분석한 연구이다. 국내외 무선망에 대한 시뮬레이션이 가능한 툴인 Remcom's Wireless InSite Real Time (RT) 모듈, WinProp: W-LAN, Fixed WiMAX, Mobile WiMAX, SMI 시스템은 무선 전파 신호 세기 분석에 비중을 두었고 이러한 무선 전파 신호 세기로 데이터 전송률을 고려할 수 있도록 설계되었다. 그러나 우리는 이들 시뮬레이션 툴(들)의 특성과 달리 다른 관점으로 본 연구를 접근하였다. 즉, 무선 전파 신호 세기 분석이 아닌 유무선 통합망을 기반으로 한 종단간 가상망 모델링이 가능하고 각 구간(예: 무선사용자, 기지국 또는 AP, HTTP 서버)마다 얼마만큼의 패킷이 전달되었는지를 시각적으로 분석할 수 있는 OPNET Modeler Wireless Suite를 활용한 연구로 접근하였다. 왜냐하면 패킷 통계는 무선서비스 성능 매트릭 중 하나의 지표로 종단간 중요한 QoS 분석 척도가 되기 때문이다. 특히나 WiMAX와 같이 QoS를 보장하는 무선사용자에겐 패킷 통계 지표는 더더욱 필수적인 항목임에 틀림이 없다. OPNET Modeler Wireless Suite로 가상 무선망을 실제에 가깝게 모델링 후 시뮬레이션 결과를 통해 우리는 흥미로운 결과를 찾아낼 수 있었고 그 실험/관측결과를 효율적이고 다각적으로 보여줄 수 있었다.

• 융합보안논문지
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• 제2권2호
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• pp.29-38
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• 2002

무선 인터넷에 대한 수요가 날로 증가하고 있는 가운데 무선 인터넷이 보다 활성화되기 위해서는 반드시 해결해야 될 문제가 있는데, 보안 문제가 바로 그것이다. 특히 음성 위주의 이동통신에서는 도청만이 문제가 되었지만 증권이나 뱅킹같이 단순한 정보 서비스를 뛰어넘는 상거래 활동이 이루어지는 데이터 서비스에서는 사용자 인증, 데이터 무결성 보장 등 해결해야 할 문제가 많다. 이에 무선 인터넷 환경에서 안전한 서비스를 제공하기 위해 유선 인터넷 환경에서와 같은 보안 서비스를 제공할 수 있는 무선 PH(WPKI: Wireless Public Key Infrastructure)의 필요성이 대두되었다. 즉, 유선 인터넷 환경에서 제공되는 기밀성, 무결성, 부인봉쇄 등의 보안 서비스를 무선 인터넷 환경에서도 제공하기 위해서는, 먼저 무선 PKI가 구축되고 서비스가 활성화되어야 할 것이다. 본 논문에서는 안전한 무선 인터넷 서비스를 위한 다양한 무선 인터넷 기술들과 그에 사용되는 무선 PKI기술 그리고 이에 적용 가능한 무선 PKI 표준들에 대해 분석하였다. 본 논문의 수행 결과로는 안전한 무선 PKI 서비스의 활성화와 더불어 무선 인터넷 뱅킹 서비스, 주식 거래, 온라인 쇼핑 등 무선 인터넷을 이용한 전자 상거래의 활성화에 기여할 것으로 기대된다.

• 한국전자통신학회논문지
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• 제7권6호
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• pp.1337-1342
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• 2012

최근 몇 년간, 홈 네트워킹에 관한 많은 연구가 활발히 진행되고 있다. 홈 네트워킹을 위한 대부분의 기술들은 유선을 기반으로 하지만, 무선 연결을 위한 기술도 필요하다. 본 논문은 홈 네트워크 분야 중에서 무선 네트워크에 초점을 맞추고 있다. 무선 LAN, 블루투스, HomeRF와 같은 많은 무선 통신 기술중에서, 본 논문은 특히 무선 센서 네트워크라는 새로운 기술을 무선 홈네트워크에 적용하는 것을 제안한다. 본 논문은 무선 센서 노드와 무선 센서 네트워크를 위한 하드웨어 및 프로토콜 스택 설계시 필요한 고려 사항을 제시하고, 홈 네트워킹에 무선 센서 네트워크를 적용하기 위한 방법과 다양한 센서 노드로 무선 홈 네트워킹을 구성하는 방법을 제시한다. 마지막으로, 본 논문은 자체적으로 설계된 무선 센서 노드 시스템을 소개하고 이 글을 맺는다.

• Nuclear Engineering and Technology
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• 제47권6호
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• pp.729-737
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• 2015

Wireless communication technologies, especially smartphones, have become increasingly common. Wireless technology is widely used in general industry and this trend is also expected to grow with the development of wireless technology. However, wireless technology is not currently applied in any domestic operating nuclear power plants (NPPs) because of the highest priority of the safety policy. Wireless technology is required in operating NPPs, however, in order to improve the emergency responses and work efficiency of the operators and maintenance personnel during its operation. The wired telephone network in domestic NPPs can be simply connected to a wireless local area network to use wireless devices. This design change can improve the ability of the operators and personnel to respond to an emergency situation by using important equipment for a safe shutdown. IEEE 802.11 smartphones (Wi-Fi standard), Internet Protocol (IP) phones, personal digital assistant (PDA) for field work, notebooks used with web cameras, and remote site monitoring tablet PCs for on-site testing may be considered as wireless devices that can be used in domestic operating NPPs. Despite its advantages, wireless technology has only been used during the overhaul period in Korean NPPs due to the electromagnetic influence of sensitive equipment and cyber security problems. This paper presents the electromagnetic verification results from major sensitive equipment after using wireless devices in domestic operating NPPs. It also provides a solution for electromagnetic interference/radio frequency interference (EMI/RFI) from portable and fixed wireless devices with a Wi-Fi communication environment within domestic NPPs.

• KSII Transactions on Internet and Information Systems (TIIS)
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• 제7권5호
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• pp.998-1013
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• 2013

Wireless wearable sensor networks have emerged as a promising technique for human motion tracking due to the flexibility and scalability. In such system several wireless sensor nodes being attached to human limb construct a wearable sensor network, where each sensor node including MEMS sensors (such as 3-axis accelerometer, 3-axis magnetometer and 3-axis gyroscope) monitors the limb orientation and transmits these information to the base station for reconstruction via low-power wireless communication technique. Due to the energy constraint, the high fidelity requirement for real time rendering of human motion and tiny operating system embedded in each sensor node adds more challenges for the system implementation. In this paper, we discuss such challenges and experiences in detail during the implementation of such system with wireless wearable sensor network which includes COTS wireless sensor nodes (Imote 2) and uses TinyOS 1.x in each sensor node. Since our system uses the COTS sensor nodes and popular tiny operating system, it might be helpful for further exploration in such field.

• 한국정보통신학회논문지
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• 제13권6호
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• pp.1077-1082
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• 2009

무선 메쉬 네트워크는 네트워크 구성의 용이성과 비용적인 장점으로 각광받고 있는 무선 백본 네트워크 기술이다. 최근 상용화된 제품이 출시되고 있지만, 대부분의 기존 연구 기술은 시뮬레이션을 통해 성능을 분석하였다. 본 논문에서는 실제 상황을 고려하여 무선 메쉬 네트워크 테스트베드를 구축하였다. 본 테스트 베드는 무선 분산 시스템(Wireless Distribution System)과 브릿지를 응용하여 멀티채널 멀티 인터페이스와 동적인 위치기반 라우팅 프로토콜을 지원한다. 위치기반 라우팅 프로토콜은 링크 채널 변화와 물리적 거리를 고려한 메트릭을 이용하여 무선 간섭에 강하게 설계하였다. 그리고 메쉬 클라이언트들은 중앙 집중 주소 관리 서버를 통해 주소를 할당 받아 통신하며, 간이 망 네트워크 관리 프로토콜을 통해 망을 관리하도록 설계 및 구현하였다.