• Journal of the Institute of Electronics Engineers of Korea TC
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• v.44 no.10
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• pp.127-136
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• 2007

It is easy to install and maintain a mobile multi-hop wireless network due to its self-organizing characteristics. However it has security weakness of the authentication of mobile multi-hop relay stations. Specially, the mobile multi-hop relay network in the IEEE 802.16j has the additional security weakness caused by the requirement of backward compatibility for mobile stations of the conventional IEEE 802.16 system. In this paper, we propose a novel mutual authentication scheme applicable to IEEE 802.16j-based mobile multi-hop relay network architecture. The scheme is able to resolve the initial trust gain problem of a multi-hop node at its entry to the network, the problem of rogue mobile multi-hop node and the problem of hop-by-hop authentication between multi-hop nodes. Effectively, the scheme is a hybrid scheme of the distributed authentication method and the centralized authentication method which have been considered to be deployed in the wireless ad-hoc network and the wireless network connected to wired authentication servers, respectively. Also, we analyze the effectiveness of the proposed hybrid authentication method.

• KIPS Transactions on Computer and Communication Systems
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• v.5 no.5
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• pp.103-108
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• 2016

In this paper, we propose a resource allocation scheme that guarantees transmission rate for each mobile stations by mitigating interference between a base station-to-mobile station link and a relay station-to-mobile station link. Specifically, we dynamically adjust the boundary between access zone and relay zone using signal to interference plus noise ratio. Moreover, we cluster the mobile stations under sever interference and manage the channel quality of these mobile stations by allocating additional radio resource. Our simulation results show that the proposed scheme can improve the efficiency of radio resources and ensure fairness among mobile stations.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.34 no.5A
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• pp.372-380
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• 2009

In this paper, we analyze the active RFID systems ISO/IEC 18000-7 and ISO/IEC 18000-4. In order to improve the coverage in sensor networks, which consist active RFID tag, we propose RFID multi-hop relay system using active RFID relay tag. To compare the performance between the existing ISO/IEC 18000-7 system and the proposed RFID multi-hop relay system, we introduce new system efficiency measure and sensitivity-based measure of achieved coverage. Also, we analyze the performance of the proposed system and compare it with that of the existing system through MCL (Minimum Coupling Loss) analysis and SLS (System Level Simulation) analysis.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.35 no.6A
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• pp.594-599
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• 2010

This paper studies the effect of the deployment position of the relay stations on the downlink signal-to-interference-noise-ratio (SINR) in multihop cellular networks. Two different relay deployment scenarios are considered where relay stations are located either inside cells or on the boundary among adjacent cells. The fundamental contribution is to compare fairly the average SINR between two scenarios with the proposed relay modeling framework that includes multi-cell geometries and inter-cell interferences. The mathematical results show that the SINR increases when relay stations are located inside cells because of higher received signal power.

• Journal of the Institute of Electronics Engineers of Korea TC
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• v.44 no.5
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• pp.33-39
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• 2007

In this paper, we investigate the throughput capacity of a multi-hop relay with cognitive radio (CR) enabled relay stations (RS). We suggest a TDMA/FDMA based frame structure where RSs dynamically select unused channels to communicate with the base station (BS) using CR techniques to analyze the throughput capacity. We develop the throughput capacity model for the proposed system based on utilization factor. The analytical results based on those equations show significant improvement in throughput capacity for CR enabled multi-hop relay system.

• Journal of Korea Society of Industrial Information Systems
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• v.17 no.7
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• pp.1-8
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• 2012

In this paper, we consider an efficient protocol for the multi-hop relay transmission on a sensor network which can be utilized in a ubiquitous environment. More specifically, we propose an efficient relaying protocol for the distance and position recognition on the proposed sensor network which performs with the differentially bi-orthogonal chirp spread spectrum (DBO-CSS) in the industrial, scientific and medical (ISM) bands. For an efficient networking access, we design and implement four different packet structures, zone information packet, hop information packet, tag information packet, and application serial packet. Additionally, we also propose an efficient position recognition algorithm. Finally, for verification of our proposed protocol's efficiency, we build the testbed system which consists of $15m{\times}15m$ multi-cell and 10 hops in the network.

• Information and Communications Magazine
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• v.25 no.5
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• pp.30-37
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• 2008

릴레이(Relay station)는 이동통신 시스템에서 음영 지역 해소를 위해 도입된 기술로서 현재 널리 사용되고 있다. 과거의 방식이 단순히 신호를 증폭해서 보내는 리피터(Repeater)의 기능에 국한된 것에 비해 최근에는 보다 지능화된 형태로 발전하고 있다. 더 나아가 릴레이 기술은 차세대 이동통신 시스템에서 기지국 증설 비용과 백홀 통신망의 유지비용을 줄이는 동시에 서비스 커버리지 확대와 데이터처리율 향상을 위해 반드시 필요한 기술로 평가받고 있다. 이에 본 고에서는 릴레이 기술의 일반적인 분류와 도입 시나리오 및 요소 기술에 대해 살펴보고 표준화가 진행 중인 IEEE 802.16j Relay TG (Task group)의 동향 그리고 무선 인지 환경하에서의 릴레이 도입의 가능성에 대해 기술한다.

• Journal of The Institute of Information and Telecommunication Facilities Engineering
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• v.8 no.2
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• pp.47-52
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• 2009

최근 통신사업자들이 초고속 무선 인터넷 서비스를 위하여 와이브로 네트워크를 설치하고 있으나, 산간 지역이나 네트워크 인프라를 구축하기 어려운 지역에서는 와이브로 서비스를 제공받지 못하는 경우가 생긴다. 현재 와이브로 네트워크에서는 서비스를 제공받지 못하는 음영지역을 중계기를 이용하여 해소하고 있다. 본 논문에서는 이러한 음영지역에 고정 중계기를 설치하는 대신 고정 중계기 비용 절감 및 능동적인 네트워크 확장이 가능하도록 WLAN 네트워크에서 연구되고 있는 ad-hoc 기반의 멀티홉 릴레이 방식을 사용하여 음영지역 문제를 해결하고자 한다

• Proceedings of the Korea Information Processing Society Conference
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• 2015.10a
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• pp.317-318
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• 2015

무선 링크는 유선 링크에 비해서 신뢰성(reliability)이 상대적으로 많이 낮으며, 이러한 환경에서 네트워크 코딩을 수행하는 경우 네트워크 코딩 이득이 낮아지는 문제점이 있다. 따라서 본 논문에서는 멀티 홉 무선 네트워크 환경에서 네트워크 코딩을 함에 있어서 무선 링크의 비신뢰성을 극복하기 위한 방법을 제안한다. 제안하는 방법에서는 릴레이 노드가 무선 링크의 신뢰도를 측정하고 이 정보를 이용해서 적응적으로 네트워크 코딩을 수행한다.

• Journal of KIISE:Information Networking
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• v.34 no.6
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• pp.423-434
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• 2007

Vehicular ad-hoc network (VANET), a kind of mobile ad-hoc network (MANET), is a key technology for building intelligent transportation system (ITS). VANET is automatically and temporarily established through vehicle-to-vehicle communication without network infrastructure. It has the characteristics that frequent changes of network topology and node density are occurred and messages are disseminated through several relay nodes in the network. Due to frequent change of network topology and node density, however, VANET requires an effective relay node selection scheme to disseminate messages through the multi-hop broadcast. In this paper, we propose a contention window based multi-hop broadcast scheme for VANET. Each node has an optimized contention window and competes with each other for a relay node. The experimental results show that the proposed scheme has a better performance than the distance-based deterministic broadcast scheme in terms of message propagation delay and network traffic.