• The Journal of Korean Institute of Communications and Information Sciences
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• v.22 no.9
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• pp.2014-2026
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• 1997

In this paper, the performances of wireless asynchronous transfer mode (ATM) cell transmission in mobile work are analyzed. We adopt 16Star QAM as amodulation technique in wireless channel and considered Reed-Solomon, convolutional, and concatenated coding to improve the error rate performances, and also proposed the Partial Concatenated Coding (PCC) technique as UEP(unequal error protection) code for efficient transmission of ATM cell in the air interface. We consider Doppler's effect, Rician fading, and diversity technique of maximal-ratio combining (MRC) for mobile channel model. For performance measure, we analyze bit error rate, ATM cell loss probability, ATM cell error probability, and network performances of ATM cell transmission delay and throughput. The numerical results show that the adoption of PCC is a prospective way for the evolution of future wireless ATM network on mobile environment.

• Information and Communications Magazine
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• v.29 no.11
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• pp.81-93
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• 2012

60GHz 주파수는 최대 9GHz 까지 엄청난 대역폭을 활용하여 Gbps급의 무선전송이 가능한 대역으로서, 최근 이 대역을 댁내 무선전송장치 및 초고속 무선랜에 활용하기 위한 연구가 활발히 진행되고 있다. 이와 같이 60GHz에 대한 관심도가 높아진 이유는, 밀리미터파 통신이 기존에는 무선 백홀용으로 주로 사용되었던것에 비해 지금은 가정 및 사무실내에서의 초고속 네트워크 또는 영상가전에서의 무선 전송장치 등 응용분야의 다변화가 예상됨에 따라, ISM 대역이면서 광대역을 활용할 수 있는 60GHz가 급부상하게 된 것으로 본다. 이와 함께 CMOS 칩기술의 꾸준한 발전으로 현재는 수 십 나노공정을 이용하여 테라헤르쯔 대역에서도 동작하는 칩이 발표되고 있는 바 그동안 60GHz 시장 확산의 가장 큰 걸림돌이 었던 무선 전송장치의 높은 가격, 사이즈, 소모전력의 문제를 한꺼번에 해결할 수 있게 된 점도 이유중 하나이다. 따라서 이와 관련하여 본고에서는 ETRI와 KETI를 중심으로 진행되어 온 "60GHz 무선 전송장치에 탑재 가능한 범용 CMOS 송수신 칩 및 이를 활용한 빔포밍 트랜시버 기술에 관한 연구"를 소개하고자 한다.

• Journal of KIISE:Computing Practices and Letters
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• v.14 no.8
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• pp.778-782
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• 2008

The performance in combination of wired and wireless mesh network which will be a main access network in future internet is directly linked with service quality to users. In this paper, we evaluate variant TCP performance and analyze traffic characteristics on Wireless (Seoul National University Mesh testbed) - Wired (KOREN/Abilene) - Wireless (HP Mesh testbed in the USA) Network. We found that RTT is proper in this network to serve a VoIP service. Also we propose an enhanced TCP protocol which can perform well in both wireless network which has many packet losses and wired network which has high bandwidth and long delay.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.30 no.6B
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• pp.338-348
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• 2005

Currently, IEEE 802.11 Wireless LAN (WLAN) is rising as the most popular means for the broadband wireless access network. In this thesis, we propose a QoS(Quality of Service)-Oriented mechanism using handshaking method of scanning phase in IEEE 802.11 handoff. In conventional process for handoff, the major criterion to select the best AP(Access Point) among candidates is normally based on the RSS(Received Signal Strength), which does not always make the selected network guarantee the maximum achievable performance. Even though the link quality with a neighboring AP is excellent, the AP may not be a good candidate to handoff to simply because MAC(Medium Access Control) protocol of IEEE 802.11 standard is contention-based such as CSMA/CA. Therefore, if we apply network level information to AP selection criteria, we can achieve better handoff efficiency rather than before. The analysis and simulation results applied to our new mechanism show clearly better performance than AP selection based on traditional handoff method.

• Information and Communications Magazine
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• v.29 no.5
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• pp.3-9
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• 2012

본 논문에서는 재난 통신 및 네트워크 기술 그리고 앞으로의 발전 방향에 대해서 소개 하고자 한다. 제 1장에서는 주요 공공재난안전통신 기술들을 소개한다. 특히 동적 그룹통신기술(Push-To-Talk), 망 복구 및 생존성 향상 기술, 긴급호 구현 기술을 소개하며 또한 재난통신기술 표준화 필요성에 대해서 간단히 설명한다. 제 2장에서는 국내외 재난통신기술 동향을 살펴본다. 특히 미국, 유럽, 아시아에서 사용하는 주파수 대역 및 협대역 및 준광대역 주파수 공용 무선통신 기술인 TETRA(Terrestrial Trunked Radio), iDEN(Integrated Digital Enhanced Network) 및 APCO-P25(Association of Public Safety Communications Officials - Project 25)에 대해서 다룬다. 제 3장에서는 재난대비 미래 광대역 통신체계에 대해서 설명하며 마지막으로 제 4장에서는 본 논문의 결론을 맺는다.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.12 no.10
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• pp.1801-1807
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• 2008

A home network is a collection and connection of many electronic and electrical devices in home in order to make daily life comfortable, entertaining and safe. The convergence of Ethernet and wireless technology to a single shared broadband connection in residential gateway is the key feature of the home network. This kind of heterogeneous network has realized the need to implement different QoS mechanisms. Basically, in this paper we propose to integrate IP QoS and Wireless QoS mechanisms for QoS assurance in home network. This paper compares the combination of PCF with two queuing algorithms Low Latency Queuing (LLQ) and Custom Queuing (CQ) and concludes that the combination of CQ and PCF performs best for home network.

• Journal of the Korean Society for Railway
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• v.18 no.3
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• pp.223-231
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• 2015

This paper proposes a new wireless backhaul technology based on MHN(Mobile Hotspot Network) which uses a wide frequency band of millimeter wave to provide wideband Wi-Fi services for subway passengers. Performance analysis of MHN up and down links, based on data: up and down links structure analysis of physical layer and simulation study of the MHN wireless backhaul link model, show that the proposed MHN-based wireless backhaul network can transmit data at a 1.2Gbps data rate and provide Internet service 100 times faster than that of conventional WiBro-based wireless backhaul networks. These results indicate that the proposed MHN technology is appropriate for subway mobile networks.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.31 no.11A
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• pp.1101-1112
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• 2006

With the recent growth in demand for high-data rate multimedia services in the wireless environments, the Mobile Broadband Wireless Access (MBWA) technologies, such as WiBro (Wireless Broadband internet) system, are gradually coming into the spotlight. Unlike the conventional mobile communication networks based on cellular system, the WiBro system basically consists of IP based backbone networks that will be ultimately deployed by Ipv6 (IP version six) based backbone networks according to the All-IP trend for the network evolution. In such wireless mobile environments, it is needed to support the mobility management protocol on network layer as well as physical layer and Medium Access Control (MAC) layer in WiBro system. Accordingly, in this paper, we propose a fast handover scheme for improving the handover performance in IPv6 based WiBro system and show that the proposed scheme achieves loss-free and low handover latency during inter-subnet movement of the mobile stations through the simulation.

• Journal of Korea Society of Industrial Information Systems
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• v.16 no.4
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• pp.19-26
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• 2011

Relay-assisted multiple input multiple output (MIMO) technique has become a promising candidate for next generation broadband wireless communications. In this paper, we propose maximum ratio combining (MRC) minimum mean-square-error (MMSE) equalization for single carrier-frequency domain equalizer (SC-FDE) in amplify-and-forward (AF) relaying networks. The performance of SC-FDE system can be improved considerably by achieving both the diversity gain and the MMSE equalization gain when the signals from source-destination (S->D) and source-relay-destination (S->R->D) are combined and equalized by means of the MMSE criteria. We find the weighting coefficients of MRC combining and the tap coefficients of MMSE equalizer for SC-FDE in AF relaying networks. Simulation results show that the proposed relay-based system considerably outperforms the conventional SC-FDE system.

• Proceedings of the IEEK Conference
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• 2005.11a
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• pp.15-18
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• 2005

Cooperative diversity is a transmission technique, in which multiple terminals pool their resources to form a virtual antenna array that realizes spatial diversity gain in a distributed fashion. In this paper, we propose a new type of cooperative transmission protocol with a full rate and show that its BER performance is improved by 8dB over the existing protocol under the AF (amplify-and-forward) mode of relaying.