• The Journal of Korean Institute of Communications and Information Sciences
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• v.28 no.7B
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• pp.620-627
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• 2003

Ethernet passive optical networks (EPONs) are an emerging access network technology that provide a low-cost method of deploying optical access lines between a carrier's central office and customer sites. Dynamic bandwidth allocation (DBA) provides statistical multiplexing between the optical network units for efficient upstream channel utilization. To support dynamic bandwidth distribution, 1 propose an cyclic polling-based DBA algorithm for differentiated classes of service in EPONs. And, I show that an interleaved polling scheme severely decreases downstream channel capacity for user traffics when the upstream network load is low. To obtain realistic simulation results, I used synthetic traffic that exhibits the properties of self-similarity and long-range dependence I then analyzed the network performance under various loads, specifically focusing on packet delays for different classes of traffic.

• Electronics and Telecommunications Trends
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• v.24 no.6
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• pp.99-109
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• 2009

현재 주목을 받고 있는 테라헤르츠 대역의 주파수를 이용한 무선통신시스템 응용기술 동향에 대하여 기술한다. 테라헤르츠 대역은 전자파 스펙트럼에서 밀리미터파 대역과 원적외선 대역의 중간에 위치하는 100GHz~10THz 사이의 주파수이다. 현재 시점에서 10년 이내에 약 15Gbps의 데이터 속도가 필요할 것으로 판단되며, 10Gbps 이상의 전송속도를 실현하기 위해서는 기존의 밀리미터파에서 사용하는 주파수 대역폭 보다 더 넓은 대역폭이 필요하며, 이 대역폭을 얻기 위해서는 테라헤르츠 주파수 대역으로 자연적으로 옮겨가지 않을 수 없다. 본 고에서는 테라헤르츠 대역의 전파 특성, 가용 주파수 대역과 무선통신시스템 응용을 위한 옥내 채널 모델, 테라헤르츠 무선통신시스템 연구동향, RF 송수신기 핵심부품 및 MMIC 기술개발 동향을 소개하고자 한다.

• Journal of Satellite, Information and Communications
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• v.5 no.2
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• pp.97-103
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• 2010

In this paper, we present an efficient design scheme based on analysis of design requirements and considerations of baseband packet switch for S-band satellite/terrestrial hybrid multi-beam satellite communication systems. To establish design requirements and considerations, we analyze required functions of baseband packet switch, specifications of multi-beam satellite communications, communication services and performance requirements. And also we analyze and compare conventional layer-2 and layer-3 satellite baseband packet switching techniques, packet switching protocols and packet switch architectures, to apply from analyzed results. Finally, we propose a hardware design scheme of MPEG based layer-2 baseband packet switch using analyzed results.

• Journal of the Institute of Electronics Engineers of Korea TC
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• v.49 no.1
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• pp.73-77
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• 2012

In this article, we designed a wide bandpass filter in order to apply microwave reflectometry for KSTAR. The proposed wide bandpass filter consists of a metamaterial structure which is to get a wide band, a lower insertion loss, and a high skirt. This is applied to VCO's output to enhance the linearity. A pass band is 18-28 GHz and the out of pass band is stopped over 20 dB. To confirm of the metamaterial, we suggest a dispersion diagram. The proposed filter in lower band and upper band of pass band is respectively a left handed and right handed characteristics. A group delay is below 0.5 ns.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.23 no.3
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• pp.314-319
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• 2012

In this paper, a repeater antenna operating at MICS and ISM bands is proposed and the antenna performance including the human body effect is investigated. The proposed antenna is composed of a ZOR(Zeroth Order Resonator) and a loop antenna. A loop antenna is operated at ISM band and a loop antenna capacitively coupled with a ZOR acts as an antenna for MICS band. Simulation was carried out in order to analyze the effects of human body on antenna performance when a human body is located in the near field of an antenna. According to the simulated and measured results, the proposed antenna has -10 dB $S_{11}$ bandwidth wide enough to cover both MICS and ISM bands. The measured peak gains are -28.53 dBi and 3.85 dBi at MICS and ISM band, respectively. The dual band and radiation properties of the proposed antenna are well suited for the WBAN repeater system.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.31 no.12B
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• pp.1017-1027
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• 2006

Recently, Internet service providers are offering triple play service which combines voice and video services with the existing high speed Internet service under the common network infrastructure of IP protocol, so that they can create more benefit from operating a single network architecture. In line with this movement in the convergence of network and services, in this work we propose a bandwidth dimensioning method for the subscriber network of the IP network at flow level. To that purpose, let us propose a series of bandwidth dimensioning methods: bandwidth for best effort service only, bandwidth dimensioning for premium services, and bandwidth dimensioning schemes for the premium Internet services as well as the best effort service which comprise the TPS. Our link dimensioning method is based on the flow level that incorporates the flow blocking probability as a measure of grade of services(GoS), and investigates the characteristics of the proposed methods via extensive numerical experiments. After that, let us carry out a simulation experiment concerning the delay and loss performance of the packet scheduling for the premium services (QoS) using the bandwidth designed by our proposed method, via which the packet level quality of service (QoS) for the proposed link dimensioning method can be observed.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.29 no.11B
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• pp.891-899
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• 2004

Ethernet passive optical network (EPON) has drawn many attention as a promising access network technology because it can provide a high bandwidth with a low cost. Since the uplink in the EPON system is shared by many users, it is necessary for an EPON system to have an efficient bandwidth allocation mechanism. In addition, as the users demand more QoS-oriented applications, it is necessary for an EPON system to have an efficient mechanism supporting QoS. In this paper, we propose a variable window dynamic bandwidth allocation (DBA) algorithm for the EPON system. Unlike the previously proposed DBA algorithms, the variable window algorithm guarantees the QoS for the highest priority class, and at the same time provides more enhanced QoS for the lower priority classes by dynamically allocating bandwidth if necessary. It is verified through the simulations that the variable window algorithm can provide more enhanced QoS performance than other DBA algorithms.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.37 no.6
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• pp.609-614
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• 2009

The TT&C communication subsystem of STSAT-3 is consisted of communication link to send telemetry data of spacecraft to the ground station and receive command data from ground station. The S-band receiver is used to receive command data from ground station, Engineering Qualification Model of S-band receiver has been designed and manufactured. The Designed S-band Receiver uses a single conversion for a simple frequency conversion, including a DC-DC Converter and EMI Filter. Also, Digital demodulation part designed using FPGA and RS-422 data interface. The performance of S-band Receiver in functional and space environments test satisfies the requirements of STSAT-3.

• The Journal of The Korea Institute of Intelligent Transport Systems
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• v.10 no.6
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• pp.84-90
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• 2011

In this paper, a dual-band pseudo-combline narrow bandpass filter is proposed. The proposed bandpass filter adopts the open resonant stubs and the proposed bandpass filter can be used for ITS(Intelligent Transport System) and X-band satellite systems application. The proposed bandpass filter has the insertion and return losses of 1.72 dB and 15.5 dB at the bandwidth of 3.6 % and center frequency of 5.8 GHz, respectively. Also, the second operating frequency band for insertion and return losses are 1.92 dB and 16.3 dB at the bandwidth of 3% and center frequency of 8.5 GHz, respectively.

• Proceedings of the Korea Information Processing Society Conference
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• 2000.10b
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• pp.1107-1110
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• 2000

망 복구에 있어서 주요한 과제는 복구의 대상으로 하고 있는 작업 경로(working path)에 대한 복구경로(restoration path) 흑은 대체 경로(backup path)를 설정하는 것이다. 대체 경로를 설정할 때 작업경로의 대역을 보장할 수 있는 대체 경로를 설정해야 한다. 따라서 이 과제는 대역의 보장을 고려하여 경로를 설정하는 QoS 라우팅의 해결책이 요구된다. 본 논문에서는 동일 링크의 작업 경로가 아닐 경우 대체 경로의 대역을 공유함으로써 최대한 대역의 소비를 피하면서, 작업 경로의 대역을 보장하는 대체 경로를 설정하는 disjoint 경로를 계산하는 알고리즘을 제시하고 시뮬레이션을 통해서 대체 경로로 인한 대역의 소비(bandwidth consumption) 효과를 분석하였다.