• The Journal of Korean Institute of Communications and Information Sciences
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• 제34권1A호
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• pp.58-64
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• 2009

In this paper, we propose an dynamic random channel allocation scheme increasing probability of channel acquisition and reducing delay by limiting the number of minimum RCHs(Random CHannels) as an optimal factor $\beta$. The MAC protocol of HIPERLAN/2 is based on TDMA/TDD and MT(Mobile Terminal) can obtain chance of traffic transmission through channel competition in RCH period. And AP(Access Point) can dynamically schedule the number of RCHs based on the number of the collision in each RCH of the previous frame. Therefore, the proposed scheme increases a probability of channel acquisition and reduces delay by means of guaranteeing the number of minimum RCHs. With a practical Internet traffic, it is concluded that by the proposed scheme the delay reduction of the order of 19% and slightly better throughput are obtained compared to the conventional algorithm.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• 제17권9호
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• pp.874-882
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• 2006

We surveyed the international and national spectrum & technical standardization trends of extremely adaptive frequency bands $57\sim64GHz$ that can provide 1 Gbps bit-rate ultra broadband service in above 30 GHz millimeter waves, and analyzed service scenarios and the characteristics of these bands, As a result of these analysises, 1 Gbps ASK channel bandwidth needs 2.5 GHz and total bandwidth calculated 7 GHz for dual FDD. finally, we proposed the nationally suitable allocation plan of millimeter wave bands $57\sim64GHz$.

• The Magazine for Energy Service Companies
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• 통권70호
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• pp.64-65
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• 2011

지난 3월 9일부터 11일까지 태국 방콕 더 웨스틴 호텔에서 한-태국 에너지효율 컨퍼런스가 성황리에 개최되었다. 이 행사는 에너지효율 분야에서 양국 공공기관, 기업간 협력 채널을 구축하고 협력사업을 촉진하기 위하여 마련된 행사로 한국과 태국의 정부관계자 및 업계 관계자들이 모여 양국의 에너지절약정책, 에너지진단 및 ESCO산업과 LED산업, 에너지라벨링 프로그램 등 관련내용을 교차 발표하는 형식으로 이루어졌다.

• 전기의세계
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• 제38권4호
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• pp.36-45
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• 1989

보 소고에서는 1T cell을 이용한 DRAM 집적도의 향상에 따른 몇가지의 한계요인을 생각해 보았다. 특별한 물질의 획기적 방법이 없는한, Cell의 수직대 수평 Aspect Ratio가 2이상 되고, 스위칭 소자의 채널 도평이 5 * $10^{17}$/$cm^{3}$ 이상이 되는 64M DRAM에 필요한 최소 선폭은 0.3-0.4.mu.m정도로 예측되는데 실제로 최소 선폭에 관한한 한계는 이보다 훨씬 더 작아질 것이다.다.

• The Journal of Korean Institute of Communications and Information Sciences
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• 제26권6A호
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• pp.929-938
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• 2001

CDMA 2000 1X EV.(HDR, 1XTREME, LAS-CDMA)에서는 고속데이터 전송을 위한 변조방식으로 M-ary QAM을 제안하고 있다. 그러나, M-ary QAM을 사용한 DS-CDMA 시스템은 고속 데이터 전송이 가능한 반면에 M-ary 수가 증가할수록 잡음(AWGN)과 타 사용자에 의한 다중접속간섭(MAI)의 영향이 커져 비트에러율(BER)이 증가하고 채널용량이 급격히 줄어드는 문제점이 있다. 따라서, DS-CDMA/M-ary QAM 시스템에서 많은 사용자에게 고속의 데이터 서비스를 제공하기 위해서는 잡음을 줄이거나 MAI를 경감시킬 수 있는 성능 개선 기법이 요구된다. 본 논문에서는 성능 개선 기법으로서 다단병렬간섭제거기(MPIC : Multistage Parallel Interference Canceller)와 부분 다단병렬간섭제거기(partial MPIC)를 채용한 비동기 DS-CDMA/M-ary QAM 시스템의 성능 개선을 이론적으로 분석하고 이를 검증하기 위한 컴퓨터 시뮬레이션을 수행하였다. 결과에서, MPIC와 partial MPIC를 채용함으로써 4 QAM, 16 QAM 및 64 QAM을 사용한 DS-CDMA 시스템의 BER과 채널용량이 크게 개선됨을 확인하였다. MPIC를 채용한 경우는 AWGN 채널의 BER에 근접하였다. 또한, MPIC는 partial MPIC보다 BER 성능이 우수하였으며 더 많은 채널용량 개선을 달성하였다. 그러나, MPIC는 partial MPIC 보다 계산량이 훨씬 많고 복잡한 구조를 갖기 때문에 실제 시스템 구현에 있어서 성능과 복잡도 사이에 타협(tradeoff)이 필요하다.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• 제14권12호
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• pp.1300-1310
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• 2003

In this paper, the performance of a multicarrier CDMA system using adaptive modulation and adaptive subchannel allocation scheme is analyzed in Rayleigh fading channel. The proposed adaptive modulator consists of modulation schemes using QPSK 16 QAM, 64 QAM and 256 QAM and constellations are pointed by Gray code. In addition, the threshold of the analysis is average E$\_$b//N$\_$o/ when the BER is 1 %. In the multicarrier system with adaptive subchannel allocation scheme, each DS waveform of user is transmitted over the K subchannels with the biggest fading among L subchannels. In case of the proposed system, total 4 subchannels are used and data are transmitted over 2 subchannels with the biggest fading, which results in the threshold of each channels is 5.2 dB, 9 dB, 13.2 dB and 8.4 dB, 12.2 dB, 16.3 dB. In the case of proposed system, the BER of 10$\^$-3/ is satisfied if average E$\_$b//N$\_$o/ is 8.1 dB. This is increased performance of 12.9 dB in comparison with conventional system. The BPS according to average channel is needed average E$\_$b//N$\_$o/ of about 15 dB in 7 bit. In the case of subchannel error, the BER of 10$\^$-3/ is 13.6 dB and is declined about 5.5 dB.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• 제15권11호
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• pp.1034-1042
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• 2004

In this paper, as one of countermeasure techniques for a frequency selective fading, an adaptive analog slope equalizer(ASE) applicable to 64-QAM digital radio relay system is presented in terms of principle, implementation, and its performance. Also interference of cross-talk between I- and Q-channel caused by a fiequency selective lading has been analyzed by doing channel model in the baseband, which make it possible to derive the solution for implementing ASE in If-band. The effects of signal for the faded channel are investigated in the time and the frequency domains, respectively, with/without ASE. As system performance, it is shown that the signature is improved up to 6.2 dB at the edge of signal bandwidth for a given BER 10$\^$-3/.

• Journal of the Institute of Electronics and Information Engineers
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• 제54권5호
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• pp.123-127
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• 2017

This paper fabricated and analyzed the image rejection mixer that uses FET's channel resistance. It can be applied for capacity 64QAM that has 50MHz~90MHz of IF band, 8.17GHz of LO frequency and 8.08~8.12GHz of RF band. When IF input power is -20dBm and LO input power is 10dBm, RF output power is obtained -33.2dBm. In this case, conversion loss is 12.9dB, the suppression of 14.3dB for LO frequency and 10.4dB for image frequency. The result of two tone test shows great IMD characteristics with 51.7dBc.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• 제12권5호
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• pp.777-786
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• 2001

In this paper, as one of countermeasure techniques for a frequency selective fading, a digital slope equalizer(DSE) for 64-QAM digital radio relay system is analyzed in terms of principle, channel modeling, and digital implementation. Also computer simulations have been performed for DSE with a complex 13-tap adaptive time domain equalizer chip. It is shown that about 4.5 dB improvement in system signature can be obtained at the channel edge, and a variety of simulated results are reviewed in view of DSE modeling limit, operating frequency, control coefficient, signal constellation, and system signature. Finally, the functions of DSE chip confirmed up to 61 MHz clock operation are illustrated.

• Journal of Advanced Navigation Technology
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• 제10권3호
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• pp.275-281
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• 2006

Simple-relay aided resource allocation (SRARA) schemes are incorporated with throughput guarantee scheduling (TGS) in IEEE 802.16 type time division duplex - orthogonal frequency division multiple access (TDD-OFDMA) downlink in order to enhance service coverage, where the amount of resources for relaying at each relay is limited due to either its available power which is much smaller than base station (BS) power or the overhead required for exchanging feedback information. The performance of SRARA schemes is evaluated with schedulers such as proportional fair (PF) and TGS at 64kbps and 128kbps user throughput requirements when total MS power is set to 500mW or 1 W. For 64kbps throughput requirement level, more improvement comes from relay than scheduler design. For 128kbps case, it comse from scheduler design than relay due to the fact that simple relay can't help using strictly limited amount of resources for relaying function.