• The Journal of Korean Institute of Communications and Information Sciences
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• v.30 no.10A
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• pp.930-937
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• 2005

In this paper, a processing time and traffic capacity analysis algorithm for RFID system using LBT-serial searching scheme is proposed. Service time, carrier sensing time, additional delay time required for contiguous frequency channel occupancy, and additional delay time required for the contiguous using the same frequency channel are considered and the processing delay and frequency channel capacity are analyzed for the steady state operation of the system. The simulation results showing maximum capacity of the system and explaining the accuracy of the algorithm are provided.

• The Journal of the Korea institute of electronic communication sciences
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• v.6 no.5
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• pp.723-729
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• 2011

In this paper, we simulate and evaluate the performance of MIMO systems adopting MMSE-OSUC receiver algorithm under Rayleigh fading channel environment. In the simulation, BPSK, QPSK, 16QAM, and 64QAM modulation is used with frame length of 100 symbols. First, the concept of MIMO is introduced by the analytical basis of the channel capacity of MIMO system. From the performance analysis results, the channel capacity is identified by the function of channel and it is affected by the channel characteristic. Next, based on this approach, the algorithm for performance evaluation over MIMO channel was analyzed. From the performance analysis results, it is found that MMSE-OSUC receiver algorithm generally outperform conventional ZF-OUSC receiver algorithm in performance but the performance difference between the two algorithms is reduced as modulation scheme with larger constellation point is used.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.13 no.1
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• pp.33-39
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• 2002

In mobile communication systems, there are areas where signal coverage is not adequately accomplished by base stations. These areas may be underground parking zones, underground stores, tunnels, and insides of buildings, etc. In these areas, repeaters are broadly used as an economical solution. However, the capacity is decreased as the number of repeaters increases because the noise power that flows to a base station in the reverse link is proportional to the number of repeaters. The reduction of capacity in the reverse link is no longer negligible in the case that several tens or hundreds repeaters are connected to a base station. In this paper, we propose c repeater that is switched off automatically when there is no active user within its coverage. With the switching repeater, we can reduce the unnecessary noise level enhancement when there is no active user within the repeaters coverage. The reverse link capacity of a DS/CDMA system with AOS repeater is analyzed mathematically and compared with that without switching repeater. From the numerical results, noticeable improvement with the switching repeaters is shown.

• Journal of the Institute of Electronics Engineers of Korea SD
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• v.41 no.7
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• pp.1-6
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• 2004

For MOSFET devices with nanometer range gate length, accurate extraction of effective gate length is highly important because transistor characteristics become very sensitive to effective channel length. In this paper, we propose a new approach to extract the effective channel length of nanometer range MOSFET by Capacitance Voltage(C-V) method. The effective channel length is extracted using gate to source/drain capacitance( $C_{gsd}$). It is shown that 1/$\beta$ method, Terada method and other C-V method are inadequate to extract the accurate effective channel length. Therefore, the proposed method is highly effective for extraction of effective channel length of 100nm CMOSFETs.s.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.13 no.6
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• pp.453-460
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• 1988

The error probability for coherent frequency-hopped spread-spectrum multiple-access communications is computed by using characteristic function method. We employ PSK as a modulation scheme. The channel capacity is performance measure and the minimum bit signal-to-noise ratio for reliable communications is obtained.

• Electronics and Telecommunications Trends
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• v.21 no.3 s.99
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• pp.48-58
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• 2006

다중 송수신 안테나 시스템은 추가적인 주파수나 송신전력의 할당 없이도 채널 용량을 안테나 수에 비례하여 증가시킬 수 있는 장점으로 인해 차세대 통신기술의 핵심으로 부각되고 있다. 본 원고에서는 이동통신 시스템에서 다중 송수신 안테나간 채널 특성을 활용하여 무선링크의 신뢰도와 전송률을 증대시키는 다중 송수신 안테나 전송기술과 전체 채널용량을 증가시키기 위한 다중사용자 다중 송수신 안테나 전송기술의 내용 및 동향을 소개한다.

• The Magazine of the IEIE
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• v.29 no.4
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• pp.77-91
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• 2002

스마트 안테나 기술은 CDMA 이동통신 시스템에서 다른 사용자 간섭신호 및 무선 채널 특성에 의한 성능 열하 현상에 대해 효과적으로 성능 및 채널 용량을 개선할 수 있는 대표적인 해결 방법으로 알려지고 있다. 본 논문에서는 이러한 스마트 안테나 기술의 개요 및 국내외 기술동향에 대하여 기술하고, 단말기의 mobility를 고려한 스마트 안테나 채널 모델을 제안하였으며, W-CDMA FDD 상향 링크에서 칩 레벨 빔 형성 알고리즘을 적용한 스마트 안테나 기술의 성능을 분석하였다. 시뮬레이션 결과를 통하여 스마트 안테나 기술을 적용한 경우, 채널 용량이 증가함을 알 수 있으며, 특히 DD(Decision-Directed)모드의 칩 레벨 빔 형성 알고리즘을 적용했을 경우에 성능이 더욱 향상됨을 알 수 있다.

• Journal of Satellite, Information and Communications
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• v.1 no.2
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• pp.83-88
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• 2006

Future communication systems are to be designed to support and serve multimedia and multipledata transmission. Nowadays, requirement of mobile subscribers for the various information such as movie, GPS(Global Positioning System) information, news-is increasing significantly. However, due to practical reasons, the capacity and number of capable channels are limited. To solve this problem, a large number of methods and schemes have been proposed and are under research. In this paper, we demonstrate how satellite DMB (Digital Multimedia Broadcasting) system works with hierarchical modulation scheme. By using hierarchical modulation, we can analyze the capacity. Meanwhile, system performance os evaluated and compared to conventional DMB system without using hierarchical modulation.

• 한국IT서비스학회:학술대회논문집
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• 2010.05a
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• pp.202-206
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• 2010

무선 메쉬 네트워크(Wireless Mesh Network, WMN)는 유비쿼터스 환경 및 무선 브로드 밴드 액세스를 제공하기 위한 차세대 핵심기술로 떠오르고 있다. 다양한 멀티미디어 서비스가 존재하는 유비쿼터스 환경에서 실시간 서비스 제공을 위해서는 네트워크 용량 증대가 요구되며, 이를 위하여 WMN에서 네트워크 용량을 증대시키기 위한 다중 인터페이스 활용 기술이 중요한 이슈로 대두되고 있다. 하지만 WMN에서 주로 사용하는 인터페이스 기술인 IEEE 802.11 표준에서는 IEEE 802.11b/g 또는 IEEE 802.11a와 같은 스펙에 따라 간섭 없이 사용할 수 있는 채널은 3개 또는 12개로 한정되어 있기 때문에 다중 인터페이스 활용을 통해 증대된 가용 자원 효율성을 극대화하기 위해서 효율적인 채널 할당 기법의 연구가 요구되며, 이에 따라 본 논문에서는 채널 그룹 설정을 통하여 간섭 발생을 최소화하며 채널스캐닝 과정을 수행하지 않고 채널 변경을 진행함으로써 채널 스캐닝 과정으로 발생하는 전송 지연을 최소화하여 네트워크 성능을 향상시킬 수 있는 채널 할당 기법을 제안한다.

• Journal of the Institute of Electronics and Information Engineers
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• v.50 no.8
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• pp.3-14
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• 2013

We demonstrate a fashion of quantum channel combining and splitting, called polar quantum channel coding, to generate a quantum bit (qubit) sequence that achieves the symmetric capacity for any given binary input discrete quantum channels. The present capacity is achievable subject to input of arbitrary qubits with equal probability. The polarizing quantum channels can be well-conditioned for quantum error-correction coding, which transmits partially quantum data through some channels at rate one with the symmetric capacity near one but at rate zero through others.