• Title/Summary/Keyword: 서브캐리어

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IS-OFDM performance analysis for narrow band interference channel (협대역 간섭 채널환경에서 IS-OFDM 성능 분석)

  • 강현정;이정재
    • Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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    • 2003.05a
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    • pp.119-123
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    • 2003
  • In this paper, a new OFDM scheme, IS-OFDM(Interference Suppressing Orthogonal Frequency Division Multiplexing), which has the capabilities of suppressing narrow-band interference for wide-band wireless communication systems, is introduced. This IS-OFDM system is composed of the parallel stages of ordinary OFDM, and each sub-carrier contains all of the transmitted symbols. Using Hadamard sequences, the transmitted information symbols in the same sub-carriers are separated from the other sub-carriers in the receiver. After analyzing and evaluating the performance of IS-OFDM system using Monte-Carlo simulation, the effective improvements of performance in IS-OFDM compare favorably with that of a conventional OFDM system in a narrow-band channel, is shown.

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Characteristics of active optical ring network and performance evaluation in Bandwidth on Demand (능동형 광 링 네트워크의 특징 및 요구 대역폭에 따른 성능 분석)

  • Lee Sang-Wha;Song Hae-Sang
    • Journal of the Korea Society of Computer and Information
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    • v.10 no.6 s.38
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    • pp.209-218
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    • 2005
  • In this paper, we present an Active Optical Network(AON) . The AON uses the Dense Wavelength Division Multiplexing(DWDM) from optical communication access network of ring type, and will be able to provide the smoothly service in the Bandwidth on Demand by using DWDM. It supports the connection of the multiple wavelength and the Sub-Carrier from the optical gigabit ethernet switch. The Wavelength Add Drop Multiplexer(WADM) extracts a specific wavelength, and composes a node of the ring network. The specific wavelength becomes demultiplexing in the Sub-Carrier and it is distributed in the user The active connection of optical gigabit ethernet switch where the distribution of access network is started and access terminal connection equipment is possible. By the BoD from the AON it compares the buffer size which changes, and it analyzes. Also the Time delay of bit compares with the throughput of server The limit of amount of time is decided. Consequently it will be able to realize the dynamic use protocol and an efficient algorithm of the network.

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Resource Allocation Scheme for Ensuring QoS of Heterogeneous Traffic in OFDMA System (OFDMA 시스템에서 이종 트래픽의 QoS를 보장하기 위한 자원 할당 기법)

  • Gwak, Yong-Su;Koh, Chung Ha;Kim, Young-Yong
    • The Journal of Korean Institute of Communications and Information Sciences
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    • v.35 no.5A
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    • pp.447-451
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    • 2010
  • We propose an advanced BMPA (balanced multimedia packet allocation) scheme. The proposed scheme considers the optimal resource allocation problem in OFDMA system. When NRT (non-real time), RT (real time), multicast packets arrive at the same time in OFDMA system, the advanced BMPA chooses the best sub-carrier as a multicast channel for multicast packets, gives more weight to RT packets and multicast packets than NRT packets and allocates sub-carriers according to the total weight sum of packets in each user. With simulation results, this paper shows that the advanced BMPA scheme ensures QoS (long-term system throughput and multimedia packet delay) in heterogeneous traffic compared with multicast MU-WF (multi-user water-filling) and BMPA schemes.

Inter-carrier Interference of Multicarrier-CDMA System in Time Selective Fading Channel (시간선택적 페이딩 환경에서 멀티캐리어-CDMA 시스템의 서브캐리어간 간섭)

  • 김명진;김성필;하경민
    • Proceedings of the IEEK Conference
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    • 2000.06a
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    • pp.53-56
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    • 2000
  • In MC-CDMA systems effects of delay spread of the channel are reduced with increased symbol duration by simultaneously transmitting data symbols on the parallel subcarriers. However, the increased symbol duration causes the system to be more vulnerable to time selective fading. In other words, although MC-CDMA systems are robust against frequency selective fading in a multipath environment, they are sensitive to Doppler spread and hence inter-carrier interference is increased. In this paper, we investigate the effects of time selective fading characteristics of the mobile channel from the viewpoint of desired signal power to inter-carrier interference power ratio at the combiner output of the MC-CDMA receiver.

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Transit Time Diodes Using Velocity Overshoot Effects for Submillimeter-Wave Frequency Range Operation (속도 오버슈트 효과를 이용하여 서브밀리미터파 주파수 영역에서 동작하는 주행 시간 다이오드)

  • 송인채
    • Journal of the Institute of Electronics Engineers of Korea SD
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    • v.39 no.10
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    • pp.9-15
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    • 2002
  • We propose a new transit time device to extend the operating frequency to submillimeter-wave(extreme infrared) ranges by utilizing velocity overshoot effects in the drift region. We name it a velocity overshoot transit time (OVTT) diode. This device adopts fast heterostructure tunneling as injection mechanism and a short drift region to optimize the velocity overshoot effects. To enhance dc-to-RF conversion efficiencym the drift region is designed with a bandgap grading method. Simulation results demonstrate that a VOTT diode can be operated at THz ranges.

Method for Improving the Usage Efficiency of Frequency in Terrestrial DMB (지상파 DMB에서 주파수 이용 효율을 개선하기 위한 방법)

  • Lee, Gwang-Soon;Lee, Hyun;Bae, Jae-Hwui;Lee, Soo-In
    • Proceedings of the Korean Society of Broadcast Engineers Conference
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    • 2010.07a
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    • pp.370-371
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    • 2010
  • 본 논문은 지상파 DMB에서 각 서비스 사업자들을 위해 이미 할당된 주파수 블록(block)들간 가드밴드내에 신규 블록을 추가로 할당함으로써 주파수 이용 효율을 높이기 위한 방법을 제안한다. 본 논문은 특히 6 MHz TV 대역내에 이미 할당되어 서비스 중인 현재의 지상파 DMB 서비스와 역방향 호환성을 유지하면서 주파수 가드밴드 영역을 최대한 활용하기 위해, 종래의 송신 시스템에 새로운 서브캐리어를 삽입하고 단일 6MHz 주파수 대역의 전송신호를 생성하기 위한 방법을 제시하고 있다. 본 논문에서의 제안한 방법을 활용하면, 서비스 사업자 입장에서는 가변적인 주파수 대역폭 이용을 통해 좀 더 다양한 서비스 모델을 구상할 수 있고, 사용자 측면에서는 단말 상황에 따라서 기본적인 서비스부터 고품질의 모바일 멀티미디어 서비스를 제공받을 수 있을 것이다.

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A Sub-optimal Joint Subcarrier and Power Allocation Algorithm for Qos Supporting in Muliuser OFDM Systems (멀티 유저 OFDM 시스템에서 QoS 보장을 위한 서브캐리어와 파워 할당에 관한 연구)

  • Sim, U-Cheol;Lee, Sang-Jae;Kim, Se-Heon
    • Proceedings of the Korean Operations and Management Science Society Conference
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    • 2006.11a
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    • pp.417-420
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    • 2006
  • This paper suggests that resource allocation algorithm in multiuser orthogonal frequncy divisioin multiplexing (OFDM). The proposed algorithm considers throughput maximization with power constraint and quality of service (QoS) constraint. This problem has a optimal solution with using well known water-filling algorithm but the algorithm requires high computational complexity. Therefore the problem needs a sub-optimal algorithm for decreasing computational complexity. We propose a sub-optimal joint subcarrier and power allocation algorithm for multiuser OFDM system and compare with previous resource allocation algorithm.

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Performance Analysis of MIMO-OFDMA System Applying Dynamic Resource Allocation (동적 자원 할당 기법을 적용한 MIMO-OFDMA 시스템 성능 분석)

  • Lee, Yun-Ho;Kim, Kyung-Seok
    • The Journal of Korean Institute of Electromagnetic Engineering and Science
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    • v.19 no.6
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    • pp.669-676
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    • 2008
  • The adaptive resource optimization problem in multi-input multi-output orthogonal frequency division multiple access (MIMO-OFDMA) systems is addressed. This paper, adaptive modulation and coding(AMC) and power control algorithms is proposed with SFC(Space-Frequency Coding), which aims to maximize the system capacity based on the CQI(Channel Quality Information). Firstly, power level is decided to each sub-channels with received feedback signal to noise ratio(SNR). In the second step, sub-carriers are allocated according to modulation type. Simulation results show that the proposed algorithm achieves a better performance than conventional algorithm in terms of capacity.

Analysis of Dimension Dependent Subthreshold Swing for FinFET Under 20nm (20nm이하 FinFET의 크기변화에 따른 서브문턱스윙분석)

  • Jung, Hak-Kee
    • Journal of the Korea Institute of Information and Communication Engineering
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    • v.10 no.10
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    • pp.1815-1821
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    • 2006
  • In this paper, the subthreshold swing has been analyzed for FinFET under channel length of 20nm. The analytical current model has been developed , including thermionic current and tunneling current models. The potential distribution by Poisson equation and carrier distribution by Maxwell-Boltzman statistics are used to calculate thermionic emission current and WKB(Wentzel-Kramers-Brillouin) approximation to tunneling current. The cutoff current is obtained by simple adding two currents since two current is independent. The subthreshold swings by this model are compared with those by two dimensional simulation and two values agree well. Since the tunneling current increases especially under channel length of 10nm, the characteristics of subthreshold swing is degraded. The channel and gate oxide thickness have to be fabricated as am as possible to decrease this short channel effects, and this process has to be developed. The subthreshold swings as a function of channel doping concentrations are obtained. Note that subthreshold swings are resultly constant at low doping concentration.

Effect of surface damage remove etching of Reactive Ion Etching for Crystalline silicon solar cell

  • Park, Jun-Seok;Byeon, Seong-Gyun;Park, Jeong-Eun;Lee, Yeong-Min;Lee, Min-Ji;Im, Dong-Geon
    • Proceedings of the Korean Vacuum Society Conference
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    • 2016.02a
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    • pp.404-404
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    • 2016
  • 태양전지 제작 시 표면에 피라미드 구조를 형성하면 입사되는 광의 흡수를 높여 광 생성 전류의 향상에 기여한다. 일반적인 KOH를 이용한 습식 표면조직화 공정은 평균 10%의 반사율을 보였으며, 유도 결합 플라즈마를 이용한 RIE 공정은 평균 5.4%의 더 낮은 반사율을 보였다. 그러나 RIE 공정을 이용한 표면조직화는 낮은 반사율과 서브 마이크론 크기의 표면 구조를 만들 수 있지만 플라즈마 조사에 의한 표면 손상이 많이 발생하게 된다. 이러한 표면 손상은 태양전지 제작 시 표면에서 높은 재결합 영역으로 작용하게 되어 포화 전류(saturation currents, $J_0$)를 증가시키고 캐리어 수명(carrier lifetime, ${\tau}$)을 낮추는 결함 요소로 작용한다. 이러한 플라즈마에 의한 표면 손상을 제거하기 위해 HF, HNO3, DI-water를 이용하여 DRE(Damage Remove Etching) 공정을 진행하였다. DRE 공정은 HF : DI-water 솔루션과 HNO3 : HF : DI-water 솔루션의 두 가지 공정을 이용하여 공정 시간을 가변하며 진행하였다. 포화전류($J_0$), 캐리어 수명(${\tau}$), 벌크 캐리어 수명(Bulk ${\tau}$)을 비교를 하기위해 KOH, RIE, RIE + DRE 공정을 진행한 세 가지 샘플로 실험을 진행하였다. DRE 공정을 적용할 경우 공정 시간이 지날수록 반사도가 높아지는 경향을 보였지만, 두 번째의 최적화된 솔루션 공정에서 $2.36E-13A/cm^2$, $42{\mu}s$$J_0$, Bulk ${\tau}$값과 가장 높은 $26.4{\mu}s$${\tau}$를 얻을 수 있었다. 이러한 결과는 오제 재결합(auger recombination)이 가장 많이 발생하는 지역인 표면과 불균일한 도핑 영역에서 DRE 공정을 통해 나아진 표면 특성과 균일한 도핑 프로파일을 형성하게 되어 재결합 영역과 $J_0$가 감소 된 것으로 판단된다. 높아진 반사도의 경우 $SiN_x$를 이용한 반사방지막을 통해 표면 반사율을 1% 이내로 내릴 수 있어 보완이 가능하였다. 본 연구에서는 RIE 공정 중 플라즈마에 의해 발생하는 표면 손상 제거를 통하여 캐리어 라이프 타임의 향상된 조건을 찾기 위한 연구를 진행하였으며, 기존 RIE 공정에 비해 반사도의 상승은 있지만 플라즈마로 인한 표면 손상을 제거하여 오제 재결합에 의한 발생하는 $J_0$를 낮출 수 있었고 높은 ${\tau}$값인 $26.4{\mu}s$의 결과를 얻어 추후 태양전지 제작에 향상된 효율을 기대할 수 있을 것으로 기대된다.

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