• Journal of information and communication convergence engineering
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• 제12권4호
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• pp.221-227
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• 2014

In this paper, we analyze the effect of the coherence bandwidth of wireless channels on leakage suppression methods for discrete Fourier transform (DFT)-based channel estimation in orthogonal frequency division multiplexing (OFDM) systems. Virtual carriers in an OFDM symbol cause orthogonality loss in DFT-based channel estimation, which is referred to as the leakage problem. In order to solve the leakage problem, optimal and suboptimal methods have already been proposed. However, according to our analysis, the performance of these methods highly depends on the coherence bandwidth of wireless channels. If some of the estimated channel frequency responses are placed outside the coherence bandwidth, a channel estimation error occurs and the entire performance worsens in spite of a high signal-to-noise ratio.

• Journal of Multimedia Information System
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• 제3권4호
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• pp.135-140
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• 2016

To improve the throughput of Device-to-Device (D2D) communication, we focus on the scenario where D2D pair can reuse multi-channel of cellular communication. However, as sharing same channel with cellular communication can cause interference between D2D communication and cellular communication, a proper interference management is needed. In this paper, we propose interference-based channel allocation to select the channels to be used by D2D communication and a solution from game theory perspective to optimize the D2D communication throughput under multi-channel as well as guarantee the interference from it to cellular network. The simulation results verify the stability of the proposed method.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2009년도 춘계학술대회 논문집
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• pp.63-64
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• 2009

The TFTs have been fabricated with 3 different geometry SID electrodes which have the same channel W/L ratio (W/L = 5) due to constant channel resistance, The 3 samples have different channel widths (350, 150, and $25\;{\mu}m$) and channel lengths (70, 30, and $5\;{\mu}m$) by fixed channel W/L ratio simultaneously on one chip for reliable comparisons. Resultant on-current and field effect mobility are proportional to the channel width, while the subthreshold swing is inversely proportional to the channel width mainly due to the change of contact resistance. These results show that the contact resistance strongly affects the device performances and should be considered in the applications.

• 한국정보통신학회:학술대회논문집
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• 한국해양정보통신학회 2007년도 추계종합학술대회
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• pp.165-169
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• 2007

Due to the complexity of underwater acoustic channel, signal estimation in underwater acoustic communication field is considerably affected from time-varying multipath fading channels. On this reason, the original signals should have many long training signals to estimate the channel and the purposed signals, and the bit rate of signals having information may have small rate. In order to avoid this loss of efficiency in underwater communication, this paper employed a blind channel identification method which don't use training signals. Simulations have predicted performance of the employed method in multipath environment and an aquatic plant experiment has verified the simulation results.

• JSTS:Journal of Semiconductor Technology and Science
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• 제13권3호
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• pp.213-223
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• 2013

A unified channel thermal noise model valid in all operation regions is presented for short channel MOS transistors. It is based on smooth interpolation between weak and strong inversion models and consistent physical model including velocity saturation, channel length modulation, and carrier heating. From testing for noise benchmark and comparing with published noise data, it is shown that the proposed noise model could be useful in simulating the MOSFET channel thermal noise in all operation regions.

• The Korean Journal of Physiology and Pharmacology
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• 제4권6호
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• pp.445-453
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• 2000

The present investigation tested the hypothesis that the activation of protein kinase G (PKG) leads to a phosphorylation of $Ca^{2+}-activated$ potassium channel $(K_{Ca}\;channel)$ and is involved in the activation of $K_{Ca}$ channel activity in cerebral arterial smooth muscle cells of the rabbit. Single-channel currents were recorded in cell-attached and inside-out patch configurations of patch-clamp techniques. Both molsidomine derivative 3-morpholinosydnonimine-N-ethylcarbamide $(SIN-1,\;50\;{\mu}M)$ and 8-(4-Chlorophenylthio)-guanosine-3',5'-cyclic monophosphate $(8-pCPT-cGMP,\;100\;{\mu}M),$ a membrane-permeable analogue of cGMP, increased the $K_{Ca}$ channel activity in the cell-attached patch configuration, and the effect was removed upon washout of the drugs. In inside-out patches, single-channel current amplitude was not changed by SIN-1 and 8-pCPT-cGMP. Application of ATP $(100\;{\mu}M),$ cGMP $(100\;{\mu}M),$ ATP+cGMP $(100\;{\mu}M\;each),$ PKG $(5\;U/{\mu}l),$ ATP $(100\;{\mu}M)+PKG\;(5\;U/{\mu}l),$ or cGMP $(100\;{\mu}M)+PKG\;(5\;U/{\mu}l)$ did not increase the channel activity. ATP $(100\;{\mu}M)+cGMP\;(100\;{\mu}M)+PKG\;(5\;U/{\mu}l)$ added directly to the intracellular phase of inside-out patches increased the channel activity with no changes in the conductance. The heat-inactivated PKG had no effect on the channel activity, and the effect of PKG was inhibited by 8-(4-Chlorophenylthio)-guanosine-3',5'-cyclic monophosphate, Rp-isomer $(Rp-pCPT-cGMP,\;100\;{\mu}M),$ a potent inhibitor of PKG or protein phosphatase 2A (PP2A, 1 U/ml). In the presence of okadaic acid (OA, 5 nM), PP2A had no effect on the channel activity. The $K_{Ca}$ channel activity spontaneously decayed to the control level upon washout of ATP, cGMP and PKG, and this was prevented by OA (5 nM) in the medium. These results suggest that the PKG-mediated phosphorylations of $K_{Ca}$ channels, or some associated proteins in the membrane patch increase the activity of the $K_{Ca}$ channel, and the activation may be associated with the vasodilating action.

• Journal of Communications and Networks
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• 제17권1호
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• pp.21-26
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• 2015

The general wiretap channel with noiseless feedback is first investigated by Ahlswede and Cai, where lower and upper bounds on the secrecy capacity are provided in their work. The upper bound is met with equality only in some special cases. In this paper, we study a special case of the general wiretap channel with noiseless feedback (called non-degraded wiretap channel with noiseless feedback). Inner and outer bounds on the capacity-equivocation region of this special model are provided. The outer bound is achievable if the main channel is more capable than the wiretap channel. The inner bound is constructed especially for the case that the wiretap channel is more capable than the main channel. The results of this paper are further explained via binary and Gaussian examples. Compared with the capacity results for the non-degraded wiretap channel, we find that the security is enhanced by using the noiseless feedback.

• 전자공학회논문지
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• 제50권1호
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• pp.27-33
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• 2013

본 논문에서는 two-way 릴레이 네트워크에서 파일롯(pilot)기반 채널 추정 기법과, 전송시 데이터 심볼과 함께 파일롯 심볼을 전송하는 기법을 제안한다. 채널상태정보(channel state information : CSI)가 없는 경우, destination은 파일롯 심볼을 사용해 채널을 추정한다. 이 시스템에서 릴레이는 파일롯 심볼과 데이터 심볼을 증폭하고 AF(amplify and forward)프로토콜을 사용하여 destination에 전송한다. 릴레이 이득이 고정되어 있어서 릴레이는 채널을 추정할 필요가 없기 때문에 destination이 채널을 추정한다. 이 채널 추정에는 이미 잘 알려진 LS(least-square)와 MMSE(minimum mean-square error)를 사용하였다.

• 한국전자파학회논문지
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• 제27권1호
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• pp.27-32
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• 2016

본 논문에서는 다중 입출력 안테나 OFDM 통신시스템에서 가상 기준 신호(virtual pilot signal)를 사용하는 한 연판정 지향 채널 추정 기법을 제안한다. 기준 신호만을 이용하여 채널을 추정하는 기존 방식과 달리 제안하는 기법은 기준 신호와 데이터를 동시에 사용하여 채널을 추정한다. 또한, 제안하는 기법에서 채널을 추정하기 위해 사용할 데이터를 선택하는 알고리즘을 제안한다. 모의실험을 통해 제안하는 기법이 기존 채널 추정에 비해 향상된 성능을 갖는 것을 확인할 수 있다.

• 한국인터넷방송통신학회논문지
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• 제13권4호
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• pp.1-7
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• 2013

차세대 이동통신 시스템에서는 새로운 주파수 대역에서 다중 안테나 사용이 높은 데이터 전송률과 용량을 가능하도록 만들 것이다. 본 논문에서는 국내 전파 특성 측정을 통해 도출된 채널 파라미터(경로 손실, 지연 확산, 각 확산, K-factor) 간에 상관도를 분석하였다. 측정은 DTV 방송과 혼신을 피하기 위하여 제주도에서 채널 사운더와 $4{\times}4$ 안테나로 측정하였다. 채널 파라미터 간에 상관도 분석은 유사한 환경에서 통신 시스템을 설계하는데 있어서 많은 도움을 줄 것이다.