• KSII Transactions on Internet and Information Systems (TIIS)
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• 제13권4호
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• pp.1884-1903
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• 2019

Device-to-Device (D2D) communications can provide proximity based services in the future 5G cellular networks. It allows short range communication in a limited area with the advantages of power saving, high data rate and traffic offloading. However, D2D communications may reuse the licensed channels with cellular communications and potentially result in critical interferences to nearby devices. To control the interference and improve network throughput in overlaid D2D cellular networks, a novel channel assignment approach is proposed in this paper. First, we characterize the performance of devices by using Poisson point process model. Then, we convert the throughput maximization problem into an optimal spectrum allocation problem with signal to interference plus noise ratio constraints and solve it, i.e., assigning appropriate fractions of channels to cellular communications and D2D communications. In order to mitigate the interferences between D2D devices, a cluster-based multi-channel assignment algorithm is proposed. The algorithm first cluster D2D communications into clusters to reduce the problem scale. After that, a multi-channel assignment algorithm is proposed to mitigate critical interferences among nearby devices for each D2D cluster individually. The simulation analysis conforms that the proposed algorithm can greatly increase system throughput.

• 한국통신학회논문지
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• 제18권5호
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• pp.643-649
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• 1993

본 논문에서는 백색 가우스 잡음 Co-channel 간섭이 존재하는 채널에서의 2진 펄스 진폭변조 통신 시스템에서 주기적으로 삽입되는 프레임 동기 문제를 다루었다. Co-channel 간섭이 존재함으로서 발생되는 Correlation Rule의 성능 저하를 보이고 백색 가우스 잡음과 Co-channel 간섭이 존재하는 채널에서의 최대 프레임 동기 공식을 유도하였다. 최대 추정 동기 공식은 신호 에너지에 있어 Correlation Rule 보다 약 1dB 정도의 성능 향상을 보였다. 특히, 신호대잡음비가 0dB 이상일 경우 최대 추정 동기 공식은 최대 2dB 정도의 성능향상을 보였다.

• Journal of Electrical Engineering and Technology
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• 제2권2호
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• pp.267-273
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• 2007

A depletion-mode MOSFET has been analyzed to evaluate its electrical behavior using a novel 3-D numerical simulation package. The characterizing analysis of the BC MOSFET was performed through short-channel narrow-channel and small-geometry effects that are investigated, in detail, in terms of the threshold voltage. The DIBL effect becomes significant for a short-channel device with a channel length of $<\;3({\mu}m)$. For narrow-channel devices the variation of the threshold voltage was sharp for $<4({\mu}m)$ due to the strong narrow-channel effect. In the case of small-geometry devices, the shift of the threshold voltage was less sensitive due to the combination of the DIBL and substrate bias effects, as compared with that observed from the short-channel and narrow-channel devices. The characterizing analysis of the narrow-channel and small-geometry devices, especially with channel width of $<\;4({\mu}m)$ and channel area of $<\;4{\times}4({\mu}m^2)$ respectively, can be accurately performed only from a 3-D numerical simulation due to their sharp variations in threshold voltages.

• 한국환경과학회지
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• 제21권4호
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• pp.471-478
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• 2012

In this study, the flow characteristic analysis at the curved-channel of the actual channel section is compared and reviewed using the 2D RMA-2 model and the 3D FLOW-3D model. the curve section with curve rate 1.044 in the research section is analyzed applying the frequency of he project flood of 100 years. According to the result, the issue for the application of the FLOW-3D Model's three-dimensional numeric analysis result to the actual river is found to be reviewed with caution. Also, application of the 3D model to the wide basin's flood characteristic is determined to be somewhat risky. But, the applicability to the hydraulic property analysis of a partial channel section and the impact analysis and forecast of hydraulic structure is presumed to be high. In addition, if the parameters to reflect the vegetation of basin and the actual channel, more accurate topological measurement data and the topological data with high closeness to the current status are provided, the result with higher reliability is considered to be drawn.

• IEIE Transactions on Smart Processing and Computing
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• 제2권2호
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• pp.67-76
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• 2013

Under an imperfect channel estimation, a Device-to-Device (D2D) communication framework based on MIMO relay technology is presented. The model consists of a D2D pair equipped with M antennas and a relay equipped with N antennas as well as a cellular user equipped with M antennas. The outage probability under different relaying protocols (i.e. AF and DF protocol) with and without considering a direct link was derived. The actual and theoretical outage probability of the five links under different antenna numbers was emulated. The number of user antennas and channel estimation error was analyzed carefully to determine their impact on the outage probability of a system. The simulation verified the theory analyses and the results showed that MIMO relaying improves the D2D communication system performance.

• Bulletin of the Korean Chemical Society
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• 제31권6호
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• pp.1669-1680
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• 2010

The phase-shifted version of the multichannel quantum-defect theory (MQDT) was reformulated by disentangling the interloper spectrum from the perturbed dense Rydberg series for a systems involving 2 closed and more than 1 open channel. The theory was applied successfully to Martins and Zimmermann's photoionization spectra of the Rydberg series Cu I $3d^9\;4s(^1D_2)\;nd^2G_{9/2}$ perturbed by the interloper, $3d^9\;4p^2\;^4F_{9/2}$, for which Cohen's 4 channel QDT had failed. The zero surface graphic of the perturbed Fano's asymmetry parameter q of the autoionization spectrum of dense Rydberg series by the interloper was determined by only two parameters for this system. It was used as a map to trace the transformation route of the 3 channel autoionization spectra to the 4 channel spectra when the channel coupling of the closed channels with a newly added open channel was turned on progressively.

• 한국정보디스플레이학회:학술대회논문집
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• 한국정보디스플레이학회 2009년도 9th International Meeting on Information Display
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• pp.1189-1192
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• 2009

Short channel a-Si:H TFT devices with Cu electrodes have been investigated. Short channel TFTs are defined by new plasma etch process. When the channel length becomes shorter, the TFT characteristics (threshold voltage, off current, sub threshold voltage, etc.,) are degraded. These degraded characteristics can be improved through the hydrogen plasma treatment and new gate insulator structure. Using these processes, 15.0 inch XGA LCD panel was fabricated successfully where the channel length of the TFT devices was about 2.5 micrometers.

• 대한전자공학회:학술대회논문집
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• 대한전자공학회 2003년도 하계종합학술대회 논문집 I
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• pp.234-237
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• 2003

The accuracy of channel estimation significantly affects the performance of coherent OFDM receiver. It is desirable to employ a good channel estimator while requiring low implementation complexity. In this paper, we propose a channel estimator that employs a simple two-dimensional (2-D) moving average (MA) filter as the channel estimation filter. The optimum tap size of the 2-D MA FIR filter is analytically designed in the time and frequency domain in association with the channel condition and pilot signal to interference power ratio. The analytic results can be applied to the design of adaptive channel estimator. Finally, the performance of the proposed channel estimator is verified by computer simulation.

• 한국위성정보통신학회논문지
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• 제10권1호
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• pp.17-21
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• 2015

본 논문에서는 아마추어 무선 HR(HAM Radio)을 기반으로 구축되는 새로운 무선 재난통신망인 이동단말용 위성 통신 무선패키지 시스템과 이 재난통신망에 접속하려는 D2D 단말의 채널 환경에 대해 소개한다. 이러한 재난통신망과 D2D 단말이 서로 재난통신할 때 재난정보를 멀티미디어 데이터급 수준으로 원활하게 전송 및 통신하기 위해서는 D2D 단말이 처한 다양한 재난상황에 적응적으로 채널 값을 추정하는 채널 모델링 연구가 요구된다. 따라서 본 논문에서 LOS component ratio 기반의 적응적 채널 모델링 기법을 제안하고, 제안한 기법의 성능을 Okumura-Hata model의 Open area 및 Urban area model과 비교하였다. 컴퓨터 시뮬레이션 결과 거리 대비 BER 성능 및 SNR 대비 BER 성능에서 이득이 있음을 확인하였다.

• The Korean Journal of Physiology and Pharmacology
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• 제3권5호
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• pp.507-512
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• 1999

Contribution of prostaglandins $D_2,\;E_2\;and\;I_2\;(PGD_2,\;PGE_2\;and\;PGI_2)$ on the regulation of ATP-sensitive $K^+$ channel $(K_{ATP}\;channel)$ was investigated in isolated single rat ventricular cardiac myocytes using the patch clamp technique. $PGD_2,\;PGE_2\;and\; PGI_2$ did not affect $K_{ATP}$ channel activity in the inside-out patch, but increased channel activity in a dose-dependent manner when the channel activities were attenuated by the administration of 100 ${\mu}M$ ATP to the internal solution in the inside-out patch. Channel activations by the prostaglandins were abolished by 50 ${\mu}M$ glibenclamide, a $K_{ATP}$ channel blocker. Dose-response curves of relative channel activity against the ATP concentrations of internal solution in the inside-out patch were shifted to the right in the presence of those three prostaglandins. The rank order of the channel stimulatory potencies $(as\;IC_{50}\;for\;ATP)$ calculated from the dose-response curves were $PGI_2\;>\;PGD_2\;>\;PGE_2.$ Conductance of the channel was not changed by those three prostaglandins. In conclusion, we suggest that prostaglandins $D_2,\;E_2\;and\;I_2$ are involved in the regulation of $K_{ATP}$ channel activity in certain circumstances, and that those three prostaglandins may cause myocardial relaxation by opening $K_{ATP}$ channels, thus protecting the heart from ischema.