• 한국인터넷방송통신학회논문지
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• 제10권2호
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• pp.39-44
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• 2010

본 논문에서는 디지털 워터마킹 기법을 이용하여 부가데이터를 전송하기 위해 일반화된 K 페이딩 채널에서의 채널용량 수식을 유도하였다. 대역확산 워터마킹 기법(Spread Spectrum Watermarking: SSW)은 디지털 워터마킹 기법 중의 하나로 무선 채널에서 잡음에 대해 강인한 특성을 지니며, 수신단에서의 신호 검출이 상관기에 의해 간단히 이루어지기 때문에 널리 사용되는 방식이다. 대역확산 워터마킹 기법에 의해 생성된 부가데이터를 무선통신 시스템에 적용하기 위해서는 워터마킹 신호가 무선 채널에 의해 받는 영향에 대한 연구가 필수적으로 요구된다. 모의실험 결과로부터 대역확산 워터마킹 시스템의 채널용량이 HWR, WNR, fx, 그리고 PN 시퀀스의 길이에 따라 변화함을 확인하였고, 또한 적정 데이터를 전송하기 위하여 필요한 HWR과 WNR의 레벨을 수식으로부터 결정할 수 있음을 보였다. 본 논문의 결과는 PN 시퀀스를 이용하는 일반적인 대역확산 워터마킹 시스템에 적용할 수 있다.

• Journal of Communications and Networks
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• 제16권6호
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• pp.627-638
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• 2014

In this paper, we study the joint price and power allocation in spectrum sharing macro-femtocell networks. The proposed game theoretic framework is based on bi-level Stackelberg game where macro base station (MBS) works as a leader and underlaid femto base stations (FBSs) work as followers. MBS has fixed data rate and imposes interference price on FBSs for maintaining its data rate and earns revenue while FBSs jointly adjust their power for maximizing their data rates and utility functions. Since the interference from FBSs to macro user equipment is kept under a given threshold and FBSs compete against each other for power allocation, there is a need to determine a power allocation strategy which converges to Stackelberg equilibrium. We consider two cases for MBS power allocation, i.e., fixed and dynamic power. MBS can adjust its power in case of dynamic power allocation according to its minimum data rate requirement and number of FBSs willing to share the spectrum. For both cases we consider uniform and non-uniform pricing where MBS charges same price to all FBSs for uniform pricing and different price to each FBS for non-uniform pricing according to its induced interference. We obtain unique closed form solution for each case if the co-interference at FBSs is assumed fixed. And an iterative algorithm which converges rapidly is also proposed to take into account the effect of co-tier interference on interference price and power allocation strategy. The results are explained with numerical simulation examples which validate the effectiveness of our proposed solutions.

• 한국통신학회논문지
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• 제38B권2호
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• pp.115-121
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• 2013

LED-ID (Light Emitting Diode-Identification) network is envisioned to be the next generation indoor wireless communication medium by which simultaneously high speed data transmission, identification, and illumination are possible. In spite of being extremely promising, it suffers from much impairment. Signals having different propagation paths can suffer from delays, and phase shifts which will eventually result interference. The probability of interference is also increased when communication links are established between a tag and several readers. Therefore it is necessary to reduce the interference in LED-ID network to ensure quality of service. It is possible to avoid interference by knowing the information about readers prior to assign the available spectrum. In this paper, we have proposed dynamic spectrum decision using cognitive radio concept. The simulation results justify that the proposed scheme is better than the conventional scheme.

• Journal of Astronomy and Space Sciences
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• 제24권4호
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• pp.261-268
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• 2007

We have studied the temporal variation in the North-South asymmetry of the sunspot area during the period from 1874 to 2007. Though the 9-year periodicity is commonly reported, shorter periodicities is still under study. We employ the cepstrum analysis method to analyze the noisy power spectrum of the North-South asymmetry. We demonstrate that the cleaned power spectrum shows reduction of the spurious back-ground noise level. Some of short period peaks in the power spectrum disappear after deconvolution. It should be, however, pointed out that power spectrum might look less noisy because of a filtering process during deconvolution. We conclude by pointing out that a more sophisticate filtering algorithm is required to produce a precise and reliable periodicity estimate.

• 경영과학
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• 제23권3호
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• pp.225-242
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• 2006

The Spectrum Usage Fee System which has been introduced and enforced since 1993 has had a great role for effective use of the radio frequency resources and the promotion of radio wave industry. However, the current system has been criticized due to several drawbacks. For example, broadcasting stations and national institutions are exempted whereas the overdue utility rate on some frequency has been imposed. So there has been rising the questions on whether the principles of fair imposition are broken. Another problem regarding the current system is that how to calculate the fee is too much complicated, and it needs to be revised into a simpler and clearer formulation. In this regard, this study intends to propose a new calculation framework for the radio spectrum usage fee and then prove its validity empirically on the basis of real data gathered from MIC and focus group interview.

• KSII Transactions on Internet and Information Systems (TIIS)
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• 제10권1호
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• pp.58-78
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• 2016

Compressed sensing (CS) possesses the potential benefits for spectrum sensing of wideband signal in cognitive radio. The sparsity of signal in frequency domain denotes the number of occupied channels for spectrum sensing. This paper presents a scheme of adaptively adjusting the number of compressed measurements to reduce the unnecessary computational complexity when priori information about the sparsity of signal cannot be acquired. Firstly, a method of sparsity estimation is introduced because the sparsity of signal is not available in some cognitive radio environments, and the relationship between the amount of used data and estimation accuracy is discussed. Then the SNR of the compressed signal is derived in the closed form. Based on the SNR of the compressed signal and estimated sparsity, an adaptive algorithm of adjusting the number of compressed measurements is proposed. Finally, some simulations are performed, and the results illustrate that the simulations agree with theoretical analysis, which prove the effectiveness of the proposed adaptive adjusting of compressed measurements.

• 한국의학물리학회지:의학물리
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• 제4권2호
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• pp.37-47
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• 1993

Jones 모델 및 HKB모델을 이용하여 Laplace transform방법으로 6MV X-ray의 대략적인 에너지 스펙트럼을 분석하였다. Jones모델은 투과계수 0.1이하에서는 Laplace transform방법이 적용될 수 없는 심한 제약을 받는다는 것을 알 수 있었다. HKB모델에 의한 에너지 스펙트럼은 대체로 실제의 에너지 스펙트럼과 일치하는 형태를 나타내지만 6MeV에너지 이상의 영역에서 길게 꼬리를 이루는 단점이 있었다.

• Journal of the Optical Society of Korea
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• 제20권1호
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• pp.204-211
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• 2016

Oil pollution seriously endangers the biological environment and human health. Due to the diversity of oils and the complexity of oil composition, it is of great significance to identify the oil contaminants. The 3-D fluorescence spectrum combined with a second order correction algorithm was adopted to measure an oil mixture with overlapped fluorescence spectra. The self-weighted alternating trilinear decomposition (SWATLD) is a kind of second order correction, which has developed rapidly in recent years. Micellar solutions of #0 diesel, #93 gasoline and ordinary kerosene in different concentrations were made up. The 3-D fluorescence spectra of the mixed oil solutions were measured by a FLS920 fluorescence spectrometer. The SWATLD algorithm was applied to decompose the spectrum data. The predict concentration and recovery rate obtained by the experiment show that the SWATLD algorithm has advantages of insensitivity to component number and high resolution for mixed oils.

• 한국수산과학회지
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• 제22권1호
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• pp.41-47
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• 1989

Using computer simulated irregular waves, variations of ocean wave statistics according to sea state are analyzed, and the reasonable conditions that transform the energy spectrum to individual wave statistics are discussed. Ocean wave statistics varying with sea state are found to respond linearly to the spectral peakedness parameter $Q_p$ and spectrum moments $m_n$ (n = 0, 1, 2${\cdots}{\cdots}\;\infty$ ). It is clarified that the 2nd-order spectrum moment is a reasonable parameter which represents the wave statistics including wave periods, and that the spectrum analysis should be carried out under the conditions of minimum data length of 10 times of peak period $T_p$ with time lag of $7T_p$ to satisfy the stable condition of wave statistics.

• 한국통신학회논문지
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• 제14권2호
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• pp.164-176
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• 1989

본 논문에서는 종래부터 연구되어 왔던 SS(Spread Specturm) 통신방식을 재검토하고 그의 문제점을 제기한 다음 해결방법의 하나로 PNCPM(Pseudo Noise Code Polarity Modulation) 방식을 제안하였다. 그리고 제안된 PNCPM 방식이 비동기검파방식에서 간단한 하드웨어(Hardware) 구성으로 데이터를 후레임(Frame)마다 쉽게 복조할 수 있음을 나타내고 CCD(Charge Couled Device) 상관기에 변복조방식과 장치구성 및 SSMA(Spread Spectrum Multiple Acces)에 응용하는 것을 제안하였다.