• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.25 no.8
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• pp.821-827
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• 2014

Many researches on the usage of shared spectrum have continuously been carried out to solve the recent frequency shortage problem and to use efficiently the spectrum without interference. Also, exponential mobile data growth and the solutions needed to address this challenge are parallel key objectives addressed in many countries. Spectrum policy innovation to meet this challenge is the ASA/LSA (Authorized Shared Access/Licensed Shared Access), which is the best access model to employ the small cell technology to meet this mobile traffic growth. Because 3.5 GHz bands is considered as the ASA/LSA frequency, in this paper, we propose the SAM(Spectrum Access Model) in 3~4 GHz bands to estimate the available ASA/LSA bands and to open more free spectrum. These results are utilized as the data to develop the SAM for the small cell and the open frequency in future.

• KSII Transactions on Internet and Information Systems (TIIS)
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• v.8 no.11
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• pp.3751-3774
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• 2014

With the rapid development of wireless communication, the confliction between the scarce frequency resources and the low spectral efficiency caused by the stationary spectrum sharing strategies seriously restricts the evolution of the future mobile communication. For this purpose, cognitive radio (CR) emerges as one of the most promising inventions which can overcome the spectrum shortage. As the key technology and main objective of CR, spectrum sharing can make full use of the limited spectrum, alleviate the scarcity of frequency resources and improve the system utilities, playing thereby an important role in improving the system performance of cognitive radio networks (CRNs). In this survey, the spectrum sharing in CRNs is discussed in terms of the sharing process, mainstream sharing technologies and spectrum sharing models. In particular, comparisons of different spectrum sharing strategies are concluded, as well as that of different spectrum sensing schemes in sharing procedure. Moreover, some application examples of the spectrum sharing in CRNs, such as smart grid, public safety, cellular network and medical body area networks are also introduced. In addition, our previous related works are presented and the open research issues in the field of spectrum sharing are stated as well.

• Bulletin of the Korean Chemical Society
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• v.31 no.6
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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.

• The Bulletin of The Korean Astronomical Society
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• v.8
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• pp.5.1-5.1
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• 1983

• The Journal of the Institute of Internet, Broadcasting and Communication
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• v.17 no.1
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• pp.253-259
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• 2017

As ICT industrial paradigm changes and wireless communication services evolve, demands on spectrum information are soaring. We conducted demand survey of experts and public in general on spectrum information and prioritized what we should disclose. And we looked into overseas cases and analyzed their policy, the current status, exceptions for opening spectrum information. In this paper, we suggested a direction on how to make spectrum information public in Korea. Also, we made a proposal to establish management system and legislation for opening spectrum information.

• The Transactions of the Korean Institute of Electrical Engineers P
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• v.63 no.1
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• pp.34-39
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• 2014

In cognitive radios, secondary users can use the spectrum exclusively allocated to a primary wireless system if the secondary users detect the spectrum in idle states. Because the secondary users can utilize the idle state of the spectrum, the utilization rate of the spectrum can be improved. The idle states can be detected by using secondary users' sensing schemes. However, the wireless channel environment where secondary users perform the spectrum sensing is not very friendly to secondary users because the signal-to-noise ratio of the received primary signal is very low. Hence, cooperative sensing scheme where more than one secondary user take part in the spectrum sensing is generally used in cognitive radios. In this paper, we investigate the cooperative sensing performance for machine-to-machine communication devices operated by batteries with limited energy. In general, the energy consumed for the spectrum sensing increases as the length of the sensing period and the number of cooperative sensing nodes. Accordingly, even though the total amount of the consumed energy is the same, an energy allocation methodology how to distribute the energy to the sensing period and sensing nodes can achieve the optimum sensing performance, which is numerically analyzed.

• Journal of Korean Society of Coastal and Ocean Engineers
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• v.31 no.1
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• pp.17-27
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• 2019

We carry out the numerical simulation to test a hypothesis that freak waves can be triggered by the infragravity waves of bound mode underlying the ever-present swells and its constructive interaction with swells using the Tool Box called the ihFoam that has its roots on the OpenFoam, and Bi-spectrum. Numerical simulation is implemented for the SamChcuk LNG Plant where freak waves have been reported in front of the private wharf during its construction phase due to the uncompleted northern breakwater. Infra-gravity waves of bound mode is generated using the difference wave-wave interaction between the local wind waves of 7 s and a swell of 11.4 s based on the Bi-spectrum. For the sake of comparison, numerical simulation for infra-gravity waves of free mode is also carried out. Numerical results show that stem waves along the private wharf for SamChcuk LNG Plant can be triggered by the infra-gravity waves of bound mode coming from the north, which eventually leads to freak waves when encounters the reflected waves from the south jetty.

• Journal of Digital Convergence
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• v.17 no.10
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• pp.13-21
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• 2019

The restricted network or the unbalanced distribution of spectrum is causing the problems of lack of spectrum resources and deterioration of the service quality. In addition, the existing centralized radio sharing method has not been a fundamental solution for radio sharing and is inefficient in terms of cost, convenience, and security. In this paper, we propose a blockchain-based spectrum sharing as a low-cost, trustworthy, high-efficiency platform that can distribute and share spectrum resources, and propose policies to realize this. In the spectrum sharing platform, spectrum information about Wi-Fi AP and LTE mobile hotspot is registered in the blockchain, and spectrum sharers and users can conclude peer-to-peer spectrum sharing contract quickly and efficiently through smart contract. The pay for the shared spectrum resources and reward for spectrum quality management open platform ecosystem to activate the circulation-sharing and it can provide a convenient and efficient public wireless infrastructure.

• Journal of The Korean Astronomical Society
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• v.29 no.spc1
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• pp.23-24
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• 1996

We reexamined CDM texture large-scale structure (LSS) formation model. We confirmed that texture model is consistent with 4-year COBE data both in an open and a critical matter density (${\Omega}_0$ = 1) universes, and then obtained normalization for density perturbation power spectrum. We next compare the power spectrum with LSS observation data. Contrary to the previous literature, we found that texture model matches with these data in an open universe no better than in an ${\Omega}_0$ = 1 universe. We also found that the model is more likely to fit these data in a cosmological constant dominated ($\Lambda-$) universe.

• Publications of The Korean Astronomical Society
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• v.7 no.1
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• pp.9-17
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• 1992

The power spectrum of the galaxy distribution is accurately measured up to wavelengths over $100\;h^{-1}$ Mpc from the CfA 1 and 2 catalogs. We find that our results agree with power spectra calculated by others from smaller samples of optical, radio and infrared galaxies. The power spectrum of an open CDM model (${\Omega}h$ = 0.2 and ${\delta}_8$ = 1; see below for definitions) best approximates the observed power spectrum. The power spectrum of the standard COM model (${\Omega}h$ = 0.5 and ${\delta}_8$ = 1) is inconsistent with the observed one at the 99% confidence level. Our best estimation of the corresponding correlation function in real space is ${\xi}(r)\;=\;(r/6.2h^{-1}Mpc)^{-1.8}$ for r < $20h^{-1}$ Mpc.