• Journal of the Korea Institute of Information and Communication Engineering
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• v.7 no.8
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• pp.1629-1637
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• 2003

In this paper, we analyzed the performance of a hybird DS/SFH(Direct­Sequency­Slow Frequency­Hopping) Spread Spectrum system with BFSK modulation over Nakagami­m fading channel with multitone jamming. The performance of the system was improved when a frequency bowing rate increased. In case that process gain of hybrid DS/SFH Spread Spectrum system to be fixed, the hybrid DS/SFH Spread Spectrum takes the low bit error probability than a DS Spread Spectrum system. Also, when the fading index m increases, the fading effect decrease, when the JSR(jamming to signal power ratio) increases ,the performance of a hybrid DS/SFH Spread Spectrum system improved than DS Spread Spectrum system. The result, we have been proved that performance of a hybrid DS/SFH Spread Spectrum was superior to DS Spend Spectrum system over Nakagami­m fading with tome jamming.

• Journal of Information Technology Applications and Management
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• v.20 no.4
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• pp.19-31
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• 2013

There is tremendous increasing demand on spectrum resource which is boosted by spread of cloud computing and M2M telecommunication as well as smart phone and tablet PC. Recently, spectrum sharing technology has drawn attention to the spectrum policy makers as a promising way to overcome limitation of scarce spectrum resource. To succeed in commercialization of spectrum sharing technology, it is necessary to prospect the future business ecosystem of spectrum sharing and develop appropriate policies and laws at the same time along with the advance of spectrum sharing technology. The purpose of this paper is to prospect future spectrum sharing ecosystem and analyze business ecosystem of spectrum sharing with casual loop map. With the causal map and system dynamics method, it is possible to analyze feedback loops which is not limited to linear thinking and build policies which optimize positive dynamics in business ecosystem of spectrum sharing.

• Proceedings of the KIEE Conference
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• 1987.07b
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• pp.1217-1220
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• 1987

We have developed a Ultra Sound Pulsed Doppler System with two-dimensional M-mode image and Spectrum analyzer. The image of the M-mode is composed of time and depth axes. The Spectrum analyzer shows the spectrum of Doppler signal which represents the velocity component of time dependent blood-flow behavior. The spectrogram using Spectrum analyzer is composed of frequency and amplitude axes. The outputs of the system are audio signals, velocity curves, velocity profiles, M-mode images and spectrogram.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.24 no.8
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• pp.820-830
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• 2013

As wireless traffic drastically increase with the expansion of smart equipment, it is necessary to develop spectrum sharing technologies and introduce spectrum sharing policy for utilizing limited radio resources efficiently. In order to meet these new changes, this parper investigated the government-held (or license) spectrum to seek candidate frequency bands of spectrum sharing. Based on the database of the existing radio station, the investigated candidate frequency bands of spectrum sharing was experimented locally, considering the central frequency, bandwidths, and the region where the radio station is usedIn conclusion, we found out about 901 MHz bandwidths for regional spectrum sharing within the spectrum of 1~4.5 GHz. These bandwidths can be utilized in M2M and WiFi services, etc. based on spectrum sharing technology in the future.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.25 no.10
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• pp.983-994
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• 2014

In this paper, we analyze the telecom services and their socio-economic effect of using open spectrum, which is to access sharing spectrum. For this, we suggest a concept and a classification of open spectrum as spectrum access model and make a survey for analyzing the socio-economic effect of spectrum, 2,605 MHz which is candidated for sharing between 2.9~5.925 Hz in Korea. From survey results, we propose Mobile Telecommunications Assist Service and WiFi as the most effective services and Smart Car Service and M2M, IoT, and RFID/USN Service as the effective services to open spectrum.

• Korean Journal of Mathematics
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• v.20 no.3
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• pp.285-291
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• 2012

Let $M_n$ be the algebra of all complex $n{\times}n$ matrices and ${\phi}:M_n{\rightarrow}M_n$ a surjective map (not necessarily additive or multiplicative) satisfying one of the following equations: $${\det}({\phi}(A){\phi}(B)+{\phi}(X))={\det}(AB+X),\;A,B,X{\in}M_n,\\{\sigma}({\phi}(A){\phi}(B)+{\phi}(X))={\sigma}(AB+X),\;A,B,X{\in}M_n$$. Then it is an automorphism, where ${\sigma}(A)$ is the spectrum of $A{\in}M_n$. We also show that if $\mathfrak{A}$ be a standard operator algebra, $\mathfrak{B}$ is a unital Banach algebra with trivial center and if ${\phi}:\mathfrak{A}{\rightarrow}\mathfrak{B}$ is a multiplicative surjection preserving spectrum, then ${\phi}$ is an algebra isomorphism.

• Journal of the Korea Society of Computer and Information
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• v.16 no.10
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• pp.137-145
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• 2011

In this paper, we modeled digital M/W transmission channel by frequency non-selective fading channel and analyzed the power spectrum magnitude of digital M/W transmission systems adopting OFDM modulation scheme through simulation. From the simulation results, it was found that deep does not appear in the specified fixed bandwidth under the AWGN environment. Also, lower power spectrum magnitude was shown in frequency non-selective fading channel than that in AWGN channel. Futhermore, the power spectrum magnitude value became more lowered when carrier frequency and vehicle speed became higher.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.24 no.8
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• pp.831-840
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• 2013

In this paper, we analyze the telecom services and their socio-economic value for sharing spectrum, which is suitable to access. For this, we suggest a concept and a classification model of sharing spectrum and make a survey for analyzing the socio-economic value of spectrum, 910 MHz which is candidated for sharing between 1.4~4.5 GHz in Korea. Also, we propose mobile telecom service, WiFi, ASA, public service, M2M, and smart home and factory service as service for suitable to sharing spectrum.

• The Korean Journal of Zoology
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• v.2 no.1
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• pp.11-16
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• 1959

가물치(Ophice phalus argus)의 안구망막에 존재하는 시각물질을 spectrophotometry 한 결과 다음과 같다. (1) 암순응된 가물치 안구망막에서 2 % digitonin 으로 시각물질을 추출하여 광조사전의 흡광 spectrum을 측정한 결과 흡광 maximum 은 350$\mu\textrm{m}$, 420$\mu\textrm{m}$, 550$\mu\textrm{m}$, 590$\mu\textrm{m}$에 있으며 있었으며 광조사후의 흡광 spectrum과의 difference spectrum 의 흡광 maximum 은 390$\mu\textrm{m}$, 427 $\pm$2$\mu\textrm{m}$, 550$\mu\textrm{m}$, 595$\mu\textrm{m}$에 있었다. (2) 가물치 망막중의 시각물질인 390$\mu\textrm{m}$, 427$\mu\textrm{m}$, 550$\mu\textrm{m}$, 595$\mu\textrm{m}$의 삼원색광에 대한 감광도는 다음과같다. a. 390$\mu\textrm{m}$은 blue light > red light = green light > white light . b.427$\mu\textrm{m}$ 은 red light >blue light > white light > green light c. 550 $\mu\textrm{m}$과 595$\mu\textrm{m}$ 은 blue light > red light > green light > white light (3) 390 $\mu\textrm{m}$ 과 427$\mu\textrm{m}$에서 흡광 spectrum의 maximum을 가지는 시각물질은 그 존재를 예시하던 새로운 색소이다. (4) 가물치의 시각물질은 증류수에도 용출되나 2 % digitonin 수용액으로 추출하였을때보다 명확하지 못하였다. (5) 가물치는 담수어임에도 불구하고 거북류와 같이 visual voilet 는 발견할 수 없었다.

• The Journal of Korea Institute of Information, Electronics, and Communication Technology
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• v.10 no.2
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• pp.184-191
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• 2017

This paper presents cluster based hybrid spectrum sensing system for M2M services. For each cluster, secondary nodes within the transmission radius of the primary node use hard decision method through local spectrum sensing to determine whether the primary node exists. And the other secondary nodes and the secondary nodes having poor radio channel conditions judge the existence of the primary node through the soft decision method of the values obtained by performing the cooperative spectrum sensing. In the proposed hybrid spectrum sensing system, the performance according to the number of secondary nodes is analyzed with the conventional system over Rayleigh fading channel. As the number of cooperative sensing users increased to 2, 3 and 4, the cluster error probability decreased to 0.5608, 0.5252 and 0.4001 at SNR of -10[dB] respectively. Since the proposed system uses less overhead traffic, it is found that it is more effective in terms of frequency usage than the conventional system using soft decision-soft decision and soft decision-hard decision methods.