• KSII Transactions on Internet and Information Systems (TIIS)
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• v.16 no.1
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• pp.350-364
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• 2022

Traditionally, in multi-user multi-carrier systems, the neighboring subband will be gapped by one subcarrier, which is set as guard band to reduce multiple access interference (MAI) between neighboring subbands. The empty subcarrier for guard band will degrade the spectral efficiency of the whole system. In order to enhance the spectral efficiency of multi-user filter bank multiple carrier (FBMC) systems, a new subband allocation method is introduced, in which the neighboring subband is gapped by half subcarrier instead of one subcarrier. Meanwhile, in order to implement the proposed resource allocation scheme, an optimized FBMC prototype filter is designed to decrease the inter-subband interference to the neighboring subband. The detailed simulations about the comparison between the proposed spectrum assignment and traditional FBMC are given, as well as the performance in the different interference scenarios. The simulation results show that the combination of the proposed spectrum assignment scheme and the optimized filter has better performance compared to the traditional scheme. The proposed scheme can be used in the system which serves massive users to get higher spectrum efficiency.

• Proceedings of the Technology Innovation Conference
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• 2004.02a
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• pp.108-131
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• 2004

Having the characteristics of public goods, Radio Spectrum had been controlled by Government Authorities. In the past, technological side of spectrum, such as cross protection, was the main concern, but as the telecommunication industry is developing gradually, economic side of spectrum is becoming an important part. To uplift the Economic efficiency of spectrum management policy, clarifying the basic value of spectrum is one of the most important things. Also, both government authorities and spectrum licensees will have to choose license or investment under uncertainties such as license timing, time to market, technology standard, and so on. Considering all things, this paper gives the value to the spectrum by real options theory, which is a powerful method concerning uncertainty, especially for government, And we applied it to a specific spectrum band for the portable Internet in Korea. These results can provide information about the technological standard, optimal market-entry time as well as the value of spectrum for the portable Internet.

• KSII Transactions on Internet and Information Systems (TIIS)
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• v.16 no.11
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• pp.3738-3760
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• 2022

Due to increasing spectrum demand for new wireless devices applications, cooperative spectrum sensing (CSS) paradigm is the most promising solution to alleviate the spectrum shortage problem. However, in the interweave cognitive radio (CR) system, the inherent nature of CSS opens a hole to Byzantine attack, thereby resulting in a significant drop of the CSS security and efficiency. In view of this, a weighted differential sequential single symbol (WD3S) algorithm based on MATLAB platform is developed to accurately identify malicious users (MUs) and benefit useful sensing information from their malicious reports in this paper. In order to achieve this, a dynamic Byzantine attack model is proposed to describe malicious behaviors for MUs in an interweave CR system. On the basis of this, a method of data transmission consistency verification is formulated to evaluate the global decision's correctness and update the trust value (TrV) of secondary users (SUs), thereby accurately identifying MUs. Then, we innovatively reuse malicious sensing information from MUs by the weight allocation scheme. In addition, considering a high spectrum usage of primary network, a sequential and differential reporting way based on a single symbol is also proposed in the process of the sensing information submission. Finally, under various Byzantine attack types, we provide in-depth simulations to demonstrate the efficiency and security of the proposed WD3S.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2006.05a
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• pp.549-554
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• 2006

The objective of this paper is to propose a system by means of which the utilization of radio frequency spectrum may be improved from the state of extreme inefficiency at the present time in Kazakhstan to a state of efficiency and equilibrium in the future. The main solutions to efficiently use radio frequency spectrum in Kazakhstan will be described in this paper. There are 'Spectrum Utilization, Spectrum Sharing and Reuse the Spectrum' in which the radio frequency can be propagated in wide range using smalt amount of spectrum, or broadcast several channels via one spectrum sharing. In order to embed these systems in practice it will be better to make modifications consider Government policy and geographical and social requirements.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.30 no.6
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• pp.452-466
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• 2019

As the spectrum demand increases, securing spectrum resources in a timely manner becomes necessary. This paper proposes a spectrum-band prioritization scheme for establishing an efficient spectrum-use policy. The criteria for spectrum-band prioritization are derived from articles of the Radio Waves Act, and a four-level matrix for priority evaluation is proposed, considering both demand urgency and supply ease. The prioritization processes and items to consider for measuring each criteria are also proposed in order to implement the proposed prioritization scheme. It is expected that the proposed scheme can help secure the spectrum in a timely manner, protect incumbent users properly, and promote new spectrum-based businesses.

• Journal of Radiation Protection and Research
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• v.32 no.1
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• pp.9-13
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• 2007

From HPGe calibration spectrum of liquid mixed source in cylindrical vial, we developed simulated spectrum for spectrum analysis education. It is the spectrum that combine peaks separated from measured spectrum. After that, spectrum removed statistical variation of channel counts. Statistical fluctuation of the spectrum is made by Box-Muller function. The spectrum contains 18 peaks. The peak's centroid and area were defined exactly. Developed spectra are calibration spectrum, sample spectrum, background spectrum and spectra for efficiency correction for geometry and cascade coincidence.

• 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.

• Journal of KIISE
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• v.43 no.1
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• pp.119-125
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• 2016

Cognitive radio technology can allow secondary users (SUs) to access unused licensed spectrums in an opportunistic manner without interfering with primary users (PUs). Spectrum sensing is a key technology for cognitive radio (CR). However, few studies have examined energy-efficient spectrum sensing in cognitive radio sensor networks (CRSNs). In this paper, we propose an energy-efficient cooperative spectrum sensing nodes selection scheme for cluster-based cognitive radio sensor networks. In our proposed scheme, false alarm probability and energy consumption are considered to minimize the number of spectrum sensing nodes in a cluster. Simulation results show that by applying the proposed scheme, spectrum sensing efficiency is improved with a decreased number of spectrum sensing nodes. Furthermore, network energy efficiency is guaranteed and network lifetime is substantially prolonged.

• Journal of Communications and Networks
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• v.8 no.2
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• pp.151-157
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• 2006

In a continuously expanding wireless world, the number of radio systems increases every day and efficient spectrum usage becomes a more significant requirement. Ultra-wideband (UWB) and cognitive radio are two exciting technologies that offer new approaches to the spectrum usage. The main objective of this paper is to shed the first light on the marriage of these two important approaches. The strength of orthogonal frequency division multiplexing (OFDM) based UWB in co-existing with licensed systems is investigated. The opportunity concept is defined, and the requirements of the opportunistic spectrum usage are explained. It is proposed to take the UWB-OFDM from the current underlay implementation, and evolve it to a combined underlay and opportunistic spectrum usage technology, leading to cognitive UWB-OFDM. This way, we aim at making UWB more competitive in the wireless market with extended range, higher capacity, better performance, and a wide variety of applications.

• ETRI Journal
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• v.18 no.3
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• pp.181-193
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• 1996

A blue light emitting device has been successfully fabricated using a polymer with regulated conjugation length containing trimethylsilyl substituted phenylenevinylene units. Electroluminescence from the device has an emission maximum at 470 nm. The device shows typical diode characteristics with operating voltage of 20 V and the light becomes visible at a current density of less than $0.5;mA/cm^2$. The electroluminescence spectrum is virtually identical with the photoluminescence spectrum, indicating that the radiation mechanisms are the same for both. A light emitting device using the blend of a large band gap polymer and a small band gap polymer was also fabricated. Light emission from the small band gap polymer shows much improved quantum efficiency, but there is no light emission from the large band gap polymer. Quantum efficiency of the blend increases up to about two orders of magnitude greater than that of the small band gap polymer with increasing proportion of the large band gap polymer. The improvement in quantum efficiency is interpreted in terms of exciton transfer and the hole blocking behaviour of the large band gap polymer. Finally, we have fabricated a patterned flexible light emitting device using the high quantum efficiency polymer blend system.