• Title, Summary, Keyword: spectrum

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Two-Stage Spectrum Sensing Scheme Using Fuzzy Logic for Cognitive Radio Networks

  • Satrio, Cahyo Tri;Jaeshin, Jang
    • Journal of information and communication convergence engineering
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    • v.14 no.1
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    • pp.1-8
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    • 2016
  • Spectrum sensing in cognitive radio networks allows secondary users to sense the unused spectrum without causing interference to primary users. Cognitive radio requires more accurate sensing results from unused portions of the spectrum. Accurate spectrum sensing techniques can reduce the probability of false alarms and misdetection. In this paper, a two-stage spectrum sensing scheme is proposed for cooperative spectrum sensing in cognitive radio networks. In the first stage, spectrum sensing is executed for each secondary user using energy detection based on double adaptive thresholds to determine the spectrum condition. If the energy value lies between two thresholds, a fuzzy logic scheme is applied to determine the channel conditions more accurately. In the second stage, a fusion center combines the results of each secondary user and uses a fuzzy logic scheme for combining all decisions. The simulation results show that the proposed scheme provides increased sensing accuracy by about 20% in some cases.

Achieving Agility in Blind Spectrum Rendezvous in Cognitive Radio Networks (인지무선네트워크에서 블라인드 스펙트럼 랑데부 지연의 단축)

  • Byun, Sang-Seon
    • IEMEK Journal of Embedded Systems and Applications
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    • v.15 no.4
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    • pp.189-196
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    • 2020
  • In cognitive radio networks, secondary transmitters should cease its transmission immediately on detecting of primary transmission in the spectrum they are accessing. Then they should exploit another idle spectrums and handoff to the newly found idle spectrums, which is called spectrum rendezvous. With regards to spectrum rendezvous, most of related work presume the existence of dedicated common control channel used by secondary users for exchanging the information of idle spectrums. However, this presumption is not feasible in real world cognitive radio scenario. Therefore we address a blind spectrum rendezvous scheme with no need of separate control channel. Furthermore we consider maintaining one or more extra spectrums (channels) to expedite the spectrum rendezvous. Our scheme lets secondary users maintain extra spectrums by exchanging the spectrum information periodically during normal communications. The one of the extra spectrums are regarded as a candidate spectrum that the users can handoff to on detecting the primary transmission. We evaluate that our blind scheme can help to reduce the rendezvous delay in a real world cognitive radio environments with USRPs.

Spectrum Usage Forecasting Model for Cognitive Radio Networks

  • Yang, Wei;Jing, Xiaojun;Huang, Hai
    • KSII Transactions on Internet and Information Systems (TIIS)
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    • v.12 no.4
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    • pp.1489-1503
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    • 2018
  • Spectrum reuse has attracted much concern of researchers and scientists, however, the dynamic spectrum access is challenging, since an individual secondary user usually just has limited sensing abilities. One key insight is that spectrum usage forecasting among secondary users, this inspiration enables users to obtain more informed spectrum opportunities. Therefore, spectrum usage forecasting is vital to cognitive radio networks (CRNs). With this insight, a spectrum usage forecasting model for the occurrence of primary users prediction is derived in this paper. The proposed model is based on auto regressive enhanced primary user emergence reasoning (AR-PUER), which combines linear prediction and primary user emergence reasoning. Historical samples are selected to train the spectrum usage forecasting model in order to capture the current distinction pattern of primary users. The proposed scheme does not require the knowledge of signal or of noise power. To verify the performance of proposed spectrum usage forecasting model, we apply it to the data during the past two months, and then compare it with some other sensing techniques. The simulation results demonstrate that the spectrum usage forecasting model is effective and generates the most accurate prediction of primary users occasion in several cases.

Development of Neural-Networks-based Model for the Generation of an Earthquake Response Spectrum and a Design Spectrum (지진 응답 스펙트럼과 설계용 응답 스펙트럼 생성을 위한 신경망 모델의 개발)

  • 조빈아;이승창;한상환;이병해
    • Proceedings of the Computational Structural Engineering Institute Conference
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    • pp.447-454
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    • 1998
  • The paper describes the second half of the research for the development of Neural-Networks-based model for the generation of an Artificial earthquake and a Response Spectrum(NNARS). Based on the redefined traditional processes related to the generation of an earthquake acceleration response spectrum and design spectrum, four neural-networks-based models are proposed to substitute the traditional processes. RS_NN tries to directly generate acceleration response spectrum with basic data that are magnitude, epicentral distance, site conditions and focal depth. The test results of RS_NN are not good because of the characteristics of white noise, which is randomly generated. ARS_NN solve this problem by the introduction of the average concept. IARS_NN has a role to inverse the ARS_NN, so that is applied to generate a ground motion accelerogram compatible with the shape of a response spectrum. Additionally, DS_NN directly produces design spectrum with basic data. As these four neural networks are simulated as a step by step, the paper describes the methods to generate a response spectrum and a design spectrum using the neural networks.

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Measurement of Spectrum Quantification Using Spectrum Use Factor (스펙트럼 사용계수를 이용한 스펙트럼 정량화 측정)

  • Shin Yong-Seop;Hong Ic-Pyo;Kim Young-Soo;Park Han-Kyu
    • The Journal of Korean Institute of Electromagnetic Engineering and Science
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    • v.17 no.1
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    • pp.81-88
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    • 2006
  • In this paper, spectrum use factor as the ratio between used spectrum bandwidth by the existing system and total spectrum resources at specific locations was derived and calculated. Spectrum use factor was also presented as a function of antenna patterns and transmitter power of existing systems. Real spectrum use factor was calculated for fixed radio station as a validity of this paper. With the results of this paper, we can use the spectrum more efficiently because the white space of spectrum space is replaced by the quantificated spectrum space.

Spectrum Requirements for the Future Development of IMT-2000 and Systems Beyond IMT-2000

  • Yoon Hyun-Goo;Chung Woo-Ghee;Jo Han-Shin;Lim Jae-Woo;Yook Jong-Gwan;Park Han-Kyu
    • Journal of Communications and Networks
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    • v.8 no.2
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    • pp.169-174
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    • 2006
  • In this paper, the algorithm of a methodology for the calculation of spectrum requirements was implemented. As well, the influence of traffic distribution ratio among radio access technology groups, spectral efficiency, and flexible spectrum usage (FSU) margin was analyzed in terms of the spectrum requirements, with a view toward for future development of international mobile telecommunication (IMT)-2000 and systems beyond IMT-2000. The calculated spectrum requirement in the maximum spectral efficiency case is reduced by approximately 40% compared to a minimum spectral efficiency case. The effect of the distribution ratio on the required spectrum is smaller than the effect of the spectral efficiency. As the flexible spectrum usage margin increases by 1.0 dB, the total spectrum requirement decreases by 0.9 dB. The required spectrum for the market input parameter, ${\rho}$ = 0.5 is 801.63 MHz, while the required spectrum for ${\rho}$ = 1.0 is 6295.4 MHz. This is equivalent to an increase of 785.32 %.

Measurement of Spectrum Utilization Efficiency Considering Spectrum Sharing (주파수 공유를 고려한 전파자원 이용효율 측정 방안)

  • Kim, Taehan;Park, Hyun-Min;Sung, Ki Won
    • The Journal of the Korea Contents Association
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    • v.14 no.9
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    • pp.589-597
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    • 2014
  • The increasing demand for various mobile telecommunication services calls for more spectrum resource. Considering the scarcity of spectrum resource and the difficulties of development of higher frequency band, the unique way to meet the increasing demand is to maximize the utilization efficiency of the current spectrum resource. Under the circumstances, various spectrum sharing plans have been in recent studies to dissolve the excess spectrum demand. In addition, spectrum efficiency measurement methods become more important to verify the effectiveness of spectrum sharing and estimate the performance of various wireless systems. Our research addresses measurement methods to estimate spectrum utilization efficiency in a rational manner. Based on ITU-R recommendations, various measuring methods for spectrum utilization efficiency are reviewed. Then a queueing based approach is newly presented as alternatives to the current models. By using the proposed model, the spectrum efficiency increment with the adoption of spectrum sharing plans can be estimated more properly.

Legal Reform Agenda for Open Spectrum Access (개방형 전파 사용을 위한 법 제도 개선 방안)

  • Lee, Hee Jung
    • The Journal of Korean Institute of Electromagnetic Engineering and Science
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    • v.25 no.10
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    • pp.995-1004
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    • 2014
  • Due to the development of spectrum use technology and various services based on radio spectrum, the scarcity of spectrum has been heightened. In this circumstances both the efficiency and fairness of spectrum use need to be raised. Open spectrum access can be a useful approach for both goal. For the open spectrum access the legal institution needs to be reformed to enable it. From the starting point of spectrum use till the end of spectrum use there can be various issues of rights and obligations. So the legal institution for various legal status of spectrum use and establishment and continuous management of DB and fast and respectable dispute resolution mechanism is required.

EPR Spectrum of the High-Temperature Superconductor $YBa_2Cu_3O_{7-x}$ Doped with Ytterbium

  • Hwang Sonjong;So Hyunsoo
    • Bulletin of the Korean Chemical Society
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    • v.10 no.1
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    • pp.23-26
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    • 1989
  • EPR spectra of the high-temperature superconductor YBa_2Cu_3O_{7-x}$ doped with ytterbium have been measured at 77-300K. The superconducting, orthorhombic phase shows a spectrum at g = 2.08 (Spectrum O). As the temperature is lowered, another line ascribable to $Yb^{3+}$ grows gradually at g = 3.31. The intensity of Spectrum O was determined using Yb as the internal reference. The semiconducting, tetragonal phase shows a spectrum at g = 2.06 (Spectrum T), different from Spectrum O. The origins of these spectra are discussed.

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On the Fine Spectrum of the Lower Triangular Matrix B(r, s) over the Hahn Sequence Space

  • Das, Rituparna
    • Kyungpook Mathematical Journal
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    • v.57 no.3
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    • pp.441-455
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    • 2017
  • In this article we have determined the spectrum and fine spectrum of the lower triangular matrix B(r, s) on the Hahn sequence space h. We have also determined the approximate point spectrum, the defect spectrum and the compression spectrum of the operator B(r, s) on the sequence space h.