• The Journal of the Institute of Internet, Broadcasting and Communication
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• v.11 no.4
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• pp.195-201
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• 2011

Cognitive radio (CR), which is proposed as a technology that utilizes the frequency resources effectively, has studied to relive scarcity of the frequency resources. CR provides opportunistically under-utilize licensed frequency to the secondary user. However, in the wireless channels, due to the effect of fading and shadowing environments, spectrum sensing performance is compromised. Besides, to detect and classify various CR systems, a novel spectrum sensing algorithm is needed. Therefore, in this paper, we proposed the spectrum sensing algorithm with water marking scheme.

• Journal of the Institute of Electronics Engineers of Korea CI
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• v.45 no.5
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• pp.8-14
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• 2008

There are two a approaches for the Cognitive Radio(CR) development. One is 'Full CR', which Joseph Mitola III proposed, and another is 'Spectrum CR', which is currently being standardized. The target approach of this paper is the latter and we develop a Cognitive Engine(CE) and simulated a channel set management(CSM), which is a core function of CE. The Channel set management evaluates channel quality and Incumbent User(IU) vacancy possibility and classifies the channel set, which is performed by using channel state history. Especially, a very important function for the channel set management is a channel state prediction and this paper proposed a Hidden Markov Model(HMM) based channel state prediction and a method for increasing performance. Also, we applied the proposed method into our simulator and simulated channel state prediction. Through the simulation, we verified as we applied our proposed scheme, the performance of channel state prediction gets better and through comparing with RS and SS, we verified the HMM based Channel state prediction is better.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.32 no.6B
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• pp.358-366
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• 2007

Recently, FCC(Federal Communications Commission) has considered for that unlicensed device leases licensed devices' channel to overcome shortage of communication channels. Therefore, IEEE 802.22 WRAN(Wireless Regional Area Networks) working group progresses CR (Cognitive Radio) technique that is able to sense and adopt void channels that are not being occupied by the licensed devices. Channel selection is of the utmost importance because it can affect the whole system performance in CR network. Thus, we propose a policy-based dynamic channel selection architecture for cognitive radio network to achieve an efficient communication. We propose three kinds of method for channel selection; the first one is weighted channel selection, the second one is sequential channel selection, and the last one is combined channel selection. We can obtain the optimum channel list and allocates channels dynamically using the proposed protocol.

• Journal of Satellite, Information and Communications
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• v.7 no.1
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• pp.39-47
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• 2012

Currently, most of the frequency spectrum resources are allocated and due to the lack of frequency, low frequency band, optimal for wireless communication environment is not used. Therefore, Cognitive Radio (CR) is a critical issue to solve the spectrum scarcity and to improve frequency spectrum utilization in wireless communication. In this paper, we implement data transmission and receive in a real CR system using the USRP(Universal Software Radio Peripheral) board and GNU Radio package of an open source development kit. Concretely, we detect the Primary User by spectrum sensing, and then we send Primary User information to the database. After receiving the information, because the database already sent optimal transmit power, bandwidth and channel information to CR equipment, CR can communicate without any interference to Primary User.

• Proceedings of the Korean Society of Broadcast Engineers Conference
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• 2006.11a
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• pp.213-217
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• 2006

방송 및 비면허 대역에서의 주파수 자원을 효율적으로 활용하기 위한 Cognitive Radio(CR)기술의 구현을 위해서는 우선적으로 해결해야할 점이 무선 상에 존재하는 관련 주파수 스펙트럼을 센싱하는 기술의 구현이라고 할 수 있다. 이러한 주파수 스펙트럼 센싱 기술이 구현되어야만, 센싱을 통해서 획득된 주파수 할당 데이터를 기반으로 CR의 개념이 원활하게 동작됨과 통시에 기존의 무선통신 주파수의 우선 이용자간의 간섭문제 또한 야기되지 않는다는 특징을 갖게 된다. 따라서, 본 논문에서는 이러한 Cognitive Radio 센서로 이용되는 Energy Detection 및 Matched Filter 기법의 기술특성 분석 및 최신기술동향에 대하여 기술하였다.

• Journal of Satellite, Information and Communications
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• v.5 no.1
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• pp.27-31
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• 2010

Recently, spectrum requirements are rapidly increasing in accordance with wireless communication development. For this reason, FCC(Federal communications commission) is considering cognitive radio system to increase spectral efficiency. In this paper, we present the performance analysis of signal detection by using RS(Reference signal) for LTE environments. Especially, we analyze the performance of detection probability in case of downlink LTE system. In the simulation, we generate OFDMA signal format which is specified in the LTE system. We assume additive white Gausssian noise channel environment. We estimate the performance by setting the threshold value of 5 % and 10 % based on CFAR(Constant false alarm rate) and false alarm rate, respectively. Finally, we discuss a future study plan on the applicability of CR to the LTE system.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.61 no.4
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• pp.629-631
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• 2012

In Cognitive Radio network, spectrum selection scheme is one of a important part to manage idle spectrums efficiently. However, in CR networks, they have to adopt time-varying channel availability to minimize the interference to primary users (PU), and be able to manage spectrum resources efficiently. In this paper, we proposed a modified PF scheduler which can be appropriate to schedule downlink CR users and channels, by considering the fairness and the throughput as well as the primary user characteristics of each channel.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.36 no.10C
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• pp.635-640
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• 2011

This paper proposes a frequency offset estimation scheme with low-complexity for orthogonal frequency division multiplexing (OFDM)-based cognitive radio (CR) systems. The proposed scheme is applicable to any type of training symbol and has a lower complexity than the scheme in [9] by using the partial periodogram. Simulation results show that the estimation performance of the proposed scheme is almost the same as that of the scheme in [9].

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2012.10a
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• pp.797-799
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• 2012

The cognitive radio (CR) network has been studied in the form of open source by vast number of communities, and the potential expectation is very high since the CR is based on reprogrammable platform. However, as the peer-to-peer software has been abused, so high is the chance that the CR network can be abused public wide. Consequently, the benefit from the study of next-generation wireless network can be at risk because law breakers could abuse the CR. In this contribution, we analyze the issues and the problems of the CR and discuss an efficient measure against security attacks.

• KSII Transactions on Internet and Information Systems (TIIS)
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• v.8 no.11
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• pp.3837-3859
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• 2014

Vehicular Ad hoc Networks (VANET) becomes more popular in industry, academia and government. However, Typical VANET is challenged by high speed mobility and insufficient spectrum resources over congested scenarios. To address those serious problems, some articles have introduced Cognitive Radio (CR) technology into VANET and formed CR-VANET. In this article, we propose an overview of CR-VANET by exploring different architectures and features. Moreover, we provide taxonomy of state-of-the-art papers in this emerging field and the key articles are well analyzed respectively. In addition, we illustrate both research and application frameworks of CR-VANET based on our works, and propose some open research issues for inspiring future work.