• Electronics and Telecommunications Trends
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• v.26 no.6
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• pp.129-138
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• 2011

미래의 고속 및 광대역 서비스에 대한 수요 증가로, 부족한 스펙트럼을 효율적으로 사용할 수 있는 스펙트럼 관리(spectrum management) 방법의 중요성이 대두되고 있다. 또한, 트래픽 폭증 및 멀티미디어 제공 등 서비스 확대에 대응할 수 있는 유연한 스펙트럼 접속(spectrum access) 기술, 공유(sharing)에 대한 필요성도 증대되고 있다. 이러한 중요성 및 필요성에 기인해, 효율적으로 스펙트럼을 공유할 수 있는 방법으로 언더레이, 오버레이 방식 등이 제안되었고, UWB 및 인지무선(cognitive radio)과 같은 공유 기술 등이 발전하게 되었다. 본 고에서는 효율적 주파수 이용을 위한 스펙트럼 관리 방법 및 주파수 공유 기술로 기존의 주파수 대역에서 충분히 낮은 출력으로 전파를 송출하는 언더레이 방식, 기회주의적인 오버레이 동적접속 기술, 면허권자인 1차 우선 사용자(primary user)와 2차 면허권자(secondary user) 간의 동적접속 기술에 대한 국내 외 기술동향을 상세히 소개하고자 한다.

• The Journal of the Institute of Internet, Broadcasting and Communication
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• v.13 no.6
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• pp.93-99
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• 2013

The proposed protocol is to get better performance compared to the existing method, also it can save the node number. There is needed a lot of secondary user for cooperative spectrum detection in Rayleigh fading channel. In this proposal, we suggest the new cooperative spectrum detector which can choose one secondary user with high power, while other SUs can be used as relays.

• Broadcasting and Media Magazine
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• v.12 no.3
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• pp.14-36
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• 2007

다양한 무선 통신 서비스의 등장으로 주파수 자원의 수요가 급증하여 스펙트럼 이용 효율을 극대화하기 위한 새로운 기술 개발의 필요성이 대두되고 있으며, 이에 대한 기술로 Cognitive Radio (CR) 기술이 주목받고 있다. CR 기술은 선택된 주파수 대역에 최적의 QoS를 제공하기 위해서는 먼저 주파수 환경에 적응성을 갖는 스펙트럼 센싱 (Spectrum Sensing) 기술이 필요하며, CR 기술이 적용된 무선 브로드밴드 네트워크 (AWBN : Adaptive Wireless Broadband Network) 모듈은 최근 각광받고 있는 방통융합 솔루션의 Hot Issue인 QoS 보장 홈네트워크 기반의 멀티미디어 전송(TV Portal Service)용 네트워크에 최적화된 솔루션으로 활용될 것으로 기대하고 있을 뿐만 아니라, IEEE 802.22 그룹에서 연구되고 있는 비어있는 TV 대역 및 마이크로폰 대역에 활용될 뿐만 아니라, 기존의 Mobile WiMax에 의한 브로드밴드 네트워크에도 활용 가능하다. 본 고에서는 IEEE 802.22/16d 시스템 규격에 의해 개발된 AWBN 시스템 개발 내용을 기술한다.

• Proceedings of the Korean Society of Broadcast Engineers Conference
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• 2017.11a
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• pp.21-23
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• 2017

본 논문에서는 스펙트럼 감지 무선 인지 네트워크에서 동기화 에러가 존재하는 환경을 고려한다. 동기화에러가 존재 할 때 주어지는 오검출 확률(miss detection probability)을 이용하여 일차 사용자와 이차 사용자들 간의 충돌 확률(collision probabliyt)를 유도한다. 유도된 수식을 몬테 카를로 모의실험(Monte Carlo simulation)을 통해 확인한다.

• KSII Transactions on Internet and Information Systems (TIIS)
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• v.10 no.3
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• pp.996-1015
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• 2016

A common concern regarding cooperative spectrum sensing (CSS) schemes is the occupied bandwidth and the energy consumption during the transmissions of sensing information to the fusion center over the reporting control channels. This concern is intensified if the number of cooperating secondary users in the network is large. This article presents a new fusion strategy for a CSS scheme, aiming at increasing the energy efficiency of a recently proposed bandwidth-efficient fusion scheme. Analytical results and computational simulations unveil a high increase in energy efficiency when compared with the original approach, yet achieving better performances in some situations, and lower implementation complexity.

• Journal of Communications and Networks
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• v.17 no.4
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• pp.362-369
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• 2015

This study addresses the effects of channel estimation error and mutual interference between licensed and unlicensed systems on outage performance of reactive relay selection in unlicensed systems over independent non-identical (i.n.i) Rayleigh fading channels and under both the maximum transmit power constraint and primary outage constraint. Toward this end, power allocation for unlicensed users is first recommended to satisfy both constraints and account for channel estimation error and mutual interference. Then, we derive an exact closed-form outage probability representation for unlicensed systems to quickly evaluate this effect in key operation parameters. Various results corroborate the derived expressions and provide useful insights into system performance.

• Journal of Communications and Networks
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• v.14 no.3
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• pp.225-229
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• 2012

We examine spectrum sensing in a situation of uncertain channel model. In particular, we assume that, besides additive noise, the observed signal contains an interference term whose probability distribution is unknown, and only its range and maximum power are known. We discuss the evaluation of the detector performance and its design in this situation. Although this paper specifically deals with the design of spectrum sensors, its scope is wider, as the applicability of its results extends to a general class of problems that may arise in the design of receivers whenever there is uncertainty about how to model the environment in which one is expected to operate. The theory expounded here allows one to determine the performance of a receiver, by combining the available (objective) probabilistic information with (subjective) information describing the designer's attitude.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.35 no.5A
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• pp.490-495
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• 2010

In this paper, we propose an sequential spectrum sensing algorithm utilizing DFT. The conventional sensing algorithm using FFT contains redundant computation due to the characteristic of FFT which computes all frequency components at one time. The proposed sensing algorithm utilizing DFT computes a frequency component once at a time according to the priority and decides presence of signal. The proposed sensing algorithm can provide similar detection performance to the conventional scheme while computations of the sensing process could be reduced significantly depends on an early detection of signal.

• Journal of Communications and Networks
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• v.16 no.6
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• pp.600-612
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• 2014

In this paper, we consider the problem of spectrum sensing for advanced television systems committee (ATSC) digital television (DTV) signal detection. To exploit the cyclostationarity of the ATSC DTV signals, we employ spectral correlation density (SCD) as the decision statistic and propose an optimal detection algorithm. The major difficulty is in obtaining the probability distribution functions of the SCD. To overcome the difficulty, we probabilistically model the pilot frequency location and employ Gaussian approximation for the SCD distribution. Then, we obtain a practically implementable detection algorithm that outperforms the industry leading systems by 2-3 dB. We also propose various techniques that greatly reduce the system complexity with performance degradation by only a few tenths of decibels. Finally, we show how robust the system is to the estimation errors of the noise power spectral density level and the probability distribution of the pilot frequency location.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.42 no.5
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• pp.982-984
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• 2017

In time domain, a radar signal is divided into two segments: one is for a transmitted pulse and the other is for receiving possible returns from radar targets. Also the received signal is relatively weak and consists of background noise except for the reflected signals from radar targets. In this Letter, we present an energy detection based spectrum sensing for a radar signal in the presence of noise power uncertainty exploiting this characteristics.