• Journal of the Korea Institute of Information and Communication Engineering
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• v.16 no.8
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• pp.1606-1612
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• 2012

Cognitive radio technology enables us to utilize the extra spectrum which is not used by the primary users by sensing the channel condition. To use such an extra spectrum, spectrum allocation is one of the important issues in the cognitive radio networks. The network is dynamic and the available channels are changeable, and the opportunistic channel allocation is required to use the resource efficiently without interference to the primary networks. In this paper, modified proportional fairness scheduling is proposed for cognitive radio networks to satisfy the both fairness and system throughput, and the modified scheduling was designed to reduce the interference to the primary users.

• Journal of KIISE:Information Networking
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• v.35 no.2
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• pp.130-138
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• 2008

The scheme for recognizing the channel availability is one of the most important research issues in cognitive radio systems utilizing unused frequency bands. In this paper, we propose a novel scheme of selecting sensing channel in order to improve the sensing ability of frequency status in cognitive radio ad hoc networks. To fully exploit the sensing ability of each cognitive radio user, we adopt a master for a cluster which is made of several cognitive radio users. By gathering and analyzing the sensing information from cognitive radio users in the cluster, the cooperative sensing is realized. Since the transmission range of a licensed user is limited, it is possible that a master determines different sensing channels to each cognitive radio users based on their location. By making cognitive radio users sense different channels, the proposed scheme can recognize the state of wireless spectrum fast and precisely. Using the simulation, we compare the performance of the proposed scheme with those of two different compared schemes that one makes cognitive radio users recognize the frequency status based on their own sensing results and the other shares frequency status information but does not utilize the location information of licensed user. Simulation results show that the proposed scheme provides available channels as many as possible while detecting the activation of licensed user immediately.

• Journal of KIISE:Information Networking
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• v.37 no.4
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• pp.301-306
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• 2010

We propose the control channel access scheme for multi-interface multi-hop cognitive radio (CR) environment having a cluster structure. Due to the difficulty of obtaining common channels across the entire CR network, most multi-interface multi-hop CR networks put the control channel outside the CR bandwidth and dedicate one network interface to it in order to exchange the control information such as the activation of licensed users. However, this will be the waste of the network interface. Our focus is how to alternate between the control and the data channel without multichannel hidden node problem under the cluster structure where CR nodes connect with neighbors through multiple data channels. By using simulation, we evaluate the performance of the proposed scheme. The results show that the proposed scheme achieves higher network throughput than the dedicated scheme where one network interface card should dedicate to the control channel and cannot be used for data transmission.

• Proceedings of the Korean Society of Broadcast Engineers Conference
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• 2013.06a
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• pp.29-31
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• 2013

본 논문에서는 기존라디오(primary) 네트워크와 스펙트럼을 공유하는(spectrum sharing) 인지라디오(cognitive radio) 네트워크에서 비재생적(non-regenerative) 다중안테나 중계 (relay) 시스템을 위한 소스(source) 및 중계기 프리코딩(precoding) 기법을 제안한다. 제안된 기법은 소스와 중계기 프리코딩 행렬의 최적해를 구하기 위해 QCQP(Quadratically Constrained Quadratic Programming) 문제를 통해 구한다. 제안된 기법은 기존라디오 수신기에서의 간섭세기 제한을 만족하면서 낮은 MSE(Mean squared error)와 높은 MI(Mutual Information)를 달성함을 모의실험결과를 통해 보인다. 또한 아주 빠른 속도로 최적해로 수렴함을 보이고 있다.

• The Journal of Korea Institute of Information, Electronics, and Communication Technology
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• v.12 no.1
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• pp.58-71
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• 2019

This paper proposes architecture of a cognitive radio engine platform and the allowable frequency channel reasoning method that enables acquisition of the allowable channels for the military tactical network environment. The current military tactical wireless communication system is increasing need to secure a supplementary radio frequency to ensure that multiple wireless networks for different military wireless devices coexist, so that tactical wireless communication between the same or different systems can be operated effectively. This paper presents the allowable frequency channel reasoning method based on cognitive radio engine for realizing DSA(Dynamic Spectrum Access) as an optimal available frequency channel. To this end, a case-based allowable frequency channel reasoning method for cognitive radio devices is proposed through modeling of primary user's traffic status and calculation of channel occupancy probability. Also through the simulation of the performance analysis, changing rate of collision probability between the primary users' occupancy channel and the available channel acquisition information that can be used by the cognitive radio device was analysed.

• Journal of KIISE:Information Networking
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• v.37 no.3
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• pp.249-253
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• 2010

Resource of wireless frequency bandwidth is gradually going to be deficient due to explosive increase of traffic and saturated non-licensed frequency band such as ISM. In the contrary, many licensed frequency bands are revealed to be low in utilization by several measurement based researches. To alleviate this inefficiency, a concept of cognitive radio is suggested. Cognitive radio lets non-licensed user exploit the licensed frequency band as long as non-licensed user does not interfere licensed user and as a result, it is possible to harness wireless frequency more efficiently. IEEE 802.22 is the first standard network with cognitive radio technology and it employs Two-Stage channel sensing mechanism to accomplish both enough licensed user protection and efficient channel utilization. In this paper, we analyze the overhead of Two-Stage channel sensing mechanism and identify the influence of channel sensing time to the overhead.

• The Journal of the Korea Contents Association
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• v.9 no.7
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• pp.95-101
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• 2009

Cognitive Radios are encouraging solutions to improve the utilization of the radio spectrum In this paper, we propose channel allocation model for cognitive radio and analyse the performance of the model with Petri Nets. We design the model with an assumption that only partial information about current channel allocation information is known to CR users. The model is designed to communicate efficiently avoiding interference with primary and CR users and contains channel reobtaining process of CR users. The dropping rate and throughput of CR users under the various channel utilization of primary users are given as performance index.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.15 no.9
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• pp.1889-1894
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• 2011

Channel allocation is one of the important issues in the multichannel transmission. In the cognitive radio networks, channel allocation scheme should be designed to improve spectrum efficiency without interfering with the transmission of licensed users. In this paper, we propose a spectrum hole prediction based channel allocation scheme. The proposed channel allocation scheme, predicts spectrum hole by using the channel success rate, and limit the transmission of secondary user's data, and it reduces the interference to the primary user. The performance of proposed channel allocation scheme is evaluated by the computer simulation.

• The Magazine of the IEIE
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• v.36 no.6
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• pp.39-51
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• 2009

현대 사회에서 기하급수적으로 증가하는 방송 및 통신 시스템으로 인해 무선 주파수 자원의 고갈이 심각한 문제로 대두되고 있다. 가장 중요한 문제는 대부분의 주파수 분배 상황을 살펴보았을 때 거의 모든 주파수 대역이 고정 할당 되어있고, 특히 양질의 서비스를 제공 할 수 있는 주파수 대역에는 여분의 주파수가 거의 없다는 것이다. 이러한 문제를 해결하기 위해 유휴 주파수를 사용하는 인지 라디오(Cognitive Radio)기술이 주목 받고 있다. 이 기술을 효과적으로 활용하기 위해서는 채널 센싱과 채널 변경 기법의 연구가 필수적이다. 따라서 본고에서는 현재까지 진행된 인지 라디오 요소 기술에 대해 알아보고, 표준안을 살펴봄으로써 인지 라디오 기술의 동향을 알아보고자 한다.

• Journal of KIISE
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• v.42 no.1
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• pp.130-137
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• 2015

With the rapid increase of energy consumption and environmental problems, the need for green techniques is increasing. Network coding can provide a solution by reducing unnecessary data transmission and by estimating traffic patterns. In addition, it can amplify the synergy with the cognitive radio network (CR) since the CR has recognition and optimal decision functionalities. In this paper, we propose a network coding based green cognitive radio network. With the simulations, we show that the proposed scheme is up to 25% better than the previous work.