• 한국항행학회논문지
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• 제16권5호
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• pp.794-800
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• 2012

본 논문에서는 셀룰러 기반 무선 인지망에서 핸드오프 호를 위한 가드채널할당기법(guard channel scheme)의 자원이용률의 저하를 개선하기 위해 무선인지 기술을 사용하여 자원 이용률을 향상시키면서, 무선 인지망의 부 사용자(cognitive radio user) 손실률을 줄이는 방법을 제안한다. 제안한 방법에서는 핸드오프 호의 전용채널(guard channel)을 부 사용자가 이용하도록 하고, MMOSPRED(Multi-Media One Step Prediction)기법으로 핸드오프 호의 발생을 예측한 다음, 핸드오프 호가 발생하면 핸드오프 호의 전용채널을 넘겨주고, 부 사용자는 예약된 자원으로 스펙트럼 핸드오프를 하여 서비스를 완료 하도록 한다. 시뮬레이션을 통하여, 제안한 기법의 자원 이용률과 부 사용자의 손실률에 대한 성능이 기존의 가드채널 할당기법과 모바일의 이동성을 예측하지 않은 채널할당기법 보다 우수함을 보인다.

• 한국항행학회논문지
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• 제23권4호
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• pp.322-327
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• 2019

본 논문에서는 셀룰러 인지 라디오 망에서 주 사용자들 (PU; primary user)의 다중 채널상에서 발생하는 스펙트럼 홀 (spectrum hole)을 그룹핑(grouping)하여, 광대역 인지 사용자 (WCRU; wideband cognitive radio user)의 서비스 품질 (QoS; quality of service)을 향상시킬 수 있는 방법을 제안한다. 제안하는 스펙트럼 홀 그룹핑 방법은 같은 시간에 발생하는 스펙트럼 홀들을 위너예측과정으로 예측하고, 예측된 스펙트럼 홀을 그룹핑하여 광대역 인지 사용자를 지원함으로써 인지 사용자의 서비스 품질을 향상시킨다. 시뮬레이션을 통하여 단일 스펙트럼 홀 채널을 이용한 경우와 비교하여 핸드오프 호의 손실률과 초기 발생 호의 차단률을 줄일 수 있음을 보인다.

• KSII Transactions on Internet and Information Systems (TIIS)
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• 제9권3호
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• pp.1074-1086
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• 2015

We Relay-assisted cellular network architecture has been developed to cover cell-edge users and to improve capacity. However, the deployment of relay stations (RSs) in cellular networks may increase the total energy consumption. Though energy efficiency has become a major concern in cellular networks, little work has studied the energy efficiency of relay-assisted cellular networks by sleep scheduling. In this paper, a distributed base stations (BSs) sleep scheduling scheme in relay-assisted cellular networks is proposed. The goal is to maximize the energy efficiency under the spectral efficiency constraint. Firstly, whether the BSs should be sleeping or active is determined by the traffic profile. Then, the transmission powers of the active BSs are optimized within the game-theoretic framework, by using an interior-point method, so as to maximize the energy efficiency. Simulation results demonstrate that the effectiveness of the proposed scheme is superior to that turning on all the BSs without sleep scheduling.

• International Journal of Computer Science & Network Security
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• 제24권2호
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• pp.178-188
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• 2024

In the near future, it is expected that there will be billions of connected devices using fifth generation (5G) network services. The recently available base stations (BSs) need to mitigate their loads without changing and at the least monetary cost. The available spectrum resources are limited and need to be exploited in an efficient way to meet the ever-increasing demand for services. Device to Device communication (D2D) technology will likely help satisfy the rapidly increasing capacity and also effectively offload traffic from the BS by distributing the transmission between D2D users from one side and the cellular users and the BS from the other side. In this paper, we propose to apply D2D overlay communication with cognitive radio capability in 5G networks to exploit unused spectrum resources taking into account the dynamic spectrum access. The performance metrics; throughput and delay are formulated and analyzed for CSMA-based medium access control (MAC) protocol that utilizes a common control channel for device users to negotiate the data channel and address the contention between those users. Device users can exploit the cognitive radio to access the data channels concurrently in the common interference area. Estimating the achievable throughput and delay in D2D communication in 5G networks is not exploited in previous studies using cognitive radio with CSMA-based MAC protocol to address the contention. From performance analysis, applying cognitive radio capability in D2D communication and allocating a common control channel for device users effectively improve the total aggregated network throughput by more than 60% compared to the individual D2D throughput without adding harmful interference to cellular network users. This approach can also reduce the delay.

• 한국항행학회논문지
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• 제21권4호
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• pp.347-352
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• 2017

본 논문에서는 셀룰러 기반 무선 인지망에서 스펙트럼 인지(CR)기술을 이용하여 모바일 사용자의 핸드오버 호의 손실확률을 줄이는 방법을 제안한다. 제안한 방법에서는 모바일이 방문할 셀을 Ziv-Lempel 알고리듬을 이용하여 예측하고, 방문할 셀에 할당된 채널이 부족할 때는 CR기술에 기초한 스펙트럼 홀 자원을 예측하여 모바일 사용자를 지원한다. 스펙트럼 홀 자원의 크기는 신경망기법으로 예측하며, 예측된 스펙트럼 홀 자원은 핸드오버 호가 초기 발생 호 보다 우선하여 사용할 수 있게 한다. 시뮬레이션을 통하여 셀룰러 이동 통신망에 CR기술을 사용함으로써 모바일 사용자의 핸드오버 호 손실확률을 줄일 수 있음을 보인다.

• 대한전자공학회:학술대회논문집
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• 대한전자공학회 2007년도 하계종합학술대회 논문집
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• pp.97-98
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• 2007

In this paper, we investigate the throughput capacity of a multi-hop relay network with cognitive radio (CR) enabled relay stations (RS). We suggested a TDMA/FDMA based frame structure where RSs dynamically select unused channels to communicate with the base station (BS) using CR techniques to analyze the throughput capacity. We developed the throughput capacity model for the proposed system based on utilization factor. The analytical results based on those equations show significant improvement in throughput capacity for CR enabled multi-hop relay system.

• KSII Transactions on Internet and Information Systems (TIIS)
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• 제8권11호
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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.

• 한국통신학회논문지
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• 제34권5A호
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• pp.391-400
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• 2009

최근 이동 통신 네트워크는 2G에서 3G로 이동하고 있으며 주파수의 효율성을 추구하고자 한다. 인지 무선 통신(Cognitive radio) 기술은 secondary 네트워크와 primary 네트워크의 공존을 허용함으로써 주파수의 효율성을 달성할 수 있는 기술로 떠오르고 있다. 하지만, primary 네트워크의 주파수 재사용율을 고려하지 않는 기존 인지무선 통신 방식은 primary 네트워크와 secondary 네트워크를 포함한 전체 네트워크의 성능을 저하시키게 된다. 본 논문에서는 secondary 네트워크가 primary 네트워크의 파일럿 신호를 감지하여 최적의 가용 주파수를 선택하는 복잡도가 낮은 방식을 제안한다. 그리고, primary 네트워크의 간섭을 최소화하는 제약조건을 가지면서 업링크와 다운링크의 용량을 최대화하는 최적화 문제를 고려한다. 시뮬레이션을 통하여 제안방법과 기존방법의 성능을 비교하였으며, 제안방법이 기존방법보다 primary 네트워크의 주파수 재사용율이 작고 채널 사용 변화가 심할 때 특히 우수한 성능을 보임을 확인할 수 있었다.

• 한국군사과학기술학회지
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• 제14권5호
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• pp.833-841
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• 2011

In this paper, we propose uncoordinated dynamic frequency(channel) allocation schemes based on cognitive radio in mobile cellular networks(MCNs). Under the assumptions that mobile base stations are equipped with cognitive radio(CR) function and they construct uncoordinated network, the proposed scheme enables the MCNs by suppression of successive channel switching and management of channel allocation in a dynamic and distributed manner. The proposed scheme is composed of two phase processes. In the first phase, highly orthogonal sequences are generated and assigned to mobile base stations. In the second phase, each mobile base station is allocated a channel according to the pre-assigned orthogonal sequences. Simulation results show that the number of successive spectrum switching is reduced significantly compared with the random switching scheme.

• KSII Transactions on Internet and Information Systems (TIIS)
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• 제16권9호
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• pp.3172-3193
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• 2022

Cognitive radio-simultaneous wireless information and power transfer (CR-SWIPT) has attracted much interest since it can improve both the spectrum and energy efficiency of wireless networks. This paper focuses on the resource sharing between a point-to-point primary system (PRS) and a multiuser multi-antenna cellular cognitive radio system (CRS) containing a large number of cognitive users (CUs). The resource sharing optimization problem is formulated by jointly scheduling CUs and adjusting the transmit power at the cognitive base station (CBS). The effect of accessing CUs' spatial channel correlation on the possible transmit power of the CBS is investigated. Accordingly, we provide a low-complexity suboptimal approach termed the semi-correlated semi-orthogonal user selection (SC-SOUS) algorithm to enhance the spectrum efficiency. In the proposed algorithm, CUs that are highly correlated to the information decoding primary receiver (IPR) and mutually near orthogonal are selected for simultaneous transmission to reduce the interference to the IPR and increase the sum rate of the CRS. We further develop a spatial correlation-based resource sharing (SC-RS) strategy to improve energy sharing performance. CUs nearly orthogonal to the energy harvesting primary receiver (EPR) are chosen as candidates for user selection. Therefore, the EPR can harvest more energy from the CBS so that the energy utilization of the network can improve. Besides, zero-forcing precoding and power control are adopted to eliminate interference within the CRS and meet the transmit power constraints. Simulation results and analysis show that, compared with the existing CU selection methods, the proposed low-complex strategy can enhance both the achievable sum rate of the CRS and the energy sharing capability of the network.