• KSII Transactions on Internet and Information Systems (TIIS)
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• 제9권1호
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• pp.149-168
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• 2015

In cognitive radio networks (CRNs), hybrid overlay and underlay sharing transmission mode is an effective technique for improving the efficiency of radio spectrum. Unlike existing works in the literature, where only one secondary user (SU) uses overlay and underlay modes, the different transmission modes should be allocated to different SUs, according to their different quality of services (QoS), to achieve the maximal efficiency of radio spectrum. However, hybrid sharing mode allocation for heterogeneous services is still a challenge in CRNs. In this paper, we propose a new resource allocation method for hybrid sharing transmission mode of overlay and underlay (HySOU), to achieve more potential resources for SUs to access the spectrum without interfering with the primary users. We formulate the HySOU resource allocation as a mixed-integer programming problem to optimize the total system throughput, satisfying heterogeneous QoS. To decrease the algorithm complexity, we divide the problem into two sub-problems: subchannel allocation and power allocation. Cutset is used to achieve the optimal subchannel allocation, and the optimal power allocation is obtained by Lagrangian dual function decomposition and subgradient algorithm. Simulation results show that the proposed algorithm further improves spectrum utilization with a simultaneous fairness guarantee, and the achieved HySOU diversity gain is a satisfactory improvement.

• 한국콘텐츠학회지
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• 제13권1호
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• pp.36-42
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• 2015

• 한국IT서비스학회지
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• 제13권4호
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• pp.109-122
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• 2014

Demand of spectrum resource is tremendously increasing recently and this trend will continues in the future due to the wide spread of IT services based on cloud computing and Internet of Things technology and as well as smart devices. Recently, spectrum sharing technology has drawn attention to the spectrum policy makers as a promising way to overcome the shortage problem of scarce spectrum resource. To succeed in commercialization of spectrum sharing technology, it is necessary to prospect the future business ecosystem of spectrum sharing and develop appropriate policies and laws at the same time along with the advance of spectrum sharing technology. The purpose of this paper is to analyze casual relationships between enablers in future business ecosystem of spectrum sharing and propose policies to vitalize spectrum sharing ecosystem based on a system dynamics causal map proposed in the previous research. With the causal map and system dynamics method, it is possible to analyze feedback loops exist in the business ecosystem of spectrum sharing and build policies which optimize positive dynamics in business ecosystem of spectrum sharing. As a result, policy leverages were found in four areas; spectrum supply, spectrum demand, spectrum quality and technology, and spectrum transaction cost. For those policy leverages, 13 policies were identified and intervention timing for each policy was discussed. Finally, the promotion policies of government and market participants to vitalize spectrum sharing ecosystem were discussed.

• 한국항행학회논문지
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• 제26권4호
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• pp.219-225
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• 2022

본 논문에서는 다중 클래스 인지 라디오 망에서 2차 사용자(SU:secondary user)의 서비스 품질 향상을 위해 RA(restricted access) 기반 동적 스펙트럼 홀 그룹핑에 의한 연결 수락 제어 기법을 제안한다. RA기반 동적 스펙트럼 홀 그룹핑은 본 논문에서 제시한 SU의 다중 클래스 서비스를 위한 일렬 스펙트럼 공유 구조를 사용한다. 다중 서비스 2차 사용자는 실시간 사용자와 비실시간 사용자의 클래스로 구분하고 실시간 사용자에게 자원 사용 우선권을 부여한다. 실시간 사용자가 요구하는 자원의 양은 위너 예측 기법과 RA기반 동적 스펙트럼 홀 그룹핑으로 요구량을 지원하고, 비실시간 사용자에 대해서는 예측 없이 유용한 나머지 홀 자원을 RA기반 동적 그룹핑하여 지원한다. 시뮬레이션을 통하여 2차 사용자의 다중 클래스 연결의 트래픽 특성에 따라 제안된 RA기반 동적 스펙트럼 홀 그룹핑에 의한 연결 수락 제어의 성능을 SU연결의 차단율(손실률)과 자원 이용률에서 비교하고, 다중 클래스 2차 사용자의 원하는 서비스 품질을 만족 시킬 수 있음을 보인다.

• KSII Transactions on Internet and Information Systems (TIIS)
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• 제7권12호
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• pp.2957-2986
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• 2013

The traditional approach of fixed spectrum allocation to licensed networks has resulted in spectrum underutilisation. Cognitive radio technology is envisioned as a promising solution that can be used to resolve the ineffectiveness of the fixed spectrum allocation policy by accessing the underutilised spectrum of existing technologies opportunistically. The implementation of cognitive radio networks (CRNs) faces distinct challenges due to the fact that two systems (i.e., cognitive radio (CR) and primary users (PUs)) with conflicting interests interact with each other. Specially, in self-organised systems such as ad-hoc CRNs (AHCRNs), the coordination of spectrum access introduces challenges to researchers due to rapid utilisation changes in the available spectrum, as well as the multi-hop nature of ad-hoc networks, which creates additional challenges in the analysis of resource allocation (e.g., power control, channel and rate allocation). Instead, game theory has been adopted as a powerful mathematical tool in analysing and modelling the interaction processes of AHCRNs. In this survey, we first review the most fundamental concepts and architectures of CRNs and AHCRNs. We then introduce the concepts of game theory, utility function, Nash equilibrium and pricing techniques. Finally, we survey the recent literature on the game theoretic analysis of AHCRNs, highlighting its applicability to the physical layer PHY, the MAC layer and the network layer.

• KSII Transactions on Internet and Information Systems (TIIS)
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• 제12권4호
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• pp.1638-1654
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• 2018

The heterogeneous network (HetNet) has been one of the key technologies in Long Term Evolution-Advanced (LTE-A) with growing capacity and coverage demands. However, the introduction of femtocells has brought serious co-layer interference and cross-layer interference, which has been a major factor affecting system throughput. It is generally acknowledged that the resource allocation has significant impact on suppressing interference and improving the system performance. In this paper, we propose a hybrid-clustering algorithm based on the $Mat{\acute{e}}rn$ hard-core process (MHP) to restrain two kinds of co-channel interference in the HetNet. As the impracticality of the hexagonal grid model and the homogeneous Poisson point process model whose points distribute completely randomly to establish the system model. The HetNet model based on the MHP is adopted to satisfy the negative correlation distribution of base stations in this paper. Base on the system model, the spectrum sharing problem with restricted spectrum resources is further analyzed. On the basis of location information and the interference relation of base stations, a hybrid clustering method, which takes into accounts the fairness of two types of base stations is firstly proposed. Then, auction mechanism is discussed to achieve the spectrum sharing inside each cluster, avoiding the spectrum resource waste. Through combining the clustering theory and auction mechanism, the proposed novel algorithm can be applied to restrain the cross-layer interference and co-layer interference of HetNet, which has a high density of base stations. Simulation results show that spectral efficiency and system throughput increase to a certain degree.

• KSII Transactions on Internet and Information Systems (TIIS)
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• 제7권7호
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• pp.1533-1546
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• 2013

Wireless multicast is considered as an effective transmission mode for the future mobile social contact services supported by Long Time Evolution (LTE). Though wireless multicast has an excellent resource efficiency, its performance suffers deterioration from the channel condition and wireless resource availability. Cognitive Radio (CR) and Device to Device (D2D) are two solutions to provide potential resource. However, resource allocation for cognitive wireless multicast based on D2D is still a great challenge for LTE social networks. In this paper, a joint sub-carriers and power allocation model based on D2D for general cognitive radio multicast (CR-D2D-MC) is proposed for Orthogonal Frequency-Division Multiplexing (OFDM) LTE systems. By opportunistically accessing the licensed spectrum, the maximized capacity for multiple cognitive multicast groups is achieved with the condition of the general scenario of imperfect spectrum sensing, the constrains of interference to primary users (PUs) and an upper-bound power of secondary users (SUs) acting as multicast source nodes. Furthermore, the fairness for multicast groups or unicast terminals is guaranteed by setting a lower-bound number of the subcarriers allocated to cognitive multicast groups. Lagrange duality algorithm is adopted to obtain the optimal solution to the proposed CR-D2D-MC model. The simulation results show that the proposed algorithm improves the performance of cognitive multicast groups and achieves a good balance between capacity and fairness.

• 경영과학
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• 제29권2호
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• pp.65-77
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• 2012

With the explosivley increasing demand in wireless telecommunication service, the shortage of radio spectrum has been worsen. The traditional approach of the current fixed spectrum allocation leads to spectrum underutilization. Recently, CR (Cognitive Radio) technologies are proposed to enhance the spectrum utilization by allocating dynamically radio resources to CR Networks. In this study, we consider a radio resource(power, subcarrier) allocation problem for OFDMA-based CRN in which a base station supports a variety of CUs (CRN Users) while avoiding the radio interference to PRN (Primary Radio Network). The problem is mathematically formulated as a general 0-1 IP problem. The optimal solution method for the IP problem requires an unrealistic execution time due to its complexity. Therefore, we propose an heuristic that gives an approximate solution within a reasonable execution time.

• 한국콘텐츠학회:학술대회논문집
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• 한국콘텐츠학회 2003년도 춘계종합학술대회논문집
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• pp.474-479
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• 2003

본 연구에서는 5㎓대역에 대한 각국의 전파 이용 현황, 주파수 및 국내외 정책동향을 분석하였으며, 각국의 초고속 무선접속 시스템에 대한 기술기준 내용과 5㎓대역의 ISM대역에 대한 주파수분배 내용을 연구하였다. 또한 초고속 무선접속시스템을 추진하기 위한 소요대역폭의 계산, 주파수 공유기법과 주파수의 효율적 이용 방안에 대한 연구를 수행하였다. 본 연구 내용을 바탕으로 5㎓초고속 무선접속시스템을 위한 주파수 확보 방안을 제시하여, 국내 주파수 정책 수립에 필요한 논리적인 근거를 마련함과 동시에 5㎓대역에 대한 주파수 분배 방안을 제시하였다.

• 한국통신학회논문지
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• 제34권9A호
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• pp.697-703
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• 2009

인지무선 통신장치(cognitive radio)는 일반적으로 일차 사용자(primary user)와의 간섭을 피하기 위해 어떠한 일차 사용자도 점유하고 있지 않은 주파수 자원을 활용한다. 그러나 비어있는 주파수 자원을 발견할 수 없을 경우, 인지무선 통신장치는 언더레이(underlay) 형태로 일차 사용자들과 주파수를 공유할 수 있으며, 이 때 스스로의 통신이 일차 사용자들에게 간섭을 미치지 않도록 전송 전력을 조절해야 한다. 본 논문은 셀룰라 네트워크의 상향링크 주파수 자원을 사용하는 언더레이 주파수 공유 방법을 제안한다. 셀룰라 네트워크의 범위 안에 존재하는 한쌍의 인지무선 통신장치들이 단방향 점대점(point-to-point) 통신 링크를 생성할 때 사용할 수 있는 전송 전력의 재한을 계산하고, 계산된 전송 전력을 적용할 수 있는 실용적인 상향 링크 공유 방안을 제시한다. 또한 시뮬레이션을 통해 제안된 상향 링크 공유 방안이 하향 링크 주파수 자원을 공유하는 것에 비해 인지무선 통신장치의 부담(overhead)을 줄일 뿐만 아니라 점대점 통신 링크의 수율(throughput) 성능을 향상시킬 수 있음을 보인다.