• ETRI Journal
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• 제32권2호
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• pp.292-301
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• 2010

Increasing convergence among heterogeneous radio networks is expected to be a key feature of future ubiquitous services. The convergence of radio networks in combination with dynamic spectrum allocation (DSA) could be a beneficial means to solve the growing demand for radio spectrum. DSA might enhance the spectrum utilization of involved radio networks to comply with user requirements for high-quality multimedia services. This paper proposes a simple spectrum allocation algorithm and presents an analytical model of dynamic spectrum resource allocation between two networks using a 4-D Markov chain. We argue that there may exist a break-even point for choosing whether or not to adopt DSA in a system. We point out certain circumstances where DSA is not a viable alternative. We also discuss the performance of DSA against the degree of resource sharing using the proposed analytical model and simulations. The presented analytical model is not restricted to DSA, and can be applied to a general resource sharing study.

• KSII Transactions on Internet and Information Systems (TIIS)
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• 제9권1호
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• pp.34-49
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• 2015

Market means of spectrum trading have been utilized as a vital method of spectrum sharing and access in future cognitive radio system. In this paper, we consider the spectrum trading with multiple primary carrier providers (PCP) leasing the spectrum to multiple secondary carrier providers (SCP) for a short period of time. Several factors including the price of the resource, duration of leasing, and the spectrum quality guides the proposed model. We formulate three trading policies based on the game theory for dynamic spectrum access in a LTE based cognitive radio system (CRS). In the first, we consider utility function based resource sharing (UFRS) without any knowledge of past transaction. In the second policy, each SCP deals with PCP using a non-cooperative resource sharing (NCRS) method which employs optimal strategy based on reinforcement learning. In variation of second policy, third policy adopts a Nash bargaining while incorporating a recommendation entity in resource sharing (RERS). The simulation results suggest overall increase in throughput while maintaining higher spectrum efficiency and fairness.

• 한국콘텐츠학회논문지
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• 제14권9호
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• pp.589-597
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• 2014

전파자원을 이용한 다양한 무선 서비스에 대한 급증하는 수요는 더 많은 주파수 자원의 확보를 요구한다. 그러나 주파수 자원의 희소성과 고대역 주파수 발굴의 어려움을 감안하면, 늘어나는 전파자원의 수요를 충족시킬 수 있는 유일한 방법은 기존 전파자원의 이용 효율을 극대화시키는 것이다. 이러한 상황에서, 전파자원에 대한 초과 수요를 해결하기 위한 다양한 주파수 공유 방안이 최근 활발히 논의되고 있다. 이와 더불어, 주파수 공유의 실효성 검증과 무선시스템의 성과 예측을 위해, 주파수 이용효율 측정의 중요성이 높아지고 있다. 본 연구에서는 전파자원 이용효율의 합리적 측정 방법을 제안한다. 국제전기통신연합(ITU) 권고안을 토대로 전파자원 이용효율의 다양한 측정 방법을 고찰하고, 대기행렬모형을 이용한 전파 자원 이용효율 측정의 대안 모델을 제시한다. 이를 통해, 주파수 공유 시 전파자원의 이용효율이 어느 정도 증대되는지를 합리적으로 예측할 수 있다.

• Journal of Communications and Networks
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• 제14권3호
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• pp.252-256
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• 2012

We consider resource allocation in femto-cell networks to maximize the throughput while minimizing interference to macro-users nearby. This can be achieved by allocating spectrum resource in a cognitive radio way. The proposed resource allocation is performed in two steps; spectrum sensing and resource scheduling. The femto base station detects idle frequency assignments (FAs) free from the occupation by macro-users and then allocates sub-channels in an idle FA to femto-users, effectively managing the interference problem. Finally, the effectiveness of the proposed scheme is verified by computer simulations.

• Journal of Information Technology Applications and Management
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• 제20권4호
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• pp.19-31
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• 2013

There is tremendous increasing demand on spectrum resource which is boosted by spread of cloud computing and M2M telecommunication as well as smart phone and tablet PC. Recently, spectrum sharing technology has drawn attention to the spectrum policy makers as a promising way to overcome limitation 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 prospect future spectrum sharing ecosystem and analyze business ecosystem of spectrum sharing with casual loop map. With the causal map and system dynamics method, it is possible to analyze feedback loops which is not limited to linear thinking and build policies which optimize positive dynamics in business ecosystem of spectrum sharing.

• 한국통신학회논문지
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• 제31권12B호
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• pp.1068-1075
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• 2006

주파수 자원 가치는 무선통신의 발전과 함께 더욱 커지고 있다. 하지만 앞으로 정보화 사회에서는 주파수 자원의 수요가 공급에 비하여 매우 많기 때문에 주파수 부족 현상이 심각하게 대두된다. 따라서 사용되지 않고 있는 주파수 자원을 효율적으로 이용하기 위한 기술로서 최근 각광을 받고 있는 Cognitive Radio 기술이 필요한 시점이다. 본 논문에서는 CR 기반의IEEE 802.22 WRAN 환경에서 효율적인 Dynamic Spectrum Allocation 기법을 제안한다. Spectrum을 좀 더 효율적으로 공유하기 위해 Variable bandwidth, Mobility의 변수를 적용한 Dynamic Spectrum Allocation 기법을 제시하고 시뮬레이션 결과들을 통해 이를 검증하였다.

• Journal of Communications and Networks
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• 제11권4호
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• pp.368-374
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• 2009

This paper focuses on a distributed multiple spectrum pricing scheme to maximize system capacity in next generation multiaccess systems, where multimode user equipments (MUEs) can connect simultaneously to multiple base stations (BSs) with multiple radio access technologies (RATs). The multi-price based scheme provides a distributed decision making for an optimal solution where radio resource allocations are determined by each MUE, unlike most centralized mechanisms where BS controls the whole radio resource. By the proposed optimal solution, MUEs can decide their share of spectrum bands and power allocation according to the spectrum price of each RAT, and at the same time the multiaccess system can achieve maximized total throughput. Numerical analysis shows that the proposed scheme achieves the maximal capacity by distributed resource allocation for the multiaccess system.

• 한국통신학회논문지
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• 제38A권10호
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• pp.898-907
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• 2013

셀룰러 네트워크에서 D2D 통신을 지원하기 위해서는 기존의 셀룰러 통신과 D2D 통신이 셀룰러 자원을 공유하므로 주파수 효율성과 간섭에 대한 고려가 반드시 필요하다. 따라서 D2D 통신을 위한 자원할당은 셀룰러 통신과의 간섭을 최소화하면서 동시에 주파수 재사용에 따른 스펙트럼 이용 효율을 최대화하는 것이 바람직하다. 본 논문에서는 D2D 단말과 기지국이 상호 협력적인 방법으로 D2D 자원을 할당하는 기법을 제안한다. D2D 단말은 스펙트럼 센싱을 통해 셀룰러 단말과 다른 D2D 단말로부터 오는 간섭을 인지하여 최적의 셀룰러 자원을 선택하여 기지국에 보고한다. 기지국은 해당 셀룰러 단말과 D2D 단말이 동일한 자원을 공유하도록 자원할당을 함으로써 간섭의 영향을 최소화한다. 3GPP LTE (Long Term Evolution)-Advanced 환경에서 모의실험을 통해 제안한 자원할당 기법의 성능을 검증한다.

• KSII Transactions on Internet and Information Systems (TIIS)
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• 제9권11호
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• pp.4387-4404
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• 2015

The energy-efficient design of sensing-based spectrum sharing of a multi-input and multi-output (MIMO) cognitive radio (CR) system with imperfect multiple antenna spectrum sensing is investigated in this study. Optimal resource allocation strategies, including sensing time and power allocation schemes, are studied to maximize the energy efficiency (EE) of the secondary base station under the transmit power and interference power constraints. EE problem is formulated as a nonlinear stochastic fractional programming of a nonconvex optimal problem. The EE problem is transformed into its equivalent nonlinear parametric programming and solved by one-dimension search algorithm. To reduce searching complexity, the search range was founded by demonstration. Furthermore, simulation results confirms that an optimal sensing time exists to maximize EE, and shows that EE is affected by the spectrum detection factors and corresponding constraints.

• ETRI Journal
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• 제44권4호
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• pp.531-542
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• 2022

With the increasing demand for unlicensed spectrum, several regulators have been opening up the 6-GHz band for unlicensed use while ensuring compliance with the technical requirement to avoid harmful interference in the existing primary services (PSs). In this paper, we present two methodologies, a channel-based method and a frequency-based method, which are applicable to a frequency coordination system that calculates the permissible transmit power in the channels or frequencies available to a secondary service (SS). In addition, we have demonstrated that the available transmit power of an SS can be maximized by adjusting the power allocation of the assigned resource units under the condition that the channel of the SS is partially overlapped with that of the PS. Based on the analysis results, it is suggested that it would be better to utilize the two methods selectively according to the operating channel conditions of the PS and the SS.