• 한국통신학회:학술대회논문집
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• 한국통신학회 2006년도 하계종합학술발표회 논문 초록집
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• pp.624-624
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• 2006

• KSII Transactions on Internet and Information Systems (TIIS)
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• 제6권10호
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• pp.2455-2472
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• 2012

Although underlay spectrum sharing has been shown as a promising technique to promote the spectrum utilization in cognitive radio networks (CRNs), it may suffer bad secondary performance due to the strict power constraints imposed at secondary systems and the interference from primary systems. In this paper, we propose a two-phase based cooperative transmission protocol with the interference cancellation (IC) and best-relay selection to improve the secondary performance in underlay models under stringent power constraints while ensuring the primary quality-of-service (QoS). In the proposed protocol, IC is employed at both the secondary relays and the secondary destination, where the IC-based best-relay selection and cooperative relaying schemes are well developed to reduce the interference from primary systems. The closed-form expression of secondary outage probability is derived for the proposed protocol over Rayleigh fading channels. Simulation results show that, with a guaranteed primary outage probability, the proposed protocol can achieve not only lower secondary outage probability but also higher secondary diversity order than the traditional underlay case.

• 한국인터넷방송통신학회논문지
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• 제15권1호
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• pp.105-110
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• 2015

인지 통신 네트워크에서 1차 송신단과 수신단 사이의 신호 대 잡음 비가 높을 경우 1차 네트워크의 수신 품질이 우수함으로 네트워크 간 지속적인 협력을 요구하지 않는다. 그러므로 협력을 필요로 하는 2차 시스템(보조)에게 스펙트럼을 제공하지 않는다. 본 논문에서는 간섭이 존재하지 않을 때 스펙트럼 공유의 빈도를 연구하였다. 또한 인지네트워크의 1차 시스템은 2차 시스템(보조)으로 인해 신호 대 잡음 비가 낮아지게 되며 이로 인한 스펙트럼 공유의 빈도의 증가에 초점을 맞추었다. 모의실험 및 이론적 결과를 바탕으로 기존의 기법에 비해 제안된 기법 스펙트럼 효율향상을 증명한다.

• KSII Transactions on Internet and Information Systems (TIIS)
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• 제9권4호
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• pp.1321-1336
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• 2015

Cooperative spectrum sensing (CSS) for vacant licensed bands is one of the key techniques in cognitive radio networks. However, current CSS schemes focus on ensuring an efficient cooperation among secondary users (SUs), but ignoring their competition. At the same time when several SUs want to a vacant band, how to win this pop vacant band for an SU becomes more and more important. Inspired by the idea that an SU who always behaves well will win a pop vacant band more easily, we propose a competition scheme called BehaveWell (BW) in this paper. By analyzing the main threats against CSS, competitive coefficient is introduced to evaluate each SU's past behaviors in CSS. A higher competitive coefficient is very helpful for an SU to win a pop vacant band. This BW scheme can not only enhance a healthy competition among SUs, but also improve the security of CSS. Simulations verify the effectiveness of the proposed scheme.

• 한국통신학회논문지
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• 제37A권11호
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• pp.943-951
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• 2012

본 논문에서는 비정규 충격성 잡음 환경에서 협력 무선인지 네트워크를 위한 순서 기반 스펙트럼 센싱 기법을 제안한다. 구체적으로는 잡음을 이변수 등방형 대칭 알파 안정 (bivariate isotropic symmetric ${\alpha}$-stable) 분포를 따르는 것으로 모형화하고, 그에 알맞은 관측 샘플의 순서와 일반화된 우도비 검정 기반 협력 스펙트럼 센싱 기법을 제안한다. 모의실험을 통해 비정규 잡음 환경에서 제안한 기법이 기존의 기법에 비해 더 좋은 스펙트럼 센싱성능을 가짐을 보인다.

• 한국통신학회논문지
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• 제32권11C호
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• pp.1095-1101
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• 2007

본 논문에서는 협대역 사용자와 스펙트럼을 공유하는 인지 라디오 시스템에서 협대역 간섭을 회피할 수 있도록 전체 TV 대역의 일부 대역을 가변적으로 사용하는 부분대역모드 기법을 소개한다. 이 때 동기 과정에서 바꿔 부분대역모드에 대한 정보를 얻을 수 있도록 프리앰블을 설계하고 부분대역모드 검출 기법을 포함한 시간 및 주파수 동기 알고리즘을 제안한다. 제안한 부분대역모드 검출 및 동기 성능을 WRAN (Wireless Regional Area Networks) 환경에서 모의 실험한 결과 동기 성능의 저하 없이 부분대역모드를 검출할 수 있음을 보인다.

• KSII Transactions on Internet and Information Systems (TIIS)
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• 제11권3호
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• pp.1336-1356
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• 2017

The spectrum scarcity crisis has resulted in a shortage of resources for many emerging wireless services, and research on dynamic spectrum management has been used to solve this problem. Game theory can allocate resources to users in an economic way through market competition. In this paper, we propose a bidding game-based spectrum allocation mechanism in cognitive radio network. In our framework, primary networks provide heterogeneous wireless service and different numbers of channels, while secondary users have diverse bandwidth demands for transmission. Considering the features of traffic and QoS demands, we design a weighted interference graph-based grouping algorithm to divide users into several groups and construct the non-interference user-set in the first step. In the second step, we propose the dynamic bidding game-based spectrum allocation strategy; we analyze both buyer's and seller's revenue and determine the best allocation strategy. We also prove that our mechanism can achieve balanced pricing schema in competition. Theoretical and simulation results show that our strategy provides a feasible solution to improve spectrum utilization, can maximize overall utility and guarantee users' individual rationality.

• Journal of Communications and Networks
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• 제12권2호
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• pp.158-167
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• 2010

The energy efficiency of wireless infrastructure and terminals has been drawing renewed attention of late, due to their significant environmental cost. Emerging green communication paradigms such as cognitive radios, are also imposing the additional requirement of flexibility. This dual requirement of energy efficiency and flexibility poses new design challenges for implementing radio functional blocks. This paper focuses on the area vs. power trade-offs for the type of channel filters that are required in the digital frontend of a flexible, energy-efficient radio. In traditional CMOS circuits, increased area was traded for reduced dynamic power consumption. With leakage power emerging as the dominant mode of power consumption in nanoscale CMOS, these trade-offs must be revisited due to the strong correlation between area and leakage power. The current work discusses how the increased timing slacks obtained by increasing the parallelism can be exploited for overall power reduction even in nanoscale circuits. In this context the paper introduces the notion of 'area efficiency' and a metric for evaluating it. The proposed metric has also been used to compare the area efficiencies of different classes of time-shared filters.

• 한국정보과학회:학술대회논문집
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• 한국정보과학회 2012년도 한국컴퓨터종합학술대회논문집 Vol.39 No.1(B)
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• pp.72-74
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• 2012

본 논문은 미래 군에서 CR (Cognitive Radio) 기술을 적용한 전투무선망에서의 효율적인 주파수 사용을 위한 정책기반 동적 채널 선정 구조를 제안한다. 전투무선망에서는 상용의 기지국과 같은 Coordinator가 존재하지 않기 때문에 효율적인 채널 사용을 위해서 각 상황마다 어떻게 대응할 것인가에 대한 고려사항이 있다. 이에 대한 해결책으로 정책기반의 동적 채널 선택 구조를 제안하며, 이는 각 상황에 따른 규칙이나 행동을 사전에 정책으로 정의하여 특정 Coordinator가 없더라도 해당 상황이 발생하면 사전 정의된 정책에 의해서 동적 채널 선택을 하는 것이다. 즉, 전투무선망에서 작전상황이나 전술통신환경의 변화에 따라 PU (Primary User)나 SU (Secondary User)를 동적으로 할당하는 것을 의미한다. 모의 실험결과 별도의 정책 없이 Random하게 동적 채널을 선택하는 기존기법보다 정책기반의 기법이 월등한 성능향상을 보였다.

• KSII Transactions on Internet and Information Systems (TIIS)
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• 제10권5호
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• pp.2067-2080
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• 2016

Cooperative spectrum sensing (CSS) for vacant licensed bands is one of the key techniques in cognitive radio networks. Currently, sequential probability ratio test scheme (SPRT) is considered as a powerful soft decision approach to improve the sensing result for CSS. However, SPRT assumes all secondary users (SU) are honest, and thus offering opportunities for malicious SUs to launch the spectrum sensing data falsification attack (SSDF attack). To combat such misbehaved behaviors, recent efforts have been made to trust mechanism. In this paper, we argue that powering SPRT with traditional trust mechanism is not enough. Dynamic SSDF attackers can maintain high trust in an alternant process of submitting honest or false sensing data, resulting in difficultly detecting them. Noting that the trust value of dymamic SSDF attackers behave highly volatile, a novel trusted SPRT scheme (VSPRT) based on volatility decay analysis is proposed in this paper to mitigate the harmful effect of dynamic SSDF attackers in the process of the soft-decision data fusion, and thus improving the accuracy of the final sensing result. Simulation results show that the VSPRT scheme outperforms the conventional SPRT schemes.