• 한국ITS학회 논문지
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• 제9권6호
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• pp.113-119
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• 2010

애드 혹 네트워크를 구성하는 무선기기들은 일반적으로 소출력 기기로서 ISM대역을 사용하였다. 그러나 무선 서비스의 사용률이 급격하게 증가함에 따라 ISM대역의 주파수 부족현상이 나타나게 되었고 주파수 부족현상을 해소하기 위하여 애드 혹 인지무선시스템이 제안되었다. 본 논문은 소출력 무선기기로 구성된 애드 혹 무선인지 시스템에서 전력소모를 줄이면서 효과적으로 유휴주파수를 검출하기 위한 스펙트럼 센싱을 제안하였다. 본 논문에서 면허 사용자와 CR 기기 사이의 무선 채널은 가우시안 (Gaussian) 채널로 모델링 하였으며 모든 CR 기기와 면허 사용자와의 거리는 모두 다르다고 가정하였고, 애드 혹 네트워크를 구성하는 CR 기기간의 채널은 완벽한 (Perfect) 채널이며 거리는 근거리로 가정하였다. CR 기기는 에너지 검출 방식을 사용하여 면허 사용자의 스펙트럼을 센싱하였다. 실험결과 상위 레벨의 에너지 값을가진 CR 기기의 센싱정보를 결합한 센싱방법이 모든 CR 기기의 센싱정보를 결합한 센싱방법에 비하여 높은 스펙트럼 센싱 성능을 나타내었으며, 향후 제안된 스펙트럼 센싱 방법을 통해 저소비전력으로 효과적인 스펙트럼 센싱을 수행하는데 참조 할 수 있다.

• KSII Transactions on Internet and Information Systems (TIIS)
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• 제8권4호
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• pp.1208-1222
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• 2014

Due to the low utilization and scarcity of frequency spectrum in current spectrum allocation methodology, cognitive radio networks (CRNs) have been proposed as a promising method to solve the problem, of which spectrum sensing is an important technology to utilize the precious spectrum resources. In order to protect the primary user from being interfered, most of the related works focus only on the restriction of the missed detection probability, which may causes over-protection of the primary user. Thus the interference probability is defined and the interference-aware sensing model is introduced in this paper. The interference-aware sensing model takes the spatial conditions into consideration, and can further improve the network performance with good spectrum reuse opportunity. Meanwhile, as so many fading factors affect the spectrum channel, errors are inevitably exist in the reporting channel in cooperative sensing, which is improper to be ignored. Motivated by the above, in this paper, we study the throughput tradeoff for interference-aware cognitive radio networks over imperfect reporting channel. For the cooperative spectrum sensing, the K-out-of-N fusion rule is used. By jointly optimizing the sensing time and the parameter K value, the maximum throughput can be achieved. Theoretical analysis is given to prove the feasibility of the optimization and computer simulations also shows that the maximum throughput can be achieved when the sensing time and the parameter of K value are both optimized.

• 정보과학회 논문지
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• 제43권1호
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• pp.119-125
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• 2016

인지 무선 기술은 보조 사용자가 (SUs) 주 사용자 (PUs)에 간섭을 주지 않고 기회주의적 방식으로 라이선스 스펙트럼을 사용할 수 있는 기술이다. 인지 라디오의 핵심 기술은 스펙트럼 센싱이다. 그러나 인지 무선 센서 네트워크에서 에너지 효율적인 스펙트럼 센싱 기법에 대한 연구는 많지 않다. 본 논문에서는 클러스터 기반의 인지 무선 센서 네트워크를 위한 에너지 효율적인 협력 스펙트럼 센싱 노드 선택 기법을 제안한다. 제안하는 기법에서, 허위 경보 확률 및 에너지 소비를 최적화하기 위하여 클러스터 내 스펙트럼 센싱 노드들의 수를 최소화하게 된다. 시뮬레이션 결과를 통하여 본 논문에서 제안한 최적의 스펙트럼 센싱 노드 수를 적용하므로 스펙트럼 센싱 효율성이 향상되었고, 또한 네트워크의 에너지 효율성도 보장된 것을 검증하였다.

• KSII Transactions on Internet and Information Systems (TIIS)
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• 제7권5호
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• pp.1131-1145
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• 2013

Energy detection is a widely used method for spectrum sensing in cognitive radios due to its simplicity and accuracy. However, it is severely affected by the noise uncertainty. To solve this problem, a blind multiband spectrum sensing scheme which is robust to noise uncertainty is proposed in this paper. The proposed scheme performs spectrum sensing over the total frequency channels simultaneously rather than a single channel each time. To improve the detection performance, the proposal jointly utilizes the likelihood function combined with Gerschgorin radii of unitary transformed covariance matrix. Unlike the conventional sensing methods, our scheme does not need any prior knowledge of noise power or PU signals, and thus is suitable for blind spectrum sensing. In addition, no subjective decision threshold setting is required in our scheme, making it robust to noise uncertainty. Finally, numerical results based on the probability of detection and false alarm versus SNR or the number of samples are presented to validate the performance of the proposed scheme.

• KSII Transactions on Internet and Information Systems (TIIS)
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• 제4권6호
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• pp.1042-1062
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• 2010

Cooperative spectrum sensing (CSS) is an effective technology for alleviating the unreliability of local spectrum sensing due to fading/shadowing effects. Unlike most existing solutions, this paper considers the use of CSS technology in decentralized networks where a fusion center is not available. In such a decentralized network, some attackers may sneak into the ranks of cooperative users. On the basis of recent advances in bio-inspired consensus algorithms, an attack-proof, decentralized CSS scheme is proposed in which all secondary users can maintain cooperative sensing by exchanging information locally instead of requiring centralized control or data fusion. Users no longer need any prior knowledge of the network. To counter three potential categories of spectrum sensing data falsification (SSDF) attacks, some anti-attack strategies are applied to the iterative process of information exchange. This enables most authentic users to exclude potentially malicious users from their neighborhood. As represented by simulation results, the proposed scheme can generally ensure that most authentic users reach a consensus within the given number of iterations, and it also demonstrates much better robustness against different SSDF attacks than several existing schemes.

• Journal of electromagnetic engineering and science
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• 제9권4호
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• pp.194-201
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• 2009

In this paper, a new spectrum sensing method based on energy detection is proposed and analyzed in a cognitive radio(CR) system. We employ a delay diversity receiver for sensing the primary user's spectrum with reasonable cost and complexity. Conventional CR with the receiver equipping multiple antennas requires additional hardware and space for installing multiple antennas in accordance with increase in the number of antennas. If the number of antennas increases, detection probability as well as hardware complexity and cost rise. Then, it is difficult to make a primary user detector practically. Therefore, we adopt a delay diversity receiver for solving problems of the conventional spectrum detector utilizing multiple antennas. We derive analytical expressions for the spectrum sensing performance of the proposed system. From the simulation results, it is demonstrated that the primary user detector with the delay diversity receiver has almost half the complexity and shows similar or improved performance as compared with that employing multiple antennas. Therefore, the proposed spectrum sensing structure can be a practical solution for enhancing the detection capacity in CR system operations. The results of this paper can be applied to legacy CR systems with simple modifications.

• KSII Transactions on Internet and Information Systems (TIIS)
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• 제11권3호
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• pp.1319-1335
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• 2017

This paper proposes an opportunistic reporting-based sensing-reporting-throughput optimization scheme that maximizes the spectral efficiency of secondary users (SUs) in cooperative cognitive radio networks with a soft combining rule. The performance of cooperative spectrum sensing depends on the sensing time, the reporting time of transmitting sensing results, and the fusion scheme. While longer sensing time and reporting time improve the sensing performance, this shortens the allowable data transmission time, which in turn degrades the spectral efficiency of SUs. The proposed scheme adopts an opportunistic reporting scheme to restrain the reporting overhead and it jointly controls the sensing-reporting overhead in order to increase the spectral efficiency of SUs. We show that there is a trade-off between the spectral efficiency of SUs and the overheads of cooperative spectrum sensing. The numerical results demonstrate that the proposed scheme significantly outperforms the conventional sensing-throughput optimization schemes when there are many SUs. Moreover, the numerical results show that the sensing-reporting time should be jointly optimized in order to maximize the spectral efficiency of SUs.

• 디지털산업정보학회논문지
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• 제7권3호
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• pp.75-83
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• 2011

Cognitive radio (CR) technology is to maximize the spectrum utilization by allocating the unused spectrums to the unlicensed users. This technology enables the sharing of channels among secondary (unlicensed) and primary (licensed) users on a non-interference basis after sensing the vacant channel and as a result, it is possible to harness wireless frequency more efficiently. To enhance the accuracy of sensing, RDSS was suggested. It is a fusion mechanism based on the reputation of sensing nodes and WSPRT (weighted sequential probability ratio test). However, in RDSS, the execution number of WSPRT could increase according to the order of inputted sensing values, and the fast defense against the forged values is difficult. In this paper, we propose a transaction signing-based authentication scheme for secure distributed spectrum sensing to response the forged values. The validity of proposed scheme is provided by BAN logic.

• Journal of Communications and Networks
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• 제15권5호
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• pp.514-526
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• 2013

With a long sensing period, the inter-frame spectrum sensing in IEEE 802.22 standard is vulnerable to the effect of the traffic of the primary user (PU). In this article, we address the two degrading factors that affect the inter-frame sensing performance with respect to the random arrival/leaving of the PU traffic. They are the noise-only samples under the random arrival traffic, and the PU-signal-contained samples under the random leaving traffic. We propose the model in which the intra-frame sensing cooperates with the inter-frame one, and the inter-frame sensing uses the time-of-arrival (ToA), and time-of-leave (ToL) detectors to reduce the two degrading factors in the inter-frame sensing time. These ToA and ToL detectors are used to search for the sample which contains either the ToA or ToL of the PU traffic, respectively, which allows the partial cancelation of the unnecessary samples. At the final stage, the remaining samples are input into a primary user detector, which is based on the energy detection scheme, to determine the status of PU traffic in the inter-frame sensing time. The analysis and the simulation results show that the proposed scheme enhances the spectrum-sensing performance compared to the conventional counter-part.

• 한국통신학회논문지
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• 제39A권1호
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• pp.19-27
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• 2014

최근 주파수 자원의 중요성이 부각됨에 따라 이미 할당된 주파수 대역을 재사용하여 주파수 이용 효율을 향상시키는 인지 무선 기술(Cognitive Radio, CR)에 대한 연구가 활발히 이루어지고 있다. CR은 주파수 대역의 사용현황에 따라 기회적으로 사용자가 주파수 대역을 이용하므로 이를 위한 정보를 얻는 센싱 단계가 성능에 중요한 영향을 미친다. 따라서 센싱 성능을 향상시키는 것은 CR에서의 중요 이슈가 되며 이를 위해 다수의 단말이 협력하여 1차 사용자의 스펙트럼 점유 여부를 검출하는 협력 스펙트럼 센싱이 고려되고 있다. 본 논문에서는 협력 스펙트럼 센싱 환경에서 각 사용자의 센싱 정보가 융합 센터(Fusion Center, FC)로 보고되는 채널의 오류 확률을 고려하는 OR 규칙 기반의 협력 스펙트럼 센싱 기법을 제안한다. 제안 기법은 보고 오류 확률을 통해 협력 센싱에 참여하는 사용자 수를 제한함으로써 기존 기법에서 나타나는 오경보 확률의 제한을 완화시킨다.