• KSII Transactions on Internet and Information Systems (TIIS)
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• 제10권12호
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• pp.5249-5267
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• 2016

Cognitive radio is an efficient technique to improve spectrum efficiency and relieve the pressure of spectrum resources. In this paper, we investigate the spectrum sensing period in cooperative relay cognitive radio networks; analyze the relationship between the available capacity and the signal-to-noise ratio of the received signal of second users, the target probability of detection and the active probability of primary users. Finally, we derive the closed form expression of the optimal spectrum sensing period in terms of maximum throughput. We simulate the probability of false alarm and available capacity of cognitive radio networks and compare optimal spectrum sensing period scheme with fixed sensing period one in these performance. Simulation results show that the optimal sensing period makes the cognitive networks achieve the higher throughput and better spectrum sensing performance than the fixed sensing period does. Cooperative relay cognitive radio networks with optimal spectrum sensing period can achieve the high capacity and steady probability of false alarm in different target probability of detection. It provides a valuable reference for choosing the optimal spectrum sensing period in cooperative relay cognitive radio networks.

• KSII Transactions on Internet and Information Systems (TIIS)
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• 제8권2호
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• pp.355-370
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• 2014

Cooperative spectrum sensing has been considered as a promising approach to improve the sensing performance in distributed cognitive radio networks. However, there may exist some selfish secondary users (SUs) who are unwilling to cooperate. The presence of selfish SUs could cause catastrophic damage to the performance of cooperative spectrum sensing. Following the social perspective, we propose a Social Tie-based Incentive Scheme (STIS) to deal with the selfish problem for cooperative spectrum sensing in distributed cognitive radio networks. This scheme inspires SUs to contribute sensing information for the SUs who have social tie but not others, and such willingness varies with the strength of social tie value. The evaluation of each SU's social tie derives from its contribution for others. Finally, simulation results validate the effectiveness of the proposed scheme.

• KSII Transactions on Internet and Information Systems (TIIS)
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• 제4권3호
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• pp.289-304
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• 2010

This paper proposes a novel scheme for cooperative spectrum sensing on distributed cognitive radio networks. A fuzzy logic rule - based inference system is proposed to estimate the presence possibility of the licensed user's signal based on the observed energy at each cognitive radio terminal. The estimated results are aggregated to make the final sensing decision at the fusion center. Simulation results show that significant improvement of the spectrum sensing accuracy is achieved by our schemes.

• Journal of information and communication convergence engineering
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• 제11권4호
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• pp.223-228
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• 2013

Cognitive radio has been recently considered a promising technology to improve spectrum utilization by enabling secondary access to licensed bands that are not used by primary users temporarily or spatially. A prerequisite to this secondary access is the lack of interference to the primary system. This requirement makes spectrum sensing a key process for cognitive radio. In this study, we consider amplify and forward (AF)-based cooperative spectrum sensing for cognitive radio networks where multiple relay nodes are utilized to amplify and forward the primary user signal for better spectrum sensing, and maximum ratio combining is used for fusion detection by a cognitive coordinator. Further, the detection probability and the bit error rate of AF-based cooperative spectrum sensing are analyzed in fading multiple cognitive relay channels. The simulation results show that the AF-based cooperative spectrum sensing scheme outperforms the conventional scheme.

• International journal of advanced smart convergence
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• 제7권1호
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• pp.15-23
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• 2018

Spectrum allocation is a key operation in cognitive radio networks (CRNs), where secondary users (SUs) are usually selfish - to achieve itself utility maximization. In view of this context, much prior lit literature proposed spectrum allocation base on non-cooperative game models. However, the most of them proposed non-cooperative game models based on complete information of CRNs. In practical, primary users (PUs) in a dynamic wireless environment with noise uncertainty, shadowing, and fading is difficult to attain a complete information about them. In this paper, we propose a non-cooperative game joint hidden markov model scheme for spectrum allocation in CRNs. Firstly, we propose a new hidden markov model for SUs to predict the sensing results of competitors. Then, we introduce the proposed hidden markov model into the non-cooperative game. That is, it predicts the sensing results of competitors before the non-cooperative game. The simulation results show that the proposed scheme improves the energy efficiency of networks and utilization of SUs.

• KSII Transactions on Internet and Information Systems (TIIS)
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• 제6권12호
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• pp.3061-3080
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• 2012

To improve the sensing performance, cooperation among secondary users can be utilized to collect space diversity. In this paper, we focus on the optimization of cooperative spectrum sensing in which multiple cognitive users efficiently cooperate to achieve superior detection accuracy with minimum sensing error probability in multiple cross-over cognitive radio networks. The analysis focuses on two fusion strategies: soft information fusion and hard information fusion. Under soft information fusion, the optimal threshold of the energy detector is derived in both noncooperative single-user and cooperative multiuser sensing scenarios. Under hard information fusion, the optimal randomized rule and the optimal decision threshold are derived according to the rule of minimum sensing error (MSE). MSE rule shows better performance on improving the final false alarm and detection probability simultaneously. By simulations, our proposed strategy optimizes the sensing performance for each cognitive user which is randomly distributed in the multiple cross-over cognitive radio networks.

• KSII Transactions on Internet and Information Systems (TIIS)
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• 제5권11호
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• pp.1976-1996
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• 2011

Cognitive radio (CR) MAC protocol provides access control of unused spectrum resources without causing interference to primary users. To achieve this goal, in this paper a TDMA based cooperative multi-channel cognitive radio MAC (MCR-MAC) protocol is proposed for wireless ad hoc networks to provide reliable protection for primary users by achieving cooperative detection of incumbent system signals around the communication pair. Each CR node maintains transmission opportunity schedules and a list of available channels that is employed in the neighbor discovery period. To avoid possible signal collision between incumbent systems and cognitive radio ad hoc users, we propose a simple but efficient emergency notification message exchanging mechanism between neighbor CR nodes with little overhead. Our simulation results show that the proposed MCR-MAC can greatly reduce interference with primary users and remarkably improve the network throughput.

• Journal of information and communication convergence engineering
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• 제14권1호
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• pp.1-8
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• 2016

Spectrum sensing in cognitive radio networks allows secondary users to sense the unused spectrum without causing interference to primary users. Cognitive radio requires more accurate sensing results from unused portions of the spectrum. Accurate spectrum sensing techniques can reduce the probability of false alarms and misdetection. In this paper, a two-stage spectrum sensing scheme is proposed for cooperative spectrum sensing in cognitive radio networks. In the first stage, spectrum sensing is executed for each secondary user using energy detection based on double adaptive thresholds to determine the spectrum condition. If the energy value lies between two thresholds, a fuzzy logic scheme is applied to determine the channel conditions more accurately. In the second stage, a fusion center combines the results of each secondary user and uses a fuzzy logic scheme for combining all decisions. The simulation results show that the proposed scheme provides increased sensing accuracy by about 20% in some cases.

• 한국항행학회논문지
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• 제12권5호
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• pp.429-436
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• 2008

본 논문에서는 무선인지통신망에서 스펙트럼 센싱을 위한 협업 센싱을 하는 경우에 센싱 시간 및 협업 센싱 단말 수의 최적값들을 결정하는 방식에 대해서 다룬다. 협업 스펙트럼 센싱에서는 전송 중인 CU (Cognitive User) 외에 휴지중인 다른 CU들이 활성화되어 센싱에 참여함으로써 센싱 시간을 줄일 수 있다. 이로 인한 전송 CU의 전송률 이득과 CU들의 센싱으로 인한 에너지 소모간의 관계를 모두 고려하는 혼합 정수 계획법 문제를 풀어서 최적값들을 구할 수 있다.

• Journal of Communications and Networks
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• 제14권6호
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• pp.614-618
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• 2012

Smart grid is widely considered to be a next generation power grid, which will be integrated with information feedback communications.However, smart grid communication technologies are subject to inefficient spectrum allocation problems. Cognitive radio networks can solve the problemof spectrumscarcity by opening the under-utilized licensed bands to secondary users. In this paper, adaptive cognitive radio spectrum sensing and sharing algorithms are developed for smart grid environments. Simulation results are presented to demonstrate the effectiveness of the proposed scheme in comparison with other existing schemes.