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In the secondary radio limited access (SR-LA) scheme, the secondary radio (SR) is limited to access parts of the frequency bins in order to obtain a tradeoff between the SR dropped probability and SR blocked probability. In this paper, we present the complete expressions of the balance equation and the blocked probability for the SR-LA scheme. Simulations and numerical analysis are conducted to verify...
In cognitive radio networks (CRNs), spectrum sensing data falsification (SSDF) is one of the most typical attack which hugely degrades the detection performance of cooperative spectrum sensing (CSS). SSDF and defense strategies have been an active field of research, but countermeasures of existing researches are sensitive to the number of malicious users (MUs). In this paper, we propose a two-stage...
Recently, researches on mobile cognitive radio network (CRN) has been paid more attention to, involving spectrum sensing, power control and spectrum access, while no schemes considering both the power and spectrum assignment at the same time. In this paper, an efficient resource allocation (RA) scheme is proposed for the orthogonal frequency division multiple access (OFDMA)-based mobile underlay CRN...
This paper aims to investigate the resource allocation problem in a relay-assisted OFDMA cognitive radio (CR) system. Different from conventional CR resource allocation problems, a joint bandwidth and power optimization framework using the bandwidth-power product metric is proposed. Besides, rate requirement of the secondary system is satisfied and interference power at the primary receiver is limited...
In a cognitive radio system, proper configuration of sensing duration enables maximization of the data throughput. However, no existing straightforward formula is available, which is desirable in the mobile context due to tightness of computation time. A set of closed-form approximate formulae of optimal sensing duration for cognitive radio are derived under different signal to noise ratio (SNR)....
The opportunistic spectrum access in cognitive radio networks has always played a key role in improving the performance of secondary users. In this paper, we propose an optimal spectrum access strategy for multi-channel access of secondary users under multiple physical considerations. Firstly we integrate path loss and Nakagami-m fading of primary and secondary links with imperfect spectrum sensing...
Cognitive radio is a promising technology to improve the spectrum utilization by allowing the unlicensed (secondary) user share a frequency bandwidth with the licensed (primary) owner under the condition that no harmful interference is imposed on the licensee. In this paper, we analyze the spatial spectrum utilization efficiency of underlay cognitive radio transmission. In particular, we apply the...
Storaci-Cognitive radio (CR) can improve spectrum utilization by allowing the secondary users to temporarily access the primary user's unutilized licensed spectrum. In fact, the secondary users' delay requirements for data transmission would be not unitary. Some secondary users' communications may be delay-sensitive such as VoIP service while some others may not such as uploading a large file. In...
Cognitive radio networks have recently emerged as an exciting technology to deal with the stringent requirement and scarcity of the radio spectrum. However, the secondary user (SU) usually needs to deal with a fundamental tradeoff between maximizing its own transmission throughput and minimizing the amount of interference caused to the primary user (PU). Accordingly dynamic resource allocation (DRA)...
In this paper, we propose a novel proportional fair scheduling algorithm for MAC-layer sensing in the cognitive radio networks (CRNs). According to the secondary user (SU) channel state information and primary user (PU) traffic patterns, the SUs are adaptively scheduled to carry out sensing and transmission in different channels. Moreover, we jointly consider multiple important design factors in the...
This paper considers cooperative sensing in cognitive networks under Spectrum Sensing Data Falsification attack (SSDF) in which malicious users can intentionally send false sensing information. One effective method to deal with the SSDF attack is the q-out-of-m scheme, where the sensing decision is based on q sensing reports out of m polled nodes. The major limitation with the q-out-of-m scheme is...
Spectrum sensing is one of the critical tasks of the cognitive radio networks. In order to solve the hidden terminal problem, cooperative spectrum sensing has been studied to improve the spectrum sensing performance. In this paper, we study the performance of cooperative spectrum sensing in both AWGN channels and Rayleigh fading channels. In particular, the paper reports results obtained through the...
In cognitive radio systems, secondary users can be coordinated to perform cooperative spectrum sensing to overcome the hidden terminal problem. However, when the number of cooperative users tends to be very large, too many cooperative users will make the whole sensing time intolerantly long and huge consumption of system resource. In this paper, we studied optimal number of secondary users in cooperative...
In cognitive radio systems, cooperative spectrum sensing is employed to detect the presence of primary user quickly and accurately. In this paper, we propose a new TDMA cooperation protocol to improve the overall agility and spectrum efficiency compared to the existing protocols. By allowing the cognitive users operating in the same band to cooperate, the detection time is reduced and thus the average...
Cooperative spectrum sensing can mitigate the effects of shadowing and fading. However, when the number of cognitive users is very large, the bandwidth for reporting their sensing results will be insufficient. In order to eliminate the fail sensing problem for a cognitive radio system with double threshold detector, a new cooperative spectrum sensing algorithm is presented based on reputation in this...
In a cognitive radio network, cooperative spectrum sensing is conducted among the secondary users so as to improve the sensing performance. However, it's not necessary to cooperate all users to perform spectrum sensing while achieve a given error bound. In this paper, we investigate the problem of optimal number of secondary users in cooperative spectrum sensing. Moreover, an efficient and robust...
Spectrum sensing is a critical phase in building a cognitive radio network. However, when the number of cognitive user is very large, the bandwidth for reporting cognitive users' sensing results will be insufficient. In this paper, we propose a new cooperative spectrum sensing algorithm to alleviate the bandwidth problem of reporting channel. Compared with conventional method, only the cognitive users...
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