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The fear of spectrum scarcity in licensed bands or the poor coexisting behavior in unlicensed bands demands the exploration of new resource sharing strategies. As a solution, dynamic spectrum access (DSA) is being addressed to allocate already assigned but sparsely used frequency bands to secondary users without causing any significant interference to primary users. It exploits opportunities in temporal...
In this paper we consider the spectrum sensing performance and requirements for detecting legacy users (LU) in cognitive radios (CR) with periodic scanning. The performance and requirements are studied based on the temporal spectral occupancy statistics of the LU and the sensing signal to noise ratio levels in order to achieve a certain level of detection probability. We model the temporal statistics...
More than an adaptive system, the cognitive radio system should be a kind of intelligent system. In the paper, a Q-learning algorithm of the intelligent control theory is adopted to solve the sensing task selection problem among cognitive radio users in the distributed cognitive radio networks. In the proposed scheme, each cognitive radio user selects its sensing task through times of interaction...
Prediction of future spectrum availability of different channels based on history information helps the cognitive radio (CR) switch proactively to the best channel before the appearance of primary user. Most existing proposals of proactive channel access serve as the guidelines of switching channels according to the environmental changes. However, few of them takes account of the drastic cost of channel...
A key enabling functionality in implementing Cognitive Radio is to reliably detect the licensed users. In recent literature, cooperation among spectrum sensing terminals is suggested to offer reliable sensing performance. We consider the problem that the presence of malfunctioning or malicious sensing terminals will severely degrade the performance of cooperative spectrum sensing. In this paper, we...
Spectrum sensing is an important component of cognitive radio technology. Cooperative spectrum sensing is regarded as the most promising method to improve the reliability of spectrum sensing. However, such cooperation also introduces overhead traffic of control signaling and result transmission which consumes more power in battery operated mobile terminals. In this paper, an RLECSS (run-length encoding...
In this paper, sensing algorithms to select the available sub-bands in the cognitive UWB system are proposed; grouped time division sensing technique and decision methods for sub-channel selection. We employ energy detection method for spectrum sensing, which has low complexity in the wide spectrum sensing. Grouped time division sensing technique is proposed to transmit training symbols and to measure...
Conflict-free power allocation for secondary user (SU) in cognitive networks is a challenging problem since the accessible spectrum of the SU is shared with the primary user (PU); the problem becomes to be especially difficult when it is wanted to achieve the maximum network capacity considering the mutual interference between PU and SU. In this paper, specifying the single SU case with multiple PUs,...
Spectrum sensing is the key enabling technology for cognitive radio networks. The main objective of the spectrum sensing is to provide more spectrum access opportunities to cognitive radio (CR) users without interfering with the licensed users. In this paper, we propose a half-voting based twice-cooperative spectrum sensing scheme. Simulation results show that the proposed sensing method can achieve...
Among variant kinds of spectrum sensing strategies in cognitive radio (CR) broadly studied before, cooperative sensing is the most popular one to detect the primary user accurately. This paper proposes a new cooperative spectrum sensing algorithm in which double threshold energy detection will be employed at local decision and different fusion rules will be used at the fusion center. Theoretic analysis...
According to dramatic increase of wireless communication demand, more spectrum resources are needed to support considerable and various wireless services. However, limited spectrum resources are regulatory assigned to licensed user and no interference needs to occur from unlicensed user to licensed user. In this paper, we propose efficient decision rule in order to get better chance to detect the...
Cognitive radio (CR), which is proposed as a technology that utilizes the frequency resources effectively, has studied to relive scarcity of the frequency resources. CR provides opportunistically under-utilize licensed frequency to the secondary user. Spectrum sensing is the most important technology to detect primary user. However, in the wireless channels, according to the effect of fading and shadowing...
Spectrum sensing is a key technology in cognitive radio (CR) and cooperative spectrum sensing is derived due to the effects of channel fading. In this paper, we focus on the optimal number of secondary users in cooperative spectrum sensing to maximize the utility in CR network. By considering both the detection error probability and the resource used by the secondary users in cooperation, we derive...
In cognitive radio, secondary users require fast and accurate spectrum sensing, so that they can dynamically monitor the spectrum and rapidly tune their parameters to utilize the spectrum available, as well as avoid causing interference to primary users. The traditional spectrum sensing methods in a wideband cognitive radio are challenging to implement since they require very high sampling rates at...
Cooperative spectrum sensing enables a Cognitive Radio (CR) networks to reliably detect primary users and avoid causing interference to primary user's communications, and data fusion technique is a key component of it. However, when the number of CR users tends to be large, the bandwidth for reporting their sensing results to the fusion center will be very enormous. In this paper, censoring schemes...
The cooperative operation can improve the sensing performance of cognitive radio networks and reduce the sensing time. Combining multiple cognitive users' local detection results and making accurate judgment is essential to improve cooperative gain. According to uploaded information from cognitive users, hard decision based on the combination of large numbers and soft decision based on the confidence...
Spectrum sensing plays a critical role in cognitive radio technology that has been considered as the key to resolve spectrum shortage in future wireless communications. This paper introduces innovative ideas adopting statistical inference to obtain information at link level and network level of cognitive radio networks, beyond traditional detection and estimation techniques. Based on a novel spectrum...
Spectrum handoff occurs when the primary users appear in the licensed band occupied by the secondary users. Spectrum handoff procedures aim to help the secondary users to vacate the occupied licensed spectrum and find suitable target channel to resume the unfinished transmission. In this paper, we discuss how to select the target channels to minimize the total service time with multiple spectrum handoffs...
In this work, a comparison between the performance of a single antenna and a multiple antenna system which have to identify two similar OFDM signals, is provided. Numerical simulations have shown that multiple antenna systems allow to obtain better performance with respect to single antenna systems with a significant reduction of the observation time, also in multipath environment.
In this paper we describe a new cooperating sensing method using double threshold energy detection technique for cognitive radio. Each secondary cognitive user takes a local decision on spectrum occupancy based on two threshold energy detection and uses 1 bit information to convey its decision to the fusion center that collects decisions from all cooperating users who are able to detect presence or...
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