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The following topics are dealt with: signal processing; cognitive radios and networks; communication systems; network protocols and performance; ad hoc sensor network; telecommunication security; and mobile computing systems and technologies.
In this paper, we analyze the effect of cooperation for spectrum sensing based on relay with equal gain combining in cognitive radio networks. The performance of energy detection in cognitive radio network over a number of cognitive radio users is evaluated. The probability of detection and probability of false alarm are calculated and simulated. We found that when the square of the sum of the gains...
In cognitive radio networks, the process of sensing the potential channels and choosing free ones to access in is called spectrum access. In this paper, three spectrum access schemes are compared. They are sensing-all before accessing scheme, Partially Observable Markov Decision Process (POMDP) based scheme and sequential channel sensing scheme. The efficacy of these schemes is studied by both theoretical...
In this paper, through jointly considering the interference caused to the primary user (PU) from one pair of secondary transceivers, the optimal power allocation is studied for the underlay cognitive two way network. Under the quality of service constraint of the PU transmission, two different objective functions are considered for the SUs to maximize the sum achievable rate or maximize the minimal...
In order to achieve better spectral efficiency, several prototypes have been suggested as physical layer candidates for cognitive radio systems as OFDM (Orthogonal Frequency Division Multiplexing), SRRC (Square Root Raised Cosine) and others. In such models, we are confronted to problems of interference between the cognitive users and licensed users which degrade the performances of using models....
In this paper, we propose a robust pre-coder design method for Cognitive Radio Multi-Input Multi-Output (CR-MIMO) system under the consumption that the channel state information (CSI) estimations are imperfect from secondary base station (SBS) to primary user (PU) and secondary user (SU). Due to the uncertainties of the channel estimation error, both the outage probability of the received SNR of SU...
In cognitive radio (CR), energy detection is a simple and feasible method to get reliable detection results on the presence of primary user (PU) in perfect channel. In imperfect channel, single-threshold cooperative spectrum detection has been proposed to improve energy detection performance, however it is sensitive to noise interference. In order to solve this problem, double-threshold cooperative...
In this paper, we investigate the impact of the asynchronism on the performance of a Cognitive Radio (CR) network, using the underlay paradigm. We are also compareing this effect depending on which modulation technique we are using. We provide a new the theoretical aspect of interference analysis in the context of orthogonal frequency division multiplexing (OFDM) and the Filter Bank Multicarrier (FBMC)...
Spectrum occupancy measurement and analysis is a very important aspect in frequency resource planning by the reason of frequency shortage for the increasing wireless systems. It is also useful in spectrum sensing in the context of cognitive radio, especially in unlicensed band. Given that, a dynamic decision threshold computing method based on SOM Neural Network in spectrum occupancy analysis is proposed...
To design an efficient and effective cognitive radio networks, the related technical aspects and economic aspects need to be considered. This paper addresses the spectrum trading in cognitive radio networks, where there are multiple primary services (sellers), multiple secondary users (buyers) and one agent. In the system, multiple secondary users compete with each other in terms of the spectrum demand...
Cognitive radios have enabled the users to utilize licensed bands opportunistically without causing harmful interference to licensed users. Spectrum analysis is an important technique in cognitive radio networks. And it helps ranking available channels using spectrum sensing results. Appropriate channel assignment decisions will be made according to the ranking results and user requirements. Here...
This Paper Investigates the effect of probability distribution equalization techniques on reducing the PAPR in NCOFDM widely used in Cognitive Radio Systems, and proposes the use of Arithmetic Coding to be used in NCOFDM for PAPR reduction. Simulation results show that the proposed Arithmetic Coding scheme can greatly reduce the PAPR of the NC-OFDM system. Furthermore, the results show that the Arithmetic...
Cognitive radio enabled dynamic spectrum access is a promising solution to alleviate the spectrum low-utilization problem. Secondary users need to sense the bands before transmitting on them to avoid collision with the licensed users. To reduce delay and energy consumption of spectrum sensing, spectrum prediction is incorporated to predict the future usage of channels before spectrum sensing. In this...
In order to exploit both spatial and temporal opportunities more thoroughly, this paper investigates the problem of spatiotemporal spectrum sensing for opportunity-heterogeneous cognitive radio networks, where secondary users located in different locations may experience different spectrum reuse opportunities. While the majority of existing researches focus on either spatial or temporal available...
In this paper, the purpose of the model is to integrate the queueing theory by implementing it through Cognitive Radio, the most recent development of Wireless Communication. In Cognitive Radio the licensed user has a higher priority than unlicensed user and so for transmitting data packets licensed user will be always getting the first opportunity. The Secondary user might detect if there is any...
For cognitive radio (CR), compressed sensing (CS) techniques have been utilized for spectrum sensing in order to alleviate the high signal acquisition costs in the wideband regime. However, the compressed spectrum reconstruction will fail owing to the non-sparsity of the spectrum when the primary (licensed) users (PU or LU) occupy most subchannels. In this paper we study the problem of detecting spectrum...
Differential frequency hopping (DFH) was believed to be an effective FH technique for increasing data rate of FH communication system. Cognitive radio (CR) users can use the CR technology to sense the surrounding RF environment, search for available spectrum resources and access spectrum dynamically. The cognitive radio technology and applied mathematics are introduced in DFH. And the Latin squares...
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