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Distributed Spectrum Sensing for Cognitive Radio Networks by Exploiting Sparsity
"... Abstract—A cooperative approach to the sensing task of wireless cognitive radio (CR) networks is introduced based on a basis expansion model of the power spectral density (PSD) map in space and frequency. Joint estimation of the model parameters enables identification of the (un)used frequency bands ..."
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Abstract—A cooperative approach to the sensing task of wireless cognitive radio (CR) networks is introduced based on a basis expansion model of the power spectral density (PSD) map in space and frequency. Joint estimation of the model parameters enables identification of the (un)used frequency bands at arbitrary locations, and thus facilitates spatial frequency reuse. The novel scheme capitalizes on two forms of sparsity: the first one introduced by the narrow-band nature of transmit-PSDs relative to the broad swaths of usable spectrum; and the second one emerging from sparsely located active radios in the operational space. An estimator of the model coefficients is developed based on the Lasso algorithm to exploit these forms of sparsity and reveal the unknown positions of transmitting CRs. The resultant scheme can be implemented via distributed online iterations, which solve quadratic programs locally (one per radio), and are adaptive to changes in the system. Simulations corroborate that exploiting sparsity in CR sensing reduces spatial and frequency spectrum leakage by 15 dB relative to least-squares (LS) alternatives. Index Terms—Cognitive radios, compressive sampling, cooperative systems, distributed estimation, parallel network processing, sensing, sparse models, spectral analysis. I.
A Survey on Security Threats and Detection Techniques in Cognitive Radio Networks
- issue: 1
"... Abstract—With the rapid proliferation of new technologies and services in the wireless domain, spectrum scarcity has become a major concern. The allocation of the Industrial, Medical and Scientific (ISM) band has enabled the explosion of new technologies (e.g. Wi-Fi) due to its licence-exempt charac ..."
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Abstract—With the rapid proliferation of new technologies and services in the wireless domain, spectrum scarcity has become a major concern. The allocation of the Industrial, Medical and Scientific (ISM) band has enabled the explosion of new technologies (e.g. Wi-Fi) due to its licence-exempt characteristic. The widespread adoption of Wi-Fi technology, combined with the rapid penetration of smart phones running popular user services (e.g. social online networks) has overcrowded substantially the ISM band. On the other hand, according to a number of recent reports, several parts of the static allocated licensed bands are under-utilized. This has brought up the idea of the opportunistic use of these bands through the, so-called, cognitive radios and cognitive radio networks. Cognitive radios have enabled the opportunity to transmit in several licensed bands without causing harmful interference to licensed users. Along with the realization
C Tellambura, Moment-based parameter estimation and blind spectrum sensing for quadrature amplitude modulation
- IEEE Trans Commun
, 2011
"... Abstract—Knowing accurate noise variance and signal power is crucial to most spectrum-sensing algorithms such as energy detection, matched filter detection, and cyclostationary detection. In this paper, we consider a practical scenario when these two parameters are unknown and are needed to be estim ..."
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Abstract—Knowing accurate noise variance and signal power is crucial to most spectrum-sensing algorithms such as energy detection, matched filter detection, and cyclostationary detection. In this paper, we consider a practical scenario when these two parameters are unknown and are needed to be estimated before the spectrum sensing. This task is non-trivial without knowing the status of the primary user, and we categorize the related spectrum sensing as a blind one. We develop the estimation algorithms for unknown parameters by exploiting the signal constellation of the primary user. Three different parameter estimators that do not require any training are then proposed based on the moments of the received signals. Since the secondary user may not know the primary user’s signal constellation, we develop a robust approach that approximates a finite quadrature amplitude modulation (QAM) constellation by a continuous uniform distribution. We also derive the modified Cramér-Rao bound (CRB) for noise variance estimation. Then the optimal moment pair is found from minimizing the mean squared error (MSE) of the signal-to-noise ratio (SNR). The method of choosing the spectrum sensing threshold by taking into consideration the estimation error is also discussed. Index Terms—Blind spectrum sensing, cognitive radio, noise variance estimation, SNR estimation. I.
Adaptive Communication Techniques for the Internet of Things
, 2013
"... The vision for the Internet of Things (IoT) demands that material objects acquire communications and computation capabilities and become able to automatically identify themselves through standard protocols and open systems, using the Internet as their foundation. Yet, several challenges still must ..."
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The vision for the Internet of Things (IoT) demands that material objects acquire communications and computation capabilities and become able to automatically identify themselves through standard protocols and open systems, using the Internet as their foundation. Yet, several challenges still must be addressed for this vision to become a reality. A core ingredient in such development is the ability of heterogeneous devices to communicate adaptively so as to make the best of limited spectrum availability and cope with competition which is inevitable as more and more objects connect to the system. This survey provides an overview of current developments in this area, placing emphasis on wireless sensor networks that can provide IoT capabilities for material objects and techniques that can be used in the context of systems employing low-power versions of the Internet Protocol (IP) stack. The survey introduces a conceptual model that facilitates the identification of opportunities for adaptation in each layer of the network stack. After a detailed discussion of specific approaches applicable to particular layers, we consider how sharing information across layers can facilitate further adaptation. We conclude with a discussion of future research directions.
Collaborative spectrum sensing optimisation algorithms for cognitive radio networks
- Article ID 424036
"... Copyright © 2010 Kamran Arshad et al. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. The main challenge for a cognitive radio is to ..."
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Copyright © 2010 Kamran Arshad et al. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. The main challenge for a cognitive radio is to detect the existence of primary users reliably in order to minimise the interference to licensed communications. Hence, spectrum sensing is a most important requirement of a cognitive radio. However, due to the channel uncertainties, local observations are not reliable and collaboration among users is required. Selection of fusion rule at a common receiver has a direct impact on the overall spectrum sensing performance. In this paper, optimisation of collaborative spectrum sensing in terms of optimum decision fusion is studied for hard and soft decision combining. It is concluded that for optimum fusion, the fusion centre must incorporate signal-to-noise ratio values of cognitive users and the channel conditions. A genetic algorithm-based weighted optimisation strategy is presented for the case of soft decision combining. Numerical results
Distributed Control of Multiple Cognitive Radio Overlay for Primary Queue Stability
"... Abstract—In this paper, we investigate distributed control of multiple secondary users attempting to access the channel of a high priority primary user. Our aim is to maximize the sum cognitive (secondary) user throughput under the constraint of primary user’s queue stability. We consider the effect ..."
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Abstract—In this paper, we investigate distributed control of multiple secondary users attempting to access the channel of a high priority primary user. Our aim is to maximize the sum cognitive (secondary) user throughput under the constraint of primary user’s queue stability. We consider the effect of primary user link adaptation that allows the primary transmitter (PTx) to adapt its transmission rate in response to the secondary interference-level at the primary receiver (PRx). To control the sum secondary interference to PRx beyond the traditional collision-avoidance paradigm, we propose a novel power-control algorithm for secondary nodes to function. To develop such a distributed algorithm and to improve secondary user adapt-ability, we allow secondary nodes to monitor primary’s radio link control information on the feedback channel. We present practical schemes that approximate the optimum solution without relying on global channel information at each secondary node. Index Terms—Wireless networks, cognitive radios, multiple access control, wireless sensor networks, Lyapunov optimization. I.
Distributed
"... Abstract In the last decade, the usage of portable communication devices has continued to increase. Autonomic Communications (AC) represents a new frontier for mobile communications because they will allow autonomous and self-regulated network and communication protocols procedures. Dynamic observat ..."
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Abstract In the last decade, the usage of portable communication devices has continued to increase. Autonomic Communications (AC) represents a new frontier for mobile communications because they will allow autonomous and self-regulated network and communication protocols procedures. Dynamic observation of the spectrum and adaptive reactions of the autonomic terminal to wireless channel conditions are hence important problems in improving the spectrum efficiency as well as in allowing a complete access to the network wherever and whenever the user needs them. Cognitive Radio probably represents the most suitable paradigm for building communication terminals/devices for AC. In this chapter, after a tutorial overview of the current State of the Art on Cognitive Radio visions and on stand-alone and cooperative/distributed approaches to spectrum sensing, the general problem of spectrum sensing will be addressed. Then a new vision, based on Embodied Cognition will be presented together with a Distributed Spectrum Sensing algorithm that is formalized within the embodied framework. Results will illustrate the effectiveness of the proposed method.
A SURVEY REPORT ON SPECTRUM SENSING TECHNIQUES IN COGNITIVE RADIO
"... A software Radio which exploits unused spectrum spaces without causing much interference to licensed spectrum users and thus optimising the use of available radio frequency is, by its virtue of its intelligence, called Cognitive Radio. By judging the current trends in wireless technologies it can be ..."
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A software Radio which exploits unused spectrum spaces without causing much interference to licensed spectrum users and thus optimising the use of available radio frequency is, by its virtue of its intelligence, called Cognitive Radio. By judging the current trends in wireless technologies it can be predicted that Cognitive Radio will be a critical part of many future radio systems and networks. Cognitive Radio uses any of the three techniques – Spectrum Sensing, Spectrum Database and Cognitive Pilot Channel to acquire information about spectrum usage. Spectrum Sensing is the inherent ability of Cognitive Radio to autonomously perform required calculations and detect unused spectrum which can be used for a multitude of purposes. Due to its advantages many studies have been focussed to improve and implement Spectrum Sensing effectively in Cognitive Radio and this lead to development of many spectrum sensing schemes. This paper provides an insight into various Spectrum Sensing technologies and also analyses the advantages and drawbacks of each.
PRACTICAL IMPLEMENTATION OF A COGNITIVE RADIO SYSTEM FOR DYNAMIC SPECTRUM ACCESS
, 2008
"... by Alice Crohas Cognitive radio for dynamic spectrum access enables opportunistic use of the radio-frequency (RF) spectrum, allowing unlicensed users to utilize licensed bands under the condition that they interfere as little as possible with the licensees. A cognitive radio transmits on bands detec ..."
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by Alice Crohas Cognitive radio for dynamic spectrum access enables opportunistic use of the radio-frequency (RF) spectrum, allowing unlicensed users to utilize licensed bands under the condition that they interfere as little as possible with the licensees. A cognitive radio transmits on bands detected as being free, leaving them whenever a primary user is sensed. This work focuses on the practical implementation of a cognitive radio for dynamic spectrum access. A power detector is chosen to sense the spectrum. The Receiver Operating Characteristic (ROC) of the detector is obtained experimentally. After sensing, the cognitive radio will transmit on one of the free channels. Detection and transmission are implemented in parallel at the cognitive transmitter. There is a tradeoff between transmission rate of the cognitive radio and interference created to the licensed user. This thesis also presents the implementation of a cognitive receiver, the coun-
