Presence Of Primary User Research Articles

Hide and Seek: A Markov-Based Defense Strategy Against Off-Sensing Attack in Cognitive Radio Networks

In a cognitive radio-based network (CRN), secondary users (SUs) opportunistically access underutilized spectrum resources and stop utilizing these resources when licensed or primary users (PUs) reappear. However, this way of opportunistic spectrum access is susceptible to novel vulnerabilities. Recently, a new attack, off-sensing (OS), has shed light on a vulnerability in the Federal Communications Commission (FCC) policy of CRN, which affects the channel utilization of the victim SU by creating an illusion of a PU's presence. However, prior work on OS-attack considers a deterministic approach that is unrealistic and is futile to fortify against conventional defense techniques. In this paper, we propose a new random approach, the random-OS attack, which adapts to realistic scenarios and is difficult to detect using conventional techniques. Then, we model the interaction between the victim SU and attackers as a stochastic zero-sum Markov game and propose a novel safeguard approach based on the Markov decision process to defend the proposed attack, namely hide and seek . Finally, we introduce an OS-attack detection strategy, which utilizes the sensing history to detect the presence of attackers without violating any policy or design constraints and without any networking overhead. Mathematical analysis and extensive simulation results exhibit the superior performance of our proposed work and advent a direction in designing safeguard strategies without amending the current FCC policies.

Intelligent and secure transceiver design and implementation for future wireless communication

In this work, we have proposed an intelligent and secure transceiver design and implemented over RF testbed for future wireless communication. To secure the communication, first of all, physical layer security (PLS) has been proposed for underlay multiple-input multiple-output cognitive radio network (MIMO-CRN) by using a bi-directional zero-forcing beamforming. Secondly, (PLS) has been proposed by using transmit beamforming for non-orthogonal multiple access (NOMA) over multiple cells and in the presence of primary user and secondary users. The proposed model has been extended for MIMO-NOMA over double cell and multiple scenarios. To improve further security an adaptive transceiver has been designed where parameter can be varied as per the system requirement and meantime, an intelligent received is developed in which parameter can be estimated through a blind process. The modulation format is also classified for single carrier, orthogonal frequency division multiplexing (OFDM) and MIMO through a statistical method. Finally, sequence design has been proposed to improve peak average power ratio for OFDM and multicarrier code division multiplexing (MC-CDMA). These sequences can also remove multiuse user interference for CDMA system over asynchronous system by improving the correlation properties within a code.

Mixture Detectors for Improved Spectrum Sensing

The energy detector and the sphericity test are two widely used spectrum sensing techniques that utilize different properties of the signal received at the secondary user terminal. In this paper we use meta analysis to combine these two techniques and derive two novel mixture detectors that outperform both techniques. Since the spectrum sensing capability of the energy detector is limited by the uncertain knowledge of the noise power, first, we analyze the performance of the energy detector with estimated noise power. We derive analytical expressions for the false alarm and the detection probabilities when the secondary user terminal is equipped with multiple antennas. Next, we apply meta analysis to combine the outputs of the energy detector and the sphericity test to derive two mixture detectors, namely, Fisher’s method and the weighted $z$ -transform method. Furthermore, we extend our analysis to consider cooperative spectrum sensing where multiple secondary user terminals cooperatively detect the presence of primary users. Based on the mixture detectors, we propose two new cooperative spectrum sensing techniques and derive simple analytical expressions for false alarm probabilities. Extensive numerical examples are used to illustrate the accuracy of our analysis and to highlight the performance gains obtained by the mixture detectors.

RETRACTED ARTICLE: Peak detection based energy detection of a spectrum under rayleigh fading noise environment

Spectrum is a resource inadequate and future licensed spectrum will only be used by spectrum holders. Reuse of licensed spectrum into unlicensed technique is Cognitive radios fresh approach. No previous data is crucial in relation to the uniqueness of the main user signal as energy detection is most commonly used spectrum sensing methods. But this energy detection calculation and assuming the presence of primary user in spectrum based on static threshold is not a simple task. It may leads to loss in the signal coefficients. Hence, in the existing method the threshold selection is adaptive which depends on the noise variance. This method increases the probability of detection i.e. the detection of presence of the primary user in the spectrum, but calculating the energy of all the received symbols may lead to computational complex and high sensing time. Hence in the proposed method, the power of all the symbols collected near the spectrum is optimized using peak detection technique. This optimization method reduces the power caused due to unwanted or noisy data and leads to less power usage. Thus energy detection for this optimized data is simple with less sensing time. The experimental results suggest that this optimization based energy detection would also useful to get 99% of detection of primary user in spectrum at low SNR also.

Development of analytical model for energy detectors with SC and MRC diversity over Inverse‐Gamma fading

SummaryAn ever‐escalating demand for wireless applications has caused great concern for the proper exploitation of the accessible radio spectrum. Cognitive radio materializes as an auspicious remedy to the present‐day crisis of spectral congestion, by detecting the licensed primary user (PU). This is accomplished with the assistance of the spectrum sensing technique, which provides an indication of the presence of PU over the spectrum. Energy detection is one of the prevailing spectrum sensing techniques due to its low implementation complexity. In the present work, the performance of an energy detector (ED) over Inverse‐Gamma (I‐Gamma) fading distribution is examined. Initially, a closed‐form expression of the probability density function for I‐Gamma distribution with maximal ratio combining diversity reception is derived. Following it, an investigation of an ED‐based cognitive radio device is carried out in the form of the average probability of detection (PD) and average area under the receiver operating characteristic curve (AUC). In addition, we also present a performance analysis of an ED with selection combining diversity. Optimization of the detection threshold is also executed alongside the low signal‐to‐noise ratio analysis. In the end, the resulting expression of the PD is exploited to examine the functioning of cooperative spectrum sensing within the erroneous environment. The validation of derived mathematical forms has been confirmed by comparing it with the Monte‐Carlo simulation and exact numerical results.

Analysis of energy harvesting cognitive relay network with cooperative spectrum sensing

In this study, the authors investigate the performance of an energy harvesting cognitive cooperative multiple relays network with spectrum sensing, where secondary user accesses the licensed spectrum according to the spectrum sensing results. Particularly, if the spectrum hole is detected, the secondary nodes harvest energy from the ambient environment, otherwise, the secondary source and relays transmit with the energy collected from the primary signals. Taking the imperfect spectrum sensing results into account, exact closed-form expressions for the total outage probability and capacity of the secondary network are derived under the context of Rayleigh fading channels, where the proposed modified selective cooperative decode-and-forward relaying transmission schemes are adopted. Compared with the conventional cognitive relay network, the authors must undertake the correlations among the received signal-to-noise ratios or signal-to-interference-plus-noise ratios caused by both the presence of primary user's interference and energy harvesting for the system understudy. It is shown that spectrum sensing phase and data transmission phase are mutual influence and mutual restraint.

Design of Wavelet-Encoded Symbol Constellations for Cyclostationary Spectrum Sensing

In mobile communication systems, the signals propagate through multipath over time-varying channels, which are subject to distortion caused by fading and Doppler shifts. In order to minimize such distortions, coding techniques and transmission diversity can be employed, e.g., wavelet coding. In this work, the wavelet coding is investigated in scenarios of cognitive radio systems with dynamic spectrum access. Cognitive radio systems with dynamic spectrum access should be able to sense unoccupied frequency bands for opportunistic transmissions, as well as detect the presence of primary users when they occupy their licensed spectrum. Therefore, an essential element for the accurate operation of cognitive radio systems encoded by wavelet coding is the ability to sense the signals encoded by this technique. It is effectively demonstrated that the possibility of sensing such signals is associated with a suitable design of the signal constellation used in the modulation of the coded symbols. The constellation design of these is performed via genetic algorithms using a multiobjective optimization approach. The developed system is evaluated according to the robustness to time-varying flat fading through a bit error probability (BER) versus Eb/N0 analysis. The spectral sensing ability is also addressed employing the cyclostationary analysis. The results denote the feasibility of using wavelet coding in radio scenarios with dynamic spectrum access, with good performance in terms of BER and signal detection rates.

Adaptive cooperative sensing in cognitive radio networks with ensemble model for primary user detection

SummaryOpportunistic spectrum sharing ability enables higher spectrum utilization in cognitive radio networks. Detecting the presence of primary user in the network is the most important functionality in cognitive radio network as the cognitive users cannot use the spectrum with interference to primary users. Most solutions proposed for primary user detection suffer from hidden terminal problem resulting from multipath fading and shadow effects. The work focus on Rayleigh and Nakagami fading channel with comparable nonfading AWGN channel in cognitive radio. An ensemble model to detect the presence of primary user with high confidence is proposed in this work. The approach is based on training machine learning models with energy vectors in presence and absence of primary users. The trained model is then used to predict the primary user based on the energy vector.

A Hybrid Framework for Spectrum Sharing in Cognitive Radio Systems With Dynamic Users

In this letter, we present a hybrid spectrum sharing approach in cognitive radio (CR) systems with dynamic users in which the secondary users (SU) may not accurately detect the presence of primary users (PU). As a consequence, there is an increased probability of collision between PU and SU transmissions, resulting in interference at the PU receiver. The proposed hybrid framework combines the interweave and underlay spectrum sharing paradigms, and limits interference to the PU through a mathematical expression that provides bounds on the SU power based on its sensing performance. The framework requires that the PU only share this expression and does not require that the PU reveal its waveform or other operating parameters to the SU. An example illustrating the proposed approach is also presented.

Guided joint spectrum sensing and resource allocation using a novel random walk grey wolf optimization for frequency hopping cognitive radio networks

SummaryEffective use of unused licensed spectrum by secondary nodes without causing any harmful interference to the primary users is one of the challenging task, and in this paper, a detailed description of joint spectrum sensing and resource allocation in cognitive radio (CR) networks is discussed. The CR system utility is maximized by joint spectrum sensing and channel resource allocation scheme based on random walk grey wolf optimization (RW‐GWO) algorithm for frequency hopping cognitive radio‐based networks. In this paper, the nodes will sense the presence of primary users in the same channel and move to another channel in the guidance of a guide node (GN) if primary signal is detected in the channel. In order to achieve collision‐free communication, primary signals and secondary signals use the channels strategically and the mechanism is described in this paper. RW‐GWO is used to derive the optimum sensing and data transmission schedules. It selects the sensing nodes to sense the spectrum and other nodes take part in transmitting the data. GNs not only guide the nodes to hop to the next channel if the primary channel is detected, but also distribute the nodes in different available secondary hopping channels. Simulation results show that reliable spectrum sensing and efficient channel allocation can be achieved in our proposed algorithm.

Unilateral left‐tail Anderson Darling test‐based spectrum sensing with Laplacian noise

This paper focuses on spectrum sensing under Laplacian noise. To remit the negative effects caused by heavy-tailed behavior of Laplacian noise, the fractional lower order moments (FLOM) technology is employed to pre-process the received samples before spectrum sensing. Via exploiting the asymmetrical difference between the distribution for the FLOM of received samples in the absence and presence of primary users, we formulate the spectrum sensing problem under Laplacian noise as a unilateral goodness-of-fit (GoF) test problem. Based on this test problem, we propose a new GoF-based detector which is called unilateral left-tail Anderson Darling (ULAD) detector. The analytical expressions for the theoretical performance, in terms of false-alarm and detection probabilities, of the ULAD are derived. Moreover, a closed-form expression for the optimal detection threshold is also derived to minimize the total error rate. Simulation results are provided to validate the theoretical analyses and to demonstrate the superior performance of the proposed detector than others.

Decision‐fusion‐based reliable CSS scheme in CR networks

Cognitive radio (CR) is a rapidly growing technology that can be employed to effectively utilise the radio spectrum. The detection accuracy of the CR user is compromised when a network is under degrading conditions like fading and shadowing effects. Cooperative spectrum sensing (CSS) has been extensively employed to overcome these issues. In CSS, all secondary users communicate with the fusion centre (FC) to share the PU information. Hard fusion schemes are applied to make a correct decision about PU presence at FC; however, such approaches lack reliable decision-making. Hence, there is a need to construct more accurate and reliable fusion schemes. In this study, a neural network (NN)-based decision fusion scheme at FC is used to construct a reliable decision. In the proposed scheme, NN is used as a machine learning tool that is trained using input data and output data to generate the desired fusion model. It has been evaluated through simulation results that the proposed fusion scheme sensing accuracy is much better as compared to conventional fusion schemes and other state-of-the-art schemes proposed in the literature. Further, the proposed fusion scheme is tested using the clustering approach to make it more reliable and accurate.

Distributed Spectrum Sensing for Cognitive Radio Networks Based on the Sphericity Test

We consider spectrum sensing in a cognitive radio network with arbitrary numbers of primary and secondary users. Based on the sphericity test, we first analyze the centralized spectrum sensing where all the data available at the secondary users are combined for the signal detection of primary users. We derive accurate approximations for the false alarm and detection probabilities that are also compared against the approximations already available in the literature. Next, we analyze the distributed spectrum sensing where only partial data from each secondary user are used in the signal detection of primary users. Two novel techniques, namely, the multisample sphericity test and metaanalysis, are proposed and analyzed. Instead of sending all the raw data received at the secondary user terminals, in the multisample sphericity test and metaanalysis, only one or two real numbers are required to be sent to a central processor to make a decision about the presence of primary users. Accurate analytical expressions on the false alarm and detection probabilities are derived, and numerical examples are provided to verify their accuracy. Receiver operating characteristic curves are also presented to compare the performance of the proposed methods.

Improving the lifetime of multichannel cognitive radio sensor networks via new spectrum sensing method

AbstractCognitive Radio Sensor Networks (CRSNs) are wireless sensor networks implemented with cognitive radio capability to provide spectrum resources for sensors in an opportunistic manner. The application of CRSNs can be found in the paradigm of Internet of Things (IoT) where each sensor represents an object in the IoT paradigm. In order to prevent simultaneous transmissions of Primary Users (PUs) and CRSN nodes, sensors should be aware of the presence of PUs. One of the most common methods for making the sensors aware of the presence of PUs is consecutive spectrum sensing. Since the sensors have the duty of both sensing environment and transmitting the results, their battery lives are highly prone to rapid drain. In addition, the lack of effective management of sensor operations for spectrum sensing may lead to short longevity of the network. In this paper, the energy consumption process of sensors in such networks has been analyzed and an energy‐based algorithm is proposed to appropriately select sensors based on their detection probabilities for spectrum sensing. The analytical and numerical results confirm the improved lifetime and performance based on our proposed algorithm in comparison with the conventional ones. Moreover, the computational complexity of the proposed algorithm is significantly lower than that of the existing methods.

Adaptive Link Utilization in Two-Way Spectrum Sharing Relay Systems Under Average Interference-Constraints

In this paper, we investigate the performance of an underlay cognitive two-way relay system with direct link using time division broadcast protocol in the presence of primary user's interference. Herein, relying on the practicability and low complexity of statistical channel state information, the secondary transmissions are in compliance with the fading-averaged interference constraints imposed by the primary receiver. For this setup, we study an adaptive link utilization scheme (ALUS) that can exploit both direct and relay links with appropriate diversity combining methods to improve the performance of secondary users. Based on ALUS, we evaluate and compare the performance of two decode-and-forward based relaying strategies viz., fixed relaying and incremental relaying. We derive the tight closed-form expressions of outage probability of the secondary communications for both the strategies over Nakagami- m fading channels. We further conduct asymptotic high signal-to-interference-plus-noise ratio analysis to examine the achievable diversity order of the considered system. In addition, we quantify the expected spectral efficiency and average transmission time for both relaying strategies. Our results illustrate that the incremental relaying strategy can significantly improve the system performance in comparison with fixed relaying. Numerical and simulation results are provided to attest our theoretical studies.

Implementation of Particle Swarm Optimization Technique for Spectrum Sensing in Cognitive Radio Network

The scarcity of spectrum can be overcome by using the spectrum efficiently and effectively. There is a need for devising techniques that can help in sensing the spectrum judiciously so that the Secondary Users can optimally access the spectrum holes. This will support higher transmission of data, thereby enhancing the throughput. Further, the presence of Primary Users should be detected accurately in order to avoid interference. The sensing-throughput trade-off problem of spectrum sensing stage of cognitive radios can be optimized by means of computational intelligence techniques like swarm intelligence. This paper implements Particle Swarm Optimization technique to optimize Throughput, Probability of false alarm and sensing time under varying Signal-to-Noise Ratio conditions. It has been studied that bigger swarm-size does not improve the results, but takes longer processing time.

Outage analysis for multiuser underlay cognitive TWRN with antenna selection and user scheduling

This paper investigates the outage performance of cellular two-way amplify-and-forward (AF) cooperative spectrum sharing systems in the presence of primary user (PU) network and multiple secondary user (SU) destinations. A general Nakagami-m fading environment has been used, where distinct fading parameters, as well as unequal average fading powers between the interference and relaying links, are assumed. Focusing on the cooperation process among the SU nodes and making use of the underlay cognitive approach, an approximate closed-form expression for the overall outage probability (OOP) of the secondary network is derived. In this analysis, an opportunistic scheduling and transmit antenna selection (TAS) algorithm in the secondary network has been employed. Considering the interference constraints due to the presence of PU receiver, power allocation of secondary user is done. The effects of fading severity, secondary network relay placement, the number of PU & SU transmit antenna, and number of SUs on the end-to-end system performance are examined through some representative numerical plots. Moreover, to minimize the secondary network OOP, we investigate the optimization problems of relay position. Monte Carlo simulation results are presented to corroborate the proposed analysis.

Spectrum sensing with a parallel algorithm for cyclostationary feature extraction

The current static management policy for spectrum allocation has shown to be inefficient when dealing with the increasing demand for wireless communication systems. More recently, opportunistic spectrum access has emerged as a promising alternative that allows non-licensed users to utilize the spectrum if no primary users are detected. Spectrum sensing based on cyclostationary feature detection can be employed to reliably identify the presence of primary users even at low SNR levels. However, the detection of modulated signals at lower SNR levels demands a higher number of analyzed samples. In this paper, we propose an architecture for spectrum sensing that enables the reduction of the computational time needed to obtain cyclostationary features of a signal when using multi-core processors. Simulation results show that the proposed architecture can achieve over 92.8% parallel efficiency, which leads to a reduction of spectrum sensing time by a factor of 29.7.

Performance Analysis of Cognitive Relay Networks With RF Hardware Impairments and CEEs in the Presence of Primary Users’ Interference

In this paper, we analyze the performance of a cognitive decode-and-forward multi-relay network (CDFMRN) with a direct link under the joint impact of transceiver hardware impairments (HIs) and channel estimation errors. We consider a practical scenario in which the secondary nodes are confronted with the interference from multiple primary users. Hereby, we take into account the hardware distortions induced by all the non-ideal secondary nodes and residual interferences originating from imperfect channel estimations. Considering these imperfections, we derive an exact closed-form expression for the outage probability of CDFMRN by employing selection cooperation between direct and relaying links over Nakagami- ${m}$ fading channels. We illustrate that HIs may invoke different ceiling effects into the system, namely relay cooperation ceiling (RCC), direct link ceiling (DLC), and overall system ceiling. Importantly, we show the detrimental impact of these prevailing effects on the system’s performance and eventually provide useful insights into the endurable level of HIs for designing the practical systems with a given rate requirement. We manifest analytically that a potential direct link and a relaying link can partially compensate for the incurred performance losses due to RCC and DLC effects, respectively. Moreover, we investigate the robustness of amplify-and-forward and decode-and-forward relaying schemes against the HIs. Finally, numerical and simulation results are presented to validate our theoretical findings.

Simultaneous cooperative spectrum sensing and wireless power transfer in multi-antenna cognitive radio

In multi-antenna cognitive radio (CR), the sensing performance of detecting the presence of primary user (PU) in fading channel can be improved through multi-antenna cooperative spectrum sensing. However, the CR may consume more stored energy due to the cooperative spectrum sensing and thus decrease its transmission performance. In this paper, to guarantee the transmission performance, a simultaneous cooperative spectrum sensing and wireless power transfer (SCSSWPT) scheme has been proposed, which can harvest the radio frequency (RF) energy of the PU signal to supply the consumed energy of spectrum sensing. Time splitting model, power splitting and antenna splitting model are proposed to implement cooperative spectrum sensing, energy harvesting and data transmission simultaneously. Three optimization problems have been formulated to maximize spectrum efficiency of the CR in the three SCSSWPT models, respectively, subject to the constraints of detection probability and harvested energy. The simulation results have shown that there is an optimal number of sensing antennas to maximize the spectrum efficiency of the CR, and the time splitting model can achieve higher spectrum efficiency.