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ABSTRACT Recently, there has been research on using cognitive radio to increase the effectiveness of spectrum resources. Secondary users (SUs) sense, identify, and access frequency bands presently unoccupied by primary users (PUs). Indeed, the precise communication methods of PUs remain consistently unknown to SUs. Designing an appropriate system for spectrum monitoring along with access is necessary to address the challenging problem of guaranteeing the quality of service (QoS) for PUs and satisfying the demand of SUs for spectrum resources. When several SUs and different channels are available, spectrum allocation and sharing must be considered. This work proposes a system for allocating spectrum to multiple users and sharing multiple channels for SUs dealing with PUs with uncertain behavior. The study focuses on analyzing the interference caused to PUs by the dynamic access of SUs. The analysis of the interference produced by SUs is conducted using renewal theory. Queuing theory determines the highest average data rate achievable by SUs while considering the limitations imposed by interference to PUs and the need to maintain stability in the secondary network. Comprehensive simulations validate the efficacy of this approach. [ABSTRACT FROM AUTHOR]

ABSTRACT Automatic modulation classification (AMC) is explained as accurately identifying a modulation of a received signal. AMC systems are a significant component of cognitive radio network (CRN) systems. It is difficult to perform modulation classification on an unsettled radio signal without any previous knowledge of the signal's properties. In this work, the deep learning‐aided AMC is suggested to solve the difficulties of the existing models. In the proposed approach, the modulation classification is attained by performing two steps: (a) data collection and (b) classification. Initially, the required data related to the cognitive environment is collected from online resources. Later, the garnered data are passed to the classification phase. The AMC is performed by the adaptive and dilated hybrid network (ADHN), which is the combination of a temporal convolution network (TCN) and a gated recurrent unit (GRU). The ADHN accurately classifies the modulation even in a noisy environment. The classification performance of the ADHN is further boosted by tuning the parameters of this network via the enriched remora optimization algorithm (EROA). This proposed modulation classification model is suitable for various channels. The comparative validation is performed to ensure the usefulness of the designed system via several measures. By experimental analysis, the proposed system acquires the high value of accuracy, precision, and f1‐score by 94.2, 80.2, and 86.7, respectively, when compared with classical approaches. In addition to this, other metrics are considered and obtained with more true value and less false value. Thus, it ensures the effectiveness of classifying the modulation types in CRNs. [ABSTRACT FROM AUTHOR]

The world is progressing at a rapid rate, and with continuous advancements in technology, the need for cooperative spectrum sensing has evolved. Cooperative spectrum sensing is an approach used to enhance detection performance, wherein secondary users collaborate with each other to sense the spectrum and identify spectrum holes. As technology improves over time, the spectrum becomes increasingly allocated to primary users. The role of cooperative spectrum sensing in cognitive radio fulfills the essential requirement of protecting primary users from harmful interference. The progressive evolution of technology has led to a reduction in available spectrum, prompting the emergence of the concepts of cognitive radio and cooperative spectrum sensing. To begin with, this paper introduces the fundamental application of cooperative spectrum sensing algorithms, encompassing primary and secondary users' models and an energy model. Subsequently, three machine learning algorithms, namely K-means, support vector machine, and logistic regression, are explained, and their schematics are presented in detail. The proposed model uses supervised and unsupervised learning techniques to develop a cooperative spectrum sensing framework. It compares the performance of three machine learning algorithms, K-means clustering, logistics regression and support vector machine. The comparison is based on accuracy, recall and precision metrics, and the results show that the K-means clustering algorithm has better performance than the other two algorithms. The findings highlight the superiority of the K-means clustering algorithm over logistic regression and support vector machine. [ABSTRACT FROM AUTHOR]

The basic requirement for cognitive radio networks is that secondary users sense spectrum to detect whether primary users have arrived the system. However, imperfect sensing always occurs due to the interference of unreliable channel and signal, which can negatively affect the performance of both primary users and secondary users. To better study the practical problems of cognitive radio networks, we combine queueing theory with it. In this paper, we consider cognitive radio networks with imperfect sensing based on retrial queues with feedback and priority. Using the method of probability generating function, the performance measures are solved. A bi-objective optimization model is established to minimize both system cost and users' sojourn time. From the perspective of secondary users, we analyze both individual equilibrium strategy and socially optimal strategy. Meanwhile, in order to eliminate the differences between two strategies, we impose admission fees on secondary users and obtain the optimal pricing strategy. [ABSTRACT FROM AUTHOR]

Cognitive radio networks offer an alternative to low spectral availability in some frequency bands due to their high demand for frequency channels. This article proposes to improve the spectral assignment based on the combinative distance-based assessment multicriteria algorithm. The metrics obtained are compared with a simple additive weighting algorithm and a RANDOM selection. To establish the algorithm's performance, five quality-of-service metrics are used: number of handoffs, number of failed handoffs, average bandwidth, average throughput, and cumulative average delay. From the analysis of the results obtained, combinative distance-based assessment (CODAS) presented the best result for the cost metrics with the lowest levels, and for the benefit metrics, the highest levels were obtained. [ABSTRACT FROM AUTHOR]

Abstract The proposed study introduces a novel anti-jamming approach for cognitive radio networks (CRNs) by integrating the Stackelberg game model with direct sequence spread spectrum (DSSS) techniques. This innovative combination enhances the security and performance of CRNs by optimizing resource allocation and fortifying network resilience against jamming attacks. The Stackelberg game model provides a strategic framework where the Defender and Adversary dynamically adjust their strategies to achieve Nash equilibrium, ensuring strategic stability. The application of DSSS further improves signal robustness, mitigating interference from jamming attempts. Simulation results demonstrate significant improvements in network security, resource utilization, and overall performance, validating the efficacy and advantages of the proposed scheme in maintaining reliable communication in the presence of adversarial threats.

The performance of the cognitive non-orthogonal multiple access (NOMA) systems with random locations is examined in the present paper. More precisely, the positions of the secondary receivers (SRs) are randomly distributed inside a disk with the centre at the secondary transmitter (ST). The primary networks (PNs), on the other hand, are not necessarily inside the transmission range of the ST. Two user selection schemes namely, path-loss-based and channel-gain-based approaches, are adopted to serve two SRs according to the power domain NOMA technique. Additionally, the impact of the imperfect hardware impairments (HIs) on both transmitters and receivers is also taken into consideration. Furthermore, a recently proposed transmit power allocation at the ST is employed to concurrently maximize the system performance of the secondary networks (SNs) and to strictly protect the quality-of-service (QoS) of the PNs. The correctness of the developed mathematical frameworks is corroborated by simulation results based on the Monte Carlo method. Finally, we unveil that there is no scheme that always outperforms another. Thus, an adaptive scheme can be proposed to optimize the networks' performance. Our findings also reveal that the outage probability (OP) under the harmful effect of HI can be effectively mitigated by increasing the transmit power of the ST. Additionally, increasing the transmit power of the PT is also beneficial for the SNs with the adopted transmit power allocation at the ST.

The proposed study introduces a novel anti-jamming approach for cognitive radio networks (CRNs) by integrating the Stackelberg game model with direct sequence spread spectrum (DSSS) techniques. This innovative combination enhances the security and performance of CRNs by optimizing resource allocation and fortifying network resilience against jamming attacks. The Stackelberg game model provides a strategic framework where the Defender and Adversary dynamically adjust their strategies to achieve Nash equilibrium, ensuring strategic stability. The application of DSSS further improves signal robustness, mitigating interference from jamming attempts. Simulation results demonstrate significant improvements in network security, resource utilization, and overall performance, validating the efficacy and advantages of the proposed scheme in maintaining reliable communication in the presence of adversarial threats. [ABSTRACT FROM AUTHOR]

To address the common issues in traditional convolutional neural network (CNN)-based spectrum sensing algorithms in cognitive radio networks (CRNs), including inadequate signal feature representation, inefficient utilization of feature map information, and limited feature extraction capabilities due to shallow network structures, this paper proposes a spectrum sensing algorithm based on a short-time Fourier transform (STFT) and residual attention dense network (RADN). Specifically, the RADN model improves the basic residual block and introduces the convolutional block attention module (CBAM), combining residual connections and dense connections to form a powerful deep feature extraction structure known as residual in dense (RID). This significantly enhances the network's feature extraction capabilities. By performing STFT on the received signals and normalizing them, the signals are converted into time–frequency spectrograms as network inputs, better capturing signal features. The RADN is trained to extract abstract features from the time–frequency images, and the trained RADN serves as the final classifier for spectrum sensing. Experimental results demonstrate that the STFT-RADN spectrum sensing method significantly improves performance under low signal-to-noise ratio (SNR) conditions compared to traditional deep-learning-based methods. This method not only adapts to various modulation schemes but also exhibits high detection probability and strong robustness. [ABSTRACT FROM AUTHOR]

In this paper, the joint radio resource management issues in a cognitive radio network driven by radio frequency energy harvesting (CRN-RF-EH) functionalities are investigated. For the CRN-RF-EH, the cognitive radio (CR) node first harvests its required energy directly from the transmitter of spectrum licensed user for its data communication and consequently transmits its data on the licensed frequency of the legacy user using the underlay accessing technique. Thus, RF-EH is an exciting innovation for energizing low-powered next-generation wireless networks (NGWNs). Consequently, due to CRN-RF-EH'd low power limitations, the resource allocation for CRN-RF-EH has to be optimized considering the trade-off among spectral efficiency, energy efficiency, and RF energy supply. Equal allocation of transmission time and/or transmission power may not be efficient for CRN-RF-EH with limited transmission time and power resources. A joint optimal time and power allocation (OTPA) strategy for CRN-RF-EH is proposed to maximise the total spectral efficiency of the CRN-RF-EH. The coupled variables in the formulated joint resource allocation problems create a non-convex optimization problem formulation. For analytical tractability, the non-convex optimization formulation is initially converted to its equivalent standard convex optimization formulation using proper variables and next, it is then solved using the convex optimization technique. The CONOPT solver, a powerful optimization-solving tool for solving convex optimization problems, is utilized to resolve the equivalent standard convex optimization problem formulation. When compared with the baseline biased random time optimum power allocation (BRTOPA) scheme, numerical simulation results show that the OTPA strategy dramatically improves the total spectral efficiency performance. In a severe radio propagation environment with a path loss exponent (PLE) equal to 3.5 such as in urban areas and less severe radio propagation environment with a path loss exponent (PLE) equal to 2.0, such as in rural areas, the OTPA outperformed the BROTPA with a mean performance improvement of approximately 23.96% and 42.94%, respectively. [ABSTRACT FROM AUTHOR]

The performance of the cognitive non-orthogonal multiple access (NOMA) systems with random locations is examined in the present paper. More precisely, the positions of the secondary receivers (SRs) are randomly distributed inside a disk with the centre at the secondary transmitter (ST). The primary networks (PNs), on the other hand, are not necessarily inside the transmission range of the ST. Two user selection schemes namely, path-loss-based and channel-gain-based approaches, are adopted to serve two SRs according to the power domain NOMA technique. Additionally, the impact of the imperfect hardware impairments (HIs) on both transmitters and receivers is also taken into consideration. Furthermore, a recently proposed transmit power allocation at the ST is employed to concurrently maximize the system performance of the secondary networks (SNs) and to strictly protect the quality-of-service (QoS) of the PNs. The correctness of the developed mathematical frameworks is corroborated by simulation results based on the Monte Carlo method. Finally, we unveil that there is no scheme that always outperforms another. Thus, an adaptive scheme can be proposed to optimize the networks' performance. Our findings also reveal that the outage probability (OP) under the harmful effect of HI can be effectively mitigated by increasing the transmit power of the ST. Additionally, increasing the transmit power of the PT is also beneficial for the SNs with the adopted transmit power allocation at the ST. [ABSTRACT FROM AUTHOR]

Spectrum sensing is pivotal in cognitive radio (CR), a burgeoning technology for optimizing radio spectrum utilization. Traditional spectrum sensing techniques like energy detection, matching filter, and cyclic stationary detection have been proposed, which rely on prior knowledge and models. These techniques suffer from challenging issues such as missed detection and false alarms, which impede the effective utilization of the spectrum. Inaccurate assumptions or limited knowledge can hinder detection. To tackle these challenging issues, we propose a novel deep learning-oriented spectrum sensing (DLoSS) technique and highlight the use of deep neural networks (DNNs) for cooperative spectrum sensing (CSS) model. Specifically, we propose a “DLSpectSenNet,” a DLoSS-based model, utilizes structural information from incoming modulated signals for spectrum sensing. Particularly, we combine convolutional neural network (CNN) and long-short-term memory (LSTM) network in series, extracting hidden spatial information and temporal data, respectively. The simulation results using the RadioML2016.10b dataset, show the proposed DLSpectSenNet’s improved detection performance, especially under low SNR conditions, surpassing traditional cooperative algorithms. It outperforms previous models, enabling improved spectrum detection. [ABSTRACT FROM AUTHOR]

Due to the deficiency of radio spectrum resources caused by the progress in technology, cognitive radio networks (CRNs) have made significant progress. CRNs have two types of users, namely, primary users (PUs) and secondary users (SUs). Considering that PUs have a higher priority and diversified data transmission requirements, this study divides PUs into two levels, namely, PU1s with a higher priority and PU2s with a lower priority. On the other hand, the occurrence of failures is inevitable in CRNs, which affects the data transmission of users. In this paper, combined with an adjustable PU packets transmission rate mechanism, a communication failure and repair mechanism with classified PUs based on the single-channel CRNs is proposed, and different preemption principles are set according to different system states. A queueing model is established and analyzed with a Markov chain, the performance index expressions that need targeted research are listed, numerical experiments are conducted, and the system performance change trends are obtained. The comparison experiment shows that the proposed communication failure and repair mechanism with classified PUs can improve the throughput of PU1 packets and reduce the blocking rate of PU1 packets compared with the conventional communication failure and repair mechanisms with unclassified PUs. [ABSTRACT FROM AUTHOR]

In cognitive radio networks, channel assembling allows secondary users (SUs) to expand network capacity and improve spectrum utilization. Scheduling strategies only based on heterogeneous service classification cannot guarantee the delivery priority of vital elastic services in special scenarios such as emergency rescue. Therefore, a priority scheduling strategy with reserved queue (Ps-rq) is proposed in this work. A static factor is defined to classify SUs into elastic services and real-time services based on message type, while a dynamic factor is defined to differentiate high-priority elastic services based on information validity, message correlation and message size. The high-priority users in the interrupted elastic services are placed in the reserved queue to ensure its services. Accordingly, the scheduling algorithm and the dynamic channel access process is presented. A continuous-time Markov chain analysis is conducted and all possible transition states, trigger events, transition rates and transition conditions of the system starting from a general state are derived. Furthermore, evaluation indexes of system performance are obtained. Study cases and simulation results prove that the proposed strategy can enhance network capacity, reduce blocking probability and forced termination probability for secondary users, and notably enhance the performance of high-priority elastic services. In addition, we analyze the characteristics of Ps-rq through a comprehensive comparison with four other schemes. The experiment proves that the Ps-rq strategy can effectively improve the service quality of the vital elastic services on the basis of providing fair scheduling. [ABSTRACT FROM AUTHOR]

In the domain of cognitive radio (CR), unlicensed users have the opportunity to efficiently use available spectrum bands without interfering with licensed primary users (PUs). Our study addresses the challenge of secondary user (SU) spectrum shortage due to high arrival rates of licensed users. We propose two models aimed at improving the average total waiting time for SUs in such scenarios. These models incorporate non-acquired and preemptive priority mechanisms within the M/D/1 model of a PU delay system. Through quantitative evaluations and Monte Carlo simulations, we evaluate the performance of these models. Our findings show significant improvements in average waiting time for both PUs and SUs, especially under the priority scheme. Furthermore, we explore these models in the context of real-time systems, considering the limited buffer capacity for both user types. This further improves the average waiting time for PUs and SUs in both priority schemes. Our contribution lies in providing effective solutions to mitigate SU shortages in CR networks, providing insight into priority-based approaches and real-time system considerations.

Imbalance and unfairness in resource allocation and utilization can lead to a degraded network environment where wireless network users experience poor quality of service (QoS) within the wireless networks. In multi-user wireless radio networks with constrained wireless network resources, such as power and bandwidth resources, uniform allocation of power or bandwidth may lead to unfairness in network resource management. The cooperative cognitive radio relay networks' (CCRRN) radio resource allocation problem among multi-users is investigated in this paper through combined resource optimization. To facilitate fairness in the multi-user networks, the maxi–min criterion is employed. The max–min fairness ensures that when the wireless network attains max–min utility fairness, no user's utility can be improved without degrading the utility performance of any other user. To maximize the worst-case user (max–min) capacity in the CCRRN using the power and bandwidth allocation strategy, a combined optimal resource allocation (COPBA) scheme is proposed. The max–min resource allocation optimization problem developed is observed to be convex. Efficient computer-based numerical optimization solver packages, such as SNOPT, exist that can solve convex optimization problems efficiently. The MATLAB software provides a robust integrated environment where the implementation of the SNOPT solver can be executed. Using the uniform bandwidth optimal power allocation (UBOPA) scheme as a benchmark, the fairness metric of the COPBA is evaluated and compared. Furthermore, the results showed the COPBA outperforming the UBOPA scheme. [ABSTRACT FROM AUTHOR]

In the domain of cognitive radio (CR), unlicensed users have the opportunity to efficiently use available spectrum bands without interfering with licensed primary users (PUs). Our study addresses the challenge of secondary user (SU) spectrum shortage due to high arrival rates of licensed users. We propose two models aimed at improving the average total waiting time for SUs in such scenarios. These models incorporate non-acquired and preemptive priority mechanisms within the M/D/1 model of a PU delay system. Through quantitative evaluations and Monte Carlo simulations, we evaluate the performance of these models. Our findings show significant improvements in average waiting time for both PUs and SUs, especially under the priority scheme. Furthermore, we explore these models in the context of real-time systems, considering the limited buffer capacity for both user types. This further improves the average waiting time for PUs and SUs in both priority schemes. Our contribution lies in providing effective solutions to mitigate SU shortages in CR networks, providing insight into priority-based approaches and real-time system considerations. [ABSTRACT FROM AUTHOR]

Summary: Cognitive radio networks (CRNs) have emerged as a promising solution to address the spectrum scarcity problem by allowing unlicensed secondary users (SUs) to opportunistically access the underutilized licensed spectrum bands. However, efficient channel assignment in CRNs, especially with user mobility and power control considerations, remains a challenging problem. Traditional channel assignment algorithms often struggle to adapt to changing network conditions, resulting in suboptimal performance. To address these challenges, this research presents a novel Taylor Tuna Optimizer‐based hybrid deep Q‐network (TayTO‐based HDQNet) for channel assignment in CRNs with user mobility and power control considerations. The proposed TayTO‐based HDQNet combines the Elman neural network architecture with the reinforcement learning framework of deep Q‐networks, tuned using the Taylor Tuna Optimizer. This hybrid approach enables intelligent channel assignment decisions while considering power consumption constraints, leading to efficient communication in CRNs. To train the HDQNet agent, a comprehensive dataset is generated through simulations of various CRN scenarios, incorporating channel availability, interference levels, and power consumption for different channel assignment decisions. The HDQNet agent undergoes iterative training using this dataset to develop an optimal channel assignment policy. Experimental results demonstrate the effectiveness of the proposed TayTO‐based HDQNet approach done by MATLAB, achieving a high success rate of 98.47% and surpassing the reliability scores of previous studies. This highlights the improved performance and reliability of the proposed approach for channel assignment in CRNs. [ABSTRACT FROM AUTHOR]

In cognitive radio networks, a group of secondary users, in the absence of primary users, attempt to utilize the spectrum without causing interference by employing opportunistic access techniques. However, the sudden reemergence of primary users in the spectrum results in user interference and escalates the frequency of channel switching in a dynamic environment. In such scenarios, analytical methods like Markov processes and game theory are utilized to forecast spectrum mobility. Additionally, given that cognitive radio networks are deployed across various platforms as mobile networks, user mobility can exacerbate the inherent instability of cognitive radio networks, posing challenges in routing. To address these challenges, this study has developed a reactive routing protocol with several advantages: (1) leveraging cognitive radio capabilities and mobility, as well as intersection models, (2) minimizing the frequency of channel switching, (3) preventing user interference, (4) utilizing the availability of channels in the AODV protocol, (5) omitting the use of a common control channel, and (6) establishing a stable path through the calculation of Link Expiration Time (LET). Numerical simulations demonstrate that, in comparison to AODV and CAODV protocols, the proposed protocol has reduced channel switching by approximately 80% with an increase in the number of nodes. Furthermore, in this protocol, control overhead has decreased by over 90% in scenarios involving an escalation in both the number of nodes and their speed. [ABSTRACT FROM AUTHOR]

The spectrum utilization problem in cognitive radio networks (CRNs) has been addressed in the existing literature from different viewpoints. However, the growing number of wireless Internet of Things (IoT) devices and the need for continuous connectivity are putting a strain on energy resources, leading to challenges in the sustainability of CRNs. Meanwhile, the explosion of the IoT introduces significant amounts of time-sensitive data with burstiness, posing challenges for designing and operating CRNs. To better trade off energy efficiency and response performance, we propose a novel energy conservation scheme subject to a periodic sleep mechanism and two sleep timers, and we introduce a Markovian arrival process to characterize the bursty arrival pattern of user packets in green CRNs. We develop a four-dimensional continuous-time Markov chain to evaluate the proposed energy conservation scheme. Using the matrix-geometric method, we obtain performance indexes, including the mean delay of packets and the energy conservation level of base stations. We provide experimental results to show how sleep parameters and correlation coefficients affect performance indexes, and we compare the proposed energy conservation scheme with the case where one timer is used. Based on the profit function, the relationship between Nash equilibrium and socially optimum spectrum access strategies is investigated, and a reasonable spectrum pricing policy is presented. [ABSTRACT FROM AUTHOR]

Abstract The basic objective of cognitive radio networks (CRNs) are to effectively utilize the limited spectrum by strategically exploiting the unoccupied bands of frequencies or by pooling the available frequencies with other networks. The two approaches that have the potential to boost spectral efficiency of next-generation wireless communication networks are massive multiple-input multiple-output (mMIMO) and CRN. In this paper, we proposed a novel spectrum sharing technique for cognitive radio with mMIMO system using 3D space data gathering and learning based on Deep Learning method. Newfangled layer architecture is designed to train the primary network information assemblage named as Deep Learning Based Environment Training (DeepEnvNet). Also using mMIMO structure in cognitive radio base station (CRBS), we angular facts of CR user equipment (UE) by utilizing the spatial resolution of CBS. Iterative Hard Thresholding (IHT) can be used for direction of Arrival (DoA) estimation. The main 3D space spectrum coverage is accomplished via contemplation of two CBS for each cell in the network at the process of spectrum prophecy. Once the spectrum sensing is performed via DeepEnvNet, the greedy spectrum scheduling is performed via the two strategy: to maximize the CR coverage, to maximize the average sum rate of the transmission in CRN mMIMO. The experimental results are analyzed with the metrics of Average Achieved Sum Rate (AASR) and Average Scheduling Number (ASN). As reducing deep learning rate and batch size, highest AASR achieved in our proposed model than the earlier works of CRN spectrum sharing.

Cognitive Radio Networks (CRNs) aim to optimize the limited frequency spectrum by enabling spectrum sharing among different networks and making use of unoccupied frequency bands. The combination of massive multiple-input multiple-output (mMIMO) and CRNs has the potential to greatly improve the efficiency of upcoming wireless communication networks. In our research, we introduce an innovative approach to spectrum sharing in cognitive radio, utilizing 3D spatial data acquisition and Deep Learning for learning and decision-making. We incorporate mMIMO structures into cognitive radio base stations (CRBS) to extract angular information from user equipment (UE) and estimate Direction of Arrival (DoA) using Iterative Hard Thresholding (IHT). Our method involves deploying two base stations per cell for comprehensive 3D spatial spectrum coverage during spectrum prediction. We employ advanced Deep Learning techniques for spectrum sensing instead of reinforcement learning, enhancing CRN performance. Our approach includes a two-fold spectrum scheduling strategy, one focused on maximizing CR coverage and the other on optimizing transmission rates in CRN mMIMO scenarios. By fine-tuning Deep Learning parameters, our model achieves significantly higher Average Aggregate Sum Rate (AASR) compared to previous CRN spectrum sharing methods, without relying on reinforcement learning for spectrum sensing. Our research underscores the effectiveness of integrating Deep Learning into cognitive radio networks, offering the potential for enhanced spectrum utilization and network performance. Additionally, we address energy efficiency using the Nakagami fading channel model and evaluate key metrics, including channel occupancy and energy efficiency, through experimental analysis.

Cognitive Radio (CR) technology has been highlighted as one of the most likely answers to the issue of spectrum shortage with the rise of fifth generation and beyond communication. Secondary users (SUs) in cognitive radio networks (CRN) must continuously monitor the spectrum to forecast channel occupancy by primary users (PUs) based on fundamental factors, such as location, time, and RF band. A hybrid deep learning model called LSTM-MLP (Long Short-Term Memory-Multilayer Perceptron) is proposed to improve idle channel prediction probability thus reducing the overall sensing time by cognitive users during spectrum sensing. Performance evaluation for the proposed model is done in terms of prediction error and efficiency, the GSM-900 spectrum dataset demonstrates that LSTM-MLP performs better in terms of improved prediction accuracy compared to existing state-of-art prediction techniques.

In this paper, we consider multiple intelligent reflecting surfaces (IRSs) assisted cognitive radio network (CRN) and investigate user-IRS association problem. The CRN consists of multiple secondary transmitters (STs), multiple secondary users (SUs) and a single primary user (PU). With the help of IRSs, the received signal strength at the SUs is improved. This is achieved by optimizing IRS phase shifts, which also helps reducing the interference at the PU. The main objective of this study is to obtain the user-IRS association that maximizes the minimum rate of the user in the network. For this purpose, we employ the well-known optimal relay assignment (ORA) algorithm, known for its polynomial-time complexity. The numerical results clearly demonstrate that the user-IRS assignment obtained through the ORA algorithm yields higher minimum rate performance compared to the sum-rate maximizing and random user-IRS assignment methods.

Malicious user recognition for spectrum sensing in Cognitive Radio Networks (CRNs) is a serious safety feature to safeguard effective and trustworthy process of these systems. Spectrum sensing permits CRNs to identify and employ accessible spectrum bands. As well as it is available to prospective interference and mischievous actions. To preserve network integrity, recognition of malicious consumers is vital. Deep learning (DL) based malicious consumer classification powers advanced neural network frameworks to recognize and flag possible threats inside a network. By examining numerous amounts of information, DL techniques can distinguish patterns as well as anomalies that are connected with malicious user performance plus system intrusions, scams or irregular action. This technique provides flexibility benefit that permits a network to learn and develop in evolving threats. It also offers an effectual revenue of improving network security in the difficult and active digital landscape. Therefore, this article develops an Optimal Deep Learning Empowered Malicious User Detection for Spectrum Sensing (ODL-MUDSS) in the CRN. The main intention of ODL-MUDSS model focused on automated identification and classification of MUs in CRN. To accomplish this, the ODL-MUDSS model primarily applies deep belief network (DBN) methodology for automated and accurate detection of MUs. In addition, recognition performance of DBN technique can be enhanced by use of sand cat swarm optimization (SCSO) algorithm and thereby improves the detection results. The performance validation of ODL-MUDSS technique is observed under different processes. The comprehensive outcomes stated enhanced performance of ODL-MUDSS model over other existing models with maximum accuracy of 97.75%, precision of 97.75%, recall of 97.75%, and F-score of 97.75%.

Cognitive radio is a technology that allows Secondary Users (SUs) to access vacant spectrum areas allocated to Primary Users (PUs) by dynamically adjusting their settings. However, the spectrum detection subsystem of SUs consumes battery power that could be used for transmission. This work aims to address the energy availability issue for cognitive radio devices by two methods: energy harvesting from the ambient environment and deep learning prediction of future energy levels. We compare three deep learning models: Long-Short Term Memory (LSTM), Convolutional Neural Network (CNN), and Convolutional Long-Short Term Memory (ConvLSTM) with three classic machine learning models: Artificial Neural Networks (ANN), Support Vector Regressor (SVR), and Extreme Gradient Boost (XGBoost). The results show that deep learning models outperform machine learning models across all datasets, with ConvLSTM being the best model with a Normalized Root Mean Squared Error (nRMSE) of 0.0632 and Mean Absolute Error (MAE) of 1.479, which are 8.80% and 9.04% better than the best machine learning model, ANN, with nRMSE of 0.0693 and MAE of 1.626.

In this paper, we suggest the use of Intelligent Reflecting Surfaces (IRS) to improve the spectrum sensing process using the energy detector and the throughput of Cognitive Radio Networks (CRN). The Primary Source (PS) harvests energy using the received signals on n r antennas from node A. The harvested energy is employed to transmit data to Primary Destination PD. The transmitted signal is reflected by IRS so that all reflections have a null phase at Secondary Source SS where spectrum sensing is performed. Spectrum sensing using IRS equipped with N = 32 reflectors offers 27 dB and 30 dB gain when compared to spectrum sensing without IRS for a number of antennas n r = 2 and 3 (Alhamad and Boujemaa in Wirel Pers Commun, 2021). We also suggest the use of IRS to increase the harvested energy and improve the spectrum sensing process. We also derive the primary throughput of CRN where the PS harvests energy using received signals on multiple antennas and there is an IRS that reflects PS signals to the PD. We derive the secondary throughput when the SS harvests energy and an IRS is located between the SS and the Secondary Destination SD. [ABSTRACT FROM AUTHOR]

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One of the major problems of cyclostationary spectrum sensing (CSS) system in cognitive radios (CR) are the implementation complexity. One possible way to reduce CSS complexity is to use efficient algorithms for performing Fast Fourier Transformation (FFT). Over the years, a lot of different FFT algorithms have been created. This includes the Split-Radix algorithm., the Fast Hartley Transform (FHT), and slide DFT. This paper investigates the suitable FFT algorithm among the aforementioned techniques, cyclostationary feature detection (CFD)-based spectrum sensing stands out. The methods have been thoroughly compared based on computational time, object size, code size, data dependence (real or complex), and the amount of mathematical operations involved in the computations. Simulation results show that slide FFT is the suitable frequency domain transformation algorithm to use in implementing cyclostationary spectrum sensing in cognitive radios as compared to the other considered algorithms where it provides a significant reduction in FFT stage computation complexity reach to 17% in SRFFT , 78% in FHT and 82% in SDFT while keeping the detection probability at satisfactory level.

To address the common issues in traditional convolutional neural network (CNN)-based spectrum sensing algorithms in cognitive radio networks (CRNs), including inadequate signal feature representation, inefficient utilization of feature map information, and limited feature extraction capabilities due to shallow network structures, this paper proposes a spectrum sensing algorithm based on a short-time Fourier transform (STFT) and residual attention dense network (RADN). Specifically, the RADN model improves the basic residual block and introduces the convolutional block attention module (CBAM), combining residual connections and dense connections to form a powerful deep feature extraction structure known as residual in dense (RID). This significantly enhances the network’s feature extraction capabilities. By performing STFT on the received signals and normalizing them, the signals are converted into time–frequency spectrograms as network inputs, better capturing signal features. The RADN is trained to extract abstract features from the time–frequency images, and the trained RADN serves as the final classifier for spectrum sensing. Experimental results demonstrate that the STFT-RADN spectrum sensing method significantly improves performance under low signal-to-noise ratio (SNR) conditions compared to traditional deep-learning-based methods. This method not only adapts to various modulation schemes but also exhibits high detection probability and strong robustness.

Due to the deficiency of radio spectrum resources caused by the progress in technology, cognitive radio networks (CRNs) have made significant progress. CRNs have two types of users, namely, primary users (PUs) and secondary users (SUs). Considering that PUs have a higher priority and diversified data transmission requirements, this study divides PUs into two levels, namely, PU1s with a higher priority and PU2s with a lower priority. On the other hand, the occurrence of failures is inevitable in CRNs, which affects the data transmission of users. In this paper, combined with an adjustable PU packets transmission rate mechanism, a communication failure and repair mechanism with classified PUs based on the single-channel CRNs is proposed, and different preemption principles are set according to different system states. A queueing model is established and analyzed with a Markov chain, the performance index expressions that need targeted research are listed, numerical experiments are conducted, and the system performance change trends are obtained. The comparison experiment shows that the proposed communication failure and repair mechanism with classified PUs can improve the throughput of PU1 packets and reduce the blocking rate of PU1 packets compared with the conventional communication failure and repair mechanisms with unclassified PUs.

This paper focuses on achieving the low-cost coexistence of the networks in an unlicensed spectrum by making them operate on non-overlapping channels. For achieving this goal, we first give a universal convergence analysis framework for the unlicensed spectrum allocation algorithm. Then, a one-timescale iteration-adjustable unlicensed spectrum allocation algorithm is developed, where the step size and timescale parameter can be jointly adjusted based on the system performance requirement and signal overhead concern. After that, we derive the sufficient condition for the one-timescale algorithm. Furthermore, the upper bound of convergence error of the one-timescale spectrum allocation algorithm is obtained. Due to the multi-timescale evolution of the network states in the wireless network, we further propose a two-timescale iteration-adjustable joint frequency selection and frequency allocation algorithm, where the frequency selection iteration timescale is set according to the slow-changing statistical channel state information (CSI), whereas the frequency allocation iteration timescale is set according to the fast-changing local CSI. Then, we derive the convergence condition of two-timescale algorithms and the upper bound of the corresponding convergence error. The experimentalresults show that the small timescale adjustment parameter and large step size can help decrease the convergence error. Moreover, compared with traditional algorithms, the two-timescale policy can achieve throughput similar to traditional algorithms with very low iteration overhead. [ABSTRACT FROM AUTHOR]

Relay-assisted hybrid beamforming plays an inevitable role in enhancing network coverage, transmission range, and spectral efficiency while simultaneously reducing hardware cost, power consumption, and hardware implementation complexity. This study investigates a cognitive radio network (CRN)-based hybrid wideband transceiver for millimeter-wave (mm-wave) decode-and-forward (DF) relay-assisted multiuser (MU) multiple-input multiple-output (MIMO) systems. It is worth mentioning that the underlying problem has not been addressed so far, which is a real motivation behind the proposed algorithm. The joint optimization of hybrid processing components and the constant amplitude constraints imposed by the analog beamforming solution make this problem non-convex and NP-hard. Furthermore, the analog beamformer common to all sub-carriers is another challenging aspect of the underlying problem. To derive the frequency-flat analog processing component in the radio frequency (RF) domain and frequency-dependent baseband processing matrices in the baseband domain, the original complicated problem is reformulated as two single-hop sum-rate maximization sub-problems. Taking advantage of this decomposition, the sum spectral efficiency is maximized through RF precoding and combining. On the other hand, the impact of interference among transmitted data streams and inter-user interference (IUI) is minimized via baseband processing matrices. Finally, computer simulations are conducted by changing system parameters, considering both perfect and imperfect channel state information (CSI). Simulation results demonstrate that the proposed algorithm achieves performance close to full-complexity precoding and outperforms other well-known hybrid beamforming techniques. Specifically, more than 95% efficiency is achieved with perfect CSI, and more than 90% efficiency is attained under the assumption of 30% error in the estimated channels. [ABSTRACT FROM AUTHOR]

In wireless communications, cognitive radio (CR) technology has significantly enhanced radio spectrum efficiency. Spectrum sensing is a key process in CR along with other major functions namely spectrum decision, sharing and mobility. Minimizing the processing delays, energy consumption of these functions and enhancing spectrum utilization is a major challenge. Spectrum inference has been proposed as a viable solution to overcome these problems. Many machine learning-based spectrum inference techniques using artificial neural networks (ANNs) and deep neural networks have been proposed in literature. In this paper we aimed to determine whether hybrid deep neural network based spectrum inference model outperform single model in time and frequency domains for spectrum occupancy dataset. Radial basis function (RBF) neural network tend to excel in extracting spatial features of spectrum data whereas bidirectional long short-term memory (BiLSTM) work very well for temporal dependencies of this data. Spectrum dataset exhibit both short-and-long term temporal/spectral dependencies. In this paper we have proposed spectrum inference based on a hybrid deep neural network RBF and BiLSTM. The proposed algorithm has been simulated using real time spectrum measurement data with time dimension ranging from (1 to 7 days), spectral range (0.7 GHz to 2.7 GHz) across three geographically varying locations Pune, Solapur and Kalaburagi in India. Hybrid deep neural network integration of RBF and BiLSTM is built, tested and compared with single models LSTM, BiLSTM for accuracy and speed. The hybrid method has outperformed single models to achieve Precision, Recall, F1 scores of 0.9959, 0.9575, 0.9763 respectively and training time improvement of 57.60% for GSM and whole band in frequency and time dimensions. [ABSTRACT FROM AUTHOR]