In this paper, we consider the design of access schemes for secondary users in cognitive radio systems based on the primary user feedback information. We consider a secondary user employing a random access scheme with an access probability that depends on the primary user feedback state. We show that the proposed scheme can enhance the system performance in terms of the secondary throughput and/or primary user delay while guaranteeing a certain quality of service (QoS) for the primary user; this is due to the fact that the proposed scheme avoids sure collisions between the primary and

In this paper, we examine a cognitive spectrum access scheme in which secondary users exploit the primary feedback information. We consider an overlay secondary network employing a random access scheme in which secondary users access the channel by certain access probabilities that are functions of the spectrum sensing metric. In setting our problem, we assume that secondary users can eavesdrop on the primary link's feedback. We study the cognitive radio network from a queuing theory point of view. Access probabilities are determined by solving a secondary throughput maximization problem

During last two decades, Differential Evolution (DE) proved to be one of the most popular and successful evolutionary algorithms for solving global optimization problems over continuous space. Proposing new mutation strategies to improve the optimization performance of (DE) is considered a significant research study. In DE, mutation operation plays a vital role in the performance of the algorithm. Therefore, in this paper, comprehensive analysis of the contributions on basic and novel mutation strategies that were proposed between 1995 and 2020 is presented. A new taxonomy based on the

In this paper, three novel fractional-order CFOA-based inverse filters are introduced. The inverse low-pass, high-pass and band-pass responses are investigated using different approximation techniques. The studied approximations for the fractional-order Laplacian operator are the continued fraction expansion and Matsuda approximations. A comparison is held between the ideal filter characteristic and the realized ones from each approximation. A comparative study is summarized between the proposed circuits with some of the released inverse filters introduced in the literature. Foster-I

This paper proposes a new design of a 2α-order fractional-order band-pass filter with tunability feature. The proposed filter is approximated with the Continued Fraction Expansion and Matsuda second-order approximations. The realized filter transfer function is based on the Inverse Follow the Leader Feedback configuration, with Operational Transconductance Amplifiers as active elements. As a result, the order of the proposed filter can be adjusted by changing a single parameter, which is the bias current Ibias. A comparison with the previous works is performed, showing the advantage of the

A differentiator-based set up is proposed as an alternative solution to measure bio-impedance. The method is modifying the differentiator circuit, replacing the capacitor with the Cole-impedance model representing the biological (fruit) sample. The proposed differentiator gain response (with the embedded fruit) is experimentally recorded. The experimental data’s post-processing is performed using meta-heuristic optimization techniques to extract the Cole-impedance model unknown parameters by solving a group of nonlinear equations. Three meta-heuristic optimization algorithms are used: the moth

This paper addresses the problem of generalized synchronization (GS) between fractional order chaotic systems. In this paper, we propose a new control strategy for a complex generalized synchronization (GS) scheme dedicated to non-identical fractional-order chaotic systems characterized by different dimensions. The proposed control parameters are nonlinear in nature. In order to ensure that the proposed scheme converge towards zero, we establish the asymptotic stability of the zero solution to the error system by means of the stability of linear fractional-order systems. In order to assess the

This work presents a novel fractional H8 robust indirect adaptive fuzzy logic control strategy based on the variable structure control theory design (FRAFC-VSC) to synchronize two fractional-order chaotic systems. The contribution of this work is the use of an adaptive fractional order PI-regulator and a saturation function to eliminate the chattering phenomena in the control and surface signals. Stability analysis is performed for the proposed method with an acceptable synchronization error level based on Lyapunov stability criterion. The synchronization of two different fractional order

In this paper a simple private communications system is proposed based on Chua's chaotic system. The system mainly consists of two synchronized chaotic circuits, the system encodes values to a message function according to the state of synchronization between the two circuits. Numerical simulations were carried out to prove the validity of the system, and spice simulations were carried out on the proposed physical system. © 2019 IEEE.

This paper presents a new hybrid chaos synchronization scheme, which assures the co-existence of the full-state hybrid function projective synchronization (FSHFPS) and the inverse full-state hybrid function projective synchronization (IFSHFPS) between wide classes of three-dimensional master systems and four-dimensional slave systems. In order to show the capability of co-existence approach, numerical example is reported, which illustrates the co-existence of FSHFPS and IFSHFPS between 3D chaotic system and 4D hyperchaotic system in different dimensions. © Springer Nature Switzerland AG 2019.