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The Reconfigurable Intelligent Surface (RIS) constitutes one of the prominent technologies for the next generation of wireless communications. It is envisioned to enhance the signal coverage in cases when the direct link of the communication is weak. Recently, beam training based on codebook selection is proposed to obtain the optimized phase configuration of the RIS. After that, the data is transmitted and received by using the classical coherent demodulation scheme (CDS). This training approach is able to avoid the large overhead required by the channel sounding process, and it also circumvents complex optimization problems. However, the beam training still requires the transmission of some reference signals to test the different phase configurations of the codebook, and the best codeword is chosen according to the measurement of the received energy of the reference signals. Then, the overhead due to the transmission of reference signals reduces the spectral efficiency. In this paper, a zero overhead beam training for RIS is proposed, relying on data transmission and reception based on non-CDS (NCDS). At the BS, the received differential data can also be used for the determination of the best beam for the RIS. Therefore, the efficiency of the system is significantly enhanced since reference signals are fully avoided. After choosing the best codebook, NCDS is still more suitable to transmit information for high mobility scenarios as compared to the classical CDS. Analytical expressions for the Signal-to-Interference and Noise Ratio (SINR) for the non-coherent RIS-empowered system are presented. Moreover, a detailed comparison between the NCDS and CDS in terms of efficiency and complexity is also given. The extensive computer simulation results verify the accuracy of the presented analysis and showcase that the proposed system outperforms the existing solutions.

Time hopping spread spectrum (THSS) system and chaotic system have been studied as candidates of the anti-jamming (AJ) systems with substantial advantages. However, THSS systems suffer from the strict synchronization prerequisite. In order to overcome the shortcomings of the THSS system and utilize the profits of the non-coherent chaotic system, we first propose a novel TH-NRDCSK system to enhance the bit error rate (BER) performance of the conventional non-coherent THSS system and relieve the strict synchronization issue of coherent THSS systems. Then, we analyze the performance of the proposed system under additive white Gaussian noise (AWGN) channel and jamming environment. Finally, we implement the simulation to demonstrate the consistency of the analysis and the simulation results and to disclose the effects of the system parameters on system's AJ performance. Moreover, the performance of the proposed system is compared to that of conventional counterparts to look at the benefits of integrating chaotic and THSS systems. The simulation results show that the proposed system significantly outperforms conventional counterparts in a practical environment.

The Birnbaum importance is one of the measures often used in importance analysis. Many algorithms for the calculation of this measure have been proposed for coherent systems. Several interpretations of the Birnbaum importance for non-coherent systems also exist. These interpretations are usually based on the prime implicants of the structure function of the system. However, identification of the prime implicants is a complex problem. In this paper, we develop a method for computation of Birnbaum importance using Boolean expression (algebraic representation) and truth table (matrix representation). Both of these representations are calculated based on Logical Differential Calculus, in particular, Boolean derivatives. The Boolean expression derived based on Boolean derivatives is equal to known definitions of the Birnbaum importance. The matrix approach for the calculation of the Birnbaum importance based on Boolean derivatives is novel. This approach can be used for calculation of the Birnbaum importance for the structure function represented by truth table and does not need transformation of the structure function into Boolean expression. An important advantage of the proposed approach (in algebraic or matrix form) is a possibility to define the Birnbaum importance for the evaluation of the non-coherent system failure (restore) with respect to simultaneous changes of states of several system components. • The Boolean expression of Birnbaum importance for non-coherent system is proposed. • The Logical Differential Calculus is developed for importance analysis of non-coherent system. • The Birnbaum importance is defined based on Boolean Derivatives. • The Birnbaum importance of several components is defined based on Boolean Derivatives. • The matrix approach for Birnbaum importance is proposed [ABSTRACT FROM AUTHOR]

Non-coherent systems represent a specific group of systems in context of reliability analysis. These systems are characteristic by existence of situations in which degradation of a system component can result in improvement of the whole system. Non-coherent systems are mostly investigated in case of Binary-State Systems (BSSs) that admit two performance levels for modeling system as well as its components. Properties of these systems have been studied and algorithms for calculation of most of reliability measures have been developed. However, in case of Multi-State Systems (MSSs), the situation is completely different. Non-coherent MSSs have been studied only marginally with focus on homogeneous MSSs. In this paper, we deal with heterogeneous non-coherent MSSs, generalize existing definitions for them and develop a new approach for computation of their critical system states, which play a key role in importance analysis. The analysis of non-coherent MSSs considered in this paper is implemented based on its representation in a form of time independent structure function. • Non-coherent Multi-State System (MSS) analysis. • The analysis of different definitions of component relevancy for MSSs. • The definition of critical system states for non-coherent MSSs. • The development of logical derivatives for analysis of non-coherent MSSs. • The computation of critical system states for non-coherent MSSs. [ABSTRACT FROM AUTHOR]