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The efficiency and high-speed data transfer rate of the communication system are increased based on Orthogonal Frequency Division Multiplexing (OFDM). The existing research in OFDM involves applying optimization methods to improve the system's efficiency. The high Peak Average Power Ratio (PAPR) value is a major limitation in the OFDM system, and this provides distortion due to the non-linear High-Power Amplifier (HPA). Local optima trap and lower convergence are two main limitations in existing optimization methods. This research proposes Enhanced Artificial Bee Colony (ABC) optimization method with a precodingcompandor technique to increase the efficiency of the OFDM system. Enhanced ABC method is applied with Boltzmann search to increase the exploitation capacity of the optimization efficiency. The selective mapping technique is applied to transform the candidate signal in the system. The ABC method increases exploration, and Boltzmann search increases exploitation. The enhanced ABC method increases the exploitation process that helps to overcome local optima traps and lower convergence. Square Root Raised Cosine (SRRC) precoding and Mu law compandor techniques were applied to reduce the PAPR. The Discrete Cosine Transform (DCT) technique is applied for domain conversion in the OFDM system. The proposed method has a convergence rate of 6.4069, and the existing one has a 6.4033 convergence rate. The enhanced ABC method provides higher efficiency in the MIMO-OFDM system regarding Symbol Error Rate (SER), PAPR, and Bit Error Rate (BER). [ABSTRACT FROM AUTHOR]

Summary: To achieve high data rates expected from beyond 5G communications, higher‐order modulation techniques have been explored. The energy‐efficient modulation technique with a high data rate has encouraged researches towards an optimum two‐dimensional hexagonal‐shaped constellation, namely, hexagonal quadrature amplitude modulation (HQAM). Thus, in this work, we analyze the average symbol error rate (ASER) of HQAM schemes by considering a two‐user nonorthogonal multiple access (NOMA) pair. Closed‐form expressions for ASER of HQAM schemes for users are derived over generalized Nakagami‐ m fading channels. Further, for the HQAM constellation feasibility in two‐user downlink NOMA systems, the power allocation criterion for the users is presented. Furthermore, the impact of modulation order of the users over the systems ASER analysis is investigated and valuable insights are drawn. [ABSTRACT FROM AUTHOR]

Summary: In underwater acoustic (UWA) communication, orthogonal frequency division multiplexing (OFDM) is a promising technology that is highly essential to get channel state information meant for channel estimation (CE). Nevertheless, higher complexity, slower convergence, and poor performance, which degrade the performance estimation, are the limitations of the traditional CE methodologies. Thus, by amalgamating the least square (LS)‐CE algorithm along with polynomial interpolated black widow optimization (PI‐BWO) model, an optimized least square sparse (OLSS) CE algorithm has been proposed to intend for a UWA‐OFDM communication system. Formerly, by utilizing the 2's complement shift left turbo encoding (2CSL‐TE) methodology, the input signal is encoded. After that, the modulated encoded signal is provided for inverse fast Fourier transform (IFFT) operations; subsequently, they are transferred over the UWA channel toward the receiver OFDM. By employing the OLSS methodology, the received OFDM signal's interference‐free region is utilized for sparse CE at the receiver. Regarding symbol error rate (SER), bit error rate (BER), mean square error (MSE), and peak signal‐to‐noise ratio (PSNR), the proposed model's experiential outcome is evaluated and analogized with the other prevailing methodologies. When analogized with the conventional models, the proposed estimation methodologies achieved better performance. [ABSTRACT FROM AUTHOR]

Average Bit Error Rate (BER), outage probability and average channel capacity expressions of a Modulating Retro-Reflector (MRR) optical communication system based on an Airy beam under weak turbulence are derived. The effects of propagation distance, width parameter and exponential truncation factor of the Airy beam itself on the communication performance of the system are discussed. Meanwhile, the performance of the system based on the Gaussian beam is compared with the same turbulence condition and propagation distance. The simulation results show that under the same conditions, the system based on the Airy beam shows a lower outage probability, average BER and larger average channel capacity compared to the system based on the Gaussian beam. Moreover, the advantages of the Airy beam are more significant as the average signal-to-noise ratio (SNR) increases. [ABSTRACT FROM AUTHOR]

This paper investigates the effect of hardware impairments (HIs) and imperfect channel state information (ICSI) on a SWIPT‐assisted adaptive nonorthogonal multiple access (NOMA)/orthogonal multiple access (OMA) system over independent and nonidentical Rayleigh fading channels. In the NOMA mode, the energy‐constrained near users act as a relay to improve the performance for the far users. The OMA transmission mode is adopted to avoid a complete outage when NOMA is infeasible. The best user selection scheme is considered to maximize the energy harvested and avoid error propagation. To characterize the performance of the proposed systems, closed‐form and asymptotic expressions of the outage probability for both near and far users are studied. Moreover, exact and approximate expressions of the ergodic rate for near and far users are investigated. Simulation results are provided to verify our theoretical analysis and confirm the superiority of the proposed NOMA/OMA scheme in comparison with the conventional NOMA and OMA protocol with/without HIs and ICSI. [ABSTRACT FROM AUTHOR]

With the tremendous increase in wireless user traffic, investigation on the end-to-end reliability of wireless networks in practical conditions such as non-homogeneous fading channel conditions is becoming increasingly widespread. Because they fit well to the experimental data, generalized channel fading distributions like κ–μ are well suited for modeling diverse fading channels. This paper analyzes the symbol error rate (SER) and outage probability (OP) performance of multiple-input multiple-output (MIMO) space-time block-code (STBC) selective decode and forward (S-DF) network over κ–μ fading channel conditions considering the additive white Gaussian noise (AWGN). First, the closed-form (CF) analytical expressions for the probability density function (PDF) and the cumulative distribution function (CDF) of the received signal-to-noise ratio (SNR) as well as its moment generating function (MGF) are derived. Second, the OP performance is then investigated for various values of the channel fading parameter and SNR regimes. The simulation findings show an increase in SER performance with an improved line-of-sight (LOS) component. Furthermore, the results show that the S-DF relaying systems can function properly even when there is no fading or LOS component. The OP has been increasing with the increase in the value of μ and κ. In medium and high SNR regimes, simulation results exactly match with analytical results. [ABSTRACT FROM AUTHOR]

Due to the reduction in costs of manufacture and launch of Low‐Earth orbit (LEO) satellites, LEO satellite communication (SATCOM) has become a promising solution to provide high data rates and low latency connectivity for future communications. However, due to the fast movement of LEO satellites, it has to face a large Doppler effect, leading to high inter‐carrier interference (ICI) power and severe received symbol error rate. To tackle this problem, a novel optimisation framework is proposed that boosts the achievable rate in LEO SATCOM networks by utilising passive beamforming of intelligent reflecting surface (IRS) to compensate for the Doppler effect. First, a carrier‐to‐interference‐noise ratio (CINR) was derived for each subcarrier and a joint optimisation problem of both power allocation is formulated to each subcarrier and passive beamforming of IRS. Moreover, a simultaneous iterative‐water‐filling‐algorithm (SIWFA) and semidefinite programing (SDP) are utilised, thereby striking a balance that minimises ICI power and maximises desired signal power. Numerical results demonstrate the superior achievable rate performance of the proposed IRS‐aided Doppler compensation for LEO SATCOM networks compared to benchmark schemes. [ABSTRACT FROM AUTHOR]

Nonorthogonal multiple access (NOMA), one of the favorable candidates of next-generation wireless networks combined with group device-to-device (D2D) networks, can sufficiently increase a system's spectral efficiency. In fact, in a cooperative scenario, successive interference cancellation (SIC) is used in NOMA receivers to reduce the complexity of relaying, as each user has to decode high-order user data. This work presents a quality of service (QoS)-based cooperative NOMA-aided group D2D system (Q-CNOMA). The Q-CNOMA system not only reduces the burden on the group transmitter by relaying the signal to a receiver in neighboring cells but also improves the overall system performance. In order to model the major components in a D2D scenario such as receivers clustering around a transmitter, the spatial distribution of D2D transmitters is modeled using a Gaussian–Poisson process (GPP). A closed-form expression of outage probability is calculated and benchmarked against conventional systems to prove the superiority of the proposed Q-CNOMA system. [ABSTRACT FROM AUTHOR]

Physical layer security (PLS) is becoming an interesting subject since it guarantees to deliver the most consistent and secure communication in wireless systems in both present and future scenarios. The security can be obtained without considering any assumption over the computational power of eavesdroppers. The massive MIMO that can render high power and spectrum effectiveness are discussed in detail in this work. The artificial noise injection zero-forcing pre-coding scheme is proposed to improve PLS of Massive MIMOs. The artificial noise is injected into the ZF pre-coder to destroy the eavesdropper's performance. In addition, the detection of eavesdrop attack is analyzed based on hypothesis condition (H0: no active attack present, H1: presence of active attack). The secrecy capacity of the system is improved by the intrusion of a game based optimization strategy. Here, the enhancement of secrecy rate is improved by the channel amplitude. The performance of the suggested model is evaluated in terms of secrecy rate, secrecy outage probability, and bit error rate and compared to existing approaches to enhance the efficacy of the suggested model. [ABSTRACT FROM AUTHOR]

Summary: The space‐time line code (STLC), which has been recently proposed in the literature, assumes fully known channel state information at the transmitter and not the receiver. However, the effective channel gain is still required at the receiver to coherently detect M‐ary quadrature amplitude modulation (MQAM) symbols. In this paper, we propose pilot‐aided STLC systems, which do not require the effective channel gain at the receiver to detect the MQAM symbols. In order to further improve the error performance of the proposed schemes, we present the pilot‐aided STLC systems with transmit antenna selection (TAS). Using a more direct and simpler approach, we derive the average symbol error probability (ASEP) of the coherent 1×2 STLC systems with TAS, which represents the lower bound of the pilot‐aided 1×2 STLC systems with TAS. For comparison, in a similar manner, we also derive the ASEP of the coherent 2×2 STLC systems without TAS, which represents the lower bound of the pilot‐aided 2×2 STLC systems. For pilot‐aided 1×2 STLC systems with TAS, the gap between the simulated symbol error rate (SER) and the derived theoretical ASEP lower bound is very small. For a given number of transmit antennas, the simulated SER and theoretical ASEP also show that the error performance of the pilot‐aided 2×2 STLC systems with or without TAS is superior to the pilot‐aided 1×2 STLC systems with TAS by at least 1.8 dB. [ABSTRACT FROM AUTHOR]

A reconfigurable intelligent surface (RIS) has potential for enhancing the performance of wireless communication. A RIS includes cheap passive elements, and the reflecting of signals can be controlled to a specific location of users. In addition, machine learning (ML) techniques are efficient in solving complex problems without explicit programming. Data-driven approaches are efficient in predicting the nature of any problem and can provide a desirable solution. In this paper, we propose a temporal convolutional network (TCN)-based model for RIS-based wireless communication. The proposed model consists of four TCN layers, one fully connected layer, one ReLU layer, and lastly a classification layer. In the input, we provide data in the form of complex numbers to map a specified label under QPSK and BPSK modulation. We consider 2 × 2 and 4 × 4 MIMO communication using one base station and two single-antenna users. We have considered three types of optimizers to evaluate the TCN model. For benchmarking, long short-term memory (LSTM) and without ML are compared. The simulation results are conducted in terms of the bit error rate and symbol error rate which show the effectiveness of the proposed TCN model. [ABSTRACT FROM AUTHOR]

We derive matrix expressions in closed form for the autocovariance function and the spectral density of Markov switching GARCH models and their powers. For this, we apply the Riesz–Fischer theorem which defines the spectral representation as the Fourier transform of the autocovariance function. Under suitable assumptions, we prove that the sample estimator of the spectral density is consistent and asymptotically normally distributed. Further statistical implications in terms of order identification and parameter estimation are discussed. A simulation study confirms the validity of the asymptotic properties. These methods are also well suited for financial market applications, and in particular for the analysis of time series in the frequency domain, as shown in some proposed real‐world examples. [ABSTRACT FROM AUTHOR]

We study the tunneling problem from the general Smith–Volterra–Cantor (SVC) potential of finite length L characterized by the scaling parameter ρ and stage G. We show that the SVC(ρ) potential of stage G is a special case of the super periodic potential (SPP) of order G. By using the SPP formalism developed by us earlier, we provide the closed form expression of the tunneling probability TG(k) with the help of the q-Pochhammer symbol. The profile of TG(k) with wave vector k is found to saturate with increasing stage G. Very sharp transmission resonances are found to occur in this system, which may find applications in the design of sharp transmission filters. [ABSTRACT FROM AUTHOR]

Environmental regimes (or environmental legacy or historical legacy) are the dynamics of environmental characteristics over a given (either long or short) time period, such as frequency of mean or extreme events and rate of change, which might be absent by using only contemporary variables. We present SER, an R package for estimating environmental regimes for different environmental variables. Using the data included in the package, several examples are shown. SER is suitable for any type of environmental or biotic variables, including nutrient concentration, light, and dissolved oxygen. In addition, by changing the argument "days_bf," it is possible to compute environmental regimes over any time period, such as days, months, or years. Our case study showed that the inclusion of environmental regimes increased the explained variation of temporal β‐diversity and its components. Environmental regimes are expected to advance the "environment–community" relationships in ecological studies. They can further be implemented in other subjects such as social science, socioeconomics, and epidemiology. [ABSTRACT FROM AUTHOR]

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The mmwave (millimeter wave) with massive MIMO (Multiple-input and multiple-output) leverages larger antennas with spatial diversity and multiplexing gain brings about positive vibe for future generation wireless networks for provisioning bandwidth hungry multimedia applications However, the fronthaul link that links a remote radio head (RRH) and carries video frames as bitstreams to the baseband unit (BBU) can fluctuate the overall speed and capacity of massive MIMO if suitable data compression (encoding-decoding) techniques are not functional. This paper presents an error detection aware compression (EDAC) scheme which first performs encoding using low-rank approximation considering both spatial and time domain to reduce video frame size; later, the encoded video frames are compressed using Huffman codewords. Experiment outcome shows the proposed video compression model achieves much better compression efficiency with improved bit error rate (BER), symbol error rate (SER), error vector magnitude (EVM), and compression ratio when compared with the fixed code dictionary huffman video coding (FCDHVC), exiting video compression (EVC) technique and huffman video coding (HVC). The proposed EDAC model achieved compression efficiency of 30.52 whereas the FCDHVC, EVC and HVC model achieved compression efficiency of 26.50, 21.75 and 22.35 respectively. [ABSTRACT FROM AUTHOR]

In this paper, we consider a coded cooperative communication network with multiple energy-harvesting (EH) relays. In order to adequately address the problem of error propagation due to the erroneous decoding at the relays, as in the case of conventional decode and forward (DF) relaying protocol, we propose coded cooperative schemes with hard information relaying (HIR) and soft information relaying (SIR) strategies. The performance of the relayed communication with EH relay depends crucially on the channel decoding capability at the relay, channel gains at the source–relay and relay–destination links, and ultimately on the power-splitting ratio of the relay EH receiver. The exact closed-form expression for the outage probability performance of the coded cooperative scheme with HIR strategy and relay selection (CC-HIR-RS) is derived for both cases, namely for constant and optimal power-splitting ratios. Concerning the coded cooperative scheme with SIR strategy, a Rayleigh Gaussian log likelihood ratio-based model is used to describe the soft estimated symbols at the output of the relay soft encoder. Directives are provided to determine the model parameters, and, accordingly, the signal-to-noise ratio (SNR) of the equivalent one-hop relaying channel is derived. A closed-form expression for the outage probability performance of the proposed coded cooperative scheme with SIR and relay selection (CC-SIR-RS) is derived. In addition, a fuzzy logic-based power-splitting scheme in EH relay applying SIR is proposed. The fading coefficients of the source–relay and relay–destination links and distance between source and relay node are considered as input parameters of the fuzzy logic system to obtain an appropriate power-splitting ratio that leads to a quasi-optimal SNR of the equivalent end-to-end channel. Monte Carlo simulations are presented to demonstrate the validity of the analytical results, and a comparison between the performance of the CC-HIR-RS scheme with constant and optimized power-splitting ratios and that of the CC-SIR-RS scheme with constant and fuzzy logic-based power-splitting ratios is provided. [ABSTRACT FROM AUTHOR]

We experimentally demonstrate a quantum-measurement-based receiver for a range of modulation schemes and alphabet lengths in a telecom C-band. We attain symbol error rates below the shot noise limit for all the studied modulation schemes and the alphabet lengths 4 ≤ M ≤ 16. In doing so, we achieve the record energy sensitivity for telecom receivers. We investigate the trade-off between energy and bandwidth use and its dependence on the alphabet length. We identify the combined (energy and bandwidth) resource efficiency as a figure of merit and experimentally confirm that the quantum-inspired hybrid frequency/phase encoding has the highest combined resource efficiency. [ABSTRACT FROM AUTHOR]

The evolution of vehicular networks towards sixth-generation (6 G) applications necessitates meeting the stringent requirements of low latency, high spectrum efficiency, and ubiquitous connectivity. This paper proposes leveraging re-configurable intelligent surfaces (RISs) in tandem with non-orthogonal multiple access (NOMA) as a promising solution to address these demands. We investigate the performance of NOMA in RIS-assisted vehicular networks from both theoretical and practical perspectives under diverse channel conditions including line-of-sight (LOS) and non-line-of-sight (NLOS). Conventionally, the performance of vehicular networks has been evaluated by assuming that the channels between the BS, RISs, and vehicles are identically distributed, which is not realistic in practice. Therefore, this paper evaluates the outage probability, ergodic rate, and sum rate performance of RIS-enabled vehicular NOMA networks over independent but not identically distributed (i.n.i.d) Nakagami-m\documentclass[12pt]{minimal}\usepackage{amsmath}\usepackage{wasysym}\usepackage{amsfonts}\usepackage{amssymb}\usepackage{amsbsy}\usepackage{mathrsfs}\usepackage{upgreek}\setlength{\oddsidemargin}{-69pt}\begin{document}$$m$$\end{document} fading channels. Analytical expressions for the cumulative distribution function of LOS and NLOS channels from the BS to the RIS and from the RIS to the vehicles are derived by taking into consideration the i.n.i.d channel characteristics. The obtained channel characteristics are then used to procure closed-form expressions for the outage probability and ergodic capacity as well as simplify the expressions of the outage probability and ergodic capacity for asymptotic analysis at a high signal-to-noise ratio. The presented analytical and simulation results demonstrate that incorporating RISs with a higher number of reflecting elements can significantly improve the outage and rate performance of vehicular networks. [ABSTRACT FROM AUTHOR]

This work investigates the performance of a full-duplex amplify-and-forward (FD-AF) relaying taking into account the residual self-interference at the relay node. We consider the α - μ distribution as fading channel model at the two links which well describes the small scale fading in terahertz (THz) communications. Full-duplex relaying can potentially double the spectral efficiency achievable by half-duplex operation considering the detrimental effects of inevitable self-interference. We derive the closed-form expressions of rate outage probability and ergodic capacity whereas an exact expression of average symbol error probability of coherently detected M-ary phase shift keying (M-PSK) is derived using the univariate and bivariate Fox's H-functions. The derived expressions are valid for arbitrary values of the α - μ fading parameters. Through simulations, it has been revealed that the performance of the system improves when the relay is closer to the source node as compared to destination node. Moreover, it has been observed that the fading parameters of the source-relay link dominates the system's performance as compared to the parameters of relay–destination link. The analytical expressions are ascertained by simulations which are found to be in excellent agreement. [ABSTRACT FROM AUTHOR]

Unmanned Aerial Vehicles (UAV) are growingly used as communication relays in this modern era due to their unique capabilities and advantages which includes enhanced connectivity, cost effectiveness, flexibility, risk reduction and real time data surveillance. UAVs offer a versatile and efficient solution for enhancing communication networks, especially in situations where traditional infrastructure is inadequate or unavailable. In this manuscript, we present the dual hop UAV enabled wireless communication system where the data is broadcasted from Source (S) to Destination (D) through a UAV working as decode and forward (DF) relay (R). The data is transmitted from S to R via Radio frequency (RF) link and then the decoded data from R is forward to D with multiple users. Closed form analytical expressions of outage probability is analyzed which is further utilized to do the optimization analysis to find the optimum altitude of the UAV in order to exaggerate its system performance. Numerical results shows that there is need to find out the optimal altitude of the UAV so as to keep down the overall outage probability of the proposed system and to enhance the system quality. We also find the outage probability at higher Signal-to-Noise ratio (SNR) to study the system behavior deeply. It is clearly observable from the numerical analysis that the exact outage probability and asymptotic outage probability are exactly matching at higher SNR values concluding the validity of the proposed system. The derived expressions are authenticated by simulated results via Monte Carlo simulations. [ABSTRACT FROM AUTHOR]

The 0.1–10 terahertz (THz) band theoretically offers the potential to provide high data rates for 6G and beyond infrastructure. Consequently, THz band communication can be utilized in wireless fiber extenders and backhaul networks. Nonetheless, THz band communication suffers significantly from losses due to molecular attenuation and pointing errors, which result from antenna misalignment caused by small antenna apertures. However, cooperative communication strategies exhibit considerable potential in enhancing the THz link. Additionally, to address THz link limitations, a blend of technologies is necessary. Therefore, in this paper, we consider a decode-and-forward (DF)-based mixed THz-radio frequency (RF) cooperative system model. Furthermore, an in-depth exploration of coherent quadrature amplitude modulation and non-coherent modulation schemes is undertaken. Exact expressions for end-to-end (e2e) outage probability (OP), moment generating function (MGF), and channel capacity (CC) are derived, along with exact average symbol error rate (ASER) expressions for both coherent and non-coherent modulation schemes. We also perform asymptotic analysis to determine the system's diversity gain and coding gain. Moreover, we conduct a thorough performance analysis to examine the impact of various parameters on e2e performance. Finally, validation through Monte-Carlo simulations ensures system accuracy, facilitating the extraction of practical design principles for optimizing THz-RF cooperative systems. [ABSTRACT FROM AUTHOR]

Visible light communication (VLC) with the use of multiple light-emitting diodes (LEDs) has recently offered extensive indoor coverage for both communication and illumination purposes. Meanwhile, index modulation refers to modulation techniques that use the indices of certain mediums to transmit additional information. The medium can be a time slot, frequency carrier, or especially antenna activation index. In this paper, we present the first attempt at semi-angle-based index modulation for a visible light communication (VLC) system by using LED with different semi-angle values. Instead of using identical semi-angle LEDs, multiple LEDs are divided into several clusters and all LEDs in each cluster have different semi-angle values. Moreover, at any time of transmission, only some clusters are active, and only a single LED of each active cluster is used to convey the pulse amplitude modulation (PAM) signal. We also proposed a minimum mean-squared error (MMSE) based maximum likelihood (ML) detector that performs ML detection on some candidates based on an initial MMSE solution. The simulation results show that the proposed scheme significantly improves the symbol error rate (SER) compared to conventional schemes. Finally, the proposed detector also proves to approach the ML detector performance while still maintaining acceptable complexity cost. [Display omitted] • An index modulation scheme for MIMO-VLC with different values of LEDs semi-angle. • A detector that can approach the ML detector with acceptable complexity. • Analyze the SER of the system and the computational complexity of the detector. • The performance are presented for a VLC scenario under different values of SNR. [ABSTRACT FROM AUTHOR]

The radio frequency spectrum became crowded because of the huge number of wireless devices, hence cognitive radio networks (CRNs) should increase the efficiency of spectrum utilization. Moreover, energy-saving techniques are becoming essential to prolong the devices' life. Consequently, this work considers a hybrid active/passive (interweave/backscatter) symbiotic network while adopting the energy harvesting technology and applying the sensing interval concept. The sensing interval concept helps the secondary users (SUs) to transmit their data for consecutive time slots depending on the sensing result of the first time slot. This concept helps the SUs to reduce the consumed energy in sensing the channel each time slot. The hybrid transmission mode improves the spectrum utilization. The energy harvesting technology, the sensing interval concept, and the backscatter mode improve the energy efficiency. These spectrum utilization and energy efficient techniques are combined, for the first time, in one model. To deal with the mixed system state (the energy of the SUs which is fully observable state and the primary users activity which is partially observable state due to the imperfect sensing) and take the future rewards into consideration, a mixed observable Markov decision process is proposed. Moreover, we derive a closed form expression for the data outage probability of the backscatter transmission with/without spectrum sensing. The numerical results show that the proposed model prevails over the other models in the literature in terms of throughput and energy efficiency. Moreover, the interference on the primary user receiver due to applying the sensing interval concept is reduced by introducing a new penalty parameter. [ABSTRACT FROM AUTHOR]

In this work, we delve into the covertness performance of the reconfigurable intelligent surface (RIS) symbiotic ambient backscatter communication (AmBC) systems, where the RIS is partitioned into two zones to serve covert and public users. To impede with the monitor's detection, the source deliberately transmits both information and interference signals. Specifically, we derive closed-form expressions for the detection error probability (DEP) and outage probabilities. Subsequently, the effective covert rate (ECR) is maximized by optimizing the power allocation factor and the number of each zone reflective elements. Finally, we investigate the energy efficiency (EE) of the considered system. Simulation results validate the accuracy of the analysis, underscoring that the RIS-segmented symbiotic AmBC systems can achieve better covertness by improving the interference cancellation capability and dividing the optimal RIS zones. [ABSTRACT FROM AUTHOR]

Aiming at the scenario where the eavesdropper try to eavesdrop on the confidential messages of secondary trusted users, two physical-layer network coding (PNC) strategies, namely dual power superposition (PS-PS) encoding strategy and bit-level exclusive-or power superposition (XOR-PS) encoding strategy, are proposed to improve the security performance of cognitive non-orthogonal multiple access (NOMA) networks with the help of the data transmitted by the primary user. Considering the overlay spectrum sharing mechanism and the imperfect successive interference cancellation (SIC) technology, we first derive the closed-form accurate expressions of the outage probability and intercept probability of the secondary network with these two schemes over Rayleigh fading, and also give the asymptotic outage probability in the high signal-to-noise ratio (SNR) regime. Then, the correctness of the theoretical results is verified by simulation. For comparison, we also use the scheme without the assistance of the primary user as the benchmark scheme, which is represented by NPS. Finally, the simulation results show that the security of the proposed PS-PS and XOR-PS schemes is much better than that of the NPS scheme in the case of without reducing the outage performance. • Two physical-layer network coding strategies are proposed to improve the security performance of cognitive non-orthogonal multiple access networks with the help of the data transmitted by the primary user. • The outage probability and intercept probability of two schemes based on overlay spectrum sharing mechanism and the imperfect successive interference cancellation technology are derived. • The simulation results show that two strategies proposed can effectively improve the security of the system without significantly reducing outage performance. [ABSTRACT FROM AUTHOR]

According to the symbol error eate (SER) of the superimposed constellation, the near-optimal space code multiple access (SCMA) codebooks were explored under uplink and downlink Rayleigh fading channels, respectively.A near-optimal codebook design scheme was proposed based on the mathematical model between the superimposed constellation and the SER formula.And the proposed design procedures could be summarized as follows, design the factor graph matrix, match the best codeword pair, and find the optimal angle.Numerical results are provided to demonstrate that the proposed scheme can achieve near-optimal SER performance.

Multiple-input multiple-output (MIMO) radar has acquired considerable attention as it offers an additional degree of freedom which results in performance gains when contrasted with the regular single antenna element radar system. Waveform optimization in MIMO radar is essential as it can offer tremendous improvements in target detection which are quantified in terms of reductions in the symbol error rate and improvements in target detection probability. In this work, we foster a strategy for the optimization of transmitter and receiver waveform in a collocated MIMO radar by only considering the second order statistics, thus relaxing the information of the instantaneous target states. Our contributions are primarily two-fold. First, we find a closed-form expression of the outage probability of an unknown target under clutter environment. For this prospect, we model the signal-to-interference-plus-noise ratio in a canonical quadratic structure, and then utilize the modern residue theory approach to characterize the distribution function. Secondly, we propose constrained and unconstrained optimization problems for the reduction in outage probability using algorithmic techniques such as interior-point, sequential-quadratic programming, and the active-set method for the optimization of the transmitter and receiver waveform. We also provide simulated re-enactments to validate our hypothetical deductions. [ABSTRACT FROM AUTHOR]

The outage performance of the cognitive relay networks is analyzed based on simultaneous wireless information and power transfer (SWIPT) and non-orthogonal multiple access (NOMA). The analytical expressions of overall outage probability and asymptotic expressions on high signal-to-noise ratio (SNR) are derived for the direct link transmission mode and the two-stage communication transmission mode. The analytical expressions are validated by Monte-Carlo simulations. The simulation results demonstrate that the outage performance is improved by through the direct link transmission. Furthermore, compared with the conventional cognitive relay networks with orthogonal multiple access (OMA), superior outage performance and high energy efficiency are achieved for the cognitive relay networks based on SWIPT-NOMA. [ABSTRACT FROM AUTHOR]

The outage performance of the cognitive relay networks is analyzed based on simultaneous wireless information and power transfer (SWIPT) and non-orthogonal multiple access (NOMA). The analytical expressions of overall outage probability and asymptotic expressions on high signal-to-noise ratio (SNR) are derived for the direct link transmission mode and the two-stage communication transmission mode. The analytical expressions are validated by Monte-Carlo simulations. The simulation results demonstrate that the outage performance is improved by through the direct link transmission. Furthermore, compared with the conventional cognitive relay networks with orthogonal multiple access (OMA), superior outage performance and high energy efficiency are achieved for the cognitive relay networks based on SWIPT-NOMA. [ABSTRACT FROM AUTHOR]

Optical wireless communication (OWC) has attracted significant interest recently in academia and industry. Free-space optical (FSO) communication systems are where free space acts as a communication channel between transceivers that are line of sight (LOS) for the successful transmission of optical signals. The FSO transmissions through the atmosphere, nevertheless, bring significant challenges, besides the uncertainty of atmospheric channels, especially the signal fading due to the atmospheric turbulence, attenuation and pointing errors caused by the random beam misalignments between transceivers, signal obstruction due to buildings or trees can pre-vent the transmitted message to reach the destination. This study theoretically investigates the average symbol error rate (ASER) of reconfigurable intelligent surfaces (RIS) assisted FSO link over log-normal turbulence channels. The RIS effect is examined by considering the influence of link distance, transmitted optical power, and quadrature amplitude modulation (QAM) scheme on the ASER. [ABSTRACT FROM AUTHOR]

The performance of speech emotion recognition systems (SER) suffers when emotional speech is spoken in different accents. One possible solution to such a problem is to identify the accent beforehand and use this knowledge in the SER task. The present work is one of the novel attempts in this regard to build effective accent recognition systems based on emotional speech. In this regard, statistical aggregation functions (like mean, std, kurtosis, etc.) have been applied on frame-level feature representations such as perceptual linear prediction (PLP), log filterbank energies (LFBE), Mel frequency cepstral coefficients (MFCC), spectral subband centroid (SSC), constant-Q cepstral coefficients (CQCC), chroma vector and Mel frequency discrete wavelet coefficients (MFDWC) to obtain utterance-level features from CREMA-D, an emotional dataset. The performance of the features for different standard classifiers is obtained by conducting experiments using clean and noisy speech signals. Finally, the experimental results show that the SSC features perform well on noisy data only when it is trained with noisy data. On the other hand, the combined MFDWC features perform well on noisy data for both clean and noisy training data. This hints at the noise-robustness of this feature set. On the other hand, we can only say that SSC is conditionally robust. We hope this work will initiate a new line of research in emotion recognition. [ABSTRACT FROM AUTHOR]

In this paper, the authors study the compensation of high‐power amplifier (HPA) non‐linear distortion in the multi‐user (MU) massive multiple‐input multiple‐output (MIMO) systems and focus on uplink transmission, where the base station (BS) uses a large antenna array. First, the authors present a non‐linear distortion iterative cancellation (NDIC) algorithm‐based MMSE and approximate message passing (AMP) at the receiver level, in order to estimate and mitigate jointly a non‐linear distortion and the channel noise. Second, the authors propose a novel distortion cancellation technique based on deep learning. At this level, the authors first introduce a multilayer neural network, trained in the Levenberg–Marquardt algorithm by eliminating HPA non‐linearities on the 'Pre distortion' transmitter and 'Post distortion' receiver side. Next, the authors developed a novel end‐to‐end (E2E) learning approach for the joint transmitter and non‐coherent receiver in the Rayleigh fading channel. The basic idea lies in the use of deep neural networks (DNNs), auto encoder (AE) for unknown channels, where DNNs are applied to perform several functions and modules existing in the transmission chain. The simulation results demonstrate the strong potential of the proposed approach E2E in terms of improving the link quality and symbol error rate (SER) compared to other compensation techniques presented in this work. [ABSTRACT FROM AUTHOR]

Summary: Multi‐user optical code division multiplexing (OCDMA) in visible light communication (VLC) is an imminent domain for providing an even distribution of available bandwidth and improved security. Q4R1Zero cross‐correlation (ZCC) codes are widely reported, and improved performance is offered by them due to insignificant multiple access interference (MAI). However, practically, MAI exists in ZCC codes due to adjacent weights (W) in the code matrix rows for each user. Therefore, a novel ZCC code with a nonadjacent W is designed in this work to eradicate MAI limitations and is named weight managed ZCC codes (WMZCC). An indoor 100 Gbps/User OCDMA‐VLC system is realised using polarisation division multiplexed quadrature phase shift keying (PDM‐QPSK) and digital signal processing (DSP). Incorporation of DSP in the coherent receiver compensates the effects of dispersion and nonlinear effects and also performs phase estimation. Further, a state‐of‐the‐art comparison of WMZCC codes with diagonal identity matrix (DIM) and zero cross‐correlation resultant weight (ZCCRW) codes has been performed in terms of log symbol error rate (SER), Q factor, error vector magnitude percentage (EVM%) and log bit error rate (BER) log at different VLC lengths, Q4R1Transmitter half angles (THA), incidence half angles (IHA) and optical concentrators (cm2). Constellations are analysed with and without DSP, and according to the author's best knowledge, a 100 Gbps VLC system for five users covering 6 m at −3.42 log BER is demonstrated for the first time. Results revealed that weight management in WMZCC codes makes its performance improve as compared with ZCCRW and DIM codes. [ABSTRACT FROM AUTHOR]

The absence of labeled samples limits the development of speech emotion recognition (SER). Data augmentation is an effective way to address sample sparsity. However, there is a lack of research on data augmentation algorithms in the field of SER. In this paper, the effectiveness of classical acoustic data augmentation methods in SER is analyzed, based on which a strong generalized speech emotion recognition model based on effective data augmentation is proposed. The model uses a multi-channel feature extractor consisting of multiple sub-networks to extract emotional representations. Different kinds of augmented data that can effectively improve SER performance are fed into the sub-networks, and the emotional representations are obtained by the weighted fusion of the output feature maps of each sub-network. And in order to make the model robust to unseen speakers, we employ adversarial training to generalize emotion representations. A discriminator is used to estimate the Wasserstein distance between the feature distributions of different speakers and to force the feature extractor to learn the speaker-invariant emotional representations by adversarial training. The simulation experimental results on the IEMOCAP corpus show that the performance of the proposed method is 2–9% ahead of the related SER algorithm, which proves the effectiveness of the proposed method. [ABSTRACT FROM AUTHOR]

Outage probability (OP) and potential throughput (PT) of multihop full-duplex (FD) nonorthogonal multiple access (NOMA) systems are addressed in the present paper. More precisely, two metrics are derived in the closed-form expressions under the impact of both imperfect successive interference cancellation (SIC) and imperfect self-interference cancellation. Moreover, to model short transmission distance from the transmit and receive antennae at relays, the near-field path-loss is taken into consideration. Additionally, the impact of the total transmit power on the performance of these metrics is rigorously derived. Furthermore, the mathematical framework of the baseline systems is provided too. Computer-based simulations via the Monte Carlo method are given to verify the accuracy of the proposed framework, confirm our findings, and highlight the benefits of the proposed systems compared with the baseline one. [ABSTRACT FROM AUTHOR]

The proposed work presents a Radio over-Free space optical (Ro-FSO) communication system at 320 Gbps channel capacity using circular polarisation division multiplexed (CPDM) 256-Quadrature amplitude modulation (256-QAM). The proposal has been validated by comparing CPDM and LPDM in 320 Gbps 256-QAM Based Ro-FSO System enabling 80 GHz under Rain and Haze Effects. CPDM is a cutting-edge technology and has dominance over Linear PDM (LPDM) due to the elimination of polarisation axis alignment requirements and uniformity in the distribution of scattered light. In order to investigate the effects of CPDM and LPDM in Ro-FSO system, a performance comparison of both the PDMs has been accomplished for a range of Ro-FSO link lengths, and input powers under the effects of different atmospheric turbulences such as clear weather, haze, and rain in terms of Error vector magnitude (EVM), Quality factor (Q factor), and log Symbol error rate (SER). Further, the effects of Digital signal processing (DSP) in the proposed system are analysed using Viterbi Phase Estimation (VPE), Blind Phase Search (BPS), and Constant Modulus Algorithm (CMA) algorithms and it is observed that the presence of DSP tremendously improves the system performance due to mitigation of dispersion, nonlinear effects, time skews, and phase errors etc. Results revealed that under the clear weather, LPDM covered 28 km and CPDM managed to reach 38 km successfully. Power degrading effects in haze and rain are greater and therefore link length has been reduced to 5.5 km in CPDM and 4.9 km in LPDM for haze; and 4.2 km in CPDM and 3.8 km in LPDM for rain. [ABSTRACT FROM AUTHOR]

This paper investigates the performance of a mixed free-space optical (FSO)/radio frequency (RF) amplify and forward (AF) one-way full-duplex relay (FDR) system by considering the impact of feedback delay and co-channel interference (CCI) at the relay node. Of course, apart from CCI, the FDR operation introduces self-interference (SI) in the relay hardware. The relay selection using the selection cooperation technique is performed based on imperfect channel state information (CSI). Importantly, the statistics of the RF link with outdated CSI for α - μ distribution have been derived, and then the exact closed form expressions for the outage probability and bit error rate (BER) have been developed for non-zero boresight error on the FSO link. In addition to this, an approximate analysis of ergodic capacity along with the diversity order of the considered system model has also been derived. Finally, the numerical results are presented to corroborate the findings, and Monte-Carlo simulations are used to validate them. [ABSTRACT FROM AUTHOR]

Speech Emotion Detection (SER) is a field of identifying human emotions from human speech utterances. Human speech utterances are a combination of linguistic and non-linguistic information. Nonlinguistic SER provides a generalized solution in human-computer interaction applications as it overcomes the language barrier. Machine learning and deep learning techniques were previously proposed for classifying emotions using handpicked features. To achieve effective and generalized SER, feature extraction can be performed using deep neural networks and ensemble learning for classification. The proposed model employed a time-distributed attention-layered convolution neural network (TDACNN) for extracting spatiotemporal features at the first stage and a random forest (RF) classifier, which is an ensemble classifier for efficient and generalized classification of emotions, at the second stage. The proposed model was implemented on the RAVDESS and IEMOCAP data corpora and compared with the CNN-SVM and CNN-RF models for SER. The TDACNN-RF model exhibited test classification accuracies of 92.19 percent and 90.27 percent on the RAVDESS and IEMOCAP data corpora, respectively. The experimental results proved that the proposed model is efficient in extracting spatiotemporal features from time-series speech signals and can classify emotions with good accuracy. The class confusion among the emotions was reduced for both data corpora, proving that the model achieved generalization. [ABSTRACT FROM AUTHOR]

In this paper, a generalized Interference-aided radio frequency energy harvesting (EH) cooperative network has been presented under Weibull faded environment. The performance analysis of the system in terms of Throughput and Outage Probability for various cooperation protocols, Decode-and-Forward, Amplify-and-Forward and Hybrid-Decode-Amplify-Forward has been shown. The throughput of the network has been optimized with respect to the EH fractions of the hybrid TSR–PSR protocol. Integral-form expressions for Outage probability and Throughput are derived for the given protocols. In addition, the throughput of the proposed network has been evaluated under different channel conditions which show the superiority of different EH fractions in different relays. Analytical expressions have been well substantiated through extensive simulation results. The influence of system parameters such as time switching and power splitting fractions, number of relay nodes, channel parameters on outage probability and throughput performance of the proposed network has been shown. Finally, the throughput of the proposed model has been compared with various benchmark techniques. [ABSTRACT FROM AUTHOR]

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Summary: This work investigates the dual impacts of co‐channel interference (CCI) on radio frequency (RF) energy harvesting (EH)‐enabled cooperative cognitive radio network (CCRN). CCRN is considered to be worked following overlay mode of spectrum sharing technique. One pair of cellular nodes are considered as primary users (PUs), and a pair of Internet‐of‐Things devices (IoDs) are considered as secondary users (SUs) of CCRN. IoDs are used to help the communication between cellular node and in benefit of that the devices can access the cellular spectrum. In one hand, the effect of CCI from different sources may deteriorate the received signal‐to‐noise ratio (SNR) at IoDs, and on the other hand, scavenge of energy at IoDs from RF signal of CCI may improve the transmission of information from IoDs. Hybrid power time switching (HPTS) technique is adopted in the proposed model for harvesting energy from RF signals at IoDs following simultaneous wireless information and power transfer (SWIPT) principle. The closed form expressions of both PU and SU outage are derived to analyse the performance of two different networks. The joint effects of both power splitting and time switching factors on both PU and SU outage are shown in simulation results. The outage performances of both PU and SU networks with respect to different interference‐to‐noise (INR) level and transmission power are also shown in the results. The performance of the proposed system is found as better than the previous work on similar network architecture. [ABSTRACT FROM AUTHOR]

In this work, we investigate a prediction-sensing based cooperative energy harvesting cognitive radio network (EH-CRN) over a Rician fading environment. Incorporating a prediction based sensing mechanism provides enhanced protection to the quality-of-service (QoS) of the primary user (PU) subsequently leading to an improved spectrum efficiency. The complex channel model in analysing the performance of the prediction-sensing based EH-CRN is taken to be as Rician considering the envisioned higher frequency communication systems. An optimal sensing time is also evaluated whereat the secondary network throughput is the maximum. The system behaviour is analysed in terms of two standard performance indices viz., outage probability (OP) and the symbol error rate (SER). The exact analytical expression for both the OP and SER in a Rician fading channel environment is obtained. The impact of Rician fading factor, signal-to-noise ratio (SNR), number of cooperative cognitive radio nodes, data rate parameter and prediction error on the detection probability, harvested energy, normalized throughput, OP and SER is analysed and discussed. The SER for different digital modulation techniques are also obtained. Monte Carlo simulations verify the correctness of the analytical modelling of the system. [ABSTRACT FROM AUTHOR]

FSO is one of the fast-growing fields towards the next generation of communication technology. FSO facilitates the requirement of high data rate. On the other hand, the impairments like, atmospheric turbulence and other nonlinear effects of optical link limits the overall system performance. To mitigate the effect of these impairments, different diversity combining schemes are implemented by different researchers. Also, it is noticeable that MGF based approach is more tractable compare to that of PDF based approach. However, performance analysis in terms of error rate and capacity under Equal Gain Combining (EGC) diversity scheme for Double Generalized Gamma fading distribution using MGF is missing from the literature of FSO. Therefore, this paper presents closed form expressions of Average Capacity (AC) and Symbol Error Rate (SER) of M-PSK and M-QAM for Double Generalized fading distribution under EGC scheme. Further, the effect of different turbulence conditions such as weak, moderate and strong turbulences is presented. Furthermore, respective AC and SER are used to deduce those over Double Weibull and Gamma-gamma as special cases of Double Generalized fading distribution. Increase in the number of diversity branches improve AC and SER of the system. Simulated results show perfect agreement with those available in the literature. [ABSTRACT FROM AUTHOR]

The development of future wireless communications systems faces a big challenge of spectrum scarcity. Co‐existence of radar and communications systems is thus of great interest. In this work, the performance of a communications system with hardware impairment (HWI) as well as interference from radar systems will be studied. The impact of radar interference, I/Q imbalance coefficients as well as channel state information (CSI) will be evaluated in terms of outage probability and symbol error rate. Simulation results prove that the proposed detectors provide explicit and conducive insights for further exploration of joint radar‐communications designs. [ABSTRACT FROM AUTHOR]

Faults and fractures are crucial parameters for geothermal systems as they provide secondary permeability allowing fluids to circulate and heat up in the subsurface. In this study, we use an ambient seismic noise technique referred to as three-component (3C) beamforming to detect and characterize faults and fractures at a geothermal field in Mexico. We perform 3C beamforming on ambient noise data collected at the Los Humeros Geothermal Field (LHGF) in Mexico. The LHGF is situated in a complicated geological area, part of a volcanic complex with an active tectonic fault system. Although the LHGF has been exploited for geothermal resources for over 3 decades, the field has yet to be explored at depths greater than 3 km. Consequently, it is currently unknown how deep faults and fractures permeate, and the LHGF has yet to be exploited to its full capacity. Three-component beamforming extracts the polarizations, azimuths and phase velocities of coherent waves as a function of frequency, providing a detailed characterization of the seismic wavefield. In this study, 3C beamforming of ambient seismic noise is used to determine surface wave velocities as a function of depth and propagation direction. Anisotropic velocities are assumed to relate to the presence of faults giving an indication of the maximum depth of permeability, a vital parameter for fluid circulation and heat flow throughout a geothermal field. Three-component beamforming was used to determine if the complex surface fracture system permeates deeper than is currently known. Our results show that anisotropy of seismic velocities does not decline significantly with depth, suggesting that faults and fractures, and hence permeability, persist below 3 km. Moreover, estimates of fast and slow directions, with respect to surface wave velocities, are used to determine the orientation of faults with depth. The north-east (NE) and north–north-west (NNW) orientation of the fast direction corresponds to the orientation of the Arroyo Grande and Maxtaloya–Los Humeros Fault swarms, respectively. NE and NNW orientations of anisotropy align with other major faults within the LHGF at depths permeating to 6 km. [ABSTRACT FROM AUTHOR]

Copyright of Journal of Chongqing University of Posts & Telecommunications (Natural Science Edition) is the property of Chongqing University of Posts & Telecommunications and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Due to the openness nature of wireless medium, security issues have increasingly become a bottleneck that restricts the development of ultra‐reliable and low‐latency communications (uRLLCs). Physical layer security (PLS) technique has been proposed to fulfill the security and confidentiality of information transmission by exploiting the characteristics of the wireless channel, which caters to the features of uRLLC. Furthermore, PLS also shows great practicality in artificial intelligence field, especially in wireless intelligent networks. However, the previous works on the study of PLS ignored the significance of mobility and limited packet length constraint required by uRLLC for satisfying low latency, in this paper, we investigate the impact of mobility on the secrecy performance of uRLLC by using the Random WayPoint (RWP) model and the Random Direction (RD) model. Specifically, with the tools of stochastic geometry, to observe the impact of key system parameters on the secrecy performance, we establish the closed‐form expression of connection outage probability, secrecy outage probability, and decoding error probability‐based secrecy transmission capacity (DEP‐STC). Furthermore, we derive the condition that achieves a positive DEP‐STC under two moving models, which can offer the network designer some greatly significant insights into achieving perfect secrecy. Simulations validate our derived theoretical results, and indicate that RWP moving receiver can obtain a higher security level than RD moving one, while RWP eavesdropper can lead to a lower security. [ABSTRACT FROM AUTHOR]

Efficient data dissemination is a key challenge for IoT applications. In this paper, we present an ergodic achievable rate analysis of the non-orthogonal multiple access (NOMA)-based cooperative transmission scheme in spectrum-sharing cognitive radio networks (CRNs). The transmission scheme consists of two phases, where the NOMA transmission strategy is employed at the secondary transmitter (ST) in the second phase to serve the primary receiver (PR) and secondary receivers (SRs). This cooperative spectrum-sharing transmission is favourable when the ST-PR link is strong and the ST faces a spectrum scarcity issue. To evaluate the performance of the network over Nakagami-m channels, ergodic achievable rates at PR and SRs are derived in closed forms, which can be used for any integer or non-integer value of fading index m. Finally, we compare the results of the analytical expressions with simulated results for validation. [ABSTRACT FROM AUTHOR]

This paper considers direct mobile-to-mobile (M2M) communications with a dual antenna selection (AS) system at a destination mobile node (DMN) in interference limited, dissimilar composite fading environments. In particular, we model dissimilar interference limited signals at the inputs of the dual branch AS system as (i) the ratio of two Nakagami-m (N) random variables (RVs) at the first branch and (ii) the ratio of two Rice RVs at the second branch, in order to account for non line-of-sight (NLOS) and line-of-sight (LOS) communications, respectively. Moreover, we assume variable powers of the desired as well as interference signals at the output of the DMN in order to account for the impact of shadowing. For the proposed model, we derive probability density functions, cumulative distribution functions, outage probabilities and average level crossing rates. The derived statistical results are evaluated for all the statistical measures considered and are graphically presented in order to provide insight into the impact of composite fading severities and LOS factors for the desired signal, as well as for the interference, on the system performances. [ABSTRACT FROM AUTHOR]