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Shadowed Beaulieu-Xie (SBX) is a composite fading model suitable for an environment with a random number of non-line-of-sight and line-of-sight signals encountered in the wireless communication system. There are many effects that undergo in the wireless channel that may degrade the performance of the system. Diversity is one popular technique to mitigate the effects of fading. Investigation of the influence of various parameters of SBX fading channels on the performance of dual-branch selection combining (SC) diversity receiver is carried out. In this paper, mathematical expressions for the probability density function (PDF) of the output signal-to-noise ratio of dual-SC diversity receiver are calculated for SBX fading channels. Outage probability and average bit error rate (ABER) for different kinds of modulation methods are obtained using the PDF-based method. A unified ABER expression for coherent and non-coherent modulations for dual-SC diversity receivers over SBX fading channels is also derived. The effect of shadowing and fading parameters on the performance of dual-SC diversity receivers is studied. [ABSTRACT FROM AUTHOR]

In this paper, the performance of a dual-hop mixed radio frequency (RF)/underwater wireless optical communication (UWOC) system with amplifying and forwarding (AF) relaying is investigated. The diversity combining technology were combined with unifying Fisher-Snedecor ( $ \mathcal{F} $ F ), extended generalized- $ {\mathcal{K}} $ K (EGK), and $ \alpha - \mu $ α − μ distribution for atmospheric turbulence in foggy conditions to analyze the probability density function (PDF) of RF links. The UWOC link experiences mixed exponential generalized gamma (EGG) fading. By utilizing diversity combination methods and considering the statistical effects of atmospheric turbulence, random fog, and underwater turbulence, we derive the expression for the PDF of the RF/UWOC system. In addition, the tight asymptotic expression for the outage probability and average bit error rate under high signal-to-noise ratio (SNR) is provided. The analytical expressions are verified by Monte Carlo method, and the effects of channel number on RF/UWOC system performance under various atmospheric, underwater and weather conditions are demonstrated. [ABSTRACT FROM AUTHOR]

In this work, we investigate the performance of dual-hop hybrid free-space optical/radio frequency (FSO/RF) systems with decode-and-forward relaying, where the FSO link experiences Gamma–Gamma turbulence with pointing errors, while the RF link undergoes Nakagami- m fading. Two scenarios are considered, in the first scenario, a hard-switching (HS) scheme is used for the hybrid system, in which one of the links is active at a time, with high priority for the FSO link, whereas in the second scenario, both the FSO and RF links are active simultaneously and a selection combining (SC) scheme is used at the receiver end. We derive exact analytical expressions for the outage probability and average bit error rate (ABER) in terms of multivariate Fox H functions, and develop Monte Carlo simulations for validation. In the numerical results, we compare the performance of the two scenarios with the dual-hop FSO system. This comparison shows a respectable improvement in the system's performance when the hybrid transmission technique is exploited over the dual-hop system. Moreover, the hybrid system with the SC scheme shows superior performance when compared to the system with the HS scheme in terms of the ABER. [ABSTRACT FROM AUTHOR]

Vehicle-to-everything (V2X) is considered a key factor in driving the future development of intelligent transport, which requires high-quality communication and fast sensing of vehicle information in high-speed mobile scenarios. However, high-speed mobility makes the wireless channel change rapidly, which requires frequent channel estimation and channel feedback between a vehicle and the roadside unit (RSU), resulting in an increase in communication overhead. At the same time, the high maneuverability of vehicles leads to frequent switching and misalignment of communication beams, so the RSU must have better beam prediction and tracking capabilities. To address this problem, this paper proposes an adaptive frame structure design scheme for sensing-assisted downlink (DL) communication. The basic idea of the scheme involves analyzing the communication model during the vehicle's movement. This analysis aims to establish a theoretical relationship between the Symbol Error Rate (SER) and the following two key factors: the vehicle's starting position and the distance it travels across. Subsequently, the scheme leverages the vehicle's position data, as detected by the RSU, to calculate the real-time SER for DL communication. The SER threshold is set based on the requirements of DL communication. If the real-time SER is below this threshold, channel estimation becomes unnecessary. This decreases the frequency of channel estimation and frees up time and frequency resources that would otherwise be occupied by channel estimation processes within the frame structure. The design of an adaptive frame structure, as detailed in the above scheme, is presented. Furthermore, the performance of the proposed method is analyzed and compared with that of the traditional communication protocol frame structure and the beam prediction-based frame structure. The simulation results indicate that the communication throughput of the proposed method can be improved by up to 6% compared with the traditional communication protocol frame structure while maintaining SER performance. [ABSTRACT FROM AUTHOR]

An end-to-end testbed for In-phase and Quadrature (I/Q) Imbalance (IQI) communication systems based on Software-Defined Radio (SDR) is presented. The scenario under consideration is a Single-Input–Single-Output (SISO) single-carrier communication where the transmitter is heavily affected by IQI, whose effects are mitigated through digital signal processing at the receiver. The presented testbed is highly configurable, enabling the testing of different communication and IQI parameters. Crucial insights into the practical implementation of IQI mitigation techniques, specifically through the use of asymmetric signaling at the receiver, are provided. Initially, a detailed description of the mathematical framework is given. This framework serves as the foundation for the subsequent discussion on system implementation, effectively bridging the gap between research on IQI mitigation and its practical application in single-carrier architectures. Over-The-Air (OTA) Symbol Error Rate (SER) measurements for different constellations validate the receiver design and implementation. The source code of the presented testbed is publicly available. [ABSTRACT FROM AUTHOR]

Distributed in-network processing has garnered much attention due to its capability to estimate the unknown parameter of interest from noisy measurements based on a set of cooperating sensor nodes. In previous studies, distributed in-network processing mainly focused on short-distance communication systems, wherein sensor nodes collect certain parameters of interest within their maximum communication distance. In addition, the estimation of certain parameter vectors of interest from noisy measurements, relying heavily on training signals, is achieved with a non-blind distributed estimation algorithm. However, in some applications, acquiring knowledge of training signals beforehand is difficult. Therefore, it is necessary to perform distributed estimation algorithms for receivers without training signals, a concept known as blind distributed estimation. In this paper, the generalized Sato algorithm is used to design the blind equalizer for the signal estimation. In addition, we consider extending the short-distance communication system to a long-distance communication system for an unmanned aerial vehicle (UAV) cooperating with sensor nodes in the wireless sensor network (WSN). In this scenario, the data signal is transmitted from a UAV to the WSN and is received by sensor nodes. However, the performance of the blind equalizer is susceptible to the transmission channel in long-distance communication systems. Here, we present a network topology reconfiguration approach to address the issue of distributed blind equalization. The objective of the proposed method is to discard the influence of ill-channels on the other sensor nodes by detecting ill-channels and redesigning the sensor node weights. Through computer simulation experiments, we evaluated the performance of the blind equalizer using the average mean square error (MSE) and average symbol error rate (SER). In the results of the computer simulation experiments, the blind equalizer using the proposed method outperformed the conventional methods in terms of prediction accuracy and convergence speed. [ABSTRACT FROM AUTHOR]

A flexible radio waveform, generalised frequency division multiplexing (GFDM) allows for significant degrees of freedom in adjusting the number of time slots, subcarriers, and pulse shaping filters. The GFDM is one of the multi-carrier techniques that has been proposed to achieve 5G requirements. Initially, this study discusses about the derivation of novel analytical expression of symbol error rate under α - μ fading channel using the GFDM system. The proposed derivation includes Rayleigh, Nakagami-m, and Nakagami-q fading channels as special cases for different α and μ values. Further, a simulation test-bed has been developed in MATLAB to access the simulation results and they are in good agreement with the derived theoretical results for various simulation parameters such as different roll-off factors, modulation orders and various fading parameters. [ABSTRACT FROM AUTHOR]

The authors investigate the performance of an original multifunction system with two in‐band full‐duplex capable joint radar, communications and security (JRCS) transceivers in the presence of an eavesdropper. The system concept can be generalised to a network of more than two JRCS transceivers and multiple eavesdroppers, despite the present study focusing on the three‐node scenario. By combining a bandlimited pseudonoise waveform with a data‐containing orthogonal frequency‐division multiplexing (OFDM) waveform, the authors are able to ensure a certain jamming‐to‐signal power ratio (JSR) at the eavesdropper, whilst ideal synchronisation ensures that jamming causes no deterioration to their own data transfer or radar sensing performance as it is possible to remove just the known pseudonoise waveform. To validate the system, the authors investigate through simulations the OFDM symbol error rates of all the receivers, radar target signal‐to‐interference‐plus‐noise power ratios as well as receiver operating characteristic curves, and eavesdropper's detection signal‐to‐noise power ratios through two‐branch receiver cross‐correlation. The results show that already a very low JSR of −20 dB can improve physical‐layer security without a significant increase in friendly symbol error rate or deterioration in radar performance. Additionally, other full‐duplex transceivers potentially occupying the same radio resources improve the secrecy even further. [ABSTRACT FROM AUTHOR]

Photonic integrated circuits (PIC) devices are impacted by fabrication tolerances and therefore, prior knowledge of such variations could improve the PIC fabrication process and overall yield. This paper presents a method for predicting the fabrication impacts on a telecommunication optical digital to analog converter (oDAC)-based pulse amplitude modulator level four (PAM-4) transmitter as a case study where the certainty of this passive device is subjected to random variation. Our findings allow us to estimate the production yield in a fabrication scenario using the symbol error rate (SER) benchmark and this contributes to the study of the viability of oDAC PAM-4 transmitters to replace conventional electrical digital to analog converter (eDAC) PAM-4 transmitters. [ABSTRACT FROM AUTHOR]

Two-wave with diffuse power (TWDP) is one of the most promising distributions for describing multipath fading in the emerging millimeter-wave (mmWave) band. However, traditional error performance analysis in these channels is mostly based on the approximate expressions, accurate only for specific combinations of TWDP parameters that describe particular channel conditions. Considering the aforementioned, this paper begins with an extensive literature overview of the existing average bit/symbol error probability (ABEP/ASEP) expressions in TWDP channels, revealing the absence of the exact expressions that could be used to accurately evaluate error performance in all channel conditions, for most modulation and diversity techniques. Next, the exact ASEP expressions are derived for M-ary rectangular quadrature amplitude modulation with coherent detection and for M-ary differential phase shift keying modulation. These expressions are then used to derive corresponding computationally simple closed-form asymptotic ASEPs, which accurately evaluate error performance for signal-to-noise ratios (SNR) greater than 30 dB. All the results are verified through Monte-Carlo simulation. [ABSTRACT FROM AUTHOR]

In this paper, the effects of energy harvesting (EH) on an automatic repeat request based cooperative communication network comprised of a source, a relay, and two destination nodes, are investigated in Rayleigh fading channels. The energy of the decode-and-forward relay is provided by EH throughout the radio frequency signal from the source. In the proposed transmission protocol, the source transmits a data packet to the relay and two destination nodes by direct links. If the transmission is successful at both destination nodes, these nodes reply by an acknowledgement (ACK) signal to the source and the relay. Otherwise, there are two alternatives: If the relay has received this data packet successfully and replied by an ACK signal, then it cooperates and transmits the data packet for a second time to two destination nodes. If the relay has failed and replied by a non-acknowledgement signal, the source in this case retransmits this packet to the destination nodes by direct links. First, a broadcast channel is considered where the source transmits the same data packet to the relay and destination nodes. Second, the non-orthogonal multiple access technique is applied to the same network where different packets are sent to each destination node by means of superposition coding. In both cases, the system throughputs are obtained from the derived closed-form expressions for the outage probabilities based on the Markov chain model. All theoretical results are supported by computer simulation results. [ABSTRACT FROM AUTHOR]

In this paper, we investigate an Internet of Things (IoT) network in severe fading environments, where the source sends some information to the destination. Due to the fading obstacle, the source cannot directly send the information to the destination. To tackle this issue, we consider the communication of IoT networks assisted by multi-hop relaying, where multiple relays can help assist the data transmission from the source to the destination. For the considered IoT networks assisted by multi-hop relaying, we evaluate the system performance by studying the transmission outage probability, where an analytical expression is derived to evaluate the IoT outage. We then evaluate the system performance by studying the transmission achievable data rate, where an analytical expression is provided to evaluate the IoT rate. Finally, we present some experimental results as well as the analytical results to verify the derived expressions for the IoT networks assisted by multi-hop relaying. In particular, the usage of multi-hop relaying can help extend the coverage area of IoT networks effectively. [ABSTRACT FROM AUTHOR]

Summary: The present research work aims to investigate the reliability of the mixed free space optical (FSO)/radio frequency (RF) decode‐and‐forward (DF) relaying system where the satellite intends to communicate with the ground station through the unmanned aerial vehicles (UAV) as the relay node. Moreover, it has been considered that a second UAV interferes with the intended UAV. The operation of the UAVs has been represented considering the small scale fading, path loss, 3‐D location, and probability of maintaining line‐of‐sight (LoS) and non line of sight (NLoS) links, while FSO link undergoes Malaga distributed turbulence. Using the aforementioned model, the closed form expressions for the outage probability and bit error rate (BER) have been derived. The exact expressions have been extended to obtain the high signal‐to‐noise ratio (SNR) results for the outage probability and BER. The analytical expressions have been numerically evaluated and the results obtained through these expressions have been verified using the Monte Carlo simulations. More importantly, long short‐term memory (LSTM)‐based deep learning model has been trained for prediction of outage probability. The model is trained offline and then utilized to predict the values of the outage probability in online mode with mean square error (MSE) and root mean square error (RMSE) of MSE = −45.02 and RMSE = −18.34 dB. [ABSTRACT FROM AUTHOR]

Summary: In this paper, we investigate the effectiveness of incremental relaying (IR)‐based underlay cognitive nonorthogonal multiple access (CNOMA) system with maximal ratio combining (MRC). Considering imperfect successive interference cancelation (i‐SIC), we derive analytical expressions for the outage probabilities experienced by the secondary users (SUs) and the system outage probability of the IR‐CNOMA system. We also derive the analytical expression for the outage probability of far SUs by considering IR‐CNOMA system with MRC. The maximum transmit power constraint of the secondary nodes and the interference threshold constraint of the primary receiver are considered in the analysis. We also evaluate the system throughput of IR‐CNOMA network. We also derive outage and throughput expression for the traditional cooperative relaying‐based CNOMA system (CR‐CNOMA) for the purpose of comparison. We derive analytical expression for the asymptotic outage probability and the asymptotic system outage probabilities of the SUs of IR‐CNOMA system. Further, we derive expressions for the optimal power allocation (OPA) factor at the secondary source that minimizes the asymptotic system outage probability of the IR‐CNOMA system. Through numerical and simulation investigations, we demonstrate that the system outage probability significantly lowers when the OPA factor is selected based on the criteria outlined in this work. It can be observed from the results that the IR‐CNOMA system outperforms the conventional CR‐CNOMA system in terms of outage probabilities and throughput. The outage probability is further reduced when IR‐CNOMA system with MRC is considered for the far SUs. [ABSTRACT FROM AUTHOR]

This paper investigates the symbol error rate (SER) and coverage probability of single reconfigurable intelligent surface (S-RIS) and double reconfigurable intelligent surface (D-RIS) systems operating over Weibull fading channels. In the S-RIS system, the RIS is positioned between the base station and user link, while in the D-RIS system, RIS-1 and RIS-2 are placed near the base station and user respectively. By leveraging the central limit theorem, we derive the statistical parameters of the received signal-to-noise ratio (SNR) and subsequently closed-form expressions for SER and coverage probability of both systems using the moment-generating function. Also, we determine the optimal location of the RISs in D-RIS system from the simulations of SER. Comparative analysis reveals that the D-RIS system exhibits superior error performance and provides better coverage than the S-RIS system, despite having an equal number of reflecting elements. In addition, we provide an energy consumption gain analysis of the D-RIS system. [ABSTRACT FROM AUTHOR]

Filter Bank Multi-Carrier (FBMC) modulation has been recognized as a consistent contender and a possible successor for Orthogonal Frequency Division Multiplexing (OFDM) in 5G and beyond because of its outstanding spectral properties. The channel is assessed in FBMC using pilot-symbol aided channel estimation that provides robust estimates even for severe channel conditions. In the present work, neutralizing the imaginary interference at the pilot positions is focused while estimating the channel. To neutralize the imaginary in terference, multiple auxiliary symbols have been proposed to enhance the throughput and channel capacity. The Iterative Minimum Mean Squared Error (IMMSE) cancellation scheme has been proposed to reduce the interference at the pilot and data positions. Transmission power, Bit Error Rate (BER) and throughput are computed for Filter Bank Multi Carrier (FBMC), OFDM and proven that better system performance is obtained for FBMC. The performance of channel estimation is evaluated through 5G standards and indicates that the usage of multiple auxiliary symbols per pilot leads to better throughput and low Bit Error Rate at low power transmission. [ABSTRACT FROM AUTHOR]

This paper investigates the performance of deep neural network (DNN)-based signal detection in multiple input, multiple output (MIMO), communication systems. MIMO technology plays a critical role in achieving high data rates and improved capacity in modern wireless communication standards like 5G. However, signal detection in MIMO systems presents significant challenges due to channel complexities. This study conducts a comparative analysis of signal detection techniques within both the single input, single output (SISO), and MIMO frameworks. The analysis focuses on the entire transmission chain, encompassing transmitters, channels, and receivers. The effectiveness of three traditional methods—maximum likelihood detection (MLD), minimum mean square error (MMSE), and zero-forcing (ZF)—is meticulously evaluated alongside a novel DNN-based approach. The proposed study presents a novel DNN-based signal detection model. While this model demonstrates superior computational efficiency and symbol error rate (SER) performance compared to more conventional techniques like MLD, MMSE, and ZF in the context of a SISO system, MIMO systems face some challenges in outperforming the conventional techniques specifically in terms of computation times. This complexity of MIMO systems presents challenges that the current DNN design has yet to fully address, indicating the need for further developments in wireless communication technology. The observed performance difference between SISO and MIMO systems underscores the need for further research on the adaptability and limitations of DNN architectures in MIMO contexts. These findings pave the way for future explorations of advanced neural network architectures and algorithms specifically designed for MIMO signal-processing tasks. By overcoming the performance gap observed in this work, such advancements hold significant promise for enhancing the effectiveness of DNN-based signal detection in MIMO communication systems. [ABSTRACT FROM AUTHOR]

Channel modeling is a first step towards the successful projecting of any wireless communication system. Hence, in this paper, we analyze the performance at the output of a multi-branch selection combining (SC) diversity receiver in a wireless environment that has been distracted by fading and co-channel interference (CCI), whereby the fading is modelled by newer Beaulieu-Xie (BX) distribution, and the CCI is modelled by the κ-µ distribution. The BX distribution provides the ability to include in consideration any number of line-of-sight (LOS) useful signal components and non-LOS (NLOS) useful signal components. This distribution contains characteristics of some other fading models thanks to its flexible fading parameters, which also applies to the κ-µ distribution. We derived here the expressions for the probability density function (PDF) and cumulative distribution function (CDF) for the output signal-to-co-channel interference ratio (SIR). After that, other performances are obtained, namely: outage probability (Pout), channel capacity (CC), moment-generating function (MGF), average bit error probability (ABEP), level crossing rate (LCR), and average fade duration (AFD). Numerical results are presented in several graphs versus the SIR for different values of fading and CCI parameters, as well as the number of input branches in the SC receiver. Then, the impact of parameters on all performance is checked. From our numerical results, it is possible to directly obtain the performance for all derived and displayed quantities for cases of previously known distributions of fading and CCI by inserting the appropriate parameter values. In the second part of the paper, a workflow for automated network experimentation relying on the synergy of Large Language Models (LLMs) and model-driven engineering (MDE) is presented, while the previously derived expressions are used for evaluation. Due to the aforementioned, the biggest value of the obtained results is the applicability to the cases of a large number of other distributions for fading and CCI by replacing the corresponding parameters in the formulas for the respective performances. [ABSTRACT FROM AUTHOR]

Short-reach optical communication networks have various applications in areas where high-speed connectivity is needed, for example, inter- and intra-data center links, optical access networks, and indoor and in-building communication systems. Machine learning (ML) approaches provide a key solution for numerous challenging situations due to their robust decision-making, problem-solving, and pattern-recognition abilities. In this work, our focus is on utilizing deep learning models to minimize symbol error rates in short-reach optical communication setups. Various channel impairments, such as nonlinearity, chromatic dispersion (CD), and attenuation, are accurately modeled. Initially, we address the challenge of modeling a nonlinear channel. Consequently, we harness a deep learning model called autoencoders (AEs) to facilitate communication over nonlinear channels. Furthermore, we investigate how the inclusion of a nonlinear channel within an autoencoder influences the received constellation as the optical fiber length increases. Another facet of our work involves the deployment of a deep neural network-based receiver utilizing a channel influenced by chromatic dispersion. By gradually extending the optical length, we explore its impact on the received constellation and, consequently, the symbol error rate. Finally, we incorporate the split-step Fourier method (SSFM) to emulate the combined effects of nonlinearities, chromatic dispersion, and attenuation in the optical channel. This is accomplished through a neural network-based receiver. The outcome of this work is an evaluation and reduction of the symbol error rate as the length of the optical fiber is varied. [ABSTRACT FROM AUTHOR]

Recent years have witnessed the remarkable progress in wireless communication systems due to the escalating demand for higher data rates, improved reliability, and increased energy efficiency. In this regard, Non-Orthogonal Multiple Access (NOMA) has emerged as a promising technology, enhancing spectral efficiency and accommodating multiple users concurrently within the same time and frequency resources. Simultaneously, the energy harvesting has surfaced as a sustainable solution, converting ambient environmental energy into usable electrical power for operating communication nodes. This paper proposes a cooperative NOMA transmission scheme integrating energy harvesting and utilizing Least Squares (LS) channel estimation for precise Channel State Information (CSI) acquisition. The objective is to establish an optimal communication path from source to destination. Relay selection methods: Optimal Relay Selection (ORS) and Max-Min Relay Selection (MMRS), are compared, focusing on their impact on the system performance. The analysis considers the influence of the number of relays and power allocation factor on the system, with a specific emphasis on the outage probability expressions. Comparative analysis between the cooperative-NOMA and the traditional cooperative relaying without NOMA reveals the superior performance of the cooperative-NOMA. Additionally, the ORS scheme outperforms MMRS in terms of the outage performance. [ABSTRACT FROM AUTHOR]

Species distribution models (SDMs) are extensively used to estimate species–environment relationships (SERs) and predict species distribution across space and time. For this purpose, it is key to choose relevant spatial grains for predictor and response variables at the onset of the modelling process. However, environmental variables are often derived from large‐scale climate models at a grain that can be coarser than the one of the response variable. Such area‐to‐point spatial misalignment can bias estimates of SER and jeopardise the robustness of predictions. We used a virtual species approach, running simulations across different levels of area‐to‐point spatial misalignment to seek statistical solutions to this problem. We specifically compared accuracy of SER estimates and predictive performances, assessed across different degrees of spatial heterogeneity in environmental conditions, of three SDMs: a GLM, a spatial GLM and a Berkson error model (BEM) that accounts for fine‐grain environmental heterogeneity within coarse‐grain cells. Only the BEM accurately estimates SER from relatively coarse‐grain environmental data (up to 50 times coarser than the response grain), while the two GLMs provide flattened SER. However, all three models perform poorly when predicting from coarse‐grain data, particularly in environments that are more heterogeneous than the training conditions. Conversely, decreasing environmental heterogeneity relative to the training dataset reduces the predictive biases. Because predictions are made from covariate‐grain data, the BEM displays lower predictive performance than the two GLMs. Thus, standard model selection methods would fail to select the model that best estimates SERs (here, the BEM), which could lead to false interpretations about the environmental drivers of species distributions. Overall, we conclude that the BEM, because it can robustly estimate SER at the response grain, holds great promise to overcome area‐to‐point misalignment. [ABSTRACT FROM AUTHOR]

In this paper, we consider a downlink non-orthogonal multiple access (NOMA) system over Nakagami-m channels. The single-antenna base station serves two single-antenna NOMA users based on statistical channel state information (CSI). We derive the closed-form expression of the exact outage probability under a given decoding order, and we also deduce the asymptotic outage probability and diversity order in a high-SNR regime. Then, we analyze all the possible power allocation ranges and theoretically prove the optimal power allocation range under the corresponding decoding order. The demarcation points of the optimal power allocation ranges are affected by target data rates and total power, without an effect from the CSI. In particular, the values of the demarcation points are proportional to the total power. Furthermore, we formulate a joint decoding order and power allocation optimization problem to maximize the sum throughput, which is solved by efficiently searching in our obtained optimal power allocation ranges. Finally, Monte Carlo simulations are conducted to confirm the accuracy of our derived exact outage probability. Numerical results show the accuracy of our deduced demarcation points of the optimal power allocation ranges. And the optimal decoding order is not constant at different total transmit power levels. [ABSTRACT FROM AUTHOR]

A hybrid satellite–terrestrial relay network is a simple and flexible solution that can be used to improve the performance of land mobile satellite systems, where the communication links between satellite and mobile terrestrial users can be unstable due to the multipath effect, obstacles, as well as the additional atmospheric losses. Motivated by these facts, in this paper, we analyze a system where the satellite–terrestrial links undergo shadowed Rice fading, and, following this, terrestrial relay applies the selection relaying protocol and forwards the information to the final destination using the communication link subjected to Nakagami-m fading. For the considered relaying protocol, we derive the exact closed-form expressions for the outage probability, outage capacity, and ergodic capacity, presented in polynomial–exponential form for the integer-valued fading parameters. The presented numerical results illustrate the usefulness of the selection relaying for various propagation scenarios and system geometry parameters. The obtained analytical results are corroborated by an independent simulation method, based on the originally developed fading simulator. [ABSTRACT FROM AUTHOR]

Orthogonal Frequency Division Multiplexing (OFDM) is the most significant transmission techniques that permits feasible modulation and demodulation. OFDM system is majorly affected by high Peak-to-Average Power Ratio (PAPR) values. To reduce this issue, this research proposed a Partial Transmit Sequence - Chaotic Sand Cat Swarm Optimization (PTS-CSCSO) technique of Cyclic Prefix-OFDM (CP-OFDM). To encode and decode the signal in the CP-OFDM system, the Space Time Block Coding (STBC) technique is utilized and for modulation and demodulation, the Quadrate Amplitude Modulation (QAM-16) is utilized. The PTS technique is utilized for PAPR reduction, in that phase factor is optimized by using the proposed PTS-CSCSO algorithm. The Additive White Gaussian Noise (AWGN) channel is utilized, that transmit the signal from transmitter to receiver. The performance of the proposed algorithm is evaluated with performance metrics of Bit Error Rate (BER), Symbol Error Rate (SER), and Complementary Cumulative Distribution Function (CCDF). The proposed algorithm attained a minimum BER of 10-8 which is superior to other existing methods like Prime Learning Ant Lion Optimization (PL-ALO) and Phase Optimizer-assisted Partial Transmit Sequence (PO-PTS). [ABSTRACT FROM AUTHOR]

Simultaneous wireless information and power transmission (SWIPT) allows the use of RF signals for both information detection and energy harvesting. Integration of cooperation, NOMA and SWIPT can provide energy-efficient, reliable, and spectral-efficient networks. Therefore, this study aims to design energy harvesting-enabled cooperative NOMA (C-NOMA) networks. This work investigates relay selection for multiple relay downlink C-NOMA networks with SWIPT in the presence of interference. The analytical closed-form outage probability expressions for the proposed relay selection are derived. Subsequently, the impact of various parameters, including the number of available relay nodes, energy harvesting parameters, and energy conversion efficiency, is analyzed on the performance of proposed networks. The finding showed that system performance improves with the number of intermediate relaying nodes, transmit power, and energy conversion efficiency. Comparative analysis of NOMA and time division multiple access TDMA proved the superiority of NOMA over traditional OMA schemes. [ABSTRACT FROM AUTHOR]

According to the theory of single channel blind source separation (SCBSS), the algorithm based on virtual channel expansion must be established in a known source number, and most algorithms can only separate two source signals. When separating multiple source signals, the performance will deteriorate sharply. Since the existing methods of this kind use only a single algorithm for virtual channel expansion, they cannot retain all the source signals' valuable information and effectively separate the multiple source signals. From the perspective of making the constructed virtual multi-channel signal contain enough information of the source signals as much as possible, this paper proposes a SCBSS algorithm based on improved wavelet packet and variational mode decomposition (IWP-VMD-SCBSS). Firstly, the source number is estimated according to the interval sampling method and the minimum description length (MDL) criterion. Secondly, the signal reconstruction method based on improved wavelet packet decomposition (IWPD) is used to reconstruct multiple purer virtual signals. Then the virtual signals are combined with the first intrinsic mode function (IMF) of two-level variational mode decomposition (VMD) and the original single-channel observed signal to constitute a virtual multi-channel signal. Finally, the joint approximate diagonalization of eigen-matrices (JADE) algorithm is used to process the virtual multi-channel observed signal to achieve BSS and obtain estimated source signals. The simulation results indicate that the IWP-VMD-SCBSS algorithm can achieve a lower symbol error rate (SER) than existing algorithms and lower computational complexity. It can solve the SCBSS problem of multiple communication signals effectively under an unknown source number. [ABSTRACT FROM AUTHOR]

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Recently, non-orthogonal multiple access (NOMA)-based space–air–ground integrated networks (SAGINs) have gained increasing attention due to their robust communication, broader coverage, and resource-saving advantages. However, it is imperative to consider physical layer security as a crucial performance metric in NOMA-based SAGINs. This study addresses this concern by constructing a NOMA-based free space optical (FSO)/radio frequency (RF) dual-hop SAGIN system with eavesdroppers on both links. The two new fading channel models were proposed, considering the FSO link's fog absorption and the RF link's stochastic distribution based on Málaga and shadowed Rician distributions. The closed-form expressions for the secrecy outage probability are derived for the SAGIN system. Monte Carlo simulations were conducted to validate the theoretical findings. The results revealed the influence of fog absorption and the stochastic geometry distribution on the SAGIN system. [ABSTRACT FROM AUTHOR]

The capacity performance of visible light communication (VLC) systems can be improved by using sparse code multiple access (SCMA). Since SCMA is a codebook-based multiple access scheme, the design of the codebook is crucial. SCMA codebook performance is severely affected by shot noise. Although several codebook design metrics have been proposed to compensate for the constellation distortion caused by shot noise, the improvement in performance is limited. In order to solve this problem, we use a separable codebook design structure to derive the analytical expression of the symbol error rate (SER) for the SCMA-VLC system under shot noise. According to the SER expression, we formulate an optimization problem and obtain a multi-user superimposed codebook to achieve a minimum SER for the SCMA-VLC system. The simulation results show that the proposed codebook significantly improves the performance of the SCMA-VLC system, especially in the case of high shot noise. [ABSTRACT FROM AUTHOR]

Wireless networks need channel estimation (CE) to function well. Deep learning (DL) has improved 5G and future-generation network communication reliability and computational complexity. Due to its lack of statistical channel information, the least squares (LS) estimation approach has significant estimate mistakes despite its cost-effectiveness and widespread usage. The MIMO-OFDM-5G-CS-AGAN architecture improves CE for 5G and beyond networks. The suggested CE architecture uses DL to outperform LS. The suggested architecture has been specifically developed using a multipath channel profile and a MIMO system, to effectively address situations characterized by mobility-induced Doppler effects in 5G and future networks. Because of its adaptability and scalability, the suggested architecture can accommodate almost unlimited transceiver antennas. Conditional Self-Attention Generative Adversarial Networks (CS-AGAN) are at the heart of the proposed method because they reliably provide high-quality CE at low error rates. Python is used for the implementation of the suggested approach. In this case, we have the performance metrics symbol error rate (SER), bit error rate (BER), uplink sum rate, downlink sum rate, Normalized CE Error, and mean square error. When compared to current methods like MIMO-OFDM-5G-Bi-LSTM, MIMO-OFDM-5G-DNN, and MIMO-OFDM-5G-CGAN, the suggested approach achieves 13.4%, 13.02%, 12.21% lower BER and 11.23%, 6.3%, 9.08% lower SER. [ABSTRACT FROM AUTHOR]

Light emitting diode (LED) non-linearities bounds the output performance of visible light communication (VLC) system. LED's front-end components and high peak to average power ratio (PAPR) of the transmitted signal are the main contributors of distortion in transmitted signal. In this work, both pre-distortion and post-distortion techniques are analyzed for the reduction of non-linear distortion of intensity modulation/direct detection (IM/DD) based channel. The modulation technique used is (OQAM-O-FBMC) offset quadrature amplitude modulation optical filter bank multi-carrier. A hybrid PAPR reduction and non-linear distortion mitigation technique for VLC is proposed. The proposed technique consists of hybrid processing algorithm partial transmit sequence (H-PTS) method for PAPR reduction and kernel minimum symbol error rate (KMSER) based post-distortion method for reduction of non-linear distortion. MATLAB based simulations have been provided for the analysis of proposed hybrid method. The results have shown that proposed hybrid technique shows 2 dB improvement in PAPR and 4 dB improvement in non-linear distortion of VLC system. [ABSTRACT FROM AUTHOR]

The paradigm of the Next Generation cellular network (6G) and beyond is machine-type communications (MTCs), where numerous Internet of Things (IoT) devices operate autonomously without human intervention over wireless channels. IoT's autonomous and energy-intensive characteristics highlight effective energy efficiency (EEE) as a crucial key performance indicator (KPI) of 6G. However, there is a lack of investigation on the EEE of random arrival traffic, which is the underlying platform for MTCs. In this work, we explore the distinct characteristics of F -composite fading channels, which specify the combined impact of multipath fading and shadowing. Furthermore, we evaluate the EEE over such fading under a finite blocklength regime and QoS constraints where IoT applications generate constant and sporadic traffic. We consider a point-to-point buffer-aided communication system model, where (1) an uplink transmission under a finite blocklength regime is examined; (2) we make realistic assumptions regarding the perfect channel state information (CSI) available at the receiver, and the channel is characterized by the F -composite fading model; and (3) due to its effectiveness and tractability, application data are found to have an average arrival rate calculated using Markovian sources models. To this end, we derive an exact closed-form expression for outage probability and the effective rate, which provides an accurate approximation for our analysis. Moreover, we determine the arrival and required service rates that satisfy the QoS constraints by applying effective bandwidth and capacity theories. The EEE is shown to be quasiconcave, with a trade-off between the transmit power and the rate for maximising the EEE. Measuring the impact of transmission power or rate individually is quite complex, but this complexity is further intensified when both variables are considered simultaneously. Thus, we formulate power allocation (PA) and rate allocation (RA) optimisation problems individually and jointly to maximise the EEE under a QoS constraint and solve such a problem numerically through a particle swarm optimization (PSO) algorithm. Finally, we examine the EEE performance in the context of line-of-sight and shadowing parameters. [ABSTRACT FROM AUTHOR]

Abstract Multiple-input–multiple-output (MIMO) systems have effectively addressed today’s high demand for 5G communications and beyond. Further, MIMO-assisted space–time block codes (STBCs) have been shown to enhance the system’s performance and provide a complete variety of coherent flat-fading channels. Additionally, the closed-form expression of the probability density function of the summation of correlated Weibull random variables remains unknown. In this work, we investigate the performance analysis of MIMO-STBC-enabled systems subject to the Weibull fading channel. New tight approximate expressions for numerous system performance metrics, e.g., outage probability, average capacity under various rate adaption methods, and average symbol/bit error rate, have been obtained. The Monte Carlo simulation method has corroborated all the presented results.

5G and next-generation physical layer advancements have being made at a breakneck speed. At the heart of it is millimeter wave technology, which uses extremely high frequency transmissions at 28, 38, and 72 GHz. These MM wave channels utilize approximately 20 GHz of spare spectrum to enable faster data rates to a larger number of mobile subscribers. In multiple-input multiple-output (MIMO) systems, transmit beamsteering through directional antenna arrays supported by maximal ratio combining (MRC) receivers is used alongwith MM wave technology to investigate link performance as a function of unfavourable inter-antenna correlations. In this paper, the system is modelled for short-range MM wave communications under separately correlated, non-line-of-sight (NLOS) Rayleigh environments. Here, exact closed form expressions are presented for the symbol error rate (SER) and asymptotic (high signal-to-noise ratio (SNR)) SER of the beamsteered MM wave model. The dependency of SER on transmit-receive correlations is seen in the derivations. The results are analyzed using double-correlated statistics for the maximum eigen value of complex Wishart matrices. Specifically, in the MM wave regime, correlation matrix entries vary with steering/response vectors. This does not hold true in the case of microwave links. It is therefore proposed to effectively adjust these vectors to attain novel minimized equicorrelations at the transmit and receive sides of the MM wave MIMO link. The minimally tuned MIMO-MRC model demonstrates significant average SER and asymptotic (high SNR) SER reductions under both uplink and downlink scenarios with two (02) antennas at the transmitter and receiver, respectively. The proposed model also showcases drastically lower average SER levels compared to those of existing non-equicorrelated systems. Simulation results validate the analytical study.

Multiple-input–multiple-output (MIMO) systems have effectively addressed today's high demand for 5G communications and beyond. Further, MIMO-assisted space–time block codes (STBCs) have been shown to enhance the system's performance and provide a complete variety of coherent flat-fading channels. Additionally, the closed-form expression of the probability density function of the summation of correlated Weibull random variables remains unknown. In this work, we investigate the performance analysis of MIMO-STBC-enabled systems subject to the Weibull fading channel. New tight approximate expressions for numerous system performance metrics, e.g., outage probability, average capacity under various rate adaption methods, and average symbol/bit error rate, have been obtained. The Monte Carlo simulation method has corroborated all the presented results. [ABSTRACT FROM AUTHOR]

Multi‐user (MU) massive multiple input multiple output (mMIMO) is considered a potential technology for fifth generation (5G) and sixth‐generation (6G) wireless systems. The presence of the antenna arrays at the base station level to communicate with the users or to serve tens of single antenna users leads to excessively high system costs and power consumption. The deployment 1‐bit digital‐to‐analogue converters (DACs) in the base station can solve these problems. This paper starts by presenting an analytical study centered on the effects of 1‐bit DACs on the system envisaged for a Rayleigh‐type fading channel. Compact‐form expressions are derived for the symbol error rate. Afterwards, an efficient end‐to‐end deep learning technique to compensate for the joint effect of 1‐bit DAC and imperfect channel state information in downlink mMIMO systems. Moreover, to improve the performance of the considered system, a DAC mixed architecture is proposed, where a number of antennas use 1 bit DACs while the others do not. The simulations results showed the improvement in transmission quality of the downlink of the MU‐mMIMO system in the presence of hardware imperfections using the considered end‐to‐end compensation technique. [ABSTRACT FROM AUTHOR]

The purpose of this study is to analyze the performance of the multiple-input multiple-output (MIMO) system in combination with the non-orthogonal multiple access (NOMA) system, taking into consideration the robust fading channel circumstances that are characterized by considerable variations in signal quality. This study examines the susceptibility of the system to various variables that impact channel impairments and the achievable data rate. It is assumed that the fading connections, which are independent and identically distributed (i.i.d.), adhere to Nakagami- m distributions. These links also have successive interference cancellation (SIC) errors, and the channel coefficients exhibit temporal variability. The variables examined in this research include the transmission power of the base station (BS), the presence of imprecise channel state information (CSI), the number of antennas used at the BS, and the power ratio assigned to NOMA users. To assess the efficacy of the system, the conventional time division multiple access (TDMA) approach has been chosen as a means of comparing the performance of the two users inside each beam. The results of the simulations also show that MIMO-NOMA systems have a higher channel capacity than traditional orthogonal multiple access (OMA) systems. This study utilizes a comprehensive dataset to demonstrate the congruence between the analytical findings and the simulation outcomes. [ABSTRACT FROM AUTHOR]

Providing reliable service to cell edge users has been a practical challenge for network operators due to the deep fading effects and limited base station (BS) resources. The low received signal strength causes the Quality of Service (QoS) degradation of the cell edge users and hence demands appropriate solutions to improve the user connectivity. To address this issue, this article proposes a two-tier partial cooperative relaying scheme, deployed in a non-orthogonal multiple access (NOMA)-based downlink network that serves the edge users with the minimum required QoS. Comparative performance analysis has been presented for two relaying schemes: amplify-and-forward (AF) and partial decode-and-forward (DF) in terms of outage probability and overall sum rate of the edge users. Additionally, the maximal ratio combining (MRC) diversity technique is integrated with the relaying network to further enhance the QoS of cell edge users. The impact of successive interference cancellation (SIC) on the outage performance has been thoroughly investigated. It has been established through extensive simulation that the partial DF technique is a promising relaying technique to improve the overall performance of cell edge users. [ABSTRACT FROM AUTHOR]

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Turbo-Coded multiple-input multiple-output orthogonal frequency division multiplexing Channel Estimation, using Chaotic Grey Wolf Optimizer and the Genetic Algorithm (TC-MIMO-OFDM-Hybrid-CGWO-GA), is proposed in this manuscript. To enhance the performance of the bit error rate (BER), the proposed turbo code lessens the maximal correlation of the channel in the frequency domain. Initially, the channel is estimated using LS-MMSE individually using Chaotic Grey Wolf Optimizer (CGWO) and the LS-MMSE is combined with a genetic algorithm to scale the best channel for reducing the error. The encoding and decoding methods are done with the help of Turbo-codes for LS channel estimation. Then, the performance of the proposed method is analyzed with different performance metrics, such as the bit error rate, mean square error, channel estimation, computational cost, overhead, and symbol error rate. From the analysis, the proposed method attains lower computational costs of 99.67%, 98.38%, 92.34% and 97.45%, lower bit error rates of 98.33%, 89.34%, 83.12% and 88.96% and lower mean square errors of 93.15%, 91.25%, 79.90% and 92.88% analyzed to the existing methods, such as TSO-CE-TC-MIMO-OFDM, MFPA-CE-MIMO-OFDM, OSBS-CEA-MIMO-OFDM, and IAMO-CE-MIMO-OFDM. [ABSTRACT FROM AUTHOR]

Signal detection turns out to be a critical challenge in massive MIMO (m-MIMO) system due to the deployment of large number of antennas at the base station. Although, the minimum mean square error (MMSE) is one of the popular signal detection method, but, it requires matrix inversion with cubic complexity. In order to reduce computational complexity, several suboptimal signal detection methods were proposed such as Gauss-Seidel, successive over relaxation, Jacobi, Richardson methods. Although, these methods provide low complexity but their performance are limited to MMSE method. In this paper, we have proposed two signal detection techniques namely QR decompositions (QRD) and ordered QRD (OQRD). Finally, the performances of proposed signal detection methods are compared with various conventional methods in terms of symbol error rate (SER) and computational complexity. The simulation results validate that the proposed methods outperform the MMSE method with substantially lower computational complexity. [ABSTRACT FROM AUTHOR]

Precoding techniques are widely used to eliminate interference between multiple user signals in a wireless fading channel environment. The linear MMSE precoding technique, one of the most widely used techniques so far, has low computational complexity but has the disadvantage of relatively poor symbol error rate (SER) performance. The symbol-level precoding (SLP) technique, on which much research has been conducted recently, has excellent SER performance but has the disadvantage of being too computationally complex. In this paper, we propose a hybrid precoding technique that simultaneously applies SLP and MMSE precoding to appropriately adjust SER performance and computational complexity performance. If two different types of precoding techniques are applied simultaneously, interference may occur between signals to which different types of precoding are applied, which can significantly deteriorate SER performance. Therefore, in this paper, precoding is designed to prevent interference between the two signals using the null space of the channel matrices. Through computer simulation, the proposed scheme showed that its SER performance was superior to that of the linear MMSE scheme, and the computational complexity was much lower than that of the SLP scheme. [ABSTRACT FROM AUTHOR]

Multi-user detection techniques are crucial in minimizing the impact of Multi-Access Interference in Multiple-Input Multiple-Output Orthogonal Frequency-Division Multiplexing (MIMO-OFDM) systems. It is suggested to combine channel estimation with multi-user identification to get rid of different interferences and lower the Bit Error Rate. In this manuscript, Channel Estimation and Data Detection for 5G MIMO Communication in Fading Channels based on Recalling Enhanced Recurrent Neural Network are proposed. The suggested method prioritizes fast communication and strives to provide high reliability even when there is just a small amount of user equipment per base station. The study of the multipath Rayleigh fading channel in MIMO-OFDM systems has a difficulty with frequency selective channel estimate. The primary air interface for 4G and 5G broadband wireless communications is MIMO-OFDM. With its emphasis on the network's active users and its ability to reduce interference, MIMO-OFDM offers further advantages in multi-user identification. When the activity factor is unknown, the deep learning technique is used to identify the active users in the multi-access system. With a high data rate, the RERNN classifier is utilized to evaluate the unknown activity component. The BS receiver scans for active users and deciphers their transmissions. Both pilot and data symbols are used in activity detection. A unique pilot allocation strategy that reduces the common relation of the measurement matrix is proposed for optimum pilot placement. The sparse channel assessment is eventually verified, and the computational cost is decreased, by selecting the best pilot patterns with the aid of improved Mexican axolotl optimization algorithm. The CE and decoder techniques both regulate the impact of sounds and MAI. It accurately decodes the received signal without channel issues using Python implementation. Here the performance metrics like of Symbol Error Rate, Bit Error Rate, Uplink Sum Rate, Downlink Sum Rate, Normalized CE Error and Mean Square Error. The suggested approach demonstrates a reduction in BER by 23.34%, 17.02%, and 32.21%, as well as a reduction in SER by 21.09%, 12.32%, and 19.08%, when compared to conventional methodologies. [ABSTRACT FROM AUTHOR]

Optical wireless communication (OWC) enables wireless connectivity using ultraviolet bands, infrared or visible. With its advantages features as high bandwidth, low cost, and operation in an unregulated spectrum. Free-space optical (FSO) communication systems are near terrestrial as a communication link between transceivers, the link is line-of-sight and successfully transmitted optical signals. Nevertheless, the optical signals transmissions over the FSO channels bring challenges to the system. To overcome the challenges posed by the FSO channels, the most common technique is to use relay stations, the most recent is the reconfigurable intelligent surfaces (RISs) technique. This study introduces a Weibull distribution model for a free-space optical communication link with RISs assisted, the parameter used to evaluate the performance of the system is the average symbol error rate (ASER). The RISs effect is examined by considering the influence of the transmitter beam waist radius, shape parameter, aperture radius, scale parameter, and signal-to-noise ratio on the ASER. [ABSTRACT FROM AUTHOR]

An opto-electronic system for non-line-of-sight (NLOS) communication using scattered laser radiation for unmanned aerial vehicle (UAV)–ground and ground–UAV schemes at a wavelength of λ = 450 nm and a ground–UAV scheme at a wavelength of λ = 510 nm are described. The symbol error rate (SER) and its standard deviation were analyzed for different schemes of the communication channel. The transceiver system included a laser source with a power supply, a modulator, a lens refractor, a bandpass filter, a photomultiplier tube (PMT), a demodulator, and a receiving computer. The experimental data obtained at nighttime showed that the NLOS atmospheric optical communication at a wavelength of λ = 450 nm was feasible for the UAV–ground scheme at a baseline distance of up to 150 m for a UAV with a transmitter at a height of 10 m and at a baseline distance of up to 125 m for a UAV at a height of 20 m. For the ground–UAV scheme, stable communication was observed at baseline distances of up to 50 m for a UAV with a receiver at a height up to 30 m. The NLOS atmospheric optical communication at a wavelength of 510 nm was obtained for the ground–UAV scheme at baseline distances of up to 100 m for a UAV with a receiver at a height up to 45 m, as well as at baseline distances of up to 385 m for UAV flying at a height up to 20 m. [ABSTRACT FROM AUTHOR]