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Antennas operating at the high-frequency (HF) band (3–30 MHz) are frequently electrically small due to the large wavelength of electromagnetic waves (10–100 m). However, the bandwidth-efficiency products of passively matched electrically small antennas (ESAs) are fundamentally limited. Wideband HF waveforms using bandwidths of 24 kHz or more have recently received significant attention in military communications applications. Efficiently radiating such signals from conventional passive ESAs is very challenging due to fundamental physical limits on bandwidth-efficiency products of ESAs. However, active antennas are not subject to the same constraints. In this work, we present the design and experimental characterization of a high-power, class-E active ESA with enhanced bandwidth-efficiency product compared to that of passively matched ESAs. Specifically, the proposed class-E active ESA can radiate wideband HF signals with bandwidths of 24 kHz or more at 3 MHz (fractional bandwidths of ≈ 1 % – 4 %), with total efficiencies ranging from 40 % up to 80 % depending on the modulation type and radiated power levels approaching 100 W. Our approach uses a highly efficient, integrated class-E switching circuit specifically designed to drive an electrically small, high-Q HF antenna over a bandwidth exceeding 24 kHz at 3 MHz. Using a high-Q RLC antenna model, we have successfully demonstrated wideband binary ASK, PSK, and FSK modulations with the proposed class-E active ESA. Experimental results indicate that the bandwidth-efficiency product of this class-E active ESA is 5.4–9.8 dB higher than that of an equivalent passive design with the same data rate and bit-error-rate. [ABSTRACT FROM AUTHOR]

The non-orthogonal multiple access (NOMA) scheme has been recognized as a promising candidate for future generation wireless communication networks that require a high data rate and spectral efficiency. In order to achieve a superior spectral efficiency, the orthogonal frequency division multiplexing (OFDM) technique with the robust channel estimation algorithm can be combined with the NOMA scheme. However, due to the inherent problem of inter-carrier interference in the OFDM-based systems, channel estimation using training symbols are not usually perfect. Furthermore, the successive interference cancellation (SIC) process commonly carried out in NOMA systems to address the interference among users is also imperfect under practical scenarios. Thus, a theoretical framework of the OFDM-based NOMA system to analyze the effect of both the imperfect SIC and channel estimation errors is presented in this paper. In particular, the effect of both the channel estimation errors and imperfect SIC, introduced at the receiver, on the bit error rate (BER) performance metric is analyzed under Rayleigh fading channel conditions. Our analytical results are compared to the corresponding simulation results for different design parameters. It is shown that the analytical and simulation results are in good agreement. Moreover, while revealing the importance of CSI and SIC, the results equally show that the assumption of perfect CSI and SIC is not practical, hence the need for accurate schemes for improved BER performance. [ABSTRACT FROM AUTHOR]

ABSTRACT In this paper, a passive reflective intelligent surface (RIS) assisted bidirectional full‐duplex (FD) wireless system in a realistic Nakagami‐m$$ m $$ fading with N$$ N $$ reflective elements and two source nodes is proposed. The source nodes are equipped with dual antennas for FD mode transmission and reception. The primary cause of degradation in the performance of the FD system is self‐interference, which can be reduced by increasing the number of reflective elements on the meta‐surface. Analytical expressions have been derived for the proposed RIS‐aided bidirectional FD wireless systems in terms of outage probability and bit error rate (BER). Numerical results show that doubling the number of reflecting elements considerably improves the outage performance of the proposed system in terms of signal‐to‐noise ratio (SNR) compared with RIS‐assisted half‐duplex (HD) mode. Additionally, different modulation schemes have been employed to evaluate the BER performance of the proposed system. The accuracy of analytical expressions is validated by matching Monte Carlo with analytical simulations. [ABSTRACT FROM AUTHOR]

Inter-Satellite Optical Wireless Communication (Is-OWC) is a pivotal technology for advancing global connectivity and the effectiveness of space-based operations. It serves as the linchpin for various applications such as global internet coverage, Earth observation, and remote sensing, bolstering our capacity to monitor the planet and deliver essential services. This paper presents the design and performance evaluation of a Polarization Division Multiplexing (PDM) and Multiple Input Multiple Output (MIMO)-based Is-OWC system operating at a data rate of 60 Gbps. The system was tested under varying transmission distances, atmospheric turbulence, and pointing error conditions. At a transmission distance of 10,000 km, the system achieved a Bit Error Rate (BER) of 6.76 × 10⁻3 for Channel 1 (X polarization) and 7.1 × 10⁻3 for Channel 4 (Y polarization), both within Forward Error Correction (FEC) limits. The introduction of a 4 × 4 MIMO configuration extended the transmission range to 14,000 km, with a corresponding BER of 9.1 × 10⁻3 for Channel 1 and 8.7 × 10⁻⁵ for Channel 4. Eye diagrams confirm successful signal reception, demonstrating that the system can maintain high data rates and low error rates over long distances. The proposed PDM-MIMO system showcases high-capacity, robust performance under challenging conditions, such as turbulence and pointing errors, validating its suitability for space-based communication applications. These findings highlight the potential of the system for future deployments in satellite networks, offering reliable, high-throughput, and low-latency data transmission over extended distances. [ABSTRACT FROM AUTHOR]

In this paper, a fast temporal multiple sparse Bayesian learning (FTMSBL)-based channel estimation method for underwater acoustic (UWA) orthogonal frequency division multiplexing (OFDM) systems is proposed, which is optimized using the fast marginalized likelihood maximization method. The algorithm fully uses the consistent sparse structure and time-domain correlation properties of channels to improve the reconstruction performance and computational efficiency, offering better performance and higher computational efficiency than the traditional Bayesian learning algorithms. At the same time, the FTMSBL algorithm does not require computing the inverse of large matrices and consumes very little storage resources in the operation, making it suitable for hardware implementation. Simulation and sea trial results show that the FTMSBL-based underwater channel estimation algorithm achieves higher channel estimation accuracy than the orthogonal matching tracking algorithm, and the system bit error rate (BER) is significantly reduced; specifically, the FTMSBL algorithm can achieve optimal performance in strong time-dependent channels. [ABSTRACT FROM AUTHOR]

Quantum dense coding (QDC) provides great potential for high‐capacity quantum communication. However, it is highly demanded for practical applications to realize high‐capacity QDC with multiple coded information. Here, a high‐capacity QDC with multiple streams is reported in different channels simultaneously through frequency‐division multiplexing (FDM). The broadband entangled state is generated from a pair of degenerate optic al parametric amplifiers with short cavity lengths. Based on the resultant broadband entanglement, multiple pieces of information coded using binary phase shift keying (BPSK) are transferred with the FDM method. As an experimental demonstration, four pieces of information composed of pseudo‐random numbers are transmitted at a rate of 4 Mbit s–1 using BPSK encoding. The decoded bit error rate reaches 10−3$ 10^{-3}$, which is an average 35‐fold improvement compared with the classical scheme. Furthermore, it is possible to make full use of sideband resource for four different information by using orthogonal FDM. This scheme can be extended to more different information by directly increasing the FDM sideband subchannels, and opens an avenue to construct high‐capacity quantum communication, while minimizing the cost of quantum resource. [ABSTRACT FROM AUTHOR]

This paper discusses a new symbol modulation scheme known as polarized amplitude and phase shift keying, (Pol$Pol$‐APSK) modulation with four rings in its basic form. The new scheme maps power‐polarized symbol pairs on its constellation in order to increase the number of data symbols. Pol$Pol$‐APSK exploits a symbol mapper based on a conjugate power splitting algorithm. Product modulation is applied, where a voltage signal of a specified amplitude and phase is multiplied by another current signal of a specified amplitude and phase, thus forming polymorphic signals in the product constellation. At the receiver, an isolated detection is performed, where the voltage signal is detected independently of the received current signal. A selection combining scheme is then used. The results depict unity peak‐to‐average power ratio and low average symbol energy, which is desirable for Green communications in 5G networks. It presents lower bit error rates when compared with the state‐of‐the art M$M$‐ary quadrature amplitude modulation, with a signal‐to‐noise ratio gap of at least 10[dB]$10\; [\text{dB}]$. The proposed analytical framework closely matches the simulations for bit error rates under M=16,32,64Pol-APSK$M=16,32,64 \ Pol\text{-APSK}$. [ABSTRACT FROM AUTHOR]

Due to the physical characteristics of acoustic channels, the performance of underwater acoustic communication networks (UACNs) is more susceptible to the impacts of multipath and Doppler effects. Channel quality can serve as a measure of the reliability of underwater communication links. A cross-layer routing protocol based on channel quality (CLCQ) is proposed to improve the overall network performance and resource utilization. First, the BELLHOP ray model is used to calculate the channel impulse response combined with the winter sound speed profile data of a specific sea area. Then, the channel impulse response is integrated into the communication system to evaluate the channel quality between nodes based on the bit error rate (BER). Finally, during the selection of the next hop node, a reinforcement learning algorithm is employed to facilitate cross-layer interaction within the protocol stack. The optimal relay node is determined by the channel quality index (BER) from the physical layer, the buffer state from the data link layer, and the node residual energy. To enhance the algorithm's convergence speed, a forwarding candidate set selection method is proposed which takes into account node depth, residual energy, and buffer state. Simulation results show that the packet delivery rate (PDR) of the CLCQ is significantly higher than that of Q-Learning-Based Energy-Efficient and Lifetime-Extended Adaptive Routing (QELAR) and Geographic and Opportunistic Routing (GEDAR). [ABSTRACT FROM AUTHOR]

The joint beamforming optimization from the perspective of the bit error rate (BER) in a reconfigurable intelligent surface (RIS)–assisted intelligent communication system is studied in this paper. A genetic algorithm (GA) is investigated to address the bottleneck of the system performance based on the dynamic adaptability theory. However, the bottleneck is caused by the interaction between the active and passive beamforming. To tackle the constraints of conventional optimization approaches, the hybrid scheme is proposed to combine the GA optimization (GAO) and fully connected neural network (FCNN) strategy. Specifically, the intelligent collaborative tuning of system parameters is achieved using this proposed technique. Simulation findings indicate that the hybrid scheme not only simplifies the calculation process to obtain the optimal network parameters, but also effectively optimizes the system structure by dynamically adjusting the RIS reflection configuration. Based on this, the signal transmission quality is improved, interference is reduced, and the stable and efficient operation of the RIS–assisted intelligent communication system is ensured in the complex wireless transmission scenario. [ABSTRACT FROM AUTHOR]

Nonlinear signal distortions are one of the main reasons limiting the throughput and length of modern fiber-optic communication lines. One of the developed approaches to nonlinear distortion compensation is based on the application of perturbation theory methods to the nonlinear Schrödinger equation, and allows one to obtain a relationship between transmitted and received symbols. Gradient methods that minimize the standard deviation between symbols are usually used to find the perturbation coefficients. However, the main parameter characterizing the data transmission quality is the bit error rate. We propose a modification of this approach in the form of a two-stage scheme for calculating the perturbation coefficients. At the first stage, the coefficients are calculated using the least squares method by minimizing the standard deviation, and at the second stage, the obtained solution is used as an initial approximation to minimize the error coefficient using the particle swarm method. In a numerical experiment, using the algorithm for compensating for received signal distortions based on the proposed scheme, a 0.9 dB gain in the signal-to-noise ratio is obtained for a multi-span line 20 × 100 km long and a 16QAM signal with a channel rate of 267 Gbit/s. An improvement in the accuracy of the algorithm (compared to a single-stage scheme) is shown, estimates of the computational complexity of the algorithm are obtained, and the relationship between its complexity and accuracy is presented. [ABSTRACT FROM AUTHOR]

The growing number of mobile stations requires relaying protocols that can efficiently transmit large volumes of data with minimal computational complexity. Systems that combine joint symbol and channel estimation with Amplify-and-Forward Multiway Relay (MWR) systems provide a highly effective solution to this problem. Thus, this study introduces a new Nested PARAFAC-based MWR system model as its primary contribution. Then, a non-iterative semi-blind receiver is designed to allow simultaneous estimation of symbols and channels. This computationally efficient approach is validated using Monte Carlo computational simulations, showing that the proposed receiver can achieve lower bit error rate values at lower computational complexity than some of its state-of-the-art competitors. [ABSTRACT FROM AUTHOR]

Peak-to-average power ratio (PAPR) in orthogonal time frequency space (OTFS) is vital for optimizing signal efficiency, minimizing distortion, and enhancing the performance of a beyond fifth-generation (B5G) system. The paper focuses on lowering the PAPR while retaining the bit error rate (BER) and power spectral density (PSD) for 64 and 256 sub-carriers. The PAPR is minimized by using a fractal optimization process known as selective mapping (SLM) and partial transmission sequence (PTS) at the transmitting block of the OTFS framework. The combination of SLM and PTS reduces peak power by selectively modifying the phase of transmitted symbols. SLM generates multiple versions of the signal, while PTS allocates power to these versions optimally, collectively mitigating amplitude peaks and minimizing PAPR. According to the simulation results, the suggested SLM+PTS works better than the traditional SLM and PTS, achieving low spectrum leakage and PAPR improvements of 5.5 dB and 4.9dB as well as SNR gains of 2.4dB and 2.1dB. In the future, SLM+PTS may work on lowering PAPR by making computers faster, researching adaptive algorithms, and combining machine learning methods for real-time optimization in various communication settings. Complex modeling, including fractal-based SLM and PTS approaches, provides a detailed understanding of waveform behavior and interference patterns, enabling more accurate and effective hybrid PAPR reduction techniques. This combination enhances the ability to manage to mitigate non-linear distortion across various sub-carriers, crucial for the performance and efficiency of 6G OTFS modulation. [ABSTRACT FROM AUTHOR]

Optical orthogonal time frequency space (OTFS) is better at handling Doppler shifts and multipath fading, making signals more reliable and valuable in places with much movement beyond the fifth generation (B5G). Using practical power amplifiers at the transmitter causes power inefficiency and signal distortion because of the OTFS system’s high peak-to-average power ratio (PAPR), severely reducing system efficiency. Combining partial transmit sequence (PTS) and selective mapping (SLM), a technique known as PTS+SLM, reduces peak power. While SLM generates numerous phase-modulated signal candidates and chooses the one with the lowest PAPR, PTS separates the signal into sub-blocks and optimizes their phases to decrease peak power. With few changes to the signal structure, this dual strategy effectively reduces PAPR while improving power spectral density (PSD) efficiency. As a result, we ensure the accuracy and dependability of the transferred data by maintaining the bit error rate (BER). Fractal optimization methods could be applied to these algorithms. For example, fractal-inspired optimization techniques might be used to explore the phase space more effectively or to discover new phase sequences that result in lower PAPR. According to the simulation findings, the suggested PTS+SLM method works better than the traditional PTS and SLM methods. [ABSTRACT FROM AUTHOR]

In the context of certain specific digital communication systems, where there are limitations such as spectral resources and energy availability, continuous phase modulation (CPM) emerges as an appealing choice among various modulation methods. Among CPM signals, multi‐h CPM is particularly noteworthy for its ability to address these constraints within the realm of single‐carrier and constant‐envelope waveforms. At the physical layer, the design of a multi‐h CPM receiver necessitates the efficient implementation of timing and frequency synchronization algorithm within a high dynamic environment. So this paper presents an innovative approach for achieving timing and frequency synchronization. To rectify timing offset and mitigate the adverse effects of noise in received signals, a re‐configurable local filter generation method is integrated into the timing synchronization algorithm. Simultaneously, an enhanced least mean square adaptive filter algorithm is applied to address frequency synchronization. A comprehensive series of simulations rigorously evaluates the outcomes of proposed novel synchronization methodology. These analyses demonstrate a notable proximity between the synchronization errors of proposed algorithm in this paper and the performance benchmark set by the modified Cramer–Rao bound. The proposed synchronization technology also exhibits the capability to substantially reduce the bit error rate, thereby effectively enhancing demodulation performance in multi‐h CPM receivers. [ABSTRACT FROM AUTHOR]

Codeword position index based sparse code multiple access (CPI‐SCMA) is an effective scheme that expands codeword positions in the time domain and carries extra information by their index. This paper proposes a dual‐mode CPI‐SCMA (DCPI‐SCMA) scheme to improve the error propagation caused by the mismatch between SCMA codewords and information bits. Furthermore, a DCPI‐SCMA with transmit diversity scheme is proposed where index bits are repeatedly transmitted to obtain a transmit diversity gain; hence, a higher reliability can be achieved with a slight loss of spectral efficiency. An optimal approach for the codebook index pattern is derived where the decision of index bits is involved in the demodulation of SCMA. It can be seen from simulation results and system analysis that the proposed schemes achieve better bit error rate performance with a decrease in complexity and obtain better robustness and flexibility compared with the existing CPI‐based SCMA schemes under the same spectral efficiency. [ABSTRACT FROM AUTHOR]

Underwater wireless communication stands as a captivating and swiftly progressing domain in recent. To support higher data rate and higher bandwidth applications, there is significant attention towards underwater acoustics along with Visible Light Communication (VLC) technology. Underwater sensor networking serves as the backbone of oceanic exploration efforts. Based on the traffic load and underwater environmental conditions, an appropriate communication link can be selected to achieve higher data rate. Acoustics supports communication over longer distances with lower data rate. Despite offering higher data rates, Visible Light Communication (VLC) faces limitations in terms of communication range, proving to be relatively short compared to other methods. A seamless transition is anticipated during data transmission and reception by employing Light Emitting Diodes (LEDs) and photo detectors on the optical-acoustic channel, bridging the gap between acoustic and optical communication methods. Utilizing MIMO-based Enhanced Reverse Polarity Orthogonal Frequency Division Multiplexing (MIMO-ERPO-OFDM) in Underwater Optical Communication (UWOC) proves to be a superior approach, achieving a high throughput of 19.9 Mbps and a lower Bit Error Rate (BER) of 10− 1. [ABSTRACT FROM AUTHOR]

With the increasing amount of data in railway communication system, the conventional wireless high-frequency communication technology cannot meet the requirements of modern communication and needs to be improved. In order to meet the requirements of high-speed signal processing, a high-speed communication signal processing method based on visible light is developed and studied. This method combines the adaptive equalization algorithm with deep learning and is applied to railway communication signal processing. In this research, the wavelength division multiplexing (WDM) and orthogonal frequency division multiplexing (OFDM) techniques are used, and fuzzy C equalization algorithm is used to softly divide the received signals, reduce signal distortion and interference suppression. The experimental results showed that increasing the step size could reduce the equalization effect, while increasing the modulation parameter will increase the bit error rate. Through deep learning to achieve channel equalization, visible light communication could effectively mitigate multi-path transmission and reflection interference, thereby reducing the bit error rate to the level of 0.0001. Under various signal-to-noise ratios, the system using the channel compensation method achieved the lowest bit error rate. This outcome was achieved by implementing hybrid modulation scheme, including Wavelength division multiplexing (WDM) and direct current-biased optical orthogonal frequency division multiplexing (DCO-OFDM) techniques. It has been proved that this method can effectively reduce the channel distortion when the receiver is moving. This study develops a dependable communication system, which enhances signal recovery, reduces interference, and improves the quality and transmission efficiency of railway communication. The system has practical application value in the field of railway communication signal processing. [ABSTRACT FROM AUTHOR]

The rapid progress in the transfer of information and its availability are the reasons behind the widespread use of the Internet. Document images are the most complicated and challenging category among various forms of digital data to which watermarking can be applied for its security and authentication. Watermarking of the document image is a very difficult task, since these images have very limited redundancy. Because of this factor there has been very little research in this area. A comprehensive research should be carried out to ensure the effective assessment, review as well as implementation of document image watermarking techniques. This paper reviews the existing document image watermarking by considering different evaluation parameters. Based on this review, a variety of challenges and directions have been prescribed for the development of effective watermarking techniques for document images. [ABSTRACT FROM AUTHOR]

Underwater Visible Light Communication (UVLC) is a promising technology for high-speed data transmission in aquatic environments. However, the performance and reliability of UVLC systems are often challenged by factors such as absorption, scattering, and oceanic turbulence. In this paper, we explore various UVLC modulation techniques, analyzing both Single Carrier Modulation and Multi-Carrier Modulation schemes, including their respective advantages and limitations. Through simulations and experimental evaluations, we investigate the effectiveness of modulation strategies such as Non-Return-to-Zero On-Off Keying, Pulse Position Modulation, and Quadrature Amplitude Modulation-Carrierless Amplitude Phase Modulation in addressing the inherent challenges of UVLC. Additionally, we examine advanced techniques like Orthogonal Frequency Division Multiplexing and space-domain index modulation, highlighting their potential to achieve higher data rates and improved reliability in UVLC systems. Our findings underscore the importance of selecting optimal modulation schemes to enhance spectral efficiency, reduce interference, and improve Bit Error Rate performance. Recent experimental advancements have showcased remarkable achievements, such as data rates exceeding 30 Gbps over distances up to 21 m, demonstrating significant progress in system reliability and transmission quality. This paper also identifies potential challenges and open research directions in UVLC, such as the need for efficient channel estimation and system configuration algorithms, contributing to the design and optimization of robust and scalable underwater communication systems. [ABSTRACT FROM AUTHOR]

Recursive least squares (RLS)–based equalizers are hindered by their high complexity in underwater acoustic (UWA) communications. This article proposes an adaptive equalizer with a phase tracking method for the UWA communication, named the error-feedback lattice-equalizer (EFLE). First, we derive the algorithm for recursively solving the least squares problem from EFLE, introducing a lattice structure using time and order updates, thereby reducing the complexity to be linearly related to its length. The error-feedback mechanism used in computing reflection coefficients ensures the numerical stability of the algorithm. By focusing on the rapid tap rotation in time-varying channels, we design phase tracking in EFLE to further improve equalization performance. To verify the bit error rate (BER) performance of the proposed EFLE, we study the UWA communication system and conduct UWA simulations and at-sea experiments. Comparisons include linear complexity equalizers such as least mean square (LMS), leaky LMS, least mean mixed-norm, and ϵ -normalized LMS equalizers, and quadratic complexity RLS equalizers. At-sea experiment results show that the BER performance of EFLE significantly outperforms its counterparts. [ABSTRACT FROM AUTHOR]

A coherent optical receiver digital signal processing (DSP) scheme is proposed based on spectral clustering, which utilises spectral clustering to cluster the signals outputted by the DSP. Compared to existing blind DSP algorithms for coherent optical receivers operating at over 100Gbps with PM‐mQAM, the proposed scheme effectively suppresses various physical impairments, achieving lower bit error rates (BERs) at the same transmission distance, thus enabling longer transmission distances under the same forward error correction threshold. Furthermore, simulations of the proposed scheme on a 14GBaud PM‐16QAM coherent optical transmission system show that, at a BER of 1.9E‐2, the maximum transmission distance increases from 1700 to 2000 km, and at a BER of 3.8E‐3, it increases from 700 to 900 km. [ABSTRACT FROM AUTHOR]

In this paper, for the sake of enhancing the security of wireless transmission, we proposed a novel system based on spatial and direction modulation (SDM) combined with generalized spatial modulation (GSM) which is aided by covert information mapping (CIM), termed as the CIM-GSDM system. In such a system, the legitimated user is equipped with distributed receivers so as to demodulate the conveyed signal by exploiting its indices while disturbing eavesdroppers for information security. More specifically, part of the information is modulated into the indices of the legitimated distributed receiver subsets with the aid of the mapped covert information and the interference matrix, while another part of the message is arranged by conventional amplitude-phase modulation. The proposed system can reap the benefits from both GSM and CIM to make eavesdropper suffer great mixture. Furthermore, the detection scheme and theoretical analysis of error performance are discussed as well. The simulation results exhibit that the bit error rate (BER) performance of legitimate user is much better than that of the eavesdropper while the proposed scheme improves the security compared to the original CIM-SDM system at the same spectral efficiency. [ABSTRACT FROM AUTHOR]

Intelligent Reflecting Surfaces (IRS) and Multiple-Input Single-Output (MISO) technologies are essential in the fifth generation (5G) networks and beyond. IRS optimizes the signal propagation and the coverage and is a viable approach to address the issues caused by fading channels that limits the spectral efficiency, while MIMO enhances data rates, reliability, and spectral efficiency by using multiple antennas at both transmitter and receiver ends. This paper proposes an IRS-assisted MISO system using the Orthogonal Space-Time Block Code (OSTBC) scheme to enhance the channel reliability and reduce the Bit Error Rate (BER) in wireless communication systems. The proposed system exploits the benefits from the transmit diversity gain of the OSTBC scheme as well as from the bit energy to noise power spectral density (Eb/No) improvement of the IRS technology. The presented work explores these combined technologies across different modulation schemes. The obtained results outperform the similar previously published works by considering higher-order modulation schemes as well as the deployment of rate ¾ OSTBC-assisted IRS. Moreover, the obtained results demonstrate that the integration of OSTBC with IRS can yield significant performance improvements in terms of Eb/No by 7 dB and 13 dB when using 16 reflecting elements and 64 reflecting elements, respectively. [ABSTRACT FROM AUTHOR]

Conventional baseband processing techniques for communication must be adapted to the specificities of terahertz channels. Currently, there is limited research on channel coding applicable to terahertz bands, particularly in terms of performing real-time tests that differentiate them from offline processing. This paper presents a test platform for a 300 GHz wireless communication system based on the PXIe platform. The experiment utilizes a high-performance, low-complexity serial scheduling approach with the Minimum Sum-Log Likelihood Ratio Belief Propagation (MS-LLR-BP) soft decision decoding algorithm to test point-to-point real-time line-of-sight communication for low-density parity-check (LDPC) code communication systems. The results indicate that the implementation of LDPC coding in QPSK terahertz wireless transmission systems results in a performance enhancement of approximately 25–55% in bit error rate (BER), demonstrating the excellent performance of LDPC codes against terahertz channel fading. This highlights their potential in future ultra-high-speed communication systems. [ABSTRACT FROM AUTHOR]

Feedback-insensitive Quantum Dot (QD) comb lasers hold significant promise for integrated dense wavelength division multiplexing photonic systems due to their ability to generate multiple wavelengths and operate without bulky isolators, facilitating the development of high-density and large-scale photonic integrated circuits. In this study, we investigated the optical feedback (OFB) influence of the InAs/GaAs QD comb laser from various perspectives. Our findings reveal that the comb laser exhibits a stable locking region with consistent optical spectra across a range of OFB strengths (−45 to −10 dB). Furthermore, under a high OFB strength of −10 dB, there is a notable 40 dB suppression of relative intensity noise in the low-frequency range (below 1 GHz). Transmission experiments demonstrate clear eye openings at 25 Gbps using a bit pattern of 231-1 pseudorandom binary sequence. Remarkably, the bit error rates decrease by five orders of magnitude under −10 dB OFB. These results indicate the ultra-robustness of 100 GHz grid QD comb laser, which exhibits great transmission enhancement under a strong OFB of −10 dB. [ABSTRACT FROM AUTHOR]

In addressing the multifaceted problem of multiple-input multiple-output (MIMO) detection in wireless communication systems, this work highlights the pressing need for enhanced detection reliability under variable channel conditions and MIMO antenna configurations. We propose a novel method that sets a new standard for deep unfolding in MIMO detection by integrating the iterative conjugate gradient method with Tikhonov regularization, combining the adaptability of modern deep learning techniques with the robustness of classical regularization. Unlike conventional techniques, our strategy treats the Tikhonov regularization parameter, as well as the step size and search direction coefficients of the conjugate gradient (CG) method, as trainable parameters within the deep learning framework. This enables dynamic adjustments based on varying channel conditions and MIMO antenna configurations. Detection performance is significantly improved by the proposed approach across a range of MIMO configurations and channel conditions, consistently achieving lower bit error rate (BER) and normalized minimum mean square error (NMSE) compared to well-known techniques like DetNet and CG. The proposed method has superior performance over CG and other model-based methods, especially with a small number of iterations. Consequently, the simulation results demonstrate the flexibility of the proposed approach, making it a viable choice for MIMO systems with a range of antenna configurations, modulation orders, and different channel conditions. [ABSTRACT FROM AUTHOR]

To mitigate inter-symbol interference (ISI) caused by Faster-than-Nyquist (FTN) technology in a multiple input multiple output (MIMO) optical wireless communication (OWC) system, we propose an ISI cancellation algorithm that combines multi-head self-attention (MHSA), a one-dimensional convolutional neural network (1D CNN), and bi-directional long short-term memory (Bi-LSTM). This hybrid network extracts data features using 1D CNN and captures sequential information with Bi-LSTM, while incorporating MHSA to comprehensively reduce ISI. We analyze the impact of antenna numbers, acceleration factors, wavelength, and turbulence intensity on the system's bit error rate (BER) performance. Additionally, we compare the waveform graphs and amplitude–frequency characteristics of FTN signals before and after processing, specifically comparing sampled values of four-pulse-amplitude modulation (4PAM) signals with those obtained after ISI cancellation. The simulation results demonstrate that within the Mazo limit for selecting acceleration factors, our proposal achieves a 7 dB improvement in BER compared to the conventional systems without deep learning (DL)-based ISI cancellation algorithms. Furthermore, compared to systems employing a point-by-point elimination adaptive pre-equalization algorithm, our proposal exhibits comparable BER performance to orthogonal transmission systems while reducing computational complexity by 31.15%. [ABSTRACT FROM AUTHOR]

In long-haul WDM (wavelength division multiplexing) optical communication systems utilizing the DP-16QAM modulation scheme, traditional methods for removing chaos have exhibited poor performance, resulting in a high bit error rate of 10 − 2 between the original signal and the removed chaos signal. To address this issue, we propose DeepChaos+, a machine learning-based approach for chaos removal in WDM transmission systems. Our framework comprises two key points: (1) DeepChaos+ automatically generates a dataset that accurately reflects the features of the original signals in the communication system, which eliminates the need for time-consuming data simulation, streamlining the process significantly; (2) it allows for the training of a lightweight model that provides fast prediction times while maintaining high accuracy. This allows for both efficient and reliable signal reconstruction. Through extensive experiments, we demonstrate that DeepChaos+ achieves accurate reconstruction of the original signal with a significantly reduced bit error rate of approximately 10 − 5 . Additionally, DeepChaos+ exhibits high efficiency in terms of processing time, facilitating fast and reliable signal reconstruction. Our results underscore the effectiveness of DeepChaos+ in removing chaos from WDM transmission systems. By enhancing the reliability and efficiency of chaotic secure channels in optical fiber communication systems, DeepChaos+ holds the potential to improve data transmission in high-speed networks. [ABSTRACT FROM AUTHOR]

Most of Optical Camera Communication (OCC) systems benefit from the rolling shutter mechanism of Complementary Metal-Oxide Semiconductor (CMOS) cameras to record the brightness evolution of the Light-Emitting Diode (LED) through dark and bright strips within images. While this technique enhances the maximum achievable data rate, the main difficulty lies in the demodulation of the signal extracted from images, subject to blooming effect. Thus, two main approaches were proposed to deal with this issue, using adaptive thresholds whose value evolves according to amplitude changes or detecting signal variations with the first-order derivative. As the second method is more robust, a new demodulation method based on the detection of the zeros of the first-order derivative of the extracted signal was proposed in this paper. Obtained results clearly show an improvement in the extracted signal demodulation compared to other methods, achieving a raw Bit Error Rate (BER) of 10−3 around 50 cm in a Line-Of-Sight scenario, and increasing the maximum communication distance by 43.5%, reaching 330 cm in the case of a Non-Line-Of-Sight transmission. [ABSTRACT FROM AUTHOR]

During probe‐to‐Earth superior conjunction, deep space communication channels will suffer from solar scintillation, leading to amplitude attenuation of received signals. This study aims to obtain the channel state information (CSI) on deep space channels affected by solar scintillation. Classical least squares (LS) and minimum mean squared error (MMSE) methods are adopted to perform channel estimation and compensate for the channel fading. Simulation results indicate that under the effect of solar scintillation, performing channel estimation technology can significantly improve bit error rate (BER) performance compared to systems without CSI, and the MMSE algorithm outperforms the LS for both BER and normalized mean squared error (NMSE). In addition, we also find that pilot density, geometric parameters, and the outer scale of solar wind turbulence has great influence on the estimation performance. Key Points: Performed channel estimation for deep space communications under solar scintillationLeast squares (LS) and minimum mean squared error (MMSE) methods were adopted for channel estimationSimulated the impact of pilot density, geometric parameters, and outer scale of solar wind turbulence on performance of channel estimation [ABSTRACT FROM AUTHOR]

We report the designing of a free-space-optics (FSO) transmission system capable of transmitting high rate information by utilising novel mode division multiplexing (MDM) transmission technique. In the work reported, 2-channels transmitting 10 Gbps data, using either non-return-to-zero (NRZ) encoding scheme or return-to-zero (RZ) encoding scheme are modulated by using different Hermite–Gaussian (HG) modal beams of the single laser beam to realize of 20 Gbps transmission system. The system proposed is simulative analysed under the effect of different weather states. Also, we have compared the bit error rate (BER) and Quality factor (Q Factor) performance for RZ and NRZ encoding schemes in the system for varying weather states. The results reported show that NRZ encoding exhibits a superior performance. Also, we have analysed the system performance by taking into consideration atmospheric scintillation effect and the reported results show notable signal degradation in the presence of scintillation. [ABSTRACT FROM AUTHOR]

In this work, the detailed investigation of the bit error rate (BER) over the α - η - μ /Inverse-Gamma composite fading channel is performed.The analysis aimed to explore the error rate characteristics over this channel under the influence of additive Laplacian noise. The findings are presented in the form of a bivariate Fox's H-function, providing a comprehensive representation of the results. Furthermore, the concise and simplified asymptotic expressions of the proposed metrics are provided, enhancing the accessibility and applicability of the results. It is observe that under conditions of high signal-to-noise ratio (SNR), these simplified statistics demonstrate a remarkable level of agreement with the closed-form results. To validate the robustness and accuracy of the proposed formulations, extensive Monte Carlo simulations are conducted to ensure the reliability and validity of our findings across various scenarios and conditions. [ABSTRACT FROM AUTHOR]

In 2023, we proposed the modified delay and Doppler profiler (mDDP) as an inter-carrier interference (ICI) countermeasure for underwater acoustic orthogonal frequency division multiplexing (OFDM) mobile communications in a multipath environment. However, the performance improvement in the computer simulation and pool experiments was not significant. In a subsequent study, the accuracy of the channel transfer function (CTF), which is the input for the mDDP channel parameter estimation, was considered insufficient. Then a sequential ICI canceling mDDP was devised. This paper presents simulations of underwater OFDM communications using an iterative one- to three-step mDDP. The non-reflective pool experiment conditions are a two-wave multipath environment where the receiving transducer moves at a speed of 0.25 m/s and is subjected to a Doppler shift in the opposite direction. As NumCOL, the number of taps in the multitap equalizer which removes ICI, was increased, the bit error rate (BER) of 0.0526661 at NumCOL = 1 was significantly reduced by a factor of approximately 45 to a BER of 0.0011655 at NumCOL = 51 for the sequential ICI canceling mDDP. [ABSTRACT FROM AUTHOR]

The terrestrial television system in Indonesia has evolved from the first-generation Digital Terrestrial Video Broadcasting (DVB-T) to the second generation (DVB-T2), enhancing broadcast quality and spectral efficiency. This paper focuses on the application of DVB-T2 within High-Speed Train (HST) communication systems, where the unique challenges faced include high Doppler shifts and multipath effects due to the high train speed which exceeds 300 km/h. Multicarrier Orthogonal Frequency Division Multiplexing (OFDM) technology was employed along with 64-QAM modulation for the investigation of the performance under various conditions. The simulations were structured around varying speeds, scatterer counts, and angles, and 15 iterations were conducted for train speeds of 10 m/s, 50 m/s, and 100 m/s. The findings indicate that the error rates varied with speed and environmental complexity. At a lower speed (10 m/s), the system performance showed significant improvement, with a reduction of 322 bits in the error rate. However, as the speed increased to 100 m/s, the performance declined, demonstrating an increase of errors by 414 bits owing to exacerbated Doppler effects. Different scatterer counts also influenced the results. For instance, with four scatterers at 10 m/s speed, the error improved by 245 bits, but at 100 m/s speed and under the same scatterer conditions, the performance worsened, increasing the error by 361 bits. [ABSTRACT FROM AUTHOR]

This study presents a thorough evaluation of satellite downlink performance in a Free Space Optics (FSO) system with a Low-Density-Parity-Check (LDPC) based Multiple-Input-Multiple-Output (MIMO) configuration. Atmospheric turbulence is characterized using a generalized K-distribution and a negative exponential distribution, with specified parameters. Key performance metrics including Bit Error Rate (BER), outage probability, and accuracy are measured. To address pointing-errors (PEs) and atmospheric turbulence (AT), a novel decoding methodology for Non-Recursive Convolutional Polynomial Encoding (NRCPE)-based Pulse Position Modulation (PPM)-Gaussian Minimum Shift Keying (GMSK)-modulated FSO transmissions is introduced, leveraging Support Vector Machines (SVM). The study introduces a sophisticated Meijer-G function for MIMO statistical analysis and proposes a power series-based Probability Density Function (PDF) with non-recursive GMSK modulation. This PDF allows closed-form derivation of BER and Outage Probability expressions, showcasing improved MIMO link performance in the presence of PEs and AT. Simulations validate the models, offering insights into their effectiveness across varying turbulence levels. The findings assist FSO-MIMO designers in minimizing PEs,AT and achieving optimal results.Subsequently, authors perform a suppression to BER, Particularly, the optimum beam width factors for p × q | 1 × 2 × 2 , & 2 × 3 , diversity degrees by a p × q | 1 × 1 , as a reference are 81.24%, 87.32%, and 89.61%, respectively, at ε nj = 4.02 and I o = 10 dBm .The proposed MIMO/FSO provides accuracy and an irradiances gain of 13.34dBm,i.e., ε nj = 5.03 at BER 10 - 9 for downlink satellite transmission over SIMO and SISO FSO links. This study provides a comprehensive framework for optimizing FSO communication systems, considering atmospheric turbulence and pointing errors. [ABSTRACT FROM AUTHOR]

The use of Unmanned Aerial Vehicles (UAVs) for military as well as civilian applications such as search and rescue operations, disaster management, parcel delivery and agriculture, is becoming increasingly popular, mainly due to their versatile nature and relatively inexpensive operating costs. However, one of the most significant barriers in the widespread adoption of UAVs for the aforementioned applications is the increasing concern for wireless communication security within the network. Unfortunately, the nodes that comprise these networks are extremely constrained in terms of storage space, processing power and battery life, which require light-weight security protocols that align with these limitations. The current standards for message authentication and verification predominantly rely on lightweight cryptographic techniques. However, there is continual scope for improvement, particularly in the realm of computational efficiency, to better align with the constraints inherent to UAVs. This paper explores data hiding in a multi-UAV environment, to form a light-weight message verification scheme to confirm the identity of the transmitting node. First, five venues having the potential to hide data are analyzed. Based on the analysis of bit error rate obtained from the simulated multi-UAV environment, both cyclic prefix and padding bits are selected. Next, a codeword is generated for each transmission and it is embedded along with the unique ID key, κ of the transmitting node into each venue respectively, and the output is transmitted as Hello packets. Subsequently, the receiving node extracts and decodes the codeword in order to verify the authenticity of the transmitting node. An evaluation of the proposed scheme has been conducted by using a simulated UAV environment. In the best case scenario, the proposed authentication scheme can achieve a successful verification rate of at least 80% at a maximum hop-count of 10 hops. Through computational cost analysis, in comparison to the conventional methods, the proposed scheme was found to have a significantly lower total execution time of 1.7 μ s . In addition, the security analysis shows that when the proposed scheme is paired with physical unclonable functions (PUFs), it is able to resist common security attacks, including man-in-the-middle, replay and cloning attacks. [ABSTRACT FROM AUTHOR]

The combination of high-order modulation formats and linewidth-tolerant carrier phase estimation (CPE) can effectively improve spectrum efficiency and relax the limitation of laser linewidth. This paper presents a simple two-stage CPE algorithm for polarization-multiplexed (PM) 32-quadrature amplitude modulation (32-QAM) coherent optical communication systems. The algorithm uses an enhanced QPSK partitioning algorithm combined with a simplified 4th power CPE method for coarse estimation in the initial stage and maximum likelihood (ML) detection in the subsequent fine stage. The CPE algorithm significantly increases the number of symbols used in the first stage of coarse estimation. This results in a significant increase in the stability and reliability of the phase estimation, and the CPE algorithm significantly reduces the computational complexity. The optimal parameters, phase estimation performance, and system performance of the algorithm were investigated by building a 22 Gbaud PM 32-QAM coherent system simulation platform and a 5 Gbaud PM 32-QAM coherent system experimental platform. The results show that the proposed two-stage CPE algorithm has a stronger linewidth tolerance difference than the conventional QPSK, and the two-stage CPE algorithm with an optimal block length of 105 performs comparable to blind phase search (BPS). The optical signal noise Ratio (OSNR) value is 21.2 dB and the bit error rate (BER) is 1.8 χ 10-3 for the optimal block length of 105. The receiving-end DSP unit with a flexible scheme and good communication performance will have potential applications in adaptive elastic optical networks. [ABSTRACT FROM AUTHOR]

Underwater wireless optical communication (UWOC) systems face challenges due to the significant temporal dispersion caused by the combined effects of scattering, absorption, refractive index variations, optical turbulence, and bio-optical properties. This collective impairment leads to signal distortion and degrades the optical receiver's bit error rate (BER). Optimising the receiver filter and equaliser design is crucial to enhance receiver performance. However, having an optimal design may not be sufficient to ensure that the receiver decision unit can estimate BER quickly and accurately. This study introduces a novel BER estimation strategy based on a Convolutional Neural Network (CNN) to improve the accuracy and speed of BER estimation performed by the decision unit's computational processor compared to traditional methods. Our new CNN algorithm utilises the eye diagram (ED) image processing technique. Despite the incomplete definition of the UWOC channel impulse response (CIR), the CNN model is trained to address the nonlinearity of seawater channels under varying noise conditions and increase the reliability of a given UWOC system. The results demonstrate that our CNN-based BER estimation strategy accurately predicts the corresponding signal-to-noise ratio (SNR) and enables reliable BER estimation. [ABSTRACT FROM AUTHOR]

The Non-orthogonal multiple access (NOMA) technique has drawn considerable attention as a promising solution for advanced wireless communication systems due to its higher data rates, lower latency, and high bandwidth efficiency. The decoding of NOMA signals requires standard successive interference cancellation (SIC) approaches. Due to the propagation delay and fading channels, multipath fading significantly impacts the SIC process and correct signal detection. This article proposes a hybrid approach using deep convolutional neural network-gated recurrent unit-support vector machine (CNN-GRU (CGRU)-SVM) to detect the uplink NOMA users' signals. The proposed deep learning (DL) CGRU-SVM-based receiver executes simultaneous channel estimation, equalization, and demodulation, performing perfect end-to-end operations. The simulation results discuss the bit error rate performance of the proposed CGRU-SVM-based receiver with the conventional least square and minimum mean-square error signal detection methods, along with other DL-based GRU, CNN, and CGRU approaches in uplink NOMA schemes. It provides the efficient extraction of spatiotemporal features with an SVM classifier. Moreover, the proposed model outperforms the other DL-based techniques concerning the accuracy, F1 score, and receiver operating characteristic with the area under the curve. [ABSTRACT FROM AUTHOR]

This manuscript suggests a modulation scheme for exploiting transmission diversity by integrating Alamouti coding and controlling the transmission by intelligent reflecting surface (IRS) in code division multiple access filter bank multicarrier offset quadrature amplitude modulation (CDMA-FBMC-OQAM) system, a promising technique for future-generation wireless communication. To neutralize the impact of channel phases, the IRS elements are in charge of intelligently adjusting the incident signal phases. By maximizing the signal-to-noise-ratio (SNR) of the received signal, the bit-error-rate (BER) performance is improved. By changing the number of IRS elements, taking into account various channel scenarios and modulation schemes, we compare the BER performance of the proposed system with that of the conventional Alamouti coded CDMA-FBMC-OQAM system in simulation results. The findings demonstrate that the IRS-assisted Alamouti coded CDMA-FBMC-OQAM transmission is a feasible choice for future-generation wireless communication systems. [ABSTRACT FROM AUTHOR]

In this paper, we analyzed Non-Orthogonal Multiple Access (NOMA) performance in the context of modern wireless cellular communications under various channel conditions. We examined different path loss models and multipath fading effects to evaluate the Bit Error Rate (BER) of NOMA. Additionally, this study was tailored for wireless communications involving multiple users in Rayleigh, Rician, AWGN, and Nakagami fading channels, all of which were considered within the framework of NOMA. To establish connections, ensure equitable user treatment, and achieve efficient spectrum utilization for multiple users across diverse channel scenarios, the Base Station (BS) adopted the NOMA technique. Furthermore, the BS employed a power allocation strategy to distribute available power among users based on their respective Power Allocation Factors (PAFs). This approach allowed users to simultaneously communicate with the BS within the same frequency range in the power domain. For users with lower PAFs, we utilized sequential interference cancellation to mitigate strong signals from other users. We validated our performance analysis using Monte-Carlo simulations, which closely aligned with the theoretical analysis. Our simulated results demonstrated that NOMA outperformed traditional Orthogonal Multiple Access (OMA) in most cases, especially in channels with various multipath fading conditions. Moreover, we observed that the effectiveness of NOMA hinged on the selection of power allocation and user pairing schemes. According to our study, NOMA exhibits significant potential to enhance the Spectral Efficiency (SE) and capacity of wireless networks in the future. We evaluated the accuracy of predicting received signal strength using various path loss models, including free space path loss, Log-normal path loss distribution, Shadowing path loss distribution, and Logdistance path loss model. In contrast to 4G networks, which are primarily affected by distancedependent path loss, 5G and beyond networks experience more significant fading effects due to their reliance on higher frequencies and wider bandwidths. [ABSTRACT FROM AUTHOR]

In this paper, new schemes have been proposed for the estimation of the additive white Gaussian noise (AWGN) channel with intersymbol interference (ISI) in an iterative equalization and decoding system using low-density parity check (LDPC) codes. This article explores the use of the least squares algorithm in various scenarios. For example, the impulse response of the AWGN channel h was initially estimated using a training sequence. Subsequently, the impulse response was calculated based on the training sequence and then re-estimated once using the sequence estimated from the output of the LDPC decoder. Lastly, the impulse response was calculated based on the training sequence and re-estimated twice using the sequence estimated from the output of the LDPC decoder. Comparisons were made between the performances of the three mentioned situations, with the situation in which a perfect estimate of the impulse response of the channel is assumed. The performance analysis focused on how the bit error rate changes in relation to the signal-to-noise ratio. The BER performance comes close to the scenario of having a perfect estimate of the impulse response when the estimation is performed based on the training sequence and then re-estimated twice from the sequence obtained from the output of the LDPC decoder. [ABSTRACT FROM AUTHOR]

The incredible growth of wireless technologies has led to an increase in demand of spectral resources for various communication systems. The allocated spectrum for GSM is insufficient to support applications that operate at high data rates (e.g., multimedia applications or 5G mobile communications). Orthogonal frequency division multiplexing (OFDM) and generalized frequency division multiplexing (GFDM) are the recent technologies with high data rates for multimedia applications and mobile communications. These are the perfect candidates for wireless applications and 5G technologies. In this paper, an in‐depth study was presented where the multicarrier models of orthogonal frequency‐division multiplexing (OFDM) and GFDM are integrated with a sub‐Nyquist sampling architecture. The primary focus is to evaluate and compare their spectrum sensing performance. Also analyzed the performance of both OFDM and GFDM under sub‐Nyquist sampling framework and measured the bit error rate (BER) as a function of the received signal‐to‐noise ratio (SNR). [ABSTRACT FROM AUTHOR]

Communication systems are greatly hampered by many disruptive noises in powerline communication systems (PLC), which come with strong interference, resulting in the malfunction of PLC systems. Hence, there is a need to model noise and its effect on communication systems. This paper presents noise modelling and mitigation techniques for indoor broadband powerline communication systems. To model the PLC noise, frequency domain measurements employing the GSP‐930 spectrum analyser were carried out to determine the noise frequency response in the frequency range of 1–30 MHz. The results obtained were plotted. While the analytical model for the noise model is presented, furthermore, noise mitigation techniques for multiple input multiple output PLC (MIMO‐PLC) systems in the form of spatial modulation PLC systems have been proposed. The SM‐PLC system employs the indices of the individual transmit lines to increase the data rate, as opposed to the traditional MIMO‐PLC systems, where the symbol to be transmitted is transmitted by duplicating the symbol across all lines. The proposed system uses the maximum likelihood (ML) detector at the receiver to obtain estimates of the transmitted symbols. The simulation results of the SM‐PLC system are compared with the already existing MIMO‐PLC system and show a significant improvement of ≈6 dB and 5.2 dB in signal‐to‐noise ratio (SNR) at a bit error rate of 10(−5) for spectral efficiencies of 4 bits per channel use (bpcu) and 6 bpcu, respectively. On comparison of the SM‐PLC system having a combination of additive white Gaussian noise and impulse noise at the receiver, the SM‐PLC system outperformed the traditional MIMO‐PLC by 3.5 and 3.8 dB in SNR for 4 and 6 bpcu, respectively. [ABSTRACT FROM AUTHOR]

Short block length "block" codes are typically not used in wireless standards as soft decision decoding is computationally intensive and hard decision decoding results in performance loss. However, short block lengths are of interest to massive machine-type communications (mMTC) and ultra-reliable low-latency communications (URLLC). In this paper, we propose a diversity preserving enhanced hard-decision decoding scheme for parity check codes (PCC) over Rayleigh fading channels. The proposed flip decoding scheme has linear complexity in the block length. Theoretical analysis and simulation results verify the correctness of the proposed detection scheme. [ABSTRACT FROM AUTHOR]

The competence of Non-Orthogonal Multiple Access (NOMA) to provide improved spectrum efficiency, support massive network elements, and low latency services make it attractive to Multiple Access (MA) technology for next-generation wireless networks. Single-Carrier Frequency Division Multiple Access (SC-FDMA) is an optimal technique in 4G wireless communication to enhance spectrum efficiency and user capacity. The amalgamation of SC-FDMA with NOMA can become a better choice for wireless communication for 5G and Beyond 5G (B5G). Discrete Wavelet Transforms (DWT) have been a better choice for improving the system's performance due to its outstanding orthogonality and spectral confinement characteristics. This study proposes a transceiver architecture that uses joint Discrete Fourier Transform (DFT) and DWT to outperform existing NOMA systems in terms of Bit Error Rate (BER). The transceiver architecture is symbolized as a joint DFT precoded DWT (JDPD) SC-FDMA NOMA System. Furthermore, we propose a Joint Low Complexity Regularized Zero forcing (JLC RZF) for JDPD SC-FDMA NOMA system to enhance the BER with low complexity. In order to illustrate the superiority of the proposed system over multipath channels, the system performance over a range of Carrier Frequency Offset (CFO) values and power allocation scenarios are also examined. [ABSTRACT FROM AUTHOR]

In wireless environments, multi-carrier modulation (MCM) schemes provides resistance against fading. These schemes have been thoroughly researched for use in 4G/5G wireless communications because of their benefits. Wireless communication systems that use multiple carriers are the most prevalent in modern technology for high-speed transmissions of data. Many researchers are currently interested in implementing new protocols and physical layers for Filter Bank Multicarrier (FBMC) with Offset Quadrature Amplitude Modulation (OQAM). 5G transmission systems are likely to utilize the FBMC/OQAM scheme. The FBMC/OQAM system has many advantages over Orthogonal Frequency Division Multiplexing (OFDM), but there are few disadvantages, one of which is its high PAPR. Because of the signal's overlapping nature in the FBMC system, conventional reduction techniques can't be applied to the subcarriers. High peak power also reduces the efficiency of FBMC/OQAM. It is essential to reduce as much as possible the peak power of a signal in communication systems. In this article, to minimize the peak-toaverage power ratio (PAPR), a Discrete Elephant Herding Optimization Algorithm (DEHOA) is used. Using the proposed method, we reduce the drawback of high PAPR with lower amalgamations of optimum phase factors for each overlapping information symbol. According to simulation results, the proposed method reduces PAPR, BER and improves spectral efficiency (SE) performance. [ABSTRACT FROM AUTHOR]

Flash memory, ubiquitous in diverse electronic devices, confronts persistent challenges stemming from inherent errors that jeopardize data integrity. This research situates itself at the intersection of these challenges and advancements, proposing an inventive error correction coding framework that harnesses the unique capabilities of analysis with a hybrid error control coding (HECC) approach. In the proposed work, a mathematical model aimed at enhancing the flash memory by identifying the error pattern within the pages using the discrete fourier transform (DFT). By incorporating distinctive DFT mathematical properties, the proposed technique intends to improve flash memory error correction beyond traditional methods. The flash storage defect detection and rectification results with hybrid error correction coding achieved bit error rate (BER) of 4.3e-6, latency 14.1, mean 15.1 and standard deviation 1.0. Error correction efficiency 98% and storage overhead 10%. With this approach results are significantly improving the error correction efficiency, reduce storage overhead and enhanced adaptability to diverse error patterns. [ABSTRACT FROM AUTHOR]

In the ever-evolving landscape of modern technology, integrating communication and sensing systems has become increasingly essential for a wide range of applications, from military and defense to autonomous vehicles and beyond. The integration offers a convergence of capabilities that enhances operational efficiency and provides adaptability in complex environments. In this paper, we develop, in simulation and experiment, an integrated communication and sensing system, exploring the cutting-edge utilization of spread spectrum and radio-over-fiber (RoF) photonic technologies. RoF technology inherits the benefits of optical fibers, which include low attenuation and longer reach distance compared to other media. First, we consider the integration of communication and sensing functions using a spread spectrum–binary phase-shift keying waveform. In this integrated system, the sensing function is performed using a radar system. The performance of the proposed system is evaluated in terms of the peak-to-sidelobe ratio of the radar correlator output and the bit error rate for the communication system. The results are obtained through extensive MATLAB simulations. Next, we consider the realization of the proposed integrated communication and sensing system using photonics technology. This phase commences with the utilization of specialized photonics-based software for extensive simulations at different fiber lengths, which is an essential foundational step toward the practical implementation of the proposed system using photonics. Lab experiments are also presented to validate the simulation results. [ABSTRACT FROM AUTHOR]

Free-space optical (FSO) communication has received widespread attention as a high-bandwidth, low-latency communication technique. However, the scintillation effect caused by atmospheric turbulence leads to intensity fluctuations of the transmission signal, which, in turn, affects the performance of the FSO communication system. This paper proposes a channel correlation-based adaptive power transmission for FSO communications. Based on the correlation between uplink and downlink turbulence channels, the power of the reverse transmission signal is adjusted by the fluctuation strength of the received uplink or downlink transmission signal and the channel correlation coefficient to improve the system's performance. The proposed technique is investigated through a simulation using established uplink and downlink channels with different link distances and turbulence intensities. The simulation results show that the bit error rate (BER) performance of the proposed technique is significantly improved compared to the fixed threshold decision (FTD) technique, and it is close to the adaptive threshold decision (ATD) technique. The proposed technique provides an effective optimization scheme for FSO communications. [ABSTRACT FROM AUTHOR]