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Multicarrier navigation modulation is a trend within next-generation global navigation satellite systems (GNSS) aiming to enhance navigation performance, but it forces amplifiers to work in nonsaturation zones, resulting in low power efficiency. This paper presents constant-envelope multiplexing (CEM) based on clipping to overcome the low transmission efficiency of orthogonal multi-binary offset carriers (OMBOCs). The clip constant-envelope OMBOC (CCE-OMBOC) features a hard limit for the original OMBOC signal, and its cross-correlation function (CCF) has a fixed ratio with the CCF of the original OMBOC. Thus, the clipping process has no adverse effect on navigation performance. Additionally, the expression of transmission and multiplexing efficiency is presented according to OMBOC's amplitude distribution. A low sampling rate is suggested for the CCE-OMBOC, which reduces the cost of signal generation. For OMBOC, the CCE-OMBOC provides multiplexing efficiency comparable to that of constant-envelope multiplexing via intermodulation construction (CEMIC). CCE-OMBOC has a straightforward generation process; in contrast, the complexity of CEMIC rises significantly with increasing subcarriers. Moreover, the CCE-OMBOC is a multicarrier CEM modulation tool that has good tracking performance and excellent compatibility. The greater the number of subcarriers, the more navigation services and the higher the navigation data rate. The CCE-OMBOC can be used in next-generation GNSS and integrated communication and navigation systems. [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]

This article covers the potential of Filter Bank Multicarrier (FBMC) modulation as an alternative to be used in the future 5 G wireless networks in which Massive Multiple-Input Multiple-Output (MIMO) is implemented. The 'energy efficient Massive Multiple Input Multiple Output (M-MIMO) Filter bank Multi-carrier Modulation (FBMC)' is necessary and beneficial for the upcoming wireless communiqué system. This is because there is an ever-increasing demand for higher data rates with higher Spectral Efficiency (SE). This paper compares orthogonal frequency division multiplexing (OFDM) with FBMC. This helps to evaluate the Spectral Efficiency (SE) of a Massive MIMO system that performs transmission under a unicellular environment. The variation in Massive MIMO allows equilibrium of the channel because FBMC has extra benefits due to the confinement of the subcarrier in an assigned range. However, the high Peak to Average Power Ratio (PAPR) in an M-MIMO-FBMC system is recognised as a serious problem that causes nonlinear signal deformation and restricts the effectiveness of the Power Amplifier (PA). In this work, to increase the SE in the system, the antenna count is optimised, such that the SNR or SNDR is maximum. For this, the antenna counts are optimised via Self Improved SSO with a Chaotic Map (SISSO-CM). [ABSTRACT FROM AUTHOR]

Orthogonal frequency division multiplexing (OFDM) – a new wireless multicarrier modulation which uses number of subcarriers that will be orthogonal to each and every other to send signals. An OFDM signal contains tightly spaced modulated providers that every have low bit info on each with the subcarriers. The major objective of our specific model is to apply MATLAB modelling to model OFDM modulation approach among 6, 12 and 15 MHz bandwidths inside the great consistency (HF) radio group (3–30 MHz). Typically, the motive of the pattern is to be able to make HF very long haul transmission more quickly and further trusted in order to each element worldwide, including typically the bulk remote elements, undergo use of rapid speed, very long haul hands-free connection. The designed unit enables us all to alter typically the bandwidth, carrier consistency, type of modulation, sign to noise rate (SNR), and photo dimensions to identify the particular blend regarding criterion provides trusted OFDM details gears in the HF radio band. Desire use four modulation techniques such while 32-QAM, 16-PSK, QPSK and BPSK. 32-QAM always transmitted typically the data the speediest despite the photo size, number regarding subcarriers and company frequency. 16-PSK seemed to be the second speediest type of modulation followed by QPSK and finally BPSK. To look with regard to the success associated with our model, all of us will figure out information rate and the particular bit to error ratio (BER) right next information transfer. Preferably, we wish to possess a bit error rate associated with 10e−5 for a good SNR that will be symbol of the particular noise intensity skilled within the ionosphere. [ABSTRACT FROM AUTHOR]

Orthogonal frequency division multiplexing (OFDM) is a famous multi-carrier modulation technique as it has a vast range of features like robustness against multi-path fading, higher bandwidth efficiency, and higher data rates. Though, OFDM has its own challenges. Among them, high peak power to average power ratio (PAPR) of the transmitted signal is the major problem in OFDM. In recent years, deep learning has drastically enhanced the performance of PAPR. In addition, the excessive training data and high computational complexity lead to a considerable issue in OFDM system. Thus, this paper implements a new PAPR reduction scheme in OFDM Systems through hybrid deep learning algorithms. A new optimized hybrid deep learning termed O-DNN + RNN is implemented by integrating the deep neural networks (DNN) and recurrent neural networks (RNN), where the parameters of both DNN and RNN are optimized using Hybrid Reptile Dragonfly Search Algorithm (HR-DSA). The new deep learning model is adopted for determining the constellation mapping and demapping of symbols on each subcarrier. This new optimized hybrid deep learning helps in reducing the PAPR and maximizes the performance. [ABSTRACT FROM AUTHOR]

This article proposes a simple and efficient carrier-based Pulse Width Modulation (PWM) technique for three-level transformer-less grid-connected Photovoltaic (PV) inverters. The three-level inverter is prone to an inherent issue of unbalanced DC-link voltages, which, when used in conjunction with transformerless grid-connected PV systems, gives rise to leakage currents. A simplified carrier-based PWM is proposed to carry out the DC-link voltage balancing and suppress the leakage current, i.e. Common Mode (CM) current, in transformer-less grid-connected inverters. The implementation of the proposed strategy is straightforward and does not require complex calculations, in contrast to space vector-based PWM techniques or multi-carrier modulation techniques. The operation of the PWM strategy is demonstrated through simulations and validated through experimental results. [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]

The main objective of the wireless industry is to satisfy the ever-growing demands of next-generation communication systems such as higher data rates and high spectral efficiency. The prominent requirement of beyond-fifth-generation (B5G) communications is to connect millions of devices around the globe to the internet for smart radio access. Besides, the spectrum allocation and the data rate improvement for B5G networks is a challenging task. This manuscript focuses on the performance enhancement of the existing physical layer design framework for B5G networks. The proposed system exploits a hybrid combination of generalized frequency division multiplexing (GFDM) and non-orthogonal multiple access (NOMA) with the multiplexing scheme in space (MS) to improve the system performance. The simulation results validate the superior performance of the proposed system in terms of enhanced data rate, sum rate, and capacity compared to the conventional GFDM-NOMA systems. More specifically, the proposed GFDM-NOMA with MS achieves a performance improvement of around 1Gbps in data rate compared to the existing system. Finally, the proposed system performance proved to be a suitable candidate for the internet of things (IoT) and device-to-device (D2D) applications in B5G communications. [ABSTRACT FROM AUTHOR]

We present a subspace-based polynomial rooting algorithm to estimate the frequency bias (FB) of generalized frequency division multiplexing (GFDM) systems employing null subcarriers and repetitive sub-symbols. The estimation process is classified into fractional FB (FFB) and integer FB (IFB) estimation. The use of repetitive sub-symbols creates a quasi-periodic structure in the FB-distorted received signal, allowing the proposed algorithm to estimate the FFB using the root-MUSIC algorithm. Based on this, the proposed algorithm compensates for the FFB in the received signal and then estimates the null subcarrier pattern (NSP) in the frequency domain. As a result, the IFB estimate can be obtained in a maximum likelihood (ML) manner. Before the NSP estimation, this study uses a sub-symbol combiner to enhance signal strength of the FFB-aligned signal, ensuring the reliability of the IFB estimate. Computer simulations show that the proposed subspace-based algorithm has several advantages over traditional FB estimation methods: 1. Unlike some existing algorithms that use a training sequence to estimate FB, the proposed approach is a semi-blind algorithm because it can deliver information through repeated sub-symbols while estimating FB; 2. The proposed algorithm demonstrates excellent estimation accuracy compared to most traditional FB estimation algorithms; and 3. The proposed algorithm is computationally efficient, making it applicable to real-time applications in future communication systems. [ABSTRACT FROM AUTHOR]

A multilevel inverter performs a major role in increasing the range of the level of output voltage without the use of a transformer in the power sector. Here an asymmetrical 15-level multilevel inverter fed from three unequal voltage sources has been proposed. The various modes of the conduction of the eight switches with the switching pattern are discussed with the circuit's operation. The performance of the circuit is analysed using various techniques under MC-PWM methodologies such as Phase disposition (PD) PWM, Alternate POD (APOD) PWM, and Phase Opposition Disposition (POD) PWM. Key Finding: The logical expression used for generating the pulse pattern of the above techniques using the level shifting PWM technique to reduce the harmonics is performed, simulated, and compared by implementing three techniques for linear and non-linear load. The performance in terms of THD of output voltage under various modulation indexes is compared for various Llvel-shifting techniques. The performance of this 15L-MLI is simulated using MATLAB/Simulink and implemented in a prototype hardware model. [ABSTRACT FROM AUTHOR]

Sixth-generation (6G) wireless networks demand a more efficient implementation of non-orthogonal multiple access (NOMA) schemes for severe multipath fading environments to serve multiple users. Using non-orthogonal multiple access (NOMA) schemes in IoT 6G networks is a promising solution to allow multiple users to share the same spectral and temporal resource, increasing spectral efficiency and improving the network's capacity. In this work, we have evaluated the performance of a novel progressive pattern interleaver (PPI) employed to distinguish the users in interleaved division multiple access (IDMA) schemes, suggested by 3GPP guidelines as a NOMA scheme, with two multi-carrier modulation schemes known as single-carrier frequency-division multiple access (SC-FDMA) and orthogonal frequency-division multiplexing (OFDM), resulting in SC-FDMA-IDMA and OFDM-IDMA schemes. Both schemes are multi-carrier schemes with orthogonal sub-carriers to deal against inter-symbol interference (ISI) and orthogonal interleavers for the simultaneous access of multiple users. It has been suggested through simulation outcomes that PPI performance is adequate with SC-FDMA-IDMA and OFDM-IDMA schemes in terms of bit error rate (BER) under multipath channel conditions. Moreover, regarding bandwidth requirement and the implementation complexity of the transmitted interleaver structure, PPI is superior to the conventional random interleaver (RI). [ABSTRACT FROM AUTHOR]

The relentless evolution of communication systems, driven by the demands of 5G and the impending 6G networks, necessitates heightened data rates and spectral efficiency. orthogonal frequency division multiplexing (OFDM), a form of multicarrier modulation employed in multi-input multioutput (MIMO) systems, stands as a pivotal technology. Yet, OFDM grapples with challenges, notably the peak-to-average power ratio (PAPR) issue. Selective mapping (SLM) has been a favored technique for mitigating PAPR in OFDM, albeit challenged by computational complexities in its pursuit of discovering optimal phase factors. This paper pioneers a transformative approach by integrating metaheuristic algorithms genetic algorithm (GA), particle swarm optimization (PSO), and the innovative fireworks algorithm (FWA) into SLM for PAPR reduction while minimizing computational complexity. Simulation results not only affirm the efficacy of SLM-based techniques but also spotlight the potential of metaheuristic algorithms in addressing PAPR challenges in modern communication systems. The study transcends single-antenna systems, extending to MIMOOFDM systems based on WiMAX standards, validating the efficacy of these techniques in multi-antenna configurations. Crucially, the FWA, proposed for the first time in this paper, emerges as a robust candidate, striking an enviable balance between computational efficiency and performance, achieving a notable PAPR reduction with a favorable search number. [ABSTRACT FROM AUTHOR]

The purpose of this article is to investigate the viability of Multi-Carrier Modulation (MCM) systems based on the Fast Walsh Hadamard Transform (FWHT). In addition, a nonlinear Joint Low-Complexity Optimized Zero Forcing Successive Interference Cancellation (JLCOZF-SIC) equalizer is proposed. To that end, general equations for the number of flops of the proposed equalizer and various other equalizers are given. This article discusses the use of Banded Matrix Approximation (BMA) as a technique for reducing complexity. The proposed equalizer uses BMA to accomplish both equalization and co-Carrier Frequency Offset (co-CFO) corrections. In addition, three cases involving the proposed equalizer were investigated. In the first case, diagonal compensation is used. In the second case, BMA compensation is used. In the third case, complete matrix compensation is used. In the presence of frequency offset, noise, and frequency-selective Rayleigh fading environments, analysis and simulation results show that the OFDM-FWHT system with the proposed equalizer outperforms the conventional OFDM system with various linear and nonlinear equalizers. [ABSTRACT FROM AUTHOR]

In contemporary wireless communication systems, multicarrier modulation schemes have become widely adopted over single-carrier techniques due to their improved capacity to address challenges posed by multipath fading channels, leading to enhanced spectral efficiency. Orthogonal frequency division multiplexing (OFDM), a prevalent multicarrier scheme in 4G, is favored for its ease of implementation, interference resilience, and high data rate provision. But it falls short of meeting the requirements for 5G and beyond due to limitations such as out-of-band (OOB) emissions and cyclic prefixes. This paper introduces the filter bank multicarrier (FBMC) and universal filtered multicarrier (UFMC) with quadrature amplitude modulation (QAM) and phase shift keying (PSK) waveforms through Additive White Gaussian Noise channel (AWGN), Rayleigh fading channel and Rician channel. The objective of this paper is to enhance the performance of UFMC with reduced complexity through the new filtering approach for achieving optimal outcomes. The proposed scheme, incorporating Tukey filtering technique, demonstrates superior performance in reducing peak-to-average power ratio (PAPR) and improving bit error ratio (BER) compared to the original UFMC signal without necessitating additional power increments. Specifically, the UFMC system with Tukey filtering achieves a notable net gain of 5 dB. Simulation results demonstrate that utilizing various filter types in FBMC and UFMC systems, combined with QAM modulation, significantly reduces OOB emissions compared to conventional systems. In aspect to BER, Tukey window showed almost 10−6 at 15 dB SNR in UFMC which is better than FBMC. [ABSTRACT FROM AUTHOR]

The Multi-Carrier Modulation (MCM) technique in the Near Vertical Incidence Skywave (NVIS) propagation mode poses a challenge due to the ionosphere’s dynamic behavior. The selection of the main bandwidth and transmission frequency in the MCM-NVIS system should consider the different ionospheric refraction indexes within each available frequency of the ionosphere channel. This ensures that all transmitted sub-carriers arrive at the receiver at an acceptable time. It is important to note that not all transmission frequencies may reach the receiver, and the propagation time of each received frequency may differ significantly. Using sub-carrier frequencies with varying propagation times in the MCM technique may negatively impact the system’s performance. Therefore, information on the NVIS propagation mode frequency window with homogeneous Time of Flight (ToF) values is crucial for successfully implementing the MCM technique. In this paper, we explore the frequency window with homogeneous ToF values for NVIS propagation based on ionograms. The width of the frequency window and its center frequency variation can be used to determine the main bandwidth and transmission frequency of the MCM-NVIS system. Our numeric simulation with the inputs of the widest frequency window based on the ionograms at Kupang in 2022 shows that the maximum value of ergodic capacity is up to $10^{6}$ bps at 20 dB SNR during the daytime.

Filter Bank Multi-Carrier (FBMC) is attracting significant interest as a multi-carrier modulation (MCM) approach for future communication systems. It offers numerous advantages in contrast to Orthogonal Frequency Division Multiplexing (OFDM). Nonetheless, similar to many other MCM techniques, FBMC encounters a significant challenge with a high Peak-to-Average Power Ratio (PAPR). Additionally, incorporating Multiple-Input and Multiple-Output (MIMO) into FBMC presents heightened difficulties due to the presence of complex interference and increased computational complexity. In this paper, we first study the performance analysis of MIMO based Quadrature Amplitude Modulation (QAM)-FBMC systems considering the system complexity and interference. To enhance coverage effectively using beamforming with multiple antennas, it is essential to reduce PAPR to minimize the input backoff (IBO) required by nonlinear power amplifiers. Therefore, we propose new PAPR reduction method for MIMO based QAM-FBMC systems leveraging the null space within the MIMO channel using clipping and filtering (CF) technique. The PAPR reduction signals generated in this process are then mapped to the null space of the overall MIMO channel for each frequency block. Through computer simulations using a nonlinear power amplifier model, we illustrate that the proposed method substantially enhances both PAPR and throughput of MIMO based FBMC systems compared to conventional methods. [ABSTRACT FROM AUTHOR]

The paper studies the performance of a free space optical communication link, which consists of a Gaussian Laser beam employing direct-current-biased optical frequency division multiplexing (DCO-OFDM) modulation, to carry information. While optical multi-carrier modulation is capable of alleviating multi-path fading, higher transmit power by virtue of dc-bias, helps the optical beam in partially off-setting signal intensity loss due to beam divergence in free space channel. In order to reduce the overall transmitted power apart from avoiding nonlinearities due to high peak-to-average-power-ratio (PAPR), we utilize a PAPR-dependent dc-bias, to generate a DCO OFDM light beam from a pre-clipped electrical baseband OFDM signal. The radiated optical beam encounters turbulence-induced impairments like beam-spreading, beam-wander, etc., which affect the signal-to-noise ratio (SNR) of the received data symbols. Further signal pre-clipping and optical source linearity generate clipping noise components resulting in compromised receiver performance or reduction of span length, to achieve target bit rate error (BER). In this paper, we derive an analytical model for evaluating the performance of the free-space optical (FSO) link, by modeling various impairments as noise variances and characterizing atmospheric turbulence by refractive index structure parameter under weak- and strong-turbulent conditions. Numerical results are obtained by varying system design parameters in the model, which graphically provide useful insight on the power penalties and various trade-offs involved in operating the link on a longer span, at a higher data rate, and with reduced transmitted power through pre-clipping while ensuring desired signal BER. [ABSTRACT FROM AUTHOR]

Filter bank multicarrier (FBMC) is a new waveform candidate in the visible light communication system (VLC). FBMC is a particular sort of multi-carrier modulation that can be viewed as an option in contrast to orthogonal frequency division multicarrier (OFDM) with CP (cyclic prefix). The point is to defeat some innate disadvantages of the normally utilized optical OFDM schemes. The principles of key transceiver should be intended to suit the necessities of the channel of IM/DD. Peak to average power ratio (PAPR) and bit error rate (BER) performance of FBMC based VLC are discussed and compared with scheme of optical OFDM. FBMC based VLC system with clipping technique has the lowest PAPR and good BER performance compared to conventional system in this paper. This paper recommends that FBMC based VLC has an incredible potential for optical wireless communication systems with high-speed. Matlab program simulations confirm the analysis. The results may shed light into potential research line on FBMC based VLC systems. [ABSTRACT FROM AUTHOR]

FBMC is a pivotal system in 5G, serving as a cornerstone for efficient use of available bandwidth while simultaneously meeting stringent requirements for high spectral efficiency. Notably, FBMC harnesses the power of multicarrier modulation (MC), a good alternative to orthogonal frequency division multiplexing (OFDM) technology that supports fourth-generation (4G) systems. The wireless communications field is full of challenges, the most important of which are channel estimation and interference cancellation, both of which deserve comprehensive study to increase the efficiency of data transmission. In this paper, our investigation takes a deliberate step towards the convergence of two prominent modulation models: OFDM and FBMC. We specifically contrast these modulation techniques with the intricate field of joint channel estimation and interference cancellation (JCEIC). In this research study, we take advantage of recurrent neural networks' (RNNs') efficiency as a vehicular channel to perform precise channel estimation and recovery of uncorrupted transmitted signals, thereby lowering the bit error rate (BER). Our channel estimation for a dual selective channel is based on the thoughtful placement of pilots scattered over the temporal and frequency dimensions, and is further improved by the interference cancellation method of low complexity that was selected. Our JCEIC proposal aims to integrate RNNs carefully, using the output sequences of JCEIC algorithms as useful inputs to this neural architecture. By clearly demonstrating a decrease in BER as compared to traditional approaches, it is evident that the performance of the novel approach is near to that of a perfect channel. Additionally, a comparison of the performance of FBMC and OFDM systems at various signal-to-noise ratios reveals a clear performance divide that favors the former in terms of system efficiency. The BER is restricted by FBMC to a commendable threshold of less than 0.1 at a modest 5 dB, continuing the higher trend started by its improved RNN-based channel estimate. The accuracy of channel estimation is clearly improved by this paradigm shift, and the computing complexity typical of 5G networks is also clearly reduced. [ABSTRACT FROM AUTHOR]

Filter Bank Multicarrier(FBMC)is considered as one of the most standardized waveform for fifth generation (5G) mobile communication system application FBMC endures lot of nonlinear effects which occurs because of high Peak Average Power Ratio (PAPR). High value of PAPR due to the large dynamic range of multicarrier signal is one of the most significant issues in FBMC multicarrier based modulation technique. This paper presents one investigated PAPR reduction technique named as Selected Mapping (SLM) to minimize high PAPR by utilizing the complex signal divide into real and imaginary parts and then select minimum PAPR signal based on Modified Forest Optimization Algorithm (MFOA)to achieve good PAPR which can maintain the FBMC based system performance with a required Bit Error Rate (BER). The associated method was produced with the aim of optimize the phase factors so that the phase rotation operation is accomplished to minimize PAPR by fixing the MFOA into the conventional SLM. The simulation results demonstrate that the proposed technique gives better performance in terms of BER and PAPR compared to other SLM based optimization techniques. [ABSTRACT FROM AUTHOR]

As one of multi-carrier modulation schemes suitable for 5G/B5G scenarios, the generalized frequency division multiplexing (GFDM) waveform has flexible time-frequency resource distribution. To further reduce out-of-band power leakage of GFDM system, a multiparameter variable GFDM prototype filter is proposed. The flexible configuration of multiparameter method achieves better out-of-band power suppression performances and a precise control of out-of-band power efficiency suppression. Simultaneously, theoretical bit error rate (BER) expression of GFDM system with multiparameter variable filter under frequency selective fading channel is derived. In addition, in order to further improve the BER performance of GFDM system in complex channel scenarios, a message passing (MP) receiver suitable for multiparameter GFDM waveforms is proposed, and the mathematical model of the MP receiving algorithm is given according to the equivalent channel matrix. Simulation results show that the MP receiver can effectively improve the BER performance of GFDM waveform in complex channels. Moreover, the variable filter based on multiparameter can effectively suppress out-of-band power with slight BER loss in comparison with traditional raised cosine (RC) filter. [ABSTRACT FROM AUTHOR]

Generalized frequency division multiplexing (GFDM) is a block-based multicarrier modulation scheme that is a potential candidate for the fifth generation (5G) and beyond wireless communication systems. A critical factor in enhancing the performance of GFDM is achieving precise synchronization. To that end, a new timing synchronization algorithm that utilizes cross-correlation and the sliding window algorithm is presented in this article. The algorithm uses a training symbol based on a chirp sequence. The simulation results of the proposed estimator and conventional CP based approach are analyzed under indoor office scenarios and urban macro cells scenarios for orthogonal frequency division multiplexing and GFDM. The performance of the proposed method is better for GFDM in terms of the three parameters: mean of the timing offset, mean square error of the timing offset, and probability of timing failure. For the proposed algorithm, the results show that the probability of timing failure decreases with increasing signal to noise ratio in the case of the GFDM system. [ABSTRACT FROM AUTHOR]

Single-carrier frequency division multiple access (SC-FDMA) is a multicarrier modulation technique that has attracted wireless communication systems. However, one of the critical drawbacks of the system is the high peak-to-average power ratio (PAPR). PAPR in SC-FDMA causes nonlinear distortion in power amplifiers leading to inter-symbol interference (ISI) and inter-carrier interference (ICI) in the system. In this paper, we propose a modified gamma correction companding (MGCC) to reduce PAPR than existing companding schemes in SC-FDMA systems substantially. It is revealed that the proposed technique can significantly improve PAPR gain and bit error rate (BER) with the proper choice of companding parameter, thus enabling flexibility in designing an optimum system for uplink data transmission. Further, the simulation results prove that MGCC with joint equalisation and carrier frequency offset (CFO) compensation can achieve superior performance and reduce ISI under multipath fading channels. [ABSTRACT FROM AUTHOR]

In order to deal with the increasing number of mobile devices and with their demand for Internet services, particularly social media platforms, streaming video, and online gaming, Radio-Frequency (RF) wireless networks have been pushed to their capacity limits. In addition to this, 80% of the total data traffic is carried out by users inside buildings. Therefore, new technologies have started to be considered for indoor wireless communications. Visible Light Communications (VLC) can provide both illumination and communications, appearing as an alternative or complement to RF wireless networks. VLC offers high bandwidth and immunity to interference from electromagnetic sources. This manuscript reviews recent high-capacity VLC demonstrations. The main focus of this work is to present digital-signal-processing techniques used in VLC systems. Different modulation formats are analyzed, which can be divided into two large groups, namely single-carrier and multi-carrier modulation schemes. Finally, some recently proposed capacity-achieving strategies are presented. We discuss how to implement these techniques and how they will be useful for the continued development of VLC systems. [ABSTRACT FROM AUTHOR]

Copyright of Study on Optical Communications / Guangtongxin Yanjiu is the property of Study on Optical Communications Editorial Office and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

This study presents a computationally efficient maximum likelihood (ML) algorithm for estimating the carrier frequency offset (CFO) of generalized frequency division multiplexing systems. The proposed algorithm uses repetitive subsymbols and virtual carriers to estimate the fractional and integer CFOs, respectively. Through the use of repetitive subsymbols, this study first calculates the ML estimate of the fractional CFO in the time domain and then, accordingly, compensates for it from the received signal. The integer CFO can then be estimated through a virtual-carrier-mapping process in the frequency domain. In addition to improving performance in terms of estimation accuracy and computational complexity, the proposed non-data-aided algorithm is spectrally efficient relative to traditional algorithms. [ABSTRACT FROM AUTHOR]

Pulse width modulation for Selective Harmonics Elimination (SHE) is mostly employed in the reduction of lower order harmonics. The PV system in this research provides input voltage to the reduced switch 31-level inverter, which is based on the Artificial Bee Colony algorithm. With a high gain DC-DC single-ended primary-inductor converter (SEPIC), the PV panel output voltage is kept constant. The Grey wolf optimization algorithm (GWO) approach is used to get the most power out PV scheme. Multi Carrier modulation, a high-frequency modulation technology, is also used in this novel design of the inverter to reduce upper order harmonics. The suggested Artificial Bee Colony (ABC) algorithm, harmonics is compared to a SHE technique based on a genetic algorithm. The hardware findings were confirmed using DSPIC30F2010 controller simulation, and the recommended system was validated using Matlab simulation. [ABSTRACT FROM AUTHOR]

Copyright of Al-Mustansiriyah Journal of Science is the property of Republic of Iraq Ministry of Higher Education & Scientific Research (MOHESR) and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

A laboratory setup is developed to experimentally reinforce the student's understanding of multilevel neutral point clamped inverter operated with various multicarrier and modulation reference signals. Sixteen combinations of carrier and reference signals out of many more possible are studied in this setup. The lab module is project-based and is designed to perform experiments for the 'advanced power electronics and drives' course at the undergraduate level. The hardware implementation details of the multilevel inverter are given in detail for reference to the teachers, students and researchers. Flexible hardware able to be driven by an analogue pulse-generation circuit is explained here or by an external digital programmable device is developed. With the help of dSPACE, complex reference signals are produced for performance analysis. [ABSTRACT FROM AUTHOR]

Multi-carrier modulation (MCM) is one of the fundamental components of beyond 5G (B5G) and 6G that meets the many requirements of contemporary use cases. Filter bank multi-carrier with offset quadrature amplitude modulation (FBCM/OQAM) is one of the most promising modulation that offers many benefits to the next generation. However, like all MCM modulations, it shows a high peak signal in the time domain, which causes in-band (IB) and out-of-band (OOB) distortions in the amplifier output signal. The present paper suggests that an FBMC/OQAM system with multi-input multi-output (MIMO) employs a new hybridization that combines repeated clipping filtering (RCF) with several companding techniques, including A-Law, Mu-Law, tangente rooting (tanhR), logarithmic rooting (logR), cos and rooting companding (RTC). The combination of RCF and Mu-Law yields the best results of peak-to-average power ratio (PAPR) reduction and bit error rate (BER). The simulation results showed a significant decrease in PAPR, with a reduction of 68.54% compared to the original signal without the reduction technique. [ABSTRACT FROM AUTHOR]

There are numerous goals in next-generation cellular networks (5G), which is expected to be available soon. They want to increase data rates, reduce end-to-end latencies, and improve end-user service quality. Modern networks need to change because there has been a significant rise in the number of base stations required to meet these needs and put the operators' low-cost constraints to the test. Because it can withstand interference from other wireless networks, and Adaptive Complex Multicarrier Modulation (ACMM) system is being looked at as a possible choice for the 5th Generation (5G) of wireless networks. Many arithmetic units need to be used on the hardware side of multicarrier systems to do the pulse-shaping filters and inverse FFT. The main goal of this study is to adapt complex multicarrier modulation (ACMM) for baseband transmission with low complexity and the ability to change it. We found that this is the first recon- figurable architecture that lets you choose how many subcarriers a subband has while still having the same amount of hardware resources as before. Also, under the new design with a single selection line, it selects from a set of filters. The baseband modulating signal is evaluated and tested using a Field-Programmable Gate Array (FPGA) device. This device is available from a commercial source. New technology outperforms current technology in terms of computational complexity, simple design, and ease of implementation. Additionally, it has a higher power spectrum density, spectral efficiency, a lower bit error rate, and a higher peak to average power ratio than existing technology. [ABSTRACT FROM AUTHOR]

The Discrete Wavelet Transform (DWT) has gained attention in the area of Multi-Carrier Modulation (MCM) because it can overcome some well known limitations of Discrete Fourier Transform (DFT) based MCM systems. Its improved spectral containment removes the need for a cyclic prefix, be it that appropriate equalization then has to be added as the cyclic convolution property no longer holds. Most DWT based MCM systems in the literature use Time-domain EQualizers (TEQs) to mitigate the channel distortion. In this paper, a Per-Wavelet EQualizer (PWEQ) is proposed which directly maximizes the Signal-to-Interference-plus-Noise Ratio (SINR) per symbol and is applicable to any wavelet family. The proposed PWEQ provides a performance upper bound for the TEQs for DWT based MCM systems. The computational complexity of the PWEQ is reduced by modifying the Filter Bank (FB) structure of the DWT. Simulations are performed to compare the PWEQ performance against the TEQs for DWT based MCM systems and the similar Per-Tone EQualizer (PTEQ) for DFT based MCM systems. The simulations are performed using measured Asymmetric Digital Subscriber Line (ADSL) and G.fast channels with Fejér-Korovkin (FK) wavelets. The proposed PWEQ increases the SINR on the received symbols compared to the TEQs at the cost of an increased computational complexity.

Visible light communication (VLC) is an emerging mode of wireless communication that supports both illumination and communication. One essential function of VLC systems is the dimming control, which requires a sensitive receiver for low-light conditions. The use of an array of single-photon avalanche diodes (SPADs) is one promising approach to enhancing receivers' sensitivity in a VLC system. However, because of the non-linear effects brought on by the SPAD dead time, an increase in the brightness of the light might degrade its performance. In this paper, an adaptive SPAD receiver is proposed for VLC systems to ensure reliable operation under various dimming levels. In the proposed receiver, a variable optical attenuator (VOA) is used to adaptively control the SPAD's incident photon rate according to the instantaneous received optical power so that SPAD operates in its optimal conditions. The application of the proposed receiver in systems with various modulation schemes is investigated. When binary on–off keying (OOK) modulation is employed due to its good power efficiency, two dimming control methods of the IEEE 802.15.7 standard based on analogue and digital dimming are considered. We also investigate the application of the proposed receiver in the spectral efficient VLC systems with multi-carrier modulation schemes, i.e., direct current (DCO) and asymmetrically clipped optical (ACO) orthogonal frequency division multiplexing (OFDM). Through extensive numerical results, it is demonstrated that the suggested adaptive receiver outperforms the conventional PIN PD and SPAD array receivers in terms of bit error rate (BER) and achievable data rate. [ABSTRACT FROM AUTHOR]

The major setback of a multi-carrier modulation (MCM) is Synchronization Errors, which includes time, frequency and phase offset. Especially, Wavelet based MCM catches the eyes of researchers due to its flexibilities which are seen as one of the strong contender for cognitive radios. Synchronization errors are mainly due to mobility between nodes and sub-optimal local oscillators and it is necessary to learn the behaviour of wavelets under these channel fading conditions. In this paper, we present the novel joint effects of Wavelet-based Cognitive Radio OFDM (CR-WOFDM) systems under Synchronization Error in terms of based bit error rate (BER). BER Outputs of WOFDM is compared with FFT based OFDM with Cyclic Prefix (CP-OFDM) systems in a doubly-selective channel by designing a communication system for computer simulation. Several well-known wavelets are chosen and analysed, including Daubechies (db), Symlets (sym), Coiflets (coif), Fejér–Korovkin (fk) filters, and biorthogonal (bior) wavelets. First, we show the behaviour of wavelets in terms of BER by considering different doubly selective channel Power Delay Profile like, AWGN, FLAT, Pedestrian and Vehicular and channel Doppler models like, Uniform and JAKES. Finally, we calculate and plot Signal-to-Interference Ratio of WOFDM with Time and Frequency Offset and compared the results with FFT based CP-OFDM. [ABSTRACT FROM AUTHOR]

We propose an early-detection scheme to reduce communications latency based on sequential tests under finite blocklength regime for a fixed-rate transmission without any feedback channel. The proposed scheme processes observations sequentially to decide in favor of one of the candidate symbols. Such a process stops as soon as a decision rule is satisfied or waits for more samples under a given accuracy. We first provide the optimal achievable latency in additive white Gaussian noise channels for every channel code given a probability of block error. For example, for a rate R = 0.5 and a blocklength of 500 symbols, we show that only 63 % of the symbol time is needed to reach an error rate equal to 10 - 5 . Then, we prove that if short messages can be transmitted in parallel Gaussian channels via a multi-carrier modulation, there exists an optimal low-latency strategy for every code. Next, we show how early detection can be effective with band-limited orthogonal frequency-division multiplexing signals while maintaining a given spectral efficiency by random coding or pre-coding random matrices. Finally, we show how the proposed early-detection scheme is effective in multi-hop systems. [ABSTRACT FROM AUTHOR]

Passive location technology has been greatly developed because of its low power consumption, long detection distance, good concealment, and strong anti-interference ability. Orthogonal frequency-division multiplexing (OFDM) is an efficient multi-carrier transmission technology, which is an important signal form of 5G communication. Researching passive locations for OFDM signals can realize the location of base stations, which is of great significance in the military. Space-borne passive location technology has a contradiction between wide coverage and high precision. Therefore, a single-satellite passive location algorithm for OFDM radiation sources based on the virtual synthetic aperture is proposed. The algorithm introduces virtual synthetic aperture technology, using antenna movement to accumulate data coherently over a long time period and synthesizing a long azimuth virtual aperture. In addition, it utilizes fast Fourier transform (FFT) to extract phase information at a specific frequency based on the multi-carrier modulation technology of the OFDM signal. Pilot technology of the communication system is used for phase compensation and noise reduction. Thus, the azimuth linear frequency modulation (LFM) signal containing the location information of the radiation source is obtained. The radiation source location can be obtained by range searching and azimuth focusing. Simulation results verify the effectiveness of the algorithm and show that the algorithm can realize high-precision and wide-coverage location for the OFDM radiation sources using a single antenna, turning the hardware structure into software to reduce the cost and complexity of the system. [ABSTRACT FROM AUTHOR]

This paper presents a prototype filter design using the orthant optimization technique to assist a filter bank multicarrier (FBMC) modulation scheme of a NextG smart e-healthcare network framework. Low latency and very high reliability are one of the main requirements of a real-time e-healthcare system. In recent times, FBMC modulation has gotten more attention due to its spectral efficiency. The characteristics of a filter bank are determined by t's, prototype filter. A prototype filter cannot be designed to achieve an arbitrary time localization (for low latency) and frequency localization (spectral efficiency), as time and frequency spreading are conflicting goals. Hence, an optimum design needed to be achieved. In this paper, a constraint for perfect or nearly perfect reconstruction is formulated for prototype filter design and an orthant-based enriched sparse ℓ1-optimization method is applied to achieve the optimum performance in terms of higher availability of subcarrier spacing for the given requirement of signal-to-interference ratio. Larger subcarrier spacing ensures lower latency and better performance in real-time applications. The proposed FBMC system, based on an optimum design of the prototype filter, also supports a higher data rate as compared to traditional FBMC and OFDM systems, which is another requirement of real-time communication. In this paper, the solution for the different technical issues of physical layer design is provided. The presented modulation scheme through the proposed prototype filter-based FBMC can suppress the side lobe energy of the constituted filters up to large extent without compromising the recovery of the signal at the receiver end. The proposed system provides very high spectral efficiency; it can sacrifice large guard band frequencies to increase the subcarrier spacing to provide low-latency communication to support the real-time e-healthcare network. [ABSTRACT FROM AUTHOR]

In filter bank multi‐carrier (FBMC) with offset quadrature amplitude modulation (OQAM) systems, the major limitation of FBMC‐OQAM signaling is the high peak‐to‐average power ratio (PAPR). High PAPR results in increased hardware complexity and is also prone to non‐linear effects of high‐power amplifiers (HPA). The existing HPA energy‐efficient optimization strategies are constrained severely by the scarcity and heterogeneity of signal distribution in the degree of freedom. This paper theorizes the optimal FBMC‐OQAM signal distribution, which has a global and steady feature and evaluates the maximal HPA efficiency‐suited multi‐carrier modulation (MCM) signal. This paper first proposes that the Binary Particle Swarm Optimization based Partial Transmit Sequence (BPSO‐PTS) with the Input‐Back Off Modulation Error Ratio (IBO‐MER) scheme traces the signal distribution for maximal HPA efficiency to save supply‐side energy. This paper further proposes Continuous‐Unconstrained Particle Swarm Optimization based PTS(CUPSO‐PTS) with IBO‐MER to obtain the theoretical boundaries and drastically accelerate convergence in the continuous‐unconstrained searching space. To decrease the computational complexity of MER calculation, this paper proposes the CUPSO with IBO Signal‐to‐Distortion Ratio (IBO‐SDR), enabling it to meet more practical applications. The simulation results show that the proposed scheme outperforms conventional IBO and HPA efficiency schemes. [ABSTRACT FROM AUTHOR]

In this work, we mainly focus on low probability detection (LPD) and low probability interception (LPI) wireless communication in cyber-physical systems. An LPD signal waveform based on multi-carrier modulation and an under-sampling method for signal detection is introduced. The application of the proposed LPD signal for physical layer security is discussed in a typical wireless-tap channel model, which consists of a transmitter (Alice), an intended receiver (Bob), and an eavesdropper (Eve). Since the under-sampling method at Bob's end depends very sensitively on accurate sampling clock and channel state information (CSI), which can hardly be obtained by Eve, the security transmission is initialized as Bob transmits a pilot for Alice to perform channel sounding and clock synchronization by invoking the channel reciprocal principle. Then, Alice sends a multi-carrier information-bearing signal constructed according to Bob's actual sampling clock and the CSI between the two. Consequently, Bob can coherently combine the sub-band signals after sampling, while Eve can only obtain a destructive combination. Finally, we derived the closed-form expressions of detection probability at Bob's and Eve's ends when the energy detector is employed. Simulation results show that the bit error rate (BER) at Alice's end is gradually decreased with the increase in the signal-to-noise ratio (SNR) in both the AWGN and fading channels. Meanwhile, the BER at Eve's end is always unacceptably high no matter how the SNR changes. [ABSTRACT FROM AUTHOR]

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Nowadays, multicarrier modulation schemes are being widely used in wireless communication system than single-carrier modulation techniques. Single-carrier modulation schemes are less capable of dealing with multipath fading channels than multicarrier modulation schemes, which results in lower spectral efficiency. Multicarrier modulation schemes have the ability to overcome multipath fading channels. Multicarrier modulation technique currently used in 4G technology in many countries is OFDM and it is easy for implementation, immune to interference, and provide fast data rate. However, the rising users demand on wireless communication resulted in need for further advancement of wireless communication system. The present OFDM transmission does not fulfill the requirements of 5G wireless communication system and beyond due to major limitations such as out of band emission and usage of cyclic prefix. To overcome the challenges of OFDM, different modulation schemes like Filter Bank Multicarrier with Offset-QAM, Filter Bank Multicarrier with QAM, Universal Filter Multicarrier, Filtered-OFDM, and Weighted Overlap and Added-OFDM are proposed. In this study, the Filter Bank Multicarrier with QAM using Hermite prototype filter is proposed to overcome drawbacks of OFDM and all other proposed waveforms. The performances of each multicarrier technique are analyzed based on power spectral density and bit error rate. Simulation result shows that the power spectral density of FBMC with QAM using Hermite filter resulted in 4.7 dB reduction of out of band emission compared to FBMC with QAM using PHYDYAS filter. The bit error rate is also reduced for Vehicular A, Vehicular B, Pedestrian A, and Pedestrian B channel models. [ABSTRACT FROM AUTHOR]