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The Last decade saw significant growth in the digital terrestrial television (DTT) subscribers. The High peak-to-average power ratio (PAPR) of the transmitted signal is implied by the large fluctuations in its amplitude, which is a serious issue in the contemporary and next generation DTT broadcasting systems. These large fluctuations prevent feeding the high power amplifier (HPA) at an operating point near its non-linear (NL) saturation region, thereby lowering its power efficiency. For a better future, energy-efficient green communications is the need of hour. This paper focuses on digital predistortion (DPD), which is among the widely used techniques for HPA linearization in order to minimize the NL effects. DPD technique requires a feedback signal. This paper proposes a novel adding signal-based digital predistortion, where the output of the HPA is gradually linearized by adding a signal at the input in an iterative manner. By Taylor series approximation, the DPD problem can be posed as a convex one. We prove that a tighter upper bound exists for the convergence factor and instead of directly solving the convex problem, we pick a convergence factor value within its bounds that offers a good trade-off between convergence speed and residual error value. The simulation results show that the proposed technique can quickly linearize the HPA with good convergence. [ABSTRACT FROM AUTHOR]

Inductively coupled mooring chain transmission technology plays a crucial role in the long-distance online monitoring of marine hydrographic information. However, the impedance characteristics of the seawater medium pose a limitation on its capability to achieve high-speed real-time transmission of underwater images. In this paper, based on the principle of inductively coupled transmission for marine applications, the selected 1920 × 1080 pixel images are segmented, packaged, and then transmitted to the sending node using the user datagram protocol (UDP), and the modulation and demodulation of the transmitted images are realized using the orthogonal frequency division multiplexing (OFDM) algorithm of least squares (LS) estimation, and eight combinations with different mapping modes and coding rates are tested in the bandwidth of 200–800 kHz and the quality of the transmitted images is evaluated using three criteria: mean squared error (MSE), peak signal to noise ratio (PSNR), and structural similarity index (SSIM). The results indicate that the image transmission quality is optimal when the mapping method is 16-quadrature amplitude modulation (16QAM), the coding rate is 1/2, and the center frequency is 800 kHz. Under these conditions, the maximum transmission rate is 0.84 Mbits−1, the SSIM criterion exceeds 0.91690 dB, and the learned perceptual image patch similarity (LPIPS) is less than 0.06000. This paper provides a solution for the underwater image transmission of inductively coupled mooring chains for marine applications. [ABSTRACT FROM AUTHOR]

With the ratification of the IEEE 802.11ad amendment to the 802.11 standard in December 2012, a major step has been taken to bring consumer wireless communication to the millimeter wave band. However, multi-gigabit-per-second throughput and small interference footprint come at the price of adverse signal propagation characteristics, and require a fundamental rethinking of Wi-Fi communication principles. This article describes the design assumptions taken into consideration for the IEEE 802.11ad standard and the novel techniques defined to overcome the challenges of mm-Wave communication. In particular, we study the transition from omnidirectional to highly directional communication and its impact on the design of IEEE 802.11ad. [ABSTRACT FROM PUBLISHER]

To detect moving weak targets in the dual function radar communication (DFRC) system of an orthogonal frequency division multiplexing (OFDM) waveform, a modified hybrid integration method is addressed in this paper. A high-speed aircraft can cause range walk (RW) and Doppler walk (DW), rendering traditional detection methods ineffective. To overcome RW and DW, this paper proposes an integration approach combining DFRC and OFDM. The proposed approach consists of two primary components: intra-frame coherent integration and hybrid multi-inter-frame integration. After the echo signal is re-fragmented into multiple subfragments, the first step involves integrating energy across fixed situations within intra-frames for each subcarrier. Subsequently, coherent integration is performed across the subfragments, followed by the application of a Radon transform (RT) to generate frames based on the properties derived from the coherent integration output. This paper provides detailed expressions and analyses for various performance metrics of our proposed method, including the communication bit error ratio (BER), responses of coherent and non-coherent outputs, and probability of detection. Simulation results demonstrate the effectiveness of our strategy. [ABSTRACT FROM AUTHOR]

This paper presents the algorithmic framework for a multimodal hearing aid (HA) prototype designed on a Field Programmable Gate Array (FPGA), specifically the RFSOC4*2 AMD FPGA, and evaluates the transmitter performance through simulation studies. The proposed architecture integrates audio and video inputs, processes them using advanced algorithms, and employs the 5G New Radio (NR) communication protocol for uploading the processed signal to the cloud. The core transmission utilizes Orthogonal Frequency Division Multiplexing (OFDM), an algorithm that effectively multiplexes the processed signals onto various orthogonal frequencies, enhancing bandwidth efficiency and reducing interference. The design is divided into different modules such as Sound reference signal (SRS), demodulation reference signal (DMRS), physical broadcast channel (PBCH), and physical uplink shared channel (PUSCH). The modulation algorithm has been optimized for FPGA parallel processing capabilities, making it better suited for the hearing aid requirements for low latency. The optimized algorithm achieves a transmission time of only 4.789 ms and uses fewer hardware resources, enhancing performance in a cost-effective and energy-efficient manner. [ABSTRACT FROM AUTHOR]

As the Internet of Things (IoT) continues to expand, wireless communication is increasingly widespread across diverse industries and remote devices. This includes domains such as Operational Technology in the Smart Grid. Notably, there is a surge in resource-constrained devices leveraging wireless communication, especially with the advances of 5G/6G technology. Nevertheless, the transmission of wireless communications demands substantial power and computational resources, presenting a significant challenge to these devices and their operations. In this work, we propose the use of deep learning to improve the Bit Error Rate (BER) performance of Orthogonal Frequency Division Multiplexing (OFDM) wireless receivers. By improving the BER performance of these receivers, devices can transmit with less power, thereby improving IoT devices' battery life. The architecture presented in this paper utilizes a depthwise Convolutional Neural Network (CNN) for channel estimation and demodulation, whereas a Graph Neural Network (GNN) is utilized for Low-Density Parity Check (LDPC) decoding, tested against a proposed (1998, 1512) LDPC code. Our results show higher performance than traditional receivers in both isolated tests for the CNN and GNN, and a combined end-to-end test with lower computational complexity than other proposed deep learning models. For BER improvement, our proposed approach showed a 1 dB improvement for eliminating BER in QPSK models. Additionally, it improved 16-QAM Rician BER by five decades, 16-QAM LOS model BER by four decades, 64-QAM Rician BER by 2.5 decades, and 64-QAM LOS model BER by three decades. [ABSTRACT FROM AUTHOR]

One of the essential aspects of life is communication and in all communication systems, modulation and demodulation perform a crucial role in the transmission of transmitter-to-receiver data. Using various multiplexing techniques such as FDMA, CDMA and TDMA to work with the communication system, faced various problems such as low bit rate, multi-path fading, ISI and time dispersion. The incorporation of the OFDM approach gives an attractive solution to the aforementioned issues. OFDM transmitters and OFDM receivers with different modulation techniques are included in the OFDM-based different communication system. CO-OFDM was recently suggested and its extreme robustness against polarisation mode dispersion and chromatic dispersion was demonstrated in proof-of-concept transmission experiments. Optical fiber-based wired networks and also free space wireless networks require a premier technique for multiplexing i.e. CO-OFDM. In this paper, we investigated the performance of various modulation techniques which highlights several benefits such as channel robustness and greater efficiency of the available spectrum where multicarrier is used as high data rate bit streams from a single source are divided into the number of small subcarriers. OFDM is commonly regarded as discrete multitone (DMT) in this case. So in this review article, OFDM systems are also incorporated with their advantages and applications. [ABSTRACT FROM AUTHOR]

This paper addresses the problem of side lobe interference in 5G networks by proposing a unique collaborative beamforming strategy based on Deep Q-Network (DQN) reinforcement learning. Our method, which operates in the sub-6 GHz band, maximizes beam steering and power management by using a two-antenna system with DQN-controlled phase shifters. We provide an OFDM cellular network environment where inter-cell interference is managed while many base stations serve randomly dispersed customers. In order to reduce interference strength and improve signal-to-interference-plus-noise ratio (SINR), the DQN agent learns to modify the interference angle. Our model integrates experience replay memory with a long short-term memory (LSTM) recurrent neural network for time series prediction to enhance learning stability. The outcomes of our simulations show that our suggested DQN approach works noticeably better than current DQN and Q-learning methods. In particular, our technique reaches a maximum of 29.18 dB and a minimum of 5.15 dB, whereas the other approaches only manage 0.77–27.04 dB. Additionally, we significantly decreased the average interference level to 5.42 dB compared to competing approaches of 38.84 dB and 34.12 dB. The average sum-rate capacity is also increased to 3.90 by the suggested strategy, outperforming previous approaches. These findings demonstrate how well our cooperative beamforming method reduces interference and improves overall network performance in 5G systems. [ABSTRACT FROM AUTHOR]

In the current context of global communications, HF (High Frequency) NVIS (Near Vertical Incidence Skywave) data networks can be of strategic importance, providing short- and medium-range communication capabilities independent of terrestrial configuration and existing conventional communications infrastructure. They are essential in critical conditions, such as natural disasters or conflicts, when terrestrial networks are unavailable. This paper investigates the development of such systems for HF NVIS data communications by introducing a customized Orthogonal Frequency Division Multiplexing (OFDM) protocol with parameters adapted to HF ionospheric propagation, implemented on Software-Defined Radio (SDR) systems, which provide extensive configurability and high adaptability to varying HF channel conditions. This work presents an innovative approach to the application of OFDM narrow-channel aggregation in the HF spectrum, a technique that significantly enhances system performance. The aggregation enables a more efficient utilization of the available spectrum and an increase in the data transmission rate, which represents a substantial advancement in NVIS communications. The implementation was realized using an SDR system, which allows flexible integration of the new OFDM protocol and dynamic adaptation of resources. The work also includes the development of a messaging application capable of using this enhanced HF communication system, taking advantage of the new features of channel aggregation and SDR flexibility. This application demonstrates the applicability of the protocol in real-world scenarios and provides a robust platform for data transmission under conditions of limited access to other means of communication. Thus, this study contributes to the technological advancement of NVIS communications and opens new research and deployment directions in HF communications. [ABSTRACT FROM AUTHOR]

Summary: Underwater acoustic channel is a challenging medium for communication due to the presence of significant multipath, high noise, frequency‐dependent propagation loss, and high and non‐uniform Doppler spread. Doppler shift is non‐negligible in underwater communication due to the low velocity of underwater signals. Synchronization and Doppler estimation are important requirements for achieving good performance in this channel. Synchronization algorithms that give good performance in radio communication do not work well in underwater communication. Hence, this area has received a lot of attention from researchers. This paper surveys important works in the area. The techniques proposed in the literature for frame synchronization, frequency and phase synchronization, and timing synchronization in single carrier communications are reviewed here. The synchronization techniques proposed for OFDM, MIMO OFDM, and spread spectrum communication are also surveyed. Doppler estimation methods proposed in the literature are also reviewed. It is found that most of the recent works in underwater acoustic communication focus on OFDM synchronization. Deep learning‐based methods proposed in the literature are also reviewed. Key open problems and areas that require future research attention in the field of synchronization and Doppler estimation in underwater communications are highlighted in this paper. The area needing most attention of underwater communication researchers was found to be MIMO OFDM due to the difficulty in synchronization in such systems while used in underwater communication. Reducing the computational complexity of the algorithms used is also important for future work. Schemes that work with Doppler due to relative velocity over 10 m/s also need to be developed. [ABSTRACT FROM AUTHOR]

As an important part of buoy-type ocean monitoring systems, the inductively coupled mooring chain solves the problem of data cotransmission through the multinode sensors that it carries, which is significant for the rapid acquisition of fish, hydrology, and other information. This paper is based on a seawater channel transmission model with a depth of 300 m and a bandwidth of 2 MHz. An orthogonal frequency division multiplexing (OFDM) technology is used to overcome the multipath effect of signal transmission on a seawater medium. The adaptive technology is integrated into the OFDM, and an improved joint subcarrier and bit power allocation algorithm is proposed. This algorithm solves the problem of dynamic subcarrier allocation during the cotransmission of underwater multinode user data in seawater channels. The results show that the algorithm complexity can be reduced by 0.18126×10−2 s during one complete OFDM system data transmission by the improved greedy algorithm, and a total of 216 bits are transmitted by the OFDM. The normalized channel capacity can be improved by 0.012 bit s−1 Hz−1. At the bit error ratio (BER) of 10−3, the BER performance can be improved by approximately 6 dB. When the numbers of users are 4 and 8, the improved algorithm increases the channel capacity, and the higher the number of users, the more evident the channel capacity improvement effect is. The results of this paper have an important reference value for enhancing the transmission performance of inductively coupled mooring chain underwater multinode data. [ABSTRACT FROM AUTHOR]

The Universal Filtered Multi-Carrier (UFMC) is a derivative of the Orthogonal Frequency Division Multiplexing (OFDM) scheme. It is considered as a candidate waveform for 5G. The considerably high computational complexity restricts the usage of UFMC based systems. This complexity is caused by the filtration process in the system. Since the flexible and efficient use of non-continuous unused spectrum for different network deployment strategies is important in the next generation communication, the selection of UFMC is inevitable because of its improved performance over OFDM and the Filter Bank Multi-Carrier (FBMC) systems. Hence, it is essential to reduce the complexity of a UFMC system. In this paper, we propose a Fast Convolution (FC) based UFMC system. The technique makes use of smaller FFTs and overlapped data frames. The proposed FC-UFMC system achieves a computation minimisation higher than 95% for systems having 64 or more fully utilised sub-channels compared to similar UFMC systems. The Peak to Average Power Ratio (PAPR) for the FC-UFMC system has a 2.27 dB improvement over the UFMC system. The BER performance of the FC-UFMC system in AWGN and ITU-R channels models are superior or similar to the corresponding UFMC system. The paper also presents the relationship of BER dependence on Signal to Noise Ratio (SNR) and Side Lobe Attenuation (SLA) of the sub-band filter. [ABSTRACT FROM AUTHOR]

Abstract - In this Paper We want to talk about the Current or Future Generations of Network and Successor of 4g networks - 5th Generation Network, 5g is a new era of technology comes with new technologies like OFDM(Orthogonal Frequency division Multiplexing), Radio Wave Technologies, BDMA(Beam Division Multiple Access) etc are some technologies of 5th Generation Networks, also about situation of 5g in India. In this paper We will discuss these points 1. What is 5g 2. Why we need 5g 3. What 5g delivers us 4. Technologies in 5g 5. Future of 5g in India and world 6. Satellite Technology 7. 5g open source architecture 8. 5g open core network and its functionality. [ABSTRACT FROM AUTHOR]

The Finite Radon Transform (FRAT) has been discussed and defined for 2-D images in many research papers. This paper explores the application of FRAT in assessing the Bit Error Rate (BER) performance of an OFDM-based WiMAX system, comparing it with the M-QAM mapper. MATLAB/Simulink simulations are conducted using the realistic time-variant Code Division Testbed (CODIT channel model). To obtain the desired number of data symbols, combinations of FRAT blocks with different sizes are employed. Low and high-sized matrices are suggested for WiMAX parameters to evaluate BER performance. Results indicate that the FRAT mapper with a smaller input matrix size exhibits improved performance and requires fewer mathematical operations than higher-order matrices. The BER performance of lower-order matrices is comparable to that of QPSK and 16QAM mapping techniques. For all scenarios, (AWGN, Fixed and Mobile communication) the BPSK and the QPSK mapping techniques show the best BER performance between all types of mapping used in this research. They need less than 12 dB to obtain 10-5 BER while transmitting using AWGN and Fixed communication in urban channels. In comparison of the same scenario for the FRAT technique, G1-G5 show better performance than those of G6-G10 where @ SNR of 36 dB, the BER for G1-G5 is about 3x10-4 and for G6-G10 about 2x10-3. [ABSTRACT FROM AUTHOR]

Due to high spectral efficiency and flexibility of orthogonal frequency division multiplexing (OFDM) technology, OFDM-based optical grids/clouds are fast replacing WDM grids/clouds. As grids and clouds process data intensive tasks, protection of optical grids and clouds from an arbitrary fiber-cut is extremely important. Employing a protection scheme leads to idle resource reservation, and data are continuously lost till protection (backup) paths become operational after a link failure. So, a protection scheme should not only minimize reservation of idle resources; it must also make the network recover quickly from a failure. In a dynamic scenario, another important issue is spectral fragmentation which leads to increased blocking of requests. In this paper, we address the problem of providing protection to OFDM-based transparent optical grids/clouds ensuring fast failure recovery with minimizing of both resource consumption and spectral fragmentation to the extent possible. To the best of our knowledge, this is the first paper to address the said problem for transparent OFDM optical grids/clouds. Performance comparisons show that the proposed polynomial time algorithm, fragmentation-aware resource-efficient protection with fast recovery (FRPFR) decreases spectrum utilization, decreases bandwidth blocking ratio and increases backup spectrum sharing by 27.88%, 35.37% and 35.94%, respectively, over algorithm protection with fast recovery (PFR) and by 11.95%, 20.29% and 14.35%, respectively, over algorithm resource-efficient protection with fast recovery (RPFR). [ABSTRACT FROM AUTHOR]

The peak-to-average power ratio (PAPR), commonly used to describe the amplitude variations of an OFDM (orthogonal frequency-division multiplex) signal, does not accurately reflect its impact on the system performance. This paper applies the mutual information as a metric to assess the effects of nonlinear PAPR reduction schemes on the performance of OFDM systems. Evaluation of the achieved mutual information shows that a significant capacity loss from clipping occurs only at high SNR (signal-to-noise ratio) and a simple compression/expansion technique is proposed to achieve close to optimal performance in this regime. The effectiveness of this method is validated through WER (word error rate) simulations with several modulation and coding schemes. [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]

The increasing volume of air traffic has placed significant stress on the current Air Traffic Management (ATM) systems, especially concerning the use of Very High Frequency (VHF) communication bands. As air traffic continues to grow, the limitations of the existing spectrum and infrastructure necessitate significant upgrades to ensure safety, efficiency, and capacity. The modernization of air traffic management systems has led to the development and introduction of the L-band Digital Aeronautical Communication System (LDACS), a new communication protocol. LDACS is designed to operate alongside existing L-band systems, ensuring compatibility with legacy users. The coexistence of LDACS with legacy systems poses significant interference challenges, as any disruption in data retrieval can critically impact flight safety. This paper proposes four potential interference mitigation techniques that LDACS can employ to detect and reduce the primary source of interference: Distance Measuring Equipment (DME). The authors introduce a prototype LDACS receiver that uses Rank-Ordered Absolute Differences (ROAD) statistics for effective interference sensing and employs GAE-enhanced pulse peak processors to mitigate Distance Measuring Equipment (DME) interference. Unlike the current GAE-enhanced pulse peak processors, the proposed methods use ROAD value-based detection for identifying DME interference. The performance of the proposed methods - ROAD GAE enhanced Pulse Peak Attenuator (RGPPA), ROAD GAE enhanced Pulse Peak Limiter (RGPPL), ROAD joint GAE enhanced Pulse Peak Attenuator (RJGPPA), and ROAD joint GAE enhanced Pulse Peak Limiter (RJGPPL) is analyzed across different threshold ROAD values to determine their efficacy in various signal conditions. Moreover, the performance of the proposed methods is compared to existing methods such as conventional pulse blanking and GAE-enhanced nonlinear devices, which use the amplitude of the received signal for the detection of interference. Furthermore, the proposed method’s performance is compared to another method, ROAD PB, which uses ROAD statistics to detect DME interference and pulse blanking for DME mitigation. The comparative results show that the proposed methods outperformed conventional pulse blanking and ROADPB. Besides, these methods outperformed existing GAE-enhanced methods for their optimum threshold ROAD value. [ABSTRACT FROM AUTHOR]

This paper presents Z-OFDM, a high-performance solution for underwater acoustic communication. Traditional underwater orthogonal frequency division multiplexing (OFDM) systems suffer from spectrum leakage and distortion due to the narrowband nature of underwater acoustic signals and the picket fence effect of the fast Fourier transform (FFT). Z-OFDM addresses these issues by integrating zoom-fast Fourier transform (ZoomFFT) with OFDM and redesigning the modulator and demodulator to replace the conventional FFT. This integration enhances spectral resolution, resulting in higher channel capacity, improved Signal to Interference plus Noise Ratio (SINR), and reduced Bit Error Rate (BER). Computer simulations using underwater acoustic channels from Fuxian Lake and Wuyuan Bay demonstrate that the Z-OFDM system achieves a 6 dB gain compared to conventional OFDM systems at a BER of 10 − 3 . These results demonstrate the effectiveness of Z-OFDM in overcoming the limitations of traditional FFT-based OFDM systems in underwater environments. [ABSTRACT FROM AUTHOR]

Summary: Intelligent fire safety systems place higher demands on the speed and reliability of data communication between sensors, controllers, and other devices. The two‐wire bus has become a significant trend in developing fire safety communication systems because of its low cost and simple maintenance. This paper proposes a two‐wire bus communication system for fire safety based on orthogonal frequency division multiplexing (OFDM) technology. First, we introduce the low‐voltage power line channel model and conduct relevant simulations, providing the conditions for subsequent simulation work. Then, we design the system's transmission and reception schemes, provide the parameters, and introduce each technology used. Finally, we conducted system simulations based on three different channel models, and the system performance is compared among different encoding, modulation, and channel estimation methods. The simulation results show that the system designed in this paper has superior performance compared with other systems and can meet the requirements of intelligent fire safety systems for communication speed and reliability. [ABSTRACT FROM AUTHOR]

Fifth-generation (5G) mobile networks offer flexibility to address various emerging use cases. Radio virtualization enhances flexibility by enabling multiple heterogeneous virtual radios to coexist on the same hardware. One method for virtualizing radio devices involves using virtual machines and containers to multiplex software radio implementations over generic multipurpose radio hardware. This paper reviews security issues in this context, evaluates the experimental bounds of communication for software-defined radio (SDR) devices, and assesses virtualization's impact on radio virtualization's performance. This study aims to determine the suitability of virtual environments for SDR applications. The results indicate that container-based radio virtualization performance is comparable to SDR applications running on native Linux. [ABSTRACT FROM AUTHOR]

A novel approach is here presented to superimpose a low-priority data stream on a high-priority data stream for OFDM systems. The main improvement with respect to conventional hierarchical modulation, which is included with the same purpose in various wireless technologies, is that the low-priority data stream can be decoded from the received subcarrier symbols without any previous equalization for multipath fading channels. As a consequence, the expected performance is nearly invariant of the channel estimation method used to equalize the channel. The low-priority stream is inserted adopting a gain-invariant dirty paper coding based on Rational Dither Modulation, which was proposed for data hiding applications. In this paper an analysis of the developed system is presented and several simulations have been carried out using DVB-T system parameters to verify the validity of the proposed approach. The experimental results show the better performance of the proposed method with respect to that of a conventional hierarchical modulation, particularly when the accuracy of the estimated channel response decreases. [ABSTRACT FROM PUBLISHER]

The universal filtered multicarrier (UFMC) modulation is among the most considered solutions for the realization of beyond orthogonal frequency division multiplexing (OFDM) air interfaces for future wireless networks. This paper focuses on the design and analysis of a UFMC transceiver equipped with multiple antennas and operating at millimeter-wave carrier frequencies. This paper provides the full mathematical model of an MIMO-UFMC transceiver, taking into account the presence of hybrid analog/digital beamformers at both ends of the communication links. Then, several detection structures are proposed, both for the case of single-packet isolated transmission and for the case of multiple-packet continuous transmission. In the latter situation, this paper also considers the case in which no guard time among adjacent packets is inserted, trading off an increased level of interference with higher values of spectral efficiency. At the analysis stage, several considered detection structures and transmission schemes are compared in terms of bit-error rate, root-mean-square error, and system throughput. The numerical results show that the proposed transceiver algorithms are effective and that the linear minimum mean-square error (MMSE) data detector is capable of well managing the increased interference brought by the removal of guard times among consecutive packets, thus yielding throughput gains of about 10%–13%. The effect of phase noise at the receiver is also numerically assessed, and it is shown that the recursive implementation of the linear MMSE exhibits some degree of robustness against this disturbance. [ABSTRACT FROM AUTHOR]

This paper proposes a modified Gradient algorithm and a modified Bi-SVD algorithm for the estimation of noise subspace and their utility in blind CFO estimation. The proposed modified Bi-SVD and modified Gradient algorithms have the dual advantageous features of not only the improved of noise subspace estimation but also the reduced computational complexities. The results obtained through the modified Gradient and modified Bi-SVD algorithms show excellent agreement with the results of the direct SVD technique requiring relatively more computational complexity. Another important contribution of this paper is the adoption of fullrank updated inverse autocorrelation matrix Rinv into the proposed noise subspace estimation algorithms. The improved noise estimation algorithms have been eventually used to aid the MUSIC algorithm to facilitate improved estimation of CFO required in OFDM systems. This paper substantiates the envisaged improved estimation accuracy of CFO through simulation results derived through proposed algorithms relative to conventional SVD. [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]

This paper derives the maximum achievable sum-rate and presents the optimal encoding/decoding framework for rate-diverse wireless network coding (RD-WNC) over broadband channels consisting of multiple parallel subchannels. RD-WNC applies to a communication scenario in which a base station wants to deliver two different messages with different rates to two users. The base station combines the two separate messages into one network-coded message and broadcasts the network-coded message to both users. Each user then extracts its desired message from the network-coded message by subtracting from it the other message, which we assume to be side information available to the user. Deriving the maximum achievable sum-rate for RD-WNC is challenging when the channel consists of multiple parallel subchannels with different channel coefficients (e.g., the subcarrier channels of OFDM systems), since apart from the rate allocation between the two users, optimal power allocation among multiple subchannels needs to be identified. The first contribution of this paper is a new “mountain-leveling” power allocation algorithm to achieve the maximum sum-rate. With the resulting power allocation, we can then achieve the corresponding optimal sum-rate by having a separate encoding/decoding mechanism for each subchannels, but doing so is cumbersome and complex when the number of subchannels is large. The second contribution of this paper is a practical encoding/decoding framework using only one encoder-decoder mechanism for all subchannels without sacrificing sum-rate optimality. We provide numerical results to corroborate our theoretical findings and to demonstrate the benefits of our encoding/decoding framework. [ABSTRACT FROM AUTHOR]

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At present, the Doppler frequency offset compensation is of interest, which affects orthogonal frequency division modulation (OFDM) transforms. There are methods of using filter weights adjustment to ensure that the received signal has the Doppler frequency suppressed through multiple iterations such as least mean squares (LMS) and recursive least squares (RLS). These approaches are quite time-consuming and do not use the advantages of receive characteristics of the antenna array to reduce bit error rate (BER). They also do not consider the effect of Doppler on the OFDM. Several other current methods of Doppler frequency compensation have been implemented where it is possible to predict the Doppler frequency offset first, that do not need LMS and RLS to find this parameter. This is because they know the receiver's direction and velocity. Some antenna techniques are involved, such as single antenna (SA), maximal ratio combining (MRC), or equal gain combining (EGC). However, the multiple-input multiple-output (MIMO) antenna is considered the best adequate Doppler compensation, done through the array beam weight vectors. The studies using MIMO often assume that the angles of arrivals (AoAs) are estimated ideal, but this is not practical. There has not been any research paper on AoAs estimation, based on which to provide an effective Doppler compensation solution. This paper proposes that a hierarchical codebook is considered a better method when giving suboptimal beam vectors after estimating AoAs of physical paths. This can lead to a significantly reduced BER compared to the case of SA, EGC, and closer to the ideal BER of the MRC when the AoAs are assumed accurately estimate [ABSTRACT FROM AUTHOR]

Recently, multiple-input–multiple-output (MIMO) orthogonal frequency-division multiplexing (OFDM) systems have gained significant attention in the field of wireless communications. The utilization of the Riemannian manifold has become prevalent in MIMO-OFDM systems. However, the existing data detection algorithms for MIMO-OFDM systems are mostly designed for block fading channels. Additionally, these algorithms often suffer from high computational complexity. In this paper, we propose a data detection algorithm on the basis of Riemannian manifold optimization for MIMO-OFDM systems under time-varying channels. The core concept of this algorithm is to optimize the transmitted signals by solving the manifold optimization problem in the case of time-varying channels. In order to reduce the computational complexity of the algorithm, we improve the proposed algorithm by dividing the transmitted signals into multiple subframes for solving the optimization problem separately and using the pilots to maintain the performance of the algorithm. In the simulation, the performance of multiple proposed algorithms and the forced-zero detection algorithm under different parameter settings are compared. The simulation results show that the proposed algorithm demonstrates good bit error rate and computational complexity performances. [ABSTRACT FROM AUTHOR]

In this paper, a 4 amplitude shift keying (4-ASK) fast orthogonal frequency division multiplexing (FOFDM) scheme was experimentally investigated over a turbulent air–water channel for optical wireless communications. The experiment results showed that the 4-ASK-FOFDM modulated signals were not sensitive to weak atmospheric turbulence, and the bit-error rate (BER) was lower than the 7% forward error correction (FEC) limit of 3.8 × 10−3. Under the condition of the same spectra efficiency, the 4-ASK-FOFDM scheme just had a tiny performance penalty compared to the 16-QAM-OFDM scheme. Consequently, the 4-ASK-FOFDM scheme is a promising alternative to the conventional 16-QAM-OFDM scheme in optical wireless communications. [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]

This paper presents the research and implementation of a China Digital Radio (CDR) experimental network in Hubei, China with two FM-CDR transmitting stations and four FM-band channels. To study the coverage discontinuity problem in a large service area, the experimental network employs an intelligent networking solution that incorporates multiple service channels carrying Broadcast and Data Services (BADS) and a Common-Regional-Information Channel (CRIC) carrying both service data and system information. The electronic service guide (ESG) carried by CRIC can inform the receivers about the available contents from current and adjacent stations, which can significantly improve the service quality in the overlapping areas, especially under mobile reception environment. Two RF tuners are used in the receiving terminals to access the CRIC, and the BADS channel, respectively. This paper first presents the frequency analysis and coverage tests of the experimental network, and then summarizes the coverage performances with different transmission parameter combinations. The goal is to gain experience in frequency planning, coverage prediction, as well as supportable services of CDR digital audio broadcasting. [ABSTRACT FROM AUTHOR]

The paper proposes a method of two-dimensional joint estimation of information symbols and channel frequency response in OFDM communication systems based on the Kalman filter. The technique consists of two stages. In the first stage, estimates are iteratively calculated in the forward and backward directions concerning the array of processed data in the frequency dimension and on each of the subcarriers in the time domain. In the second stage, the obtained results are combined. The correlation properties of the channel are assumed to be known. The statistical simulation analyzes the proposed method using a model example. The results of estimating the channel parameters by the proposed method are compared with those obtained by known methods. The computational complexity of the developed method is determined. [ABSTRACT FROM AUTHOR]

Spectrum sharing and aggregation among authorized secondary users (A-SUs) are important tasks in operating effective cognitive radio networks. Furthermore, in protecting spectrum sharing/aggregation against unauthorized secondary users (UA-SUs), secondary user access control (SUAC) is needed, which is investigated in this paper. A jamming signal is injected to degrade the spectrum sensing performance of UA-SUs, while reliable spectrum sensing performance for A-SUs can be achieved through an oblique projection-based jamming cancellation method. An orthogonal frequency division multiplexing-based transmission model is considered in this paper. The generalized likelihood ratio test algorithm is used for both authorized and unauthorized SUs in spectrum sensing. Numerical results show the effectiveness of the proposed SUAC in degrading the spectrum sensing performance of the unauthorized SUs. [ABSTRACT FROM PUBLISHER]

The two key features of millimeter wave-(mmWave) based MIMO communication are the use of large antenna arrays at the transceivers and large bandwidth. The former complicates the design of optimal beamformers, while the latter makes the system frequency-selective and, thus, requires equalization. Conventionally, for wideband mmWave channels, choosing the precoders/combiners have involved frequency-selective designs that are based on channel state information. In this paper, we show that under some assumptions, semi-unitary frequency-flat precoding and combining are sufficient for low-scattering millimeter wave channels. To show this, we evaluate the conditions and practical settings under which the dominant subspaces of the frequency-domain channel matrices are similar. We model the frequency-dependence of uniform linear antenna arrays, which leads to what is known as beam-squint, for two different practical setting to analyze the optimality of frequency-flat beamforming designs under practical hardware impairments. For the cases when the optimality conditions hold, we propose novel techniques based on compressive subspace estimation to design the optimal frequency-flat, semi-unitary precoders and combiners. Simulation results show that the system achieves near-digital spectral efficiencies at very small implementation cost of beamformers and channel training overhead. [ABSTRACT FROM AUTHOR]

The Underwater Acoustic (UWA) wireless communication system is considered one of the most challenging systems for data transmission. The Orthogonal Frequency Division Multiplexing (OFDM) system promises numerous benefits, including high spectrum efficiency and inter-Symbol interference mitigation. But, it is very sensitive to Carrier Frequency Offset (CFO). The implementation of the OFDM necessitates the use of orthogonal transforms such as the Inverse Discrete Fourier Transform (IDFT)/DFT. On the other hand, the Multiple-Input-Multiple Output (MIMO) configuration is affected by co-channel interference. In this paper, we look at another type of co-interference known as the co-CFO. The Linear Zero Forcing (LZF) equalizer suffers from noise enhancement and high computational complexity due to the direct matrix inversion. The Linear Minimum Mean Square Error Equalizer suffers from the noise enhancement problem at high values of the Signal-to-Noise Ratio (SNR), and requires the estimation of the operating SNR to work properly, besides the high computational complexity of the implementation. In this paper, we propose a Joint Low Complexity Regularized LZF equalizer for the UWA-OFDM communication system. The proposed equalizer is driven and takes the effect of the UWA co-channel effect, the noise, and the co-CFO. Simulation results show the important role of the proposed equalizer in configuring the UWA-OFDM communication system. [ABSTRACT FROM AUTHOR]

The computational complexity of resource allocation processes, in cognitive radio networks (CRNs), is a major issue to be managed. Furthermore, the complicated solution of the optimal algorithm for handling resource allocation in CRNs makes it unsuitable to adopt in real-world applications where both cognitive users, CRs, and primary users, PUs, exist in the identical geographical area. Hence, this work offers a primarily price-based power algorithm to reduce computational complexity in uplink scenarios while limiting interference to PUs to allowable threshold. Hence, this paper, compared to other frameworks proposed in the literature, proposes a two-step approach to reduce the complexity of the proposed mathematical model. In the first step, the subcarriers are assigned to the users of the CRN, while the cost function includes a pricing scheme to provide better power control algorithm with improved reliability proposed in the second stage. The main contribution of this paper is to lessen the complexity of the proposed algorithm and to offer flexibility in controlling the interference produced to the users of the primary networks, which has been achieved by including a pricing function in the proposed cost function. Finally, the performance of the proposed power and subcarrier algorithm is confirmed for orthogonal frequency-division multiplexing (OFDM). Simulation results prove that the performance of the proposed algorithm is better than other algorithms, albeit with a lesser complexity of O(NM) + O(Nlog(N)). [ABSTRACT FROM AUTHOR]

In wireless communication systems, reliability, low latency and power are essential in large scale multi-hop environment. Multi-hop based cooperative communication is an efficient way to achieve goals of wireless networks. This paper proposes a relay selection scheme for reliable transmission by selecting an optimal relay. The proposed scheme uses a signal-to-noise ratio (SNR) based Q-learning relay selection scheme to select an optimal relay in multi-hop transmission. Q-learning consists of an agent, environment, state, action and reward. When the learning is converged, the agent learns the optimal policy which is a rule of the actions that maximize the reward. In other words, the base station (BS) knows the optimal relay to select and transmit the signal. At this time, the cooperative communication scheme used in this paper is a decode-and-forward (DF) scheme in orthogonal frequency division multiplexing (OFDM) system. The Q-learning in the proposed scheme defines an environment to maximize a reward which is defined as SNR. After the learning process, the proposed scheme finds an optimal policy. Furthermore, this paper defines a reward which is based on the SNR. The simulation results show that the proposed scheme has the same bit error rate (BER) performance as the conventional relay selection scheme. However, this paper proposes an advantage of selecting fewer relays than conventional scheme when the target BER is satisfied. This can reduce the latency and the waste of resources. Therefore, the performance of the multi-hop transmission in wireless networks is enhanced. [ABSTRACT FROM AUTHOR]

In this paper, the scheme that combines LDM (Layered Division Multiplexing) with the FDM (Frequency Division Multiplexing) scheme based on BST-OFDM (Band Segmented Transmission - Orthogonal Frequency Division Multiplexing) is proposed for the next-generation DTTB (Digital Terrestrial Television Broadcasting). The proposed LDM-BST-OFDM scheme provides a more effective frequency utilization of the stream for fixed reception. The performance of the proposed scheme is evaluated by computer simulations where the effectiveness of proposed scheme for fixed reception is shown. Although LDM-BST-OFDM improves the performance, dedicated receivers that can demodulate symbols multiplexed by LDM are required. In this paper, LDM-BST-OFDM using punctured LDPC code is proposed, which can decode the stream for fixed reception even if symbols multiplexed by LDM are not demodulated. The reception characteristics of the proposed scheme are evaluated by computer simulations. [ABSTRACT FROM AUTHOR]

In this generation of high-speed internet many research organizations are still busy finding the best candidate for the upcoming next generation of cellular mobile communication. These days mobile communication is divided into two parts, one is calling service and second is internet connectivity. Though many waveforms have been suggested for the fifth generation of mobile communication but out of which getting a compared output results on the basis of channel estimation is required. Through this research paper, FBMC Aux, FBMC, and OFDM are compared in terms of BER and PAPR to find our best candidate for future 5th generation mobile and data communication. A comparison of the time index is also done to verify the merits and demerits of the FBMC and FBMC Aux in this paper. [ABSTRACT FROM AUTHOR]