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A novel spectrally efficient modified asymmetrically and symmetrically clipped optical (mASCO)-OFDM for intensity modulated direct detection (IM/DD) systems is presented. The conventional ASCO-OFDM systems use two frames to transmit the conventional asymmetrically clipped optical (ACO)-OFDM and symmetrically clipped optical (SCO)-OFDM system. The proposed mASCO-OFDM system replaces the two frame SCO-OFDM by a single frame modified SCO (mSCO)-OFDM. The mSCO-OFDM clips the data on only one side of the symmetry and performs an absolute function on the other side of the symmetry. This allows mASCO-OFDM to be 1.333 times more spectrally efficient than the conventional ASCO-OFDM. The mASCO-OFDM reduces its receiver’s complexity by estimating and eliminating the clipping noise distortion in time domain. Overall, this system has 43% lower complexity in comparison to ASCO-OFDM system. The mASCO-OFDM shows a better BER performance and a lower Peak Average Power Ratio (PAPR) than ASCO-OFDM. The proposed system also shows better BER performance than ACO-OFDM for the same spectral efficiency.

Visible light communication (VLC), which is seen as an alternative and complementary technology to radio frequency (RF) communication systems, has emerged as a promising new generation system. Because of its potential to combat inter-symbol interference (ISI), orthogonal frequency division multiplexing (OFDM) has been validated as the best candidate for high-speed optical wireless communications (OWC). Asymmetrically clipped optical OFDM (ACO-OFDM), DC-biased optical OFDM (DCO-OFDM), and Flip-OFDM, which are made suitable for intensity modulation/direct detection (IM/DD) systems, are unipolar OFDM schemes widely accepted for OWC in the literature. In this study, it is proposed to combine the lifting wavelet transform (LLWT), which uses the lazy wavelet, with these three optical OFDM waveforms to increase the performance of the ACO-OFDM, DCO-OFDM, and Flip-OFDM systems proposed for OWC systems. In the environment where M-level color shift keying (M-CSK) and M-level quadrature amplitude modulation (M-QAM) modulations are used, proposed waveforms are tested with computer simulations for bit error rate (BER) and peak average power ratio (PAPR) performance measures. From the obtained simulation results, it is observed that the proposed transform technique performs an approximately 6 dB SNR improvement on the waveforms investigated in this study in both modulation methods for the 1E-4 BER value.

Visible Light Communication (VLC) systems are favoured for numerous applications due to their extensive bandwidth and resilience to electromagnetic interference. This study delineates various constructions of Optical Orthogonal Frequency Division Multiplexing (O-OFDM) approaches employed in VLC systems. Various factors are elaborated within this context to ascertain a more effective O-OFDM approach, including constellation size, data arrangement and spectral efficiency, power efficiency, computational complexity, bit error rate (BER), and peak-to-average power ratio (PAPR). This paper seeks to assess these approaches’ BER and PAPR performance across varying modulation orders. Regrettably, in VLC systems based on OFDM methodology, the superposition of multiple subcarriers results in a high PAPR. Therefore, this study aims to diminish the PAPR in VLC systems, enhancing system performance. We propose a non-distorting PAPR reduction technique, namely the Vandermonde-Like Matrix (VLM) precoding technique. The suggested technique is implemented across various O-OFDM approaches, including DCO-OFDM, ADO-OFDM, ACO-OFDM, FLIP-OFDM, ASCO-OFDM, and LACO-OFDM. Notably, this method does not affect the system’s data rate because it does not require the mandatory transmission of side information. Furthermore, this technique can decrease the PAPR without impacting the system’s BER performance. This study compares the proposed PAPR reduction technique against established methods documented in the literature to evaluate their efficacy and validity rigorously.

This study presents a comprehensive analysis to highlight advantages and disadvantages, in terms of channel capacity and computational complexity (CC), of a so-called clustered-orthogonal frequency division multiplexing (OFDM) scheme for power line communication (PLC) technologies for access networks. By taking into account filtering, decimation and upsampling techniques, the implementations of two transmitter schemes, named 𝒫(·)-I and 𝒫(·)-II, and three receivers ones, named 𝒬(·)-I, 𝒬(·)-II and 𝒬(·)-III, that can be easily derived from the hermitian symmetric OFDM (HS-OFDM) scheme are discussed. Numerical results show that the clustered-OFDM schemes based on HS-OFDM provide the same bit-error-rate performance as that of HS-OFDM, double sideband-OFDM and single sideband-OFDM. Also, clustered-OFDM based on the combination of 𝒬(·)-II and 𝒬(·)-III offers the lowest CC for both baseband and passband data communications. Further, it is demonstrated that the clustered-OFDM schemes can trade off channel capacity for CC, which can give rise to low-priced transceivers for PLC technologies. Finally, a comparative analysis of clustered-OFDM and orthogonal frequency division multiple access (OFDMA) points out the scenarios in which clustered-OFDM can be competitive if the complexity of the OFDM transceiver is a primary consideration.

Optical-orthogonal frequency division multiplexing (O-OFDM) systems, including the direct current biased optical OFDM (DCO-OFDM) and the asymmetrically clipped optical OFDM (ACO-OFDM), are very important to achieve high data rate transmission in visible light communication (VLC). However, the DCO-OFDM and ACO-OFDM systems suffer from adjacent channel interference (ACI) caused by out of band (OOB) and a high peak to average power ratio (PAPR). In this work, a pulse-shaping signal based on a symbol-time compression (STC) scheme is presented. The proposed shaped STC-DCOOFDM and shaped STC-ACOOFDM systems are capable of reducing both the ACI and the PAPR as well. Further, the OOB, PAPR, and computing complexity are analytically investigated. The simulation results verify the analytical study of the proposed methods for OOB reduction and power savings resulting in PAPR reduction. The proposed systems are evaluated for different modulation schemes, including BPSK, QPSK and 8QAM.

One of the critical missions for next-generation wireless communication systems is to fulfill the high demand for massive Machine-Type Communications (mMTC). In mMTC systems, a sporadic transmission is performed between machine users and base station (BS). Lack of coordination between the users and BS in time destroys orthogonality between the subcarriers, and causes inter-carrier interference (ICI). Therefore, providing services to asynchronous massive machine users is a major challenge for Orthogonal Frequency Division Multiplexing (OFDM). In this study, OFDM with index modulation (OFDM-IM) is proposed as an eligible solution to alleviate ICI caused by asynchronous transmission in uncoordinated mMTC networks. In OFDM-IM, data transmission is performed not only by modulated subcarriers but also by the indices of active subcarriers. Unlike classical OFDM, fractional subcarrier activation leads to less ICI in OFDM-IM technology. A novel subcarrier mapping scheme (SMS) named as Inner Subcarrier Activation is proposed to further alleviate adjacent user interference in asynchronous OFDM-IM-based systems. ISA reduces inter-user interference since it gives more activation priority to inner subcarriers compared with the existing SMS-s. The superiority of the proposed SMS is shown through both theoretical analysis and computer-based simulations in comparison to existing mapping schemes for asynchronous systems.

The demand for high data rate, the generation of Internet of Things (IoT), and various Machine Type Communications (MTC) emerged for a new transmission phenomenon. In other words, it is substantial to communicate without synchronization, or synchronization overhead, with mixed signal types. such specifications cannot be covered by the Fourth Generation (4G) systems, which is based on Cyclic Prefix Orthogonal Frequency Division Multiplexing (CP-OFDM). However, to achieve the specifications of the next generation system, numerous waveform replacements for the CP–OFDM were suggested, Filter Bank Multi–Carrier (FBMC), Generalized Frequency Division Multiplexing (GFDM), Universal Filtered Multi–Carrier (UFMC), and Filtered OFDM (F–OFDM). The filter design occupies essential part in these replacements, thus, in this paper, novel filters are introduced where simulation results show that the proposed filters outperform previous designs in terms of spectral efficiency improved dramatically by releasing the synchronization overhead.

5G will have to cope with a high degree of heterogeneity in terms of services and requirements. Among these latter, the flexible and efficient use of non-contiguous unused spectrum for different network deployment scenarios is considered a key challenge for 5G systems. To maximize spectrum efficiency, the 5G air interface technology will also need to be flexible and capable of mapping various services to the best suitable combinations of frequency and radio resources. In this work, we propose a comparison of several 5G waveform candidates (OFDM, UFMC, FBMC and GFDM) under a common framework. We assess spectral efficiency, power spectral density, peak-to-average power ratio and robustness to asynchronous multi-user uplink transmission. Moreover, we evaluate and compare the complexity of the different waveforms. In addition to the complexity analysis, in this work, we also demonstrate the suitability of FBMC for specific 5G use cases via two experimental implementations. The benefits of these new waveforms for the foreseen 5G use cases are clearly highlighted on representative criteria and experiments.

Waveforms define the shape, structure, and frequency characteristics of signals, whereas modulation schemes determine how information symbols are mapped onto these waveforms for transmission. Their appropriate selection plays a critical role in determining the efficiency, robustness, and reliability of data transmission. In wireless communications, the choice of waveform influences key factors, such as network capacity, coverage, performance, power consumption, battery life, spectral efficiency (SE), bandwidth utilization, and the system’s resistance to noise and electromagnetic interference. This paper provides a comprehensive analysis of the waveforms and modulation schemes used across successive generations of mobile cellular networks, exploring their fundamental differences, structural characteristics, and trade-offs for various communication scenarios. It also situates this analysis within the historical evolution of mobile standards, highlighting how advances in modulation and waveform technologies have shaped the development and proliferation of cellular networks. It further examines criteria for waveform selection—such as SE, bit error rate (BER), throughput, and latency—and discusses methods for assessing waveform performance. Finally, this study presents a comparative evaluation of modulation schemes across multiple mobile generations, focusing on key performance metrics, with the BER analysis conducted through MATLAB simulations.

Optical Wireless Communication (OWC) is a new trend in communication systems to achieve large bandwidth, high bit rate, high security, fast deployment, and low cost. The basic idea of the OWC is to transmit data on unguided media with light. This system requires multi-carrier modulation such as Orthogonal Frequency Division Multiplexing (OFDM). This paper studies optical OFDM performance based on Intensity Modulation with Direct Detection (IM/DD) system. This system requires a non-negativity constraint. The paper presents a framework for wireless optical OFDM system that comprises (IM/DD) with different forms, Direct Current biased Optical OFDM (DCO-OFDM), Asymmetrically Clipped Optical OFDM (ACO-OFDM), Asymmetrically DC-biased Optical OFDM (ADO-OFDM), and Flip-OFDM. It also considers channel coding as a tool for error control, channel equalization for reducing deterioration due to channel effects, and investigation of the turbulence effects. The evaluation results of the proposed framework reveal enhancement of performance. The performance of the IM/DD-OFDM system is investigated over different channel models such as AWGN, log-normal turbulence channel model, and ceiling bounce channel model. The simulation results show that the BER performance of the IM/DD-OFDM communication system is enhanced while the fading strength is decreased. The results reveal also that Hamming codes, BCH codes, and convolutional codes achieve better BER performance. Also, two algorithms of channel estimation and equalization are considered and compared. These algorithms include the Least Squares (LS) and the Minimum Mean Square Error (MMSE). The simulation results show that the MMSE algorithm gives better BER performance than the LS algorithm.