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Background. For further development of communication networks, it is planned to use hybrid satellite networks for traffic transmission. However, satellite communication channels have features such as distortion caused by the Doppler effect and increased energy efficiency requirements. Aim of this study is to analyze variants of orthogonal frequency multiplexing methods and modulation methods in order to choose the most stable technology, taking into account destabilizing factors. Method. Comparing different signal processing technologies and studying their resistance to bit errors is the imitation modeling of the communication channel in the Matlab environment. This approach allows creating a model of the communication network, taking into account the main parameters of communication channels, such as the Doppler effect, energy deficiency and destabilizing factors. Results. The distribution of the bit error coefficient for various signal processing technologies, depending on the signal-to-noise ratio, is compared. The method of frequency multiplexing is defined, providing the minimum peak factor and the most resistant to bit error. It is also noted that the effectiveness of all the studied technologies depends on the spacing and modulation constellations, and that it is necessary to adjust the characteristics of the system for each case. Conclusion. The results of this study can be used to improve the quality of communication in difficult interference conditions of hybrid mobile networks of 5 and 6 generations using the satellite segment.

【Objective】Replenishing the power supply system of an underwater communication system is usually very expensive and impractical. The underwater Simultaneous Light-wave Information and Power Transmission (SLIPT) communication systems based on solar cells are powerful solutions. However, the communication bandwidth of the silicon solar cell receiver is very limited, and it is easy to have the phenomenon of deep fading of the Signal-to-Noise Ratio (SNR) due to the underwater light attenuation effect.【Methods】For these problems, this manuscript employs a negative-biased solar cell light receiver scheme that increases the-3 dB bandwidth of silicon solar cells from 420 kHz to 768 kHz. Aiming at the deep fading of SNR caused by various degradation effects in the water environment, a Discrete Fourier Transfor (DFT) extended Orthogonal Frequency Division Multiplexing (OFDM) modulation scheme with a low peak-average power ratio is adopted to offset the deep fading phenomenon in the system.【Results】The performance of DFT Spread OFDM (DFT-S-OFDM) and OFDM modulation systems in water environments with different turbidity (absorption and scattering characteristics) is compared. It is shown that the DFT-S-OFDM modulation and demodulation system is more robust.【Conclusion】Finally, experiments have shown that the total battery power efficiency of the energy harvesting system can be increased by 1.87 times under continuous illumination of white LEDs for 3 h, realizing synchronized energy harvesting in the communication process.

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.)

Non terrestrial network (NTN) has been regarded as an important component of beyond 5G communication. The 3rd Generation Partnership Project (3GPP) has officially started studies on NTN for the purpose of integrating satellites with New Radio (NR) terrestrial networks. However, the NR defined orthogonal frequency division multiplexing (OFDM) waveform is susceptible to doubly selective fading and nonlinear distortions in the NTN uplink, thus leading to severe performance loss. In this paper, a type of block scalable OFDM (BS-OFDM) waveform is proposed, which has modified subcarrier and sub-symbol segmentation when compared to the conventional NR defined OFDM. With our proposed framework, block scalable discrete Fourier transform spread OFDM (BS-DFT-s-OFDM) and block scalable orthogonal time frequency space (BS-OTFS) can also be implemented. To obtain a comprehensive understanding of different waveforms, performance metrics concerning peak to average power ratio (PAPR), total degradation (TD), bit error rate (BER), and complexity are presented. The simulation results demonstrate that the proposed block scalable waveforms can obtain better performance and lower complexity than existing NR waveforms in different NTN uplink scenarios, and can therefore be promising candidate waveforms for NR NTN.

The current $5^{th}$ Generation-New Radio (5G-NR) systems are designed to meet the demands of various applications, offering high data rates, low latency, and high reliability. In the current 5G-NR systems, the Discrete Fourier Transform-spread-Orthogonal Frequency Division Multiplexing (DFT-s-OFDM) waveform is the most commonly employed waveform to transmit user data in uplink transmissions, specifically in coverage-limited scenarios. To enable coherent data demodulation, pilot signals, commonly referred to as Demodulation Reference Signals (DMRS), are transmitted along with data-carrying DFT-s-OFDM symbols. However, in the current DFT-s-OFDM architecture, the DMRS and data are transmitted on distinct OFDM symbols. This time separation necessitates the demodulation process to commence only after receiving the initial DMRS symbol, resulting in significant processing delays. Furthermore, the existing architecture consumes more DMRS resources and necessitates complex time interpolation techniques to support users with high mobility. To address these challenges, we propose an improved DFT-s-OFDM architecture that enables instantaneous data demodulation, leading to a substantial reduction in processing delays. Furthermore, despite not utilizing any time interpolation techniques, the proposed method effectively caters to high-speed users, thereby conserving computational resources and hence contributing to minimizing the system complexity and latency. We thoroughly investigate the proposed architecture and evaluate its performance in different simulation settings. The results demonstrate that the proposed architecture significantly improves packet error performance, particularly in high Doppler scenarios, while using 16% lesser DMRS overhead. This reduction in DMRS overhead frees up additional resources for data transmission, ultimately enhancing data rates.

Power Amplifiers (PAs) play a vital role in mobile communication. However, their inherent nonlinearity can lead to issues such as unwanted radiation, interference with neighboring channels, and distortion within the desired frequency range. To address these problems, PAs are typically operated at a lower power level than their saturation point, sacrificing power efficiency to improve Error Vector Magnitude (EVM) performance. Consequently, more than 70-80% of the DC power is wasted as heat. This inefficiency necessitates the exploration of techniques to enhance PA efficiency while maintaining acceptable linearity and performance. Digital Pre-Distortion (DPD) is a useful technique to linearize PAs. DPD allows affordable nonlinear PAs to function with minimal distortion in their nonlinear operating regions. This results in amplified signals with increased power output and improved power efficiency. Using nonlinear functions, the output signal of the PA can be linearized, mitigate distortions, and be effectively optimized. When using various operating channels and varying time, temperature, and PA nonlinearity, the DPD must adjust. In order to increase the power efficiency of 5G systems, DPD-enabled systems are inculcating with adaptive DFT-s-OFDM employed 5G physical layer along with the Crest Factor Reduction (CFR) algorithm. [ABSTRACT FROM AUTHOR]

Integrated sensing and communications (ISAC) is emerging as a key technology of 6G. Owing to the low peak-to-average power ratio (PAPR) property, discrete Fourier transform spread orthogonal frequency-division multiplexing (DFT-s-OFDM) is helpful to improve the sensing range and suitable for high-frequency transmission. However, compared to orthogonal frequency-division multiplexing (OFDM), the sensing accuracy of DFT-s-OFDM is relatively poor. In this paper, frequency-domain spectral shaping (FDSS) is adopted to enhance the performances of DFT-s-OFDM including sensing accuracy and PAPR by adjusting the correlation of signals. Specifically, we first establish a signal model for the ISAC system, followed by the description of performance indicators. Then, we analyze the influence of amplitude fluctuation of frequency domain signals on sensing performance, which shows the design idea of FDSS-enhanced DFT-s-OFDM. Further, a FDSS-enhanced DFT-s-OFDM framework is introduced for ISAC, where two types of FDSS filters including a pre-equalization filter and an isotropic orthogonal transform algorithm (IOTA) filter are designed. The simulation results show that the proposed scheme can obtain about 4 dB performance gain in terms of sensing accuracy over DFT-s-OFDM. In addition, FDSS-enhanced DFT-s-OFDM can significantly reduce PAPR and improve the power amplifier efficiency. [ABSTRACT FROM AUTHOR]

Charging batteries in underwater scenarios is generally very expensive and impractical, and solar cell (SC)-based underwater simultaneous lightwave information and power transfer (SLIPT) systems are a powerful solution. However, silicon SC receiver devices have limited bandwidth and are prone to deep signal-to-noise (SNR) degradation during underwater light fading effects. For these problems, this manuscript proposes a negative-biased SC optical receiver scheme to increase the $-3$ dB bandwidth of silicon SC from 440 kHz to 780 kHz. For the deep fading of SNR caused by various degradation effects in the water environment, a low peak average power ratio (PAPR) discrete Fourier transform spread orthogonal frequency division multiplexing (DFT-S-OFDM) modulation scheme is employed to counteract the deep fading phenomenon in the system. Achieved a communication rate of 15.2 Mbps in a 60 cm underwater environment with a fading factor of 0.403 and a bit error rate (BER) of $1.59\times 10^{-3}$ under perturbation. Also, the performance of DFT-S-OFDM and orthogonal frequency division multiplexing (OFDM) modulation systems in water environments with different turbidity (absorption characteristics and scattering) and presence of disturbances are compared separately, and the DFT-S-OFDM system is more robust. Finally, we complete the energy harvesting during the communication process, and the experiments show that the total battery power efficiency of the energy harvesting system can be increased by 1.87 times under the white light-emitting diode (LED) continuous irradiation for three hours.

In this paper, a novel waveform with low peak-to-average power ratio (PAPR) and high robustness against phase noise (PN) is presented. It follows the discrete Fourier transform spread orthogonal frequency division multiplexing (DFT-s-OFDM) signal model. This scheme, called 3MSK, is inspired by continuous-phase frequency shift keying (CPFSK), but it uses three frequencies in the baseband model – specifically, 0 and $\pm f_{symbol}/4$ , where $f_{symbol}$ is the symbol rate – which effectively constrains the phase transitions between consecutive symbols to 0 and $\pm \pi /2$ rad. Motivated by the phase controlled model of modulation, different degrees of phase continuity can be achieved, allowing to reduce the out-of-band (OOB) emissions of the transmitted signal, while supporting receiver processing with low complexity. Furthermore, the signal characteristics are improved by generating an initial time-domain constant envelope signal at higher than the symbol rate. This helps to reach smooth phase transitions between 3MSK symbols, while the information is encoded in the phase transitions. Also the possibility of using excess bandwidth is investigated by transmitting additional non-zero frequency bins outside the active frequency bins of the basic DFT-s-OFDM model, which provides the capability to greatly reduce the PAPR. The most critical tradeoffs of the oversampled schemes are that improved PAPR is achieved with the cost of somewhat reduced link performance and, in case of excess band, also the spectrum efficiency is reduced. Due to the fact that the information is encoded in the phase transitions, a receiver model that tracks the phase variations without needing reference signals is developed. To this end, it is shown that this new modulation is well-suited for non-coherent receivers, even under strong phase noise (PN) conditions, thus allowing to reduce the overhead of reference signals. Evaluations of this physical-layer modulation and waveform scheme are performed in terms of transmitter metrics such as PAPR, OOB emissions and achievable output power after the power amplifier (PA), using a practical PA model. Finally, coded radio link evaluations are also provided, demonstrating that 3MSK has a similar bit error rate (BER) performance as that of traditional quadrature phase-shift keying (QPSK), but with significantly lower PAPR, higher achievable output power, and the possibility of using non-coherent receivers.

The prospects of utilizing single-carrier (SC) and multi-carrier (MC) waveforms in future terahertz (THz)-band communication systems remain unresolved. On the one hand, the limited multi-path components at high frequencies result in frequency-flat channels that favor low-complexity wideband SC systems. On the other hand, frequency-dependent molecular absorption and transceiver characteristics and the existence of multi-path components in indoor sub-THz systems can still result in frequency-selective channels, favoring off-the-shelf MC schemes such as orthogonal frequency-division multiplexing (OFDM). Variations of SC/MC designs result in different THz spectrum utilization, but spectral efficiency is not the primary concern with substantial available bandwidths; baseband complexity, power efficiency, and hardware impairment constraints are predominant. This paper presents a comprehensive study of SC/MC waveforms for THz communications, utilizing an accurate wideband THz channel model and highlighting the various performance and complexity trade-offs of the candidate schemes. Simulations demonstrate that discrete-Fourier-transform spread orthogonal time-frequency space (DFT-s-OTFS) achieves a lower peakto- average power ratio (PAPR) than OFDM and OTFS and enhances immunity to THz impairments and Doppler spreads, but at an increased complexity cost. Moreover, DFT-s-OFDM is a promising candidate that increases robustness to THz impairments and phase noise (PHN) at a low PAPR and overall complexity.

High frequency wireless communication aims to provide ultra high-speed transmissions for various application scenarios. The waveform design for high frequency communication is challenging due to the requirements for high spectrum efficiency, as well as good hardware compatibility. With high flexibility and low peak-to-average power ratio (PAPR), discrete Fourier transformation spreading-based orthogonal frequency division multiplexing (DFT-s-OFDM) can be a promising candidate waveform. To further enhance the spectral efficiency, we integrate faster-than-Nyquist (FTN) signaling in DFT-s-OFDM, and find that the PAPR performance can also be improved. While FTN can introduce increased inter-symbol interference (ISI), in this paper, we deploy an isotropic orthogonal transform algorithm (IOTA) filter for FTN-enhanced DFT-s-OFDM, where the compact time-frequency structure of the IOTA filter can significantly reduce the ISI. Simulation results show that the proposed waveform is capable of achieving good performance in PAPR, bit error rate (BER) and throughput, simultaneously, with 3.5 dB gain in PAPR and 50% gain in throughput. [ABSTRACT FROM AUTHOR]

The fifth-generation (5G) and beyond standards are being challenged by the diverse requirements of modern use cases. Multicarrier modulation techniques are one of the key components of the physical layer (PHY) design, which has immense potential to improve efficiency and reliability. In current state-of-the-art wireless technologies (i.e., NR and IEEE 802.11ax) orthogonal frequency division multiplexing (OFDM) is used which has many disadvantages such as peak-to-average power ratio (PAPR), out-of-band emission (OOBE), and sensitivity to carrier frequency offset (CFO). To overcome these drawbacks several alternate multicarrier modulation techniques are being considered, such as discrete Fourier transform-spread-OFDM (DFT-s-OFDM), generalized frequency division multiplexing (GFDM), and orthogonal time-frequency space (OTFS). In this paper, we develop the physical layer abstraction (PLA) of these candidate multicarrier techniques to evaluate their performance under various use cases and scenarios. The PLA is a commonly used technique to avoid time-consuming PHY simulations in system-level simulators. To improve the accuracy of PLA in different fading conditions, we derive a fitting parameter as a function of the received signal-to-interference-plus-noise ratio (SINR) variance. The validation results show that performance can be accurately estimated through the proposed multicarrier PLA. Moreover, PLA techniques are at least thousands of times faster compared to PHY simulations. [ABSTRACT FROM AUTHOR]

This paper describes and investigates a novel concept of frequency-domain spectral shaping (FDSS) with spectral extension for the uplink (UL) coverage enhancement in 5G New Radio (NR), building on discrete Fourier transform spread orthogonal frequency-domain multiplexing (DFT-s-OFDM). The considered FDSS concept is shown to have large potential for reducing the peak-to-average-power ratio (PAPR) of the signal, which directly impacts the feasible maximum transmit power under practical nonlinear power amplifiers (PAs) while still meeting the radio frequency (RF) emission requirements imposed by the regulations. To this end, the FDSS scheme with spectral extension is formulated, defining filter windows that fit to the 5G NR spectral flatness requirements. The PAPR reduction capabilities and the corresponding maximum achievable transmit powers are evaluated for a variety of bandwidth allocations in the supported 5G NR frequency ranges 1 and 2 (FR1 and FR2) and compared to those of the currently supported waveforms in 5G NR, particularly $\pi /2$ -BPSK with FDSS without spectral extension and QPSK without FDSS. Furthermore, an efficient receiver structure capable of reducing the noise enhancement in the equalization phase is proposed. Finally, by evaluating the link-level performance, together with the transmit power gain, the overall coverage enhancement gains of the method are analyzed and provided. The obtained results show that the spectrally-extended FDSS method is a very efficient solution to improve the 5G NR UL coverage clearly outperforming the state-of-the-art, while being also simple in terms of computational complexity such that the method is implementation feasible in practical 5G NR terminals.

Integrated sensing and communications (ISAC) is emerging as a key technology of 6G. Owing to the low peak-to-average power ratio (PAPR) property, discrete Fourier transform spread orthogonal frequency-division multiplexing (DFT-s-OFDM) is helpful to improve the sensing range and suitable for high-frequency transmission. However, compared to orthogonal frequency-division multiplexing (OFDM), the sensing accuracy of DFT-s-OFDM is relatively poor. In this paper, frequency-domain spectral shaping (FDSS) is adopted to enhance the performances of DFT-s-OFDM including sensing accuracy and PAPR by adjusting the correlation of signals. Specifically, we first establish a signal model for the ISAC system, followed by the description of performance indicators. Then, we analyze the influence of amplitude fluctuation of frequency domain signals on sensing performance, which shows the design idea of FDSS-enhanced DFT-s-OFDM. Further, a FDSS-enhanced DFT-s-OFDM framework is introduced for ISAC, where two types of FDSS filters including a pre-equalization filter and an isotropic orthogonal transform algorithm (IOTA) filter are designed. The simulation results show that the proposed scheme can obtain about 4 dB performance gain in terms of sensing accuracy over DFT-s-OFDM. In addition, FDSS-enhanced DFT-s-OFDM can significantly reduce PAPR and improve the power amplifier efficiency.

Copyright of Telecommunication Engineering is the property of Telecommunication Engineering 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.)

We propose a multicarrier chirp waveform, which can be generated by a circular convolution between data modulation symbols and a transmit filter, and show that it can equivalently be represented as discrete Fourier transform spread orthogonal frequency division multiplexing (DFT-s-OFDM) with frequency domain chirp filter. The chirp is defined by a complex exponential function where the phase follows a second-degree polynomial and its coefficients can be chosen to maximize the performance on a fading channel and to generate sets of orthogonal signals. The results show that the waveform outperforms OFDM and DFT-s-OFDM in terms of bit error rate (BER) and block error rate (BLER) on a time-frequency selective channel. [ABSTRACT FROM AUTHOR]

High frequency wireless communication aims to provide ultra high-speed transmissions for various application scenarios. The waveform design for high frequency communication is challenging due to the requirements for high spectrum efficiency, as well as good hardware compatibility. With high flexibility and low peak-to-average power ratio (PAPR), discrete Fourier transformation spreading-based orthogonal frequency division multiplexing (DFT-s-OFDM) can be a promising candidate waveform. To further enhance the spectral efficiency, we integrate faster-than-Nyquist (FTN) signaling in DFT-s-OFDM, and find that the PAPR performance can also be improved. While FTN can introduce increased inter-symbol interference (ISI), in this paper, we deploy an isotropic orthogonal transform algorithm (IOTA) filter for FTN-enhanced DFT-s-OFDM, where the compact time-frequency structure of the IOTA filter can significantly reduce the ISI. Simulation results show that the proposed waveform is capable of achieving good performance in PAPR, bit error rate (BER) and throughput, simultaneously, with 3.5 dB gain in PAPR and 50% gain in throughput.

In this study, we propose a framework for chirp-based communications by exploiting discrete Fourier transform-spread orthogonal frequency division multiplexing (DFT-s-OFDM). We show that a well-designed frequency-domain spectral shaping (FDSS) filter for DFT-s-OFDM can convert its single-carrier nature to a linear combination of chirps circularly translated in the time domain. Also, by exploiting the properties of the Fourier series and Bessel function of the first kind, we analytically obtain the FDSS filter for an arbitrary chirp. We theoretically show that the chirps with low ripples in the frequency domain result in a lower bit-error ratio (BER) via less noise enhancement. We also address the noise enhancement by exploiting the repetitions in the frequency. The proposed framework offers a new way to efficiently synthesize chirps that can be used in Internet-of-Things (IoT), dual-function radar and communication (DFRC) or wireless sensing applications with existing DFT-s-OFDM transceivers. [ABSTRACT FROM AUTHOR]

This paper deals with generalized discrete Fourier transform-spread-orthogonal frequency division multiplexing (G-DFT-s-OFDM) waveforms, which replace the cyclic prefix of traditional OFDM/DFT-s-OFDM with an internal guard period. Such waveforms feature significant benefits in terms of flexibility, spectral containment, and low peak-to-average power ratio. Aspects related to reference sequence design and mapping for channel estimation are thoroughly addressed, and a new estimator for the specific zero-tail DFT-s-OFDM case is proposed. Furthermore, we address the opportunity of exploiting the internal guard period at each symbol for frequent channel state information updates, thus enabling the possibility of tracking rapidly varying propagation conditions.

A new circularly pulse-shaped (CPS) precoding orthogonal frequency division multiplexing (OFDM) waveform, or CPS-OFDM for short, is proposed in this paper. CPS-OFDM, characterized by user-specific precoder flexibility, possesses the advantages of both low out-of-subband emission (OSBE) and low peak-to-average power ratio, which are two major desired physical layer signal properties for various scenarios in 5G New Radio, including fragmented spectrum access, new types of user equipments, and communications at high carrier frequencies. As opposed to most of the existing waveform candidates using windowing or filtering techniques, CPS-OFDM prevents block extension that causes extra interblock interference and envelope fluctuation unfriendly to signal reception and power amplifier efficiency, respectively. An optimization problem of the prototype shaping vector built in the CPS precoder is formulated to minimize the variance of instantaneous power with controllable OSBE power and noise enhancement penalty. In order to solve the optimization problem involving a quartic objective function, the majorization- minimization algorithmic framework is exploited. By proving the convexity of the proposed problem, the globally optimal solution invariant of incoming data is guaranteed to be attained via numbers of iterations. Simulation results demonstrate the advantages of the proposed scheme in terms of detection reliability and spectral efficiency for practical 5G cases such as asynchronous transmissions and mixed numerologies.

Enhanced time-domain spreading is proposed for block-interleaved frequency division multiple access (B-IFDMA) with discrete Fourier transform spread orthogonal frequency division multiplexing (DFT-s-OFDM). By repeating each consecutive modulation symbol prior to the spreading, we show that the DFT of the spreading sequence becomes a window function, which compared to the existing method of repeating the whole block of modulation symbols, offers a signal with both lower cubic metric (CM) and block error rate (BLER). Modulation symbol-specific spreading sequences are further shown to improve the BLER. The new transmission scheme is supported by both time- and frequency domain despreaders, as well as by two channel estimation methods for B-IFDMA. [ABSTRACT FROM AUTHOR]

In 5G New Radio, The DFT-s-OFDM is a promising multiplexing technique for enhancing the average power of subcarriers to reduce the overall peak-to-average power ratio (PAPR). The peak of subcarrier is too high then the impact of DFT-s-OFDM is quite inferior. An Adaptive DFT-s-OFDM employed multilayered novel mechanism has been proposed in this research article to reduce the PAPR. The extent of sub-band is varied in accordance with predefined threshold value to enhance average power, meanwhile clipping is applied to shape the peak value of subcarrier. The clipping technique reduced the subcarrier's peak power. The proposed approach has the greater impact in order to enhance the efficiency of non-linear Power Amplifier (PA). The PAPR is suppressed by the multilayered strategy in two ways. The first is the numerator element, which is the reduction of peak power by clipping operation, and the second is the denominator element, which is the improvement of average power through K-point DFT sub-band. The superior time–frequency localization of DFT-s-OFDM across uplink transmissions reduces the requirement for difficult node-to-node synchronization, which is potentially used by the mMTC nodes. The proposed adaptive DFT-s-OFDM modulation scheme performs better than conventional OFDM modulation, which is approximately 24% more effective at 6 dB. [ABSTRACT FROM AUTHOR]

We propose a novel modulation scheme which combines the advantages of filter bank multi-carrier (FBMC)-offset quadrature amplitude modulation and single-carrier frequency-division multiple access (SC-FDMA). On the top of a conventional FBMC system, we develop a novel precoding method based on a pruned discrete Fourier transform (DFT) in combination with one-tap scaling. The proposed technique has the same peak-to-average power ratio as SC-FDMA but does not require a cyclic prefix and has much lower out-of-band emissions. Furthermore, our method restores complex orthogonality, and the ramp-up and ramp-down period of FBMC is dramatically decreased, allowing low latency transmissions. Compared to pure SC-FDMA, the computational complexity of our scheme is only two times higher. Simulations over doubly selective channels validate our claims, further supported by a downloadable MATLAB code. Note that pruned DFT-spread FBMC can equivalently be interpreted as a modified SC-FDMA transmission scheme. In particular, the requirements on the prototype filter are less strict than in conventional FBMC systems. [ABSTRACT FROM AUTHOR]

This letter presents the design of a Gbit/s real-time light-fidelity transceiver based on field programmable gate array (FPGA). We exploit discrete Fourier transform spread orthogonal frequency division multiplexing as a modem scheme, while wavelength division multiplexing technology is employed to enhance the data rate by commercial red-green-blue light emitting diodes. The transceiver achieves a peak rate of 1.34 Gbit/s over 3.5 m of free space below the forward error correction limit of $3.8 \times 10^{-3}$. This letter also considers the requirement of mapping the proposed FPGA design into very large-scale integration. [ABSTRACT FROM AUTHOR]

This paper proposes an improved discrete Fourier transform spread single sideband(DFT-s-SSB) orthogonal frequency division multiplexing(OFDM) system that solves the problems of conventional DFT-s-SSB OFDM systems. Conventional DFT-s-SSB systems use pulse amplitude modulation(PAM) for applying SSB modulation. The higher the modulation level, the worse is the BER performance. Further, transmission is possible only through the lower sideband(LSB) spectrum. When transmitting using the LSB and upper sideband(USB) spectra simultaneously, interference occurs and spectrum recovery is not performed correctly. To solve this problem, the proposed system applies the 2/3 convolution coding to improve the bit error rate(BER) performance, adjusts the DFT size, and selects the USB spectrum to utilize the remaining spectrum resources. In addition, when using this system in an environment that supports multiuser or limited bandwidth, it uses only half of the spectrum; therefore, it can utilize the remaining spectrum resources and improve the spectral efficiency. [ABSTRACT FROM AUTHOR]

UFMC(Universal-Filtered Multi-carrier) and FBMC(Filter Bank Multi-carrier) system are receiving attention as candidate waveforms for 5G mobile communication system. But, these systems have high PAPR(Peak to Average Power Ratio) problem because these systems use a number of subcarrier. In this paper, we propose DFT(Discrete Fourier Transform) spreading based DFT-s(spreading)- UFMC system and DFT-s-FBMC system in order to overcome the PAPR drawback. In order to evaluate PAPR performance of the proposed systems, we design and simulate OFDM(Orthogonal Frequency Division Multiplexing), UFMC, FBMC, DFT-s-OFDM, DFT-s-UFMC, DFT-s-FBMC system. As simulation results, each PAPR performance of DFT-s-OFDM system, DFT-s-UFMC system, and DFT-s-FBMC system rise by 2.7 dB, 2.8 dB, and 1.1 dB respectively by DFT spreading technique. [ABSTRACT FROM AUTHOR]

Discrete Fourier transform spread orthogonal frequency division multiplexing (DFT-S-OFDM) based single carrier-frequency division multiple access (SC-FDMA) is accepted as the uplink transmission scheme by the 3GPP-long term evolution standardization organization. In this paper, the effects of carrier frequency offset (CFO) on DFT-S-OFDM system are analyzed for both single user and multiple user accessing scenarios. According to the analysis, the CFO results in the attenuation, linear phase rotation, inter-symbol interference (ISI) and inter-sub-carrier interference (ICI) on the demodulated symbols of each desired user, and the multi-user interference (MUI) among uplink users. The theoretical values of ISI, ICI, and signal to interference ratio (SIR) are presented for the DFT-S-OFDM system with full and partial bandwidth detection respectively. A phase compensation method is proposed to reduce the effect of linear phase rotation on the demodulated symbols. Finally, the analytical values are verified by the simulation results. [ABSTRACT FROM AUTHOR]