Terms Of Peak-to-average Power Ratio Research Articles

A Comprehensive Analysis of PAPR Reduction in Scrambled UFMC and OFDM Using Artificial Bee Colony Algorithm for 5G Communications

ABSTRACT With the advent of 5G communications, the demand for high data rates and improved spectral efficiency has necessitated the exploration of advanced modulation techniques. Orthogonal Frequency Division Multiplexing (OFDM) and Universal Filtered Multi-Carrier (UFMC) are two prominent modulation schemes for 5G systems. However, both OFDM and UFMC suffer from a high Peak-to-Average Power Ratio (PAPR), leading to signal distortion and inefficient power amplification. The Partial Transmit Sequence (PTS) approach is a promising strategy to minimize PAPR in OFDM and is applied to UFMC to minimize PAPR in UFMC and is known as scrambled UFMC (S-UFMC). PTS, however, involves an extensive search to identify the best phase factors that increase computational complexity. The artificial bee colony algorithm is proposed to reduce the computational complexity S-UFMC and OFDM. A novel modulation scheme, amplitude phase shift keying (APSK), is used instead of quadrature phase shift keying (QPSK) and quadrature amplitude modulation (QAM) in S-UFMC and OFDM, which has better performance than conventional modulation schemes. In this research, OFDM, PTS OFDM, UFMC and S-UFMC are compared and it is found that the proposed scrambled UFMC with APSK modulation using ABC algorithm performs better than OFDM and UFMC in terms of PAPR, spectral efficiency and computational complexity.

LADMM-Based PAPR-Aware Precoding for Massive MIMO-OFDM Downlink Systems

We tackle the peak to average power ratio (PAPR) reduction of an orthogonal frequency division multiplexing (OFDM)-based massive multi-user (MU) multiple-input multiple-output (MIMO) downlink systems in this paper. Utilizing the redundant degree of freedom (DOF) provided by a large number of antennas equipped at the base station, we first formulate OFDM modulation, MU precoding, and PAPR reduction into a non-convex optimization problem. By using the linearized alternating direction method of multipliers (LADMM), we directly address the non-convex PAPR-aware precoding problem without any relaxation in terms of PAPR and multi-user interference (MUI), which is completely different from the existing convex optimization methods based on relaxations. At the same time, the paper is also the first work to directly solve the non-convex PAPR-aware precoding optimization. The experimental results demonstrate that the LADMM method gets the comparable PAPR reduction and symbol error rate (SER), faster convergence, and lower complexity than the existing relaxed methods.

Nonlinear companding transforms for reducing the PAPR of OTFS signal

In this paper, two non-linear companding transforms, namely exponential and sine hyperbolic, are proposed to reduce the peak to average power ratio (PAPR) of the orthogonal time frequency space (OTFS) modulation signal. The companding transforms are normalized such that the average power remains the same before and after companding. The resulting transforms have a saturation kind of characteristics for larger amplitudes of a signal while enhancing the smaller amplitudes slightly, which leads to a reduction of PAPR significantly. To validate the companding transforms in the OTFS system, we analyze the results in terms of PAPR, transform gain, attenuation factor, and bit error rate (BER). Also, compared the PAPR and BER performance of OTFS with OFDM, and the existing μ-law and clipping methods in OTFS. The results signify that the proposed companding transforms outperform the existing μ-law and clipping methods for PAPR reduction.

Precoded IM-OFDM-SS for Underwater Acoustic Communication

The nature of the multipath channel and the peak-to-average power ratio (PAPR) are regarded as the main challenges restricting the design of a multicarrier reliable underwater acoustic (UWA) communication. This paper proposes a new scheme, precoded index modulation orthogonal frequency division modulation spread spectrum (IM-OFDM-SS), for UWA communication. The precoded IM-OFDM-SS is proposed to increase the transmission efficiency and exploit the spreading and multipath diversities and, at the same time, reduce the PAPR to achieve a reliable communication system. Two different precoders, discrete Hartley transform (DHT) and discrete cosine transform (DCT), are utilized in the proposed scheme and compared with the conventional IM-OFDM-SS scheme. Simulation and real experimental results demonstrate the outperformance of the proposed precoded IM-OFDM-SS in comparison to the conventional benchmarks in terms of PAPR and bit error rate (BER) performance.

CE-OFDM-CDMA Phase Modulation for 5G System

In the present work, we propose a novel modulation scheme for 5G wireless communication system. Our contribution is to combine PM-OFDM (Phase Modulation Orthogonal Frequency Division Multiplexing) and CDMA (Code Division Multiple Access) to exploit their distinctive advantages. On the one hand, PM-OFDM is an effective technique to combat multipath fading effects. On the other hand, CDMA can serve multiple users who are using the same resources of time/frequency. The aim is to make a combination of PM-OFDM and CDMA techniques. In this paper, the OFDM-CDMA scheme and its PAPR (Peak-to-Average Power Ratio) statistics are reviewed. In this paper, the proposed scheme PM-OFDM-CDMA is described and its performances in terms of PAPR, power spectral density, and BER (Bit Error Rate) are analyzed. Moreover, MMSE (Minimum Mean Square Error) equalizer is used to avoid multipath and noise effects simultaneously. The simulation through AWGN (Additive white Gaussian noise) and Rayleigh channels is performed using MATLAB. From the simulation results, we observed that PM-OFDM-CDMA is an efficient technique in terms of energy consumption (PAPR = 0dB). Besides, CE-OFDM-CDMA offers high spectral efficiency with low BER due to its low PAPR. In CE-OFDM-CDMA method, the shape of the spectrum varies according to the value of the modulation index h. The band occupied by the spectrum increases with the value of h. Therefore, CE-OFDM-CDMA could be considered as a suitable technique for 5G applications.

Multi-carrier Visible Light Communication System Using Enhanced Sub-carrier Index Modulation and Discrete Wavelet Transform

This work is aimed at providing a novel design of the Visible Light Communication (VLC) system that uses the Multi-Carrier Code-Division Multiple Access (MC-CDMA) technique to send and receive data through intensity-modulated/direct detected (IM/DD) VLC channel. The state-of-the-art framework of Enhanced Sub-Carrier Index Modulation (ESIM) is utilized to reduce the inherent peak-to-average power ratio (PAPR) in Orthogonal Frequency Division Multiplexing. Additionally, the use of cyclic prefix is omitted through the Discrete Wavelet Transform in the current system. Hence, the performance of the system is optimized in terms of PAPR, Bit Error Rate (BER), and data rate. The work presents the closed-form BER expressions for both conventional and proposed techniques in line-of-sight VLC channel. Correspondingly, the simulation programs are also executed to compared the proposed ESIM based WT-MC-CDMA system with both existing systems followed by an analysis of the results. Simulation results show the superior performance of the proposed system compared to existing systems.

A Novel Distributive Population-Based Differential Evolution Algorithm for SLM Scheme to Reduce PAPR in Massive MIMO-OFDM Systems

To achieve the ever rising demand for high data rates with high spectral efficiency, the energy efficient massive Multiple Input Multiple Output (MIMO) Orthogonal Frequency Division Multiplexing (OFDM) will be essential and useful for future wireless communication systems as well as Industrial network applications to reduce the operational costs significantly. But the high Peak to Average Power Ratio (PAPR) in a massive MIMO-OFDM system is identified as a critical issue that causes the non-linear signal distortion and restricts the efficiency of the power amplifier. Among different PAPR reduction schemes, Selected Mapping (SLM) is a distortionless technique and highly attractive due to its simple implementation capability. However, the conventional SLM scheme is inefficient for the massive MIMO-OFDM antenna system for its enormous Side Information (SI) burden and large computational complexity to search the best set of phase factors. In this paper, a Distributive Population based Switching Differential Evolution strategy is incorporated in the SLM scheme which eventually enhances the searching ability. The algorithm is employed in different antenna grouping (homogeneous and heterogeneous) based massive MIMO systems. The antenna grouping concept in the massive MIMO system minimizes the SI burden. The proposed algorithm for SLM techniques outperforms the existing techniques in terms of PAPR, Bit Error Rate, SI burden, energy efficiency and computational complexity.

Low-Complexity PAPR Reduction Method for OFDM Systems Based on Real-Valued Neural Networks

High peak-to-average power ratio (PAPR) in orthogonal frequency division multiplexing (OFDM) systems is one of the major drawbacks in wireless transmitters. In this letter, a novel low complexity PAPR reduction method based on the real-valued neural network (NN) is proposed. This method first builds the PAPR reduction module using the real-valued NN to achieve the reduction of PAPR. To reconstruct the transmission signal, the PAPR decompression module is introduced into the receiving end to recover the signal in order to minimize the bit error rate (BER) of the systems. The PAPR reduction module and the PAPR decompression module can be jointly trained offline, therefore, the reduction of PAPR and the minimization of BER can be achieved simultaneously. To reduce the process rate of the PAPR reduction, the trained model uses multiple parallel processing links to achieve the reduction of the PAPR. The extensive simulations indicate that the proposed method outperforms previously available methods in terms of PAPR and BER, while having low complexity.

Palm Date Leaf Clipping: A New Method to Reduce PAPR in OFDM Systems

Orthogonal frequency division multiplexing (OFDM) is the key technology used in high-speed communication systems. One of the major drawbacks of OFDM systems is the high peak-to-average power ratio (PAPR) of the transmitted signal. The transmitted signal with a high PAPR requires a very large linear range of the Power Amplifier (PA) on the transmitter side. In this paper, we propose and study a new clipping method named Palm Clipping (Palm date leaf) based on hyperbolic cosine. To evaluate and analyze its performance in terms of the PAPR and Bit Error Rate (BER), we performed some computer simulations by varying the Clipping Ratio (CR) and modulation schemes. The obtained results show that it is possible to achieve a gain of between 7 and 9 dB in terms of PAPR reduction depending on the type of modulation. In addition, comparison with several techniques in terms of PAPR and BER shows that our method is a strong alternative that can be adopted as a PAPR reduction technique for OFDM-based communication systems.

Iterative Dichotomy PAPR Reduction Method for Multicarrier Waveforms

OFDM: one of the well-known multicarrier modulations (MCM), has been recently chosen, by the standardization bodies, to be the Down-link waveform for the 5G systems. OFDM, like all other MCM techniques, suffers from high Peak to Average Power Ratio (PAPR). Indeed, the time domain signal has a very great dynamic. This high PAPR is problematic, when non linear power amplifiers (PA) are used at high energy efficient level. In order to relax this problem, we propose in this letter a new method called Iterative Dichotomy PAPR reduction (IDP). The main idea of this proposed algorithm is to decompose the original signal into $M$ signals with lower PAPR using (IDP) algorithm and amplify them by amplifiers with much lower saturation power. When $M = 2$ The theoretical analysis and the simulations results, presented in this letter, show a gain of $2.2~{dB}$ in terms of PAPR.

Numerical Investigation of Long-Haul Coherent Optical Generalized Frequency Division Multiplexing Signal

Generalized frequency division multiplexing (GFDM) is a recent physical layer scheme proposed for next-generation cellular systems. Like orthogonal frequency division multiplexing (OFDM), it is based on multicarrier modulation, but the filter shape is no longer rectangular (roll off ≠ 0) and the orthogonality between subcarriers is lost. With higher flexibility, low peak to average power ratio (PAPR) and reduced out-of-band emissions compared with OFDM, GFDM modulation is an attractive candidate for 5G application scenarios. This paper explores the performance of 10 Gb/s GFDM system over the optical link in terms of PAPR, quality factor ( Q factor), and mean squared error using a third-order adaptive Volterra filter with 3 and 5 taps. The impact of linear impairments (chromatic dispersion, polarization mode dispersion), laser line width, and Mach–Zehnder non-linearity have been addressed. The results of our simulations indicate that the transmitted 10 Gb/s GFDM signal through an optical fiber can reach 930 Km and Q = 11.9 dB after 700 Km at –8 dBm of launch power using 5 taps third-order adaptive Volterra equalizer with an improvement of approximately 210 Km and 1.25 dB compared with the same equalizer with 3 taps.

Partial transmit sequence to improve OFDM using BFO & PSO algorithm

The Peak to Average Power Ratio (PAPR) in Orthogonal Frequency Division Multiplexing (OFDM) system can be decreased effectively through Partial Transmit Sequence (PTS) scheme. In optimum phase factors searches of the PTM scheme, there is a very high computational cost involved and this restricts its ability to be applied in practical applications, more so in the case of high speed data transmissions. A combination of Particle Swarm Optimization (PSO), Bacterial Foraging Optimization (BFO) and Genetic Algorithm (GA) with the PTS scheme in the OFDM system has been proposed in this work which is a PAPR reduction technique with lesser computational complexity. By performing a set of simulations with different PTS schemes, the performance of the PSO–PTS, BFO–PTS and GA–PTS scheme is comparatively investigated in terms of PAPR and computational cost reductions.

Frequency-domain subcarrier diversity receiver for discrete Hartley transform OFDM systems

In recent years, there has been an increasing interest in the use of the discrete Hartley transform (DHT) for orthogonal frequency-division multiplexing (OFDM). Previous studies have not reported an improvement in bit error rate (BER) when using a DHT-based OFDM without substantial complexity increase due to the fact that the DHT cannot diagonalize a circulant channel matrix but rather produces a unique structured matrix that has only a main diagonal and anti-diagonal. In this paper, the coupling between symmetric carriers is exploited by introducing a frequency-domain subcarrier diversity receiver for DHT-based OFDM systems. The proposed simple receiver structure takes advantage of the coupling to enhance the BER performance of the DHT-OFDM system by increasing the diversity gain between subcarriers. A detailed statistical and performance analysis of the system is presented, in which closed-form expressions of the average BER were derived. The proposed system performance was compared to the conventional discrete Fourier transform OFDM (DFT-OFDM), the generalized DHT-OFDM, and the DHT-precoded OFDM systems in terms of average BER and peak-to-average power ratio (PAPR). The proposed DHT-OFDM system outperforms the generalized DHT-OFDM system by 12 dB and outperforms the conventional DFT-OFDM and the DHT-precoded OFDM systems by 17 dB at an average BER of 10−5. In terms of PAPR, the proposed DHT-OFDM system suffers from an approximately 5.5, 2, and 1 dB increase in PAPR when compared to the DHT-precoded OFDM, the conventional DFT-OFDM, and the generalized DHT-OFDM systems, respectively.

Root-Based Nonlinear Companding Technique for Reducing PAPR of Precoded OFDM Signals

Orthogonal frequency division multiplexing (OFDM) signals are characteristically independent and identically distributed Gaussian random variables that follow Rayleigh distribution. The signals also exhibit high peak-to-average power ratio (PAPR) problem due to the infinitesimal amplitude component distributed above the mean of the Rayleigh distribution plot. Since the amplitudes are nonlinearly and non-monotonically increasing, applying roots to the amplitude distribution is shown in this paper to change the probability density function (PDF) and thus reduces the PAPR. We exemplify these by imposing this constraint on standard $\mu $ -law companding (MC) technique in reducing PAPR of OFDM signals, which is known to expand the amplitudes of low power signals only without impacting the higher amplitude signals. This limits the PAPR reduction performance of the MC scheme. Since companding involves simultaneously compressing/expanding high/low amplitude OFDM signals, respectively, in this paper, we refer to the new method as a root-based MC (RMC) scheme that simultaneously expands and compresses OFDM signal amplitudes unlike MC. In addition, we express a second transform independent of the MC model. The results of the two proposed schemes outperform four other widely used companding techniques [MC, log-based modified (LMC), hyperbolic arc-sine companding (HASC) and exponential companding (EC)]. Besides these, we precode the OFDM signals using discrete Hartley transform (DHT) in order to further reduce the PAPR limits achieved by RMC by distorting the phase. While preserving the BER, DHT-precoded RMC outperforms all the four other companding schemes (MC, EC, HASC, LMC) in terms of PAPR.

Walsh Hadamard transform based transceiver design for SC-FDMA with discrete wavelet transform

This article proposes a new transceiver design for Single carrier frequency division multiple access (SCFDMA) system based on discrete wavelet transform (DWT). SCFDMA offers almost same structure as Orthogonal frequency division multiple access (OFDMA) with extra advantage of low Peak to Average Power Ratio (PAPR). Moreover, this article also suggests the application of Walsh Hadamard transform (WHT) for linear precoding (LP) to improve the PAPR performance of the system. Supremacy of the proposed transceiver over conventional Fast Fourier transform (FFT) based SCFDMA is shown through simulated results in terms of PAPR, spectral efficiency (SE) and bit error rate (BER).

Transforming the Statistical Distribution of Wireless OFDM Signal for PAPR Reduction

To reduce the high peak-to-average power ratio (PAPR) of orthogonal frequency division multiplexing (OFDM) signal, a novel nonlinear companding transform (CT) scheme is proposed in this paper. This scheme can reallocate both the amplitude/power as well as statistical distribution of the companded signal more reasonably and flexibly than existing CT methods with low computational complexity. By choosing an appropriate companding parameter, it can provide more effective PAPR reduction but at the price of a minimal amount of bit-error-rate (BER) performance degradation caused by the companding distortion. The closed-form expressions including the achievable PAPR gain, signal attenuation factor, and corresponding selection criteria for the companding parameter were derived. Computer simulations demonstrate that the scheme significantly improves the overall performances of OFDM system in terms of PAPR, BER and bandwidth efficiency under the multipath fading channel or with the high power amplifier.

PAPR analysis of wavelet based multitaper GFDM system

To guarantee a reliable, accurate communication with reduced latency and increased throughput, one of the 5G candidates Generalized Frequency Division Multiplexing (GFDM) has emerged out. Due to the non-orthogonal nature of GFDM inherent Inter Symbol Interference (ISI), Inter Carrier Interference (ICI) and high Peak to Average Power Ratio (PAPR) may occur. In order to combat such effects prolate windows are incorporated as a prototype filter to design an improved orthogonal system which provides a robust multitaper GFDM (MGFDM) carrier technique for next generation wireless networks, which outperforms conventional GFDM in terms of PAPR. In this paper, we propose a novel wavelet based MGFDM (WM-GFDM) to further reduce the PAPR by considering various wavelet transforms such as Haar, Daubechies, symlets, coiflets, Biorthogonal, Reverse Biorthogonal and Discrete Meyer Wavelets. Here, the conventional Fourier Transforms as used in traditional systems was replaced with Wavelet Transforms. The results show that PAPR performance with wavelet implementation outperformed both conventional GFDM and MGFDM by several dB. In addition, symbol error rate (SER) of WM-GFDM in comparison with conventional GFDM, MGFDM and Orthogonal FDM (OFDM) is analyzed along with spectral comparison where the results suggest that WM-GFDM follows the steps of GFDM and MGFDM.

Carrier Interferometry Coded Single Carrier FDMA (CI/SC-FDMA) for Next Generation Underwater Acoustic Communication

Underwater acoustic (UWA) communication suffers from large propagation delays, limited bandwidth, frequency dependent attenuation and severe multipath fading. Low power consumption, acceptable bit error rate and minimal complexity are three critical factors for UWA sensor network design. Orthogonal frequency division multiple access (OFDMA) is an attractive option because of its robustness against frequency selective underwater channel. But, OFDMA suffers from high peak-to-average power ratio (PAPR) and high sensitivity to frequency offsets. Single carrier FDMA (SC-FDMA) has not been well investigated over UWA channel in literature. Two variants of SC-FDMA namely interleaved FDMA (IFDMA) and localized FDMA (LFDMA) are considered here. Firstly, through simulation it has been observed that IFDMA performs significantly better than OFDMA, in terms of SER and PAPR. However, IFDMA outperforms LFDMA in terms of PAPR, but SER performance of IFDMA is poor as compared to that of LFDMA. In case of power limited uplink UWA communication, IFDMA serves as a feasible solution. But for downlink, where lower SER is an important performance parameter, LFDMA is an efficient multiple access scheme. The use of carrier interferometry (CI) codes with SC-FDMA further enhances the SER and PAPR performance over highly frequency selective UWA transmission. We have also evaluated the effect of multi-user diversity for CI/SC-FDMA over 5-tap frequency selective UWA channel by applying scheduling algorithm. The algorithm selects the sensor mote with best channel condition for transmission.

Linear Precoding Techniques for OFDM-Based NOMA over Frequency-Selective Fading Channels

ABSTRACT Non-orthogonal multiple access (NOMA) is one of the potential candidates for future radio access to address the increasing demands of mobile traffic. NOMA-based systems employ orthogonal frequency division multiplexing (OFDM) for multicarrier modulation which induces peak-to-average power ratio (PAPR). High PAPR makes conventional NOMA systems spectrally and energy inefficient. Thus, in this paper, precoded NOMA system is proposed to overcome the PAPR problem in downlink NOMA. Different unitary transforms such as Walsh Hadamard transform (WHT), Zadoff chu transform (ZCT), and discrete Hartley transform are applied as linear precoding techniques to overcome the PAPR problem in NOMA. Moreover, a new precoding technique -transform is also proposed which is a hybrid combination of WHT and ZCT. Link-level performance of power domain NOMA is analysed in terms of PAPR, spectral efficiency, bit error rate, and computational complexity. Simulation results show that in the presence of linear precoding techniques, performance of classic NOMA systems improve at the cost of slight increment in complexity.

Low Computational Complexity PTS Scheme for PAPR Reduction of MIMO-OFDM Systems

In the last decade a combination of multiple-input multiple-output (MIMO) with orthogonal frequency division multiplexing (OFDM) has lead to significant advancement in wireless communication systems. It has been receiving a great deal of attention as a solution of high-quality service for next generation. However, one of the main disadvantages of OFDM is, its high Peak-to-Average Power Ratio (PAPR) which leads to more interference and limits power efficiency of High Power Amplifier (HPA). As one of popular and promising scheme, partial transmit sequences (PTS) provides an effective solution for PAPR reduction of OFDM signals, but its exhaustive search of phase factors causes high computational complexity. This paper aims to present a novel method based on PTS, in order to improve the performance in terms of PAPR. In the proposed method, a low computational complexity phase weighting process is employed, where we use one phase {1, or -1, or j, or –j} to optimize the bloc with the maximum PAPR. The simulation results show that the proposed algorithm can not only reduces the PAPR significantly, but also decreases the computational complexity.