Peak-to-average Power Ratio Reduction Method Research Articles

A PAPR Reduction Method With EVM Constraints for OFDM Systems

In orthogonal frequency division multiplexing (OFDM) systems, high peak to average power ratio (PAPR) is one of its core issues. The OFDM signal with high PAPR passes high-power amplifier (HPA) will result in severely nonlinear distortions, which not only decreases HPA power efficiency, but also increases the whole system's bit error rate (BER). In order to attain the OFDM signal with lower PAPR and better BER, we consider PAPR optimization with error vector magnitude (EVM) constrains in this paper. Different from the second order conic programming (SOCP) scheme with high complexity proposed in the literature, we present an innovative approach based on linearized alterative direction method of multipliers (LADMM) to deal with the PAPR optimization. The proposed LADMM algorithm is a simple and efficient method with FFT/IFFT complexity in every iteration. We also prove LADMM algorithm's convergence and then perform simulations. Simulation results demonstrate that LADMM algorithm not only acquires larger PAPR reduction, but also obtains better BER.

Performance Analysis of Hybrid Peak to Average Power Ratio Reduction Techniques in 5G UFMC Systems

The universal filtered multi-carrier (UFMC) technique has been proposed as a prominent waveform candidate for fifth generation (5G) communication techniques. However, UFMC systems exhibit a high peak-to-average power ratio (PAPR), which causes serious degradation in the performance of the system. Therefore, this paper puts forward an effective hybrid PAPR reduction method to reduce the high PAPR of the UFMC system. The proposed hybrid scheme consists of a combination of precoding and non-linear companding techniques (NLCTs). A comparative analysis of the performance of different precoding methods, NLCTs, and hybrid methods are investigated in terms of the cumulative distribution function of the PAPR and the bit error rate (BER). The simulation results show that the proposed hybrid UFMC system has better PAPR reduction performance compared to conventional NLC and precoded UFMC systems. Moreover, the BER analysis of the UFMC system verifies that the proposed hybrid technique shows better BER performance compared to conventional companding techniques.

An Enhanced Iterative Clipping and Filtering Method Using Time-Domain Kernel Matrix for PAPR Reduction in OFDM Systems

Iterative clipping and filtering (ICF) is a straight-forward method for reducing the peak-to-average power ratio (PAPR) of signals in orthogonal frequency-division multiplexing (OFDM) system. Recently, convex optimization has been used to find the optimal filter coefficients that minimize the error vector magnitude (EVM) and meet the PAPR constraint. However, high-computation complexity may be incurred when solving the convex optimization problem. Therefore, we develop an efficient PAPR reduction method that uses the time-domain kernel matrix to generate the PAPR-reduction signal. Besides, we relax the assumption that the clipping noise is a series of uncorrelated parabolic pulses and apply the proposed method to more general cases. Based on the instantaneous observation of clipping noise, the proposed method constructs a simple time-domain kernel matrix and employs the curve fitting approach to optimize the corresponding scaling factors. The simulation results show that the proposed method can achieve very close performance to that using convex optimization in terms of both the PAPR reduction and EVM while the computational cost is reduced greatly. In addition, due to the decrease of iteration numbers and computational complexity, the proposed method is more efficient than some existing clipping and filtering methods.

A Hybrid PAPR Reduction Method Based on SLM and Multi-Data Block PTS for FBMC/OQAM Systems

The filter bank multicarrier employing offset quadrature amplitude modulation (FBMC/OQAM) is a candidate transmission scheme for 5G wireless communication systems. However, it has a high peak-to-average power ratio (PAPR). Due to the nature of overlapped signal structure of FBMC/OQAM, conventional PAPR reduction schemes cannot work effectively. A hybrid PAPR reduction scheme based on selective mapping (SLM) and multi data block partial transmit sequence (M-PTS) methods is proposed for FBMC/OQAM signals in this paper. Different from the simple SLM-PTS method, the proposed hybrid algorithm takes into account the overlapping effect of multiple adjacent data blocks on its PTS process. From simulation results, it can be obtained that the proposed method can offer a significant PAPR reduction performance improvement compared with the SLM, PTS and SLM-PTS methods. The proposed method can effectively reduce the PAPR in FBMC/OQAM systems.

Low-Complexity Blind Selected Mapping Scheme for Peak-to-Average Power Ratio Reduction in Orthogonal Frequency-Division Multiplexing Systems

Orthogonal frequency-division multiplexing (OFDM) is an attractive multicarrier technique for the simplicity of equalization and high data throughput. However, the transmitted OFDM signal has a very high peak-to-average power ratio (PAPR), which severely degrades the performance of practical OFDM systems and reduces the efficiency of high-power amplifiers (HPA). The selected mapping (SLM) scheme is an effective PAPR reduction method of OFDM signals. However, this approach usually requires side information (SI) transmission, which increases the difficulty of the hardware implementation with high complexity and reduces the data transmission rate. In this paper, based on designing phase rotation vectors in the time domain, a novel blind SLM method with low complexity is proposed to reduce the PAPR of OFDM signals. At the transmitter, the proposed method properly designs the phase rotation vectors in the time domain, which can be considered as an equivalent wireless channel without SI transmission. At the receiver, the effect of phase rotation vectors can be removed by the conventional channel estimation method, and the data demodulation processing can be easily performed by the frequency domain equalization. Simulation results show that the proposed scheme can achieve low complexity in PAPR reduction and has great robustness in bit error rate (BER) performance compared to the other low-complexity SLM PAPR schemes.

Low complexity reconfigurable complex filters for PAPR reduction of OFDM signals: analysis, design and FPGA implementation

In this study, the authors analyse the reconfigurable filtering techniques based on the tone reservation (TR) set and data bearing subcarriers in the time domain and frequency domain to reduce the peak-to-average power ratio (PAPR) of orthogonal frequency division multiplexing (OFDM) signals. The hardware architecture of these filters is proposed and mapped onto Xilinx Artix-7 field programmable gate array (FPGA) with 16-bit fixed-point representation to achieve a trade-off between numerical accuracy and hardware resource utilisation. The simulation results of the proposed methods and experimental results on FPGA for 16-quadrature amplitude modulation (QAM) and 64-QAM modulation are presented. These results show that the PAPR of OFDM signals is significantly reduced (about 7 dB) after 2–4 iterations. Performance comparison of the proposed methods with some typical methods of PAPR reduction, such as clipping-and-filtering and TR techniques, is presented.

GreenOFDM: a new selected mapping method for OFDM PAPR reduction

A new selected mapping orthogonal frequency division multiplexing modulation (SLM-OFDM) that generates symbol candidates using U inverse fast Fourier transform is presented. The complementary cumulative distribution function of peak-to-average power ratio (PAPR) of the so-called GreenOFDM is derived and computer simulations show that the proposed method outperforms any other SLM-OFDM proposed method so far. Also, GreenOFDM is compared with localised single carrier frequency division multiple access as it is a well-known PAPR reduction technique standardised for long-term evolution advanced.

Generalised precoding method for PAPR reduction with low complexity in OFDM systems

High peak-to-average power ratio (PAPR) is one of the major drawbacks of orthogonal frequency-division multiplexing (OFDM) systems. The precoding method is famous for providing a flexible way to reduce PAPR efficiently via adjustable precoding matrix (PM) but it also leads to high computational complexity. This study proposes a generalised precoding method that uses a generalised PM to provide a flexible scheme to generate precoded data with low PAPR and complexity. As compared to the OFDM system, the proposed generalised precoding OFDM systems achieve close bit-error ratio (BER) performance with lower PAPR reduction. Moreover, the BER performance of generalised precoding-based OFDM system is superior to that of OFDM system at low signal-to-noise ratio. The well known single-carrier frequency-division multiple access is a special case of discrete Fourier transform (DFT)-based generalised precoding method; therefore, the proposed method is promising in OFDM systems for achieving low PAPR and complexity with better BER performance.

PAPR Reduction for Hybrid ACO-OFDM Aided IM/DD Optical Wireless Vehicular Communications

Hybrid asymmetrically clipped optical orthogonal frequency division multiplexing (HACO-OFDM) improves the spectral efficiency compared to asymmetrically clipped optical OFDM (ACO-OFDM) and pulse-amplitude-modulated discrete multitone (PAM-DMT) modulation, while retaining the advantage of high power efficiency. HACO-OFDM has found favor in numerous applications, but its peak-to-average-power ratio (PAPR) has remained a concern in optical wireless communications, since the family of existing PAPR reduction methods cannot be directly invoked for the superimposed HACO-OFDM signals. Hence, we analyze the characteristics of HACO-OFDM signals and develop a specific PAPR reduction technique relying on tone injection. Our numerical results show that the proposed method achieves significantly improved PAPR statistics compared to the conventional methods, leading to a significant bit error ratio (BER) reduction.

Efficient PAPR Reduction in DCT-SCFDMA System Based on Absolute Exponential Companding Technique with Pulse Shaping

Discrete Cosine Transform based Single carrier frequency division multiple access (DCT-SCFDMA) is a prominent technique for providing high data rates in multimedia services. It also provides high Quality of Service to the users by mitigating the fading of signals. But High peak-to-average power ratio (PAPR) is a technical challenge which reduces the efficiency of RF power amplifiers. In this article, a novel joint scheme of PAPR reduction method is proposed and analyzed based on pulse shaping and absolute exponential companding (AEXP) technique. Our method proposes the use of standard raised cosine filter and square root raised cosine filter along with the AEXP companding process separately in DCT-SCFDMA system for different subcarrier mapping techniques e.g. interleaved frequency division multiple access and localized frequency division multiple access. Through extensive simulations, the numerical analysis presents that proposed architecture achieves significant improvements over the existing standard pulse shaping methods when used alone in DCT-SCFDMA system as far as the lowest PAPR is concerned.

Peak-to-Average Power Ratio Reduction in OFDM Index Modulation Through Convex Programming

Orthogonal frequency division multiplexing (OFDM) index modulation (IM) is a new multi-carrier modulation where the sub-carriers have two states, active and idle, and the indices of the active sub-carriers carry information. Although showing many advantages over OFDM, OFDM-IM also inherits the high peak-to-average power ratio (PAPR) problem. In this letter, utilizing the signal feature of OFDM-IM, a high-efficient PAPR reduction method is proposed. Concretely, a small dither in the idle sub-carrier is introduced to reduce the PAPR, and the design of the optimal dither signal can be solved by the convex programming. Simulation results show that the proposed method can achieve a large PAPR reduction when a proper amplitude constraint on the dither signal is employed.

A Low Complexity PAPR Reduction Method Based on FWFT and PEC for OFDM Systems

Orthogonal frequency division multiplexing (OFDM) is a multi-carrier modulation technique for transmitting large volumes of digital data but suffers high peak-to-average power ratio (PAPR) at the transmitter. In this paper, we propose a PAPR reduction technique based on the combination of a low complexity transform-Fast Walsh–Hadamard and Fourier transform (FWFT) and the parameter-adjustable piecewise exponential companding (PEC). To reduce algorithm complexity, FWFT uses a fast orthonormal unitary transform to calculate both the Walsh–Hadamard transform (WHT) and the discrete Fourier transform (DFT). In FWFT, WHT realizes precoding to OFDM signals and as a result the PAPR is reduced first. Moreover, the parameter-adjustable PEC transform is adopted to further reduce PAPR by transforming the statistics of the companded signal into exponential distribution with adjustable parameters. Simulation results show that the hybrid method achieves significant PAPR reduction and improves the BER performance of OFDM systems when used in multipath fading channels.

Amplitude reconstruction of clipped OFDM by using DFT-based least squares

OFDM is an e ective multicarrier transmission technique with one primary disadvantage; it su ers from high Peak-to-Average Power Ratio (PAPR). Although clipping and ltering is a simple and e ective method for PAPR reduction, it makes in-band and out-of-band noise, which degrades the bit error rate performance and spectral eficiency. Publications on this subject show that clipped samples could be reconstructed at the receiver by using oversampled signal and bandwidth expansion. By building on published literature, this paper aims to achieve a low-complexity method. The proposed method has complexity order of O(L2) to solve linear system, where L indicates the number of clipped samples. Simulation results con rm that our proposed method leads to both a better biterror rate performance and a lower complexity than similar methods. These results also show that our method o ers adequate performance, especially at low clipping ratios.

Blind SLM for PAPR reduction of Alamouti DSFBC systems

The combination of differential space-time block codes and orthogonal frequency-division multiplexing (OFDM) as differential space-frequency block coded (DSFBC)-OFDM system is a good candidate to achieve maximum diversity without the need to channel estimation. High peak-to-average-power ratio (PAPR) is a major drawback in these systems. The available PAPR reduction methods are not directly applicable in DSFBC-OFDM system. In this study, the proper application of selected mapping (SLM) method for reducing PAPR in Alamouti DSFBC-OFDM system is investigated and two different schemes are presented: conventional SLM (C-SLM) and blind differential SLM (BD-SLM). In C-SLM technique, the index of the selected phase sequence must be sent to the receiver side as the side information (SI). In the proposed BD-SLM method, specific phase mask vectors are generated with one-to-one correspondence with the different phase rotation sequences. Then at the receiver side, a differential minimum Hamming distance decoder is introduced to detect the index of optimum phase mask vectors without SI. Simulation results show that the proposed BD-SLM scheme (without the need to SI) provides good performances of both the bit error rate and PAPR reduction compared with C-SLM method.

Decision-directed iterative methods for PAPR reduction in optical wireless OFDM systems

In this paper, we propose two iterative decision-directed methods for peak-to-average power ratio (PAPR) reduction in optical-orthogonal frequency division multiplexing (O-OFDM) systems. The proposed methods are applicable to state-of-the-art intensity modulation-direct detection (IM-DD) O-OFDM techniques for optical wireless communication (OWC) systems, including both direct-current (DC) biased O-OFDM (DCO-OFDM), and asymmetrically clipped O-OFDM (ACO-OFDM). Conventional O-OFDM suffers from high power consumption due to high PAPR. The high PAPR of the O-OFDM signal can be counteracted by clipping the signal to a predefined threshold. However, because of clipping an inevitable distortion occurs due to the loss of useful information, thus, clipping mitigation methods are required. The proposed iterative decision-directed methods operate at the receiver, and recover the lost information by mitigating the clipping distortion. Simulation results acknowledge that the high PAPR of O-OFDM can be significantly reduced using clipping, and the proposed methods can successfully circumvent the clipping distortions. Furthermore, the proposed PAPR reduction methods exhibit a much lower computational complexity compared to standard PAPR reduction methods.

Performance Analysis of Layered ACO-OFDM

Layered asymmetrically clipped optical orthogonal frequency division multiplexing (LACO-OFDM) has been proposed for improving the spectral efficiency of conventional asymmetrically clipped optical OFDM. Multiple base layers that are orthogonal in the frequency domain are sequentially superimposed to form LACO-OFDM, where each superimposed layer fills the empty subcarriers left by the previous layer. As our contribution, the bit error ratio (BER) considering the effect of thermal noise, clipping distortion, inter-layer interference, and the bit rate difference between layers is analysed in this paper. Since the BER performance of LACO-OFDM is closely related to its peak-to-average power ratio (PAPR) distribution, we also provide the analytical expression of the PAPR distribution in this paper, which quantifies how the number of layers in LACO-OFDM reduces the PAPR. As a further advance, we propose a tone-injection aided PAPR reduction design for LACO-OFDM, which in turn improves the BER performance. Simulations are provided for verifying both the analytical BER performance and the PAPR distribution of LACO-OFDM. The results show that the expressions derived match well with the simulations. Furthermore, the PAPR reduction method proposed attains a 5 dB PAPR reduction at the $10^{-3}$ probability-point of the complementary cumulative distribution function, as well as a better BER performance than the original LACO-OFDM scheme.

PAPR reduction in OFDM system using hybrid PTS-RCMN scheme

Orthogonal Frequency Division Multiplexing (OFDM) is a widely accepted multi-carrier transmission scheme which is used for high data rate applications like Long-Term Evolution (LTE). It offers higher data transmission rate by efficient bandwidth usage. OFDM offers greater resistance and immunity towards inter-symbol interference (ISI) and Inter-Carrier Interference (ICI). However the major drawback associated with OFDM is high Peak to Average Power Ratio (PAPR) which forces high power amplifier (HPA) to work in the non-linear region resulting in harmonic distortions in the output. Partial transmit sequence (PTS) is a widely employed and tested method for PAPR reduction in 4G systems. In this paper we have proposed a novel scheme which uses a combination of PTS and Reduced Complexity Maximum Norm (RCMN) method to improve PAPR reduction performance of PTS system. This scheme has effectively reduced PAPR as compared to conventional PTS technique with insignificant increase in computational complexity.

PAPR reduction in OFDM system using hybrid PTS-RCMN scheme

Orthogonal Frequency Division Multiplexing (OFDM) is a widely accepted multi-carrier transmission scheme which is used for high data rate applications like Long-Term Evolution (LTE). It offers higher data transmission rate by efficient bandwidth usage. OFDM offers greater resistance and immunity towards inter-symbol interference (ISI) and Inter-Carrier Interference (ICI). However the major drawback associated with OFDM is high Peak to Average Power Ratio (PAPR) which forces high power amplifier (HPA) to work in the non-linear region resulting in harmonic distortions in the output. Partial transmit sequence (PTS) is a widely employed and tested method for PAPR reduction in 4G systems. In this paper we have proposed a novel scheme which uses a combination of PTS and Reduced Complexity Maximum Norm (RCMN) method to improve PAPR reduction performance of PTS system. This scheme has effectively reduced PAPR as compared to conventional PTS technique with insignificant increase in computational complexity.

PAPR Reduction in OFDM Systems using Partial Transmit Sequence combined with Cuckoo Search Optimization Algorithm (ICAT16-0286)

Partial transmit sequence (PTS) scheme is one of the efficacious tool for lessening peak-to-average power ratio (PAPR) in orthogonal frequency division multiplexing (OFDM) system. However, computational cost for the optimum phase factors searches of PTS scheme entails huge computational requirements and limits its applicability to practical applications especially for high-speed data transmissions. This study proposes a PAPR reduction method with a low computational complexity based on a combination of cuckoo search optimization algorithm with PTS scheme in OFDM system. In terms of PAPR and computational cost reductions, the performance of the cuckoo-PTS scheme is comparatively investigated by performing a set of simulations with different PTS schemes.

A novel constellation amplitude modification method for PAPR reduction in OFDM systems

AbstractIn this paper, we propose a constellation amplitude modification (CAM) method to reduce the peak‐to‐average power ratio (PAPR) in orthogonal frequency division multiplexing systems. The key idea of the proposed CAM method is to modify the original constellation amplitude and choose the constellation points with the minimum PAPR as the transmitted constellation points. The CAM method formulates the PAPR reduction as a convex optimization problem, and then, it applies the customized interior‐point method to solve the optimization problem. Compared with the traditional methods, the CAM method does not increase the transmit power, and the receiver has no additional operations. Simulation results show that the CAM method converges fast and offers significant PAPR reduction. Copyright © 2016 John Wiley & Sons, Ltd.