Peak-to-average Power Ratio Reduction Of Orthogonal Frequency Division Multiplexing Signals Research Articles

Optimization of Partial Transmit Sequences for PAPR Reduction of OFDM Signals Without Side Information

This paper develops a novel optimization of partial transmit sequences (PTS) with phase quantization to reduce the peak-to-average-power ratio (PAPR) of orthogonal frequency-division multiplexing (OFDM) signals and enable data detection without side information. Since the formulated optimization problem is non-convex and has exponential time complexity, we employ a convex relaxation method to convert the original optimization problem into a series of convex programming whose solutions converge to a sub-optimal point satisfying the Karush-Kuhn-Tucker (KKT) conditions in polynomial time. Moreover, the obtained phase factors are quantized to enable the maximum likelihood (ML) phase estimation at the receiver, hence removing the need of sending side information. Analytical and numerical results are provided to show that our proposed PTS design achieves better PAPR reduction over existing PTS methods, while no performance degradation is incurred in data detection when the number of phase factors is properly chosen.

Continuous-unconstrained and global optimization for PSO-PTS based PAPR reduction of OFDM signals

Orthogonal frequency division multiplexing (OFDM) is a superior technology for the high-speed data rate of wire-line and wireless communication systems. However, one of the major drawbacks of OFDM signals is the high peak-to-average power ratio (PAPR) problem inherent in 5G waveform design. High PAPR causes OFDM signal distortion in the nonlinear region of the high power amplifier (HPA), and signal distortion leads to a decrease in bit error rate (BER). Partial transmit sequence (PTS) technique is a very attractive technique for PAPR reduction. However, to match the optimum condition on PTS for PAPR reduction, the computational unpredictability and cost of traditional PTS strategy are enormous, thus it is urgent to enhance computational efficiency to obtain the optimal PTS. In this paper, an improved scheme called Continuous-Unconstrained Particle Swarm Optimization based PTS (CUPSO-PTS) technique for optimum phase rotation factors searching is presented. A class of continuous-phase PTS schemes has been proposed to obtain the global optimal phase factor, and the theoretical boundaries can be determined in the continuous-unconstrained searching space. Conversely, when the phase factor values in continuous-unconstrained domain, the equivalent unconstrained PTS optimization can drastically accelerate convergence and reduce total calculation cost. In this paper, we compare the performance of Binary PSO based PTS (BPSO-PTS) scheme and Elitist Genetic Algorithm based PTS (EGA-PTS) scheme for 16-QAM modulation scheme. Theoretical analysis and simulations show that the proposed CUPSO-PTS scheme could provide a significant PAPR reduction in the OFDM system, which outperforms the OFDM systems with the traditional PTS scheme by 0.55 dB at CCDF of 10−3 in PAPR reduction. And 84.74% computational complexity is saved.

An Efficient ACE Scheme for PAPR Reduction of OFDM Signals With High-Order Constellation

In this paper, an efficient Active Constellation Extension (ACE) based on Extension Projection Onto the Convex Sets (EPOCS-ACE) scheme is proposed for reducing Peak-to-Average Power Ratio (PAPR) of Orthogonal Frequency Division Multiplexing (OFDM) signals especially with a large number of sub-carriers and high-order constellation. Utilizing the specially designed iterative procedure, considerable PAPR reduction gains not only can be obtained with just one iteration but also can be adjusted dynamically to adapt the different designed requirements for OFDM systems. Moreover, both the novel peaks-clipping strategy and specific extension rules are designed to ensure BER performance while reducing PAPR. The theoretical analysis in terms of the selection criterion for compensation factors, optimization for correction factor, reachable bound of CCDF and computation complexity is derived. Simulation results show that, compared to existing ACE methods, EPOCS-ACE is able to obtain better overall performance in the aspect of PAPR, BER, and complexity for broadband OFDM systems.

Optimized Signal Distortion for PAPR Reduction of OFDM Signals With IFFT/FFT Complexity Via ADMM Approaches

In this paper, we propose two low-complexity optimization methods to reduce peak-to-average power ratio (PAPR) values of orthogonal frequency division multiplexing (OFDM) signals via alternating direction method of multipliers (ADMM). First, we formulate a nonconvex signal distortion optimization model based on minimizing data carrier distortion such that the constraints are placed on PAPR and the power of free carriers. Second, to obtain the model's approximate optimal solution efficiently, we design two low-complexity ADMM algorithms, named ADMMDirect and ADMM-Relax respectively. Third, we show that, in ADMM-Direct/-Relax, all the optimization subproblems can be solved semi-analytically and the computational complexity in each iteration is roughly (9(IN log <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> IN), where I and N are oversampling factor and carrier number respectively. Moreover, we show that the resulting solution of ADMM-direct is guaranteed to be some Karush-Kuhn-Tucker (KKT) point of the nonconvex model when the iteration algorithm is convergent. For ADMMRelax, we prove that it has theoretically-guaranteed convergence and can approach arbitrarily close to some KKT point of the model if proper parameters are chosen. Simulation results demonstrate the effectiveness of the proposed approaches.

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.

Improved Cross-Entropy-Based Tone Injection Scheme With Structured Constellation Extension Design for PAPR Reduction of OFDM Signals

The application of the cross entropy (CE) method to tone injection (TI) can make the peak-to-average power ratio (PAPR) of the orthogonal frequency division multiplexing (OFDM) signals reduced efficiently with great complexity savings. However, as a population-based search method, the CE method requires large samples to find a high-quality solution, which means higher complexity and more time consuming concerning convergence. To reduce the complexity while achieving promising PAPR performance, an improved CE based TI scheme is proposed in this paper. First, a structured extended constellation for rectangular quadrature amplitude modulation is designed to provide more freedom degrees. With proper parameter selection, the proposed extended constellation can offer more design flexibilities and achieve a better tradeoff between freedom degree and power increase. Then, by analyzing the impact of the subcarrier candidate population on the conventional CE based TI scheme, we derive an explicit expression for the determination of the size of the subcarrier candidate population. And, based on the prior information carried by the clipping signal, proper candidate subcarriers are selected. Finally, an improved CE based TI scheme is proposed, which can efficiently enhance the solution quality and greatly accelerate the convergence speed. Simulation results demonstrate that the improved CE based TI scheme achieves great improvements on the performance of PAPR, bit error rate, power increase and complexity compared with the conventional CE based TI scheme.

Trellis-Assisted Constellation Subset Selection for PAPR Reduction of OFDM Signals

In this paper, we propose a new peak-to-average power ratio (PAPR) reduction technique, which is referred to as trellis-assisted constellation subset selection ( TACSS , or TAX for short), for orthogonal frequency-division multiplexing (OFDM) signals. We control the signal transition by judiciously selecting the appropriate constellation subset for PAPR reduction with the controlling bits that are subject to the trellis-based constraint imposed by a bank of memories. A novel constellation design suitable for the proposed system is also introduced. A major property offered by the proposed approach is that the controlling bits and the information bits are perfectly separable at the receiver, which leads to a simple implementation of its soft-in–soft-out (SISO) decoder for coded OFDM systems. Through the performance analysis of PAPR reduction capability, power amplifier (PA) efficiency, average mutual information (AMI), and bit error rate (BER), the achievable tradeoff relationship between the transmitter and receiver performances of the proposed system is addressed. Furthermore, performance comparisons of the proposed scheme with other major PAPR reduction schemes such as trellis shaping, discrete Fourier transform (DFT) precoding, and clipping and filtering demonstrate its practical advantage in a high-spectral-efficiency regime.

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.

GA-PTS Using Novel Mapping Scheme for PAPR Reduction of OFDM Signals Without SI

In recent time orthogonal frequency division multiplexing (OFDM) has proved its mettle as a preferred choice for high speed transmission in wireless applications due its efficient mechanism to combat the inter symbol interference. However sudden high peaks in OFDM signal envelope lead to high peak to average power ratio (PAPR). Enhanced values of PAPR result into complex RF amplifier circuit with reduced efficiency. There are various methods available for PAPR reduction, out of them partial transmit sequence (PTS) is most effective proven choice for PAPR reduction. However PTS technique requires cumbersome searching of all possible phase factors to find optimal phase factor which produces lowest PAPR, the information regarding optimal phase set used at the transmitter need to be sent to the receiver as side information (SI) for decoding purpose, however transmitting SI requires additional transmission bandwidth thus reducing overall bandwidth efficiency. To reduce the exhaustive searching genetic algorithm (GA) could be used with PTS leading to GA-PTS system. In this paper a GA-PTS system is proposed which uses novel octagonal geometry for constellation extension purpose. This scheme does not require transmission of any side information for decoding purpose at receiver and at the same time GA-PTS system reduces the required number of searches. Simulations are presented to show that proposed scheme provides similar PAPR performance as conventional PTS but without need of SI transmission at reduced number of searches.

Peak-to-Average Power Ratio Reduction based Varied Phase for MIMO-OFDM Systems

One of the severe drawbacks of orthogonal fre-quency division multiplexing (OFDM) is high Peak-to-Average Power Ratio (PAPR) of transmitted OFDM signals. During modulation the sub-carriers are added together with same phase which increases the value of PAPR, leading to more interference and limits power efficiency of High Power Amplifier (HPA), it’s requires power amplifier’s (PAs) with large linear oper-ating ranges but such PAs are difficult to design and costly to manufacture. Therefore, to reduce PAPR various methods have been proposed. As a promising scheme, partial transmit sequences (PTS) provides an effective solution for PAPR reduction of OFDM signals. In this paper, we propose a PAPR reduction method for an OFDM system with variation of phases based on PTS schemes and Solid State Power Amplifiers (SSPA) of Saleh model in conjunction with digital predistortion (DPD), in order to improve the performance in terms of PAPR, the HPA linearity and for the sake of mitigating the in-band distortion and the spectrum regrowth. The simulation results show that the proposed algorithm can not only reduces the PAPR significantly, but also improves the out-of-band radiation and decreases the computational complexity.

Neural Network Based Simplified Clipping and Filtering Technique for PAPR Reduction of OFDM Signals

Many iterative clipping and filtering (ICF) based techniques have been proposed that achieve similar peak-to-average power ratio (PAPR) reduction of orthogonal frequency division multiplexing (OFDM) signals as the original ICF, but with lower complexity, such as the simplified clipping and filtering (SCF) technique. However, these low complexity methods require numerous complex fast Fourier transform (FFT) operations and parameter calculations. In this letter, we introduce a novel ICF method that uses an optimized mapper based on artificial neural network and SCF techniques. Compared to the conventional ICF based methods, the proposed scheme offers desirable cubic metric (CM) and bit error rate (BER) simulation results with significantly reduced computational complexity.

PAPR Reduction Techniques Comparison inOFDM System

In recent years, multimedia based application which requires the technology that supports high speed data transmission is growing rapidly. To achieve this high speed communication orthogonal frequency division multiplexing (OFDM) is most widely used technology. OFDM system makes the use of orthogonal subcarriers for data transmission with efficient usage of available bandwidth. However as number of subcarriers goes on increasing, Peak to average power ratio (PAPR) of OFDM signal also increasing. This high PAPR causes significant distortions when passed through non-linear amplifier. A number of promising techniques have been proposed & implemented to reduce PAPR of OFDM signal with expense of transmitted signal power, Bit error rate (BER), complexity etc. In this paper, amplitude clipping and filtering (ACF), Iterative clipping and filtering (ICF) and interleaved OFDM techniques are implemented for PAPR reduction of OFDM signal at transmitter. Comparison of these PAPR reduction techniques is done based PAPR and BER performance of the system.

Efficient Image Communication in PAPR Distortion Cases

In this paper, a proposed method for Peak-to-Average Power Ratio (PAPR) reduction of Orthogonal Frequency Division Multiplexing (OFDM) signals based on discrete transforms is presented for robust image communication. One of the discrete transforms such as discrete wavelet transform, discrete cosine transform, or discrete sine transform is applied to modify the OFDM signal at the output of the inverse fast Fourier transform stage. We first present the proposed OFDM system model with trigonometric transforms for PAPR reduction. Trigonometric transforms improve the performance of the OFDM system, and reduce the PAPR of the OFDM signal. Then, this scheme has been utilized for progressive image transmission using low-density parity-check coded OFDM over frequency-selective fading channels. The set partitioning in hierarchical trees algorithm is used for source coding of the images to be transmitted. The proposed scheme effectively resists the fading impact of frequency-selective fading channels using simple frequency-domain equalization. Simulation experiments are performed for a variety of multipath fading channels. We also propose a chaotic interleaving scheme based on the 2-D chaotic Baker map for PAPR reduction of OFDM signals. The distinctive feature of this scheme is that the transmitted signal has less correlation between samples, and hence the PAPR is minimized.

PAPR Reduction of OFDM Signal Using Sequential Phase Sequence SLM Based Transceiver without Side Information

Researches in the reduction of peak-to-average power ratio (PAPR) from orthogonal frequency division multiplexing (OFDM) output signals are being done using many techniques. Selected mapping (SLM) technique is a distortion-less technique and is a well known method to reduce high PAPR of OFDM signal. One drawback of SLM is its requirement of side information bits to recover original data block at the receiver side which lead rate of data loss. In this paper, we have proposed a sequential phase sequence SLM (SPS-SLM) based OFDM transceiver without side information and studied its performance. For the proposed method, a specific set of phase sequences is designed. MATLAB simulation shows that the proposed scheme performs well in terms of PAPR. Proposed method provides almost the same PAPR reduction performance compared to the conventional SLM method requiring side information.

A New Approach for PAPR Reduction of OFDM Signal Based on Signal Scrambling

Orthogonal Frequency Division Multiplexing (OFDM) is an attractive and promising technique for fourth generation wireless communication. In general, the High Peak-to-Average Power Ratio (PAPR) of transmitted signals for OFDM systems reduces the system efficiency and hence increases the cost of the Radio Frequency (RF) power amplifier. In this paper, we propose a distortion-less PAPR reduction schemes for multi-carrier system. The new schemes combine both the Partial Transmit Sequence (PTS) and the Selected Mapping (SLM) techniques. The performance of the new schemes is measured using the Complementary Cumulative Distribution Function (CCDF) of the PAPR. The simulation results show that the two new combined schemes have a better PAPR performances compared to PTS and SLM. On the other hand, the price paid is a slight increase in the system complexity, as well as the side information transmitted.

A Piecewise Linear Companding Transform for PAPR Reduction of OFDM Signals With Companding Distortion Mitigation

Companding is a well-known technique for the peak-to-average power ratio (PAPR) reduction of orthogonal frequency division multiplexing (OFDM) signals. However, as companding transform is an extra operation after the modulation of OFDM signals, companding schemes reduce PAPR at the expense of increasing the bit error rate (BER). In this paper, a new piecewise linear companding scheme is proposed aiming at mitigating companding distortion. In the design of the companding transform, we study the theoretical characterization of companding distortion. It demonstrates that companding larger signals with smaller amplitude increments are more favorable in reducing companding distortion. Based on the analysis results, a new piecewise linear companding transform is proposed by clipping the signals with amplitudes over a given companded peak amplitude for peak power reduction, and linearly transforming the signals with amplitudes close to the given companded peak amplitude for power compensation. With the careful design of the companded peak amplitude and the linear transform scale, the proposed transform can achieve enhanced BER and power spectral density performance, while reducing PAPR effectively.

Comparative Performance Analysis of Different Modulation Techniques for PAPR Reduction of OFDM Signal

One of the most important multi-carrier transmission techniques used in the latest wireless communication arena is known as Orthogonal Frequency Division Multiplexing (OFDM). It has several characteristics such as providing greater immunity to multipath fading & impulse noise, eliminating Inter Symbol Interference (ISI) & Inter Carrier Interference (ICI) using a guard interval known as Cyclic Prefix (CP). A regular difficulty of OFDM signal is high peak to average power ratio (PAPR) which is defined as the ratio of the peak power to the average power of OFDM Signal. An improved design of amplitude clipping & filtering technique of us previously reduced significant amount of PAPR with slightly increase bit error rate (BER) compare to an existing method in case of Quadrature Phase Shift Keying (QPSK) & Quadrature Amplitude Modulation (QAM). This paper investigates a comparative performance analysis of the different higher order modulation techniques on that design.

General Closed-Form Family of Companders for PAPR Reduction in OFDM Signals Using Amplitude Distribution Modification

In this paper, we characterize a family of closed-form companders for peak-to-average power ratio (PAPR) reduction in orthogonal frequency-division multiplexing (OFDM) signals. This new family generalizes the current state-of-the-art companders that are based on modification of the OFDM signal amplitude statistics. We derive the compander and decompander forms for a specific, parameterized member of this family. The larger parameter set characterizing these new companders provides greater design flexibility. The new companders are shown to provide solutions over regions of the operating conditions space where other current companders fail to exist. These new solutions thus widen the application of companders for PAPR reduction, and expand the trade-space over demodulation performance, PAPR reduction, and out-of-band power rejection for compander design. Through numerical result generation and simulation, we generate performance results to show that the new companders offer performance improvements over current companders.

Simplified Approach to Optimized Iterative Clipping and Filtering for PAPR Reduction of OFDM Signals

Iterative clipping and filtering (ICF) is a well-known technique to reduce the peak-to-average power ratio (PAPR) of orthogonal frequency division multiplexing (OFDM) signals. Recently, Wang and Luo investigated the clipped signal and proposed a modified algorithm called optimized ICF (OICF). This is an optimal algorithm since it can achieve the required PAPR reduction with minimum in-band distortion and far fewer iterations. However, OICF needs to solve a convex optimization problem with O(N3) complexity, where N represents the number of subcarriers. In this paper, instead of analyzing the clipped signal, we study the clipping noise and propose a simplified OICF algorithm. In the new algorithm, solving the convex optimization problem is approximated by some simple algebraic operations and the computational complexity reduces to O(N). Simulation results show that after three iterations, the original OICF algorithm can achieve the desired PAPR while the simplified one exhibits almost the same performance: for a 128-subcarrier and quadrature phase shift keying (QPSK) modulated OFDM system, the PAPR-reduction performance difference between the two algorithms are 5×10-3dB at a 10-4 clipping probability and the bit-error-rate performance difference is 6×10-3 dB at a 10-7 error probability.

An Adaptive Clipping and Filtering Technique for PAPR Reduction of OFDM Signals

In recent years, many peak-to-average power ratio (PAPR) reduction techniques have been proposed for orthogonal frequency division multiplexing (OFDM) signals. Among various techniques, the iterative clipping and filtering (ICAF) technique has been considered as a practical scheme, and widely used owing to its non-expansion of bandwidth, low computational complexity, and simplicity in implementation without receiver-side cooperation. However, the performance of conventional ICAF technique is degraded, because the same signals are iteratively clipped with a fixed clipping threshold (CT) in every clipping operation. In this paper, we analyze the performance of conventional ICAF technique, and then propose an adaptive ICAF scheme, which clips the signal with an adaptively modified CT in every clipping operation to achieve enhanced PAPR reduction of OFDM signals. Simulation results show that the proposed scheme significantly outperforms the conventional scheme, in PAPR reduction of OFDM signals at the same number of iterations.