Peak-to-average Power Ratio Reduction In Orthogonal Frequency Division Multiplexing Systems Research Articles

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 Low-Complexity Tone Injection Scheme Based on Distortion Signals for PAPR Reduction in OFDM Systems

Tone injection (TI) can effectively reduce the peak-to-average power ratio (PAPR) of orthogonal frequency division multiplexing (OFDM) signals without incurring data rate loss and extra side information. However, the optimal TI scheme requires an exhaustive search over all combinations of the possible perturbations of the expanded constellation over all perturbed subcarriers, which is not suitable for practical applications. To reduce the complexity while still achieving good PAPR performance, a low-complexity TI scheme based on distortion signals is proposed in this paper. Motivated by the goal of mitigating the distortions when OFDM signals pass high power amplifiers, we intuitively get the perturbation information for OFDM signals directly from the distortion signals. By exploiting the distribution of the perturbation vectors depending on the distortion signals, we design a search range limited extended constellation. Then, based on the statistical information of perturbed subcarriers, the number of the subcarriers to be perturbed is restricted. Moreover, to further reduce the complexity, we choose a proper subcarrier perturbation sequence from candidate subcarrier sets according to the mutual information between the peak sample and the distortion signals. With the selected subcarrier perturbation sequence, the original problem is decomposed into a sequential search problem, which provides a dramatic complexity reduction. Simulation results demonstrate that the proposed scheme can achieve significant complexity savings while maintaining a good PAPR performance.

On Companding Schemes for PAPR Reduction in OFDM Systems Employing Higher Order QAM

Large peak-to-average power ratio (PAPR) of the signal is an imperative problem in orthogonal frequency division multiplexing (OFDM) systems, as it impedes the efficient design of their analog front end. Companding is a well-known technique that reduces the PAPR by using a deterministic amplitude transform, which is designed by assuming Rayleigh distribution for the signal amplitude. But in OFDM systems employing higher order QAM, like 16- or 64-QAM, this probabilistic model is insufficient to model the true characteristics of the signal. This is due to the stochastic nature of average symbol power, which alters the complete amplitude distribution from one OFDM symbol to another. This leads to degradation in the companders' PAPR reduction performance. In this paper, we propose two novel schemes that modify the companding operation to accommodate the randomness of symbol power. Probabilistic analysis of symbol's average power, in relationship with the amplitude of its constituent samples, is carried out. This yields the theoretical framework employed in the design of the proposed low-complexity solutions. The proposed schemes essentially make the companding operation itself nondeterministic/adaptive, i.e., it adjusts to comply with the changing symbol amplitude distribution during application runtime.

Enhanced Phase Realignment Techniques for the PAPR Reduction in OFDM Systems

This paper presents a simple and effective solution for the peak-to-average power ratio (PAPR) problem in orthogonal frequency-division multiplexing (OFDM) systems. Since the OFDM signal has a high PAPR, it generates inevitable nonlinear distortions at the output of a high-power amplifier. A new technique of PAPR reduction called phase realignment (PR) and its modified version called modified PR (MPR) are proposed, which require neither side information nor do they impose any modification of the receiver. Furthermore, four possible variations of the MPR constellation structure are proposed and evaluated in terms of PAPR reduction and bit-error-rate (BER) performance. The proposed PR and MPR provide considerable reductions in PAPR. MPR <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">1</sub> gives a comparatively high PAPR reduction, followed by MPR <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sub> , PR, MPR <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> , and MPR <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">4</sub> in descending order. The PAPR reductions of MPR <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sub> and MPR <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> tend to converge to that of the PR as the modulation order increases, whereas MPR <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">4</sub> gives a low PAPR reduction. These techniques are designed to allow a certain level of BER degradation, which is defined by a transmit error vector magnitude (EVM) limited to a specified threshold, to reduce the PAPR and the average power (equally important in terms of power efficiency). The proposed techniques produce the reduced out-of-band radiation compared with the original OFDM signal and have moderate computational complexity. The EVM threshold is imposed to design optimum amplitude and phase margins for the PR and MPRs. Furthermore, we present the analytic upper bound BER expressions of the proposed techniques.

Shift Estimation with Delayed Correlation Cyclic-Selective Mapping (Cyclic-SLM) PAPR Reduction in OFDM System

Cyclic-selective mapping (SLM) for wireless orthogonal frequency division multiplexing (OFDM) systems combines an original signal and its cyclic shifted signal to reduce a peak-to-average power ratio (PAPR) in time domain. However, side information (SI) regarding to the amount of the cyclic shift is required at the receiver, and how to transmit it is one of the most challenging issues of SLM schemes because it decreases the throughput of wireless OFDM systems. The delayed correlation based estimation scheme is proposed in this paper to avoid the transmission of the SI. This scheme exploits the correlation between a guard interval sequence and a received signal with delay to estimate the amount of the cyclic shift at the receiver side. Numerical results obtained through computer simulation show that the proposed scheme can estimate the delay with an accuracy of more than 0.99 at an $$E_b/N_0$$Eb/N0 of 8 dB and achieve the PAPR that is equivalent to the conventional SLM while the bit error rate degradation is slightly different from that with perfect shift estimation.

On the Shift Value Set of Cyclic Shifted Sequences for PAPR Reduction in OFDM Systems

Orthogonal frequency division multiplexing (OFDM) signals have high peak-to-average power ratio (PAPR), which causes distortion when OFDM signal passes through a nonlinear high power amplifier. A partial transmit sequence (PTS) scheme is one of the typical PAPR reduction methods. A cyclic shifted sequences (CSSs) scheme is evolved from the PTS scheme to improve the PAPR reduction performance, where OFDM signal subsequences are cyclically shifted and combined to generate alternative OFDM signal sequences. The shift value (SV) sets in the CSS scheme should be carefully selected because those are closely related to the PAPR reduction performance of the CSS scheme. In this letter, we propose some criteria to select the good SV sets and verify its validness through simulations.

A Low-Complexity Architecture for PAPR Reduction in OFDM Systems With Near-Optimal Performance

Selected mapping (SLM) schemes are widely used to reduce the peak-to-average power ratio (PAPR) in orthogonal frequency-division multiplexing (OFDM) systems. Various time-domain approaches have been proposed for reducing the number of inverse fast Fourier transform (IFFT) operations required to generate the candidate signals in traditional SLM schemes. However, the resulting time-domain-generated signals are somewhat correlated, and thus, the PAPR reduction performance is seriously degraded. Accordingly, this paper proposes a novel PAPR reduction method in which frequency-domain phase rotation, cyclic shifting, complex conjugate, and subcarrier reversal operations are all employed to increase the diversity of the candidate signals. Furthermore, to circumvent the multiple-IFFT problem, all of the frequency-domain operations are converted into time-domain equivalents. It is shown that the subcarrier partitioning and reassembling processes are key to realizing low-complexity time-domain equivalent operations. Moreover, it is shown theoretically and numerically that the computational complexity of the proposed scheme is significantly lower than that of the traditional SLM method and that the PAPR reduction performance is within 0.001 dB of that of SLM. Overall, the results indicate that among all of the low-complexity architectures proposed in the literature, the method proposed in this paper most closely approximates the PAPR reduction performance of the traditional SLM scheme.

A Modified Shuffled Frog Leaping Algorithm for PAPR Reduction in OFDM Systems

Significant reduction of the peak-to-average power ratio (PAPR) is an implementation challenge in orthogonal frequency division multiplexing (OFDM) systems. One way to reduce PAPR is to apply a set of selected partial transmission sequence (PTS) to the transmit signals. However, PTS selection is a highly complex NP-hard problem and the computational complexity is very high when a large number of subcarriers are used in the OFDM system. In this paper, we propose a new heuristic PTS selection method, the modified chaos clonal shuffled frog leaping algorithm (MCCSFLA). MCCSFLA is inspired by natural clonal selection of a frog colony, it is based on the chaos theory. We also analyze MCCSFLA using the Markov chain theory and prove that the algorithm can converge to the global optimum. Simulation results show that the proposed algorithm achieves better PAPR reduction than using others genetic, quantum evolutionary and selective mapping algorithms. Furthermore, the proposed algorithm converges faster than the genetic and quantum evolutionary algorithms.

Tone Reservation Technique Based on Peak-Windowing Residual Noise for PAPR Reduction in OFDM Systems

Peak-to-average power ratio (PAPR) of orthogonal frequency-division multiplexing (OFDM) may be reduced by reserving several tones to generate a peak-canceling signal (PCS). However, this method suffers from high computational complexity. To address this problem, this paper proposes an algorithm based on peak-windowing residual noise, which is generated by windowing the signal samples that exceed the predetermined threshold. Filtering the residual noise to satisfy tone reservation (TR) constraints and scaling with a scaling factor determined to minimize the out-of-range power generates the PCS. Simulation results show that the proposed algorithm can achieve 6.9-dB PAPR reduction with much lower complexity than other schemes.

IGCC for PAPR Reduction in OFDM Systems Over the Nonlinearity of SSPA and Wireless Fading Channels

High peak-to-average power ratio (PAPR) in orthogonal frequency division multiplexing (OFDM) systems seriously impacts power efficiency in radio frequency section due to the nonlinearity of high-power amplifiers. In this article, an improved gamma correction companding (IGCC) is proposed for PAPR reduction and investigated under multipath fading channels. It is shown that the proposed IGCC provides a significant PAPR reduction while improving power spectral levels and error performances when compared with the previous gamma correction companding. IGCC outperforms existing companding methods when a nonlinear solid-state power amplifier (SSPA) is considered. Additionally, with the introduction of $$\alpha , \beta , \gamma $$ź,β,ź, and $$\varDelta $$Δ parameters, the improved companding can offer more flexibility in the PAPR reduction and therefore achieves a better trade-off among the PAPR gain, bit error rate (BER), and power spectral density (PSD) performance. Moreover, IGCC improves the BER and PSD performances by minimizing the nonlinear companding distortion. Further, IGCC improves signal-to-noise ratio (SNR) degradation ($$\varDelta _{\mathrm{SNR}}$$ΔSNR) and total degradation performances by 12.2 and 12.8 dB, respectively, considering an SSPA with input power back-off of 3.0 dB. Computer simulation reveals that the performances of IGCC are independent of the modulation schemes and works with arbitrary number of subcarriers (N), while it does not increase computational complexity when compared with the existing companding schemes used for PAPR reduction in OFDM systems.

A Modified PTS Scheme for PAPR Reduction in OFDM System with Low Complexity

Orthogonal Frequency Division Multiplexing (OFDM) is the most desired and attractive among the various broadband wireless communication system because of its robustness against multipath fading. However even after its so many advantages OFDM has been able to deliver upto its potential due to its “High Peak to Average Power Ratio (PAPR)” which causes power inefficiency in RF section of the transmitter effecting the throughput. The soul purpose of this paper is to provide the most effective PAPR reduction technique while doing amendments in the Partial Transmit Sequence and is termed as the modified Partial Transmit Sequence which overcomes the limitation of conventional system in which a property of cyclically shifting of IFFT is used which doesn’t require the side information and provides a system with low complexity.

A Semi-Blind SLM Scheme for PAPR Reduction in OFDM Systems With Low-Complexity Transceiver

A semi-blind selected mapping (SLM) scheme with low-complexity transceiver is addressed for peak-to-average power ratio (PAPR) reduction in orthogonal frequency-division multiplexing (OFDM) systems. In the proposed scheme, the phase rotation vectors for the data vector and those for the pilot vector in an OFDM symbol are separately designed, which enables both low computational complexity and embedding of the side information (SI) into the pilot subcarriers at the transmitter. To implement data detection at the receiver, pilot-aided embedded SI detection algorithm is introduced, and a low-complexity suboptimal SI detection algorithm is also proposed. Analysis and simulation results show that the proposed scheme can achieve much lower computational complexity than that of the available semi-blind SLM schemes at both the transmitter and receiver, whereas it has slightly worse PAPR reduction performance and almost the same bit error rate (BER) performance, even with the suboptimal SI detector, as compared with the conventional SLM (C-SLM) with perfect SI at the receiver.

Peak-power reduction using improved partial transmit sequence in orthogonal frequency division multiplexing systems

Orthogonal Frequency Division Multiplexing (OFDM) system has lead to significant advancement in wireless communication systems. In OFDM system multi-carriers are present. During modulation the sub-carriers are added together with same phase which increases the value of Peak-to-Average Power Ratio (PAPR). High PAPR leads to more interference and reduced resolution of analog to digital converter (A/D) and digital to analog converter (D/A). The Partial Transmit Sequence (PTS) is a popular technique used for PAPR reduction in OFDM systems. The modified PTS technique proposed in this paper overcomes the drawbacks of Original PTS (O-PTS) by making use of Group Phase Weighting Factor (GPW) and Recursive Phase Weighting Factor (RPW) along with All Pass Filtering. Simulations show that the proposed scheme performs very well in terms of PAPR and achieves almost the same Bit Error Rate (BER) performance under Rayleigh fading channel.

Partial phase weighting selected mapping scheme for peak‐to‐average power ratio reduction in orthogonal frequency division multiplexing system

As one of the most attractive schemes, selected mapping (SLM) provides an effective solution for peak-to-average power ratio (PAPR) reduction in orthogonal frequency division multiplexing (OFDM) system. However, in conventional SLM (CSLM), the large number of inverse fast Fourier transform (IFFT) operations are required for achieving the satisfactory PAPR reduction performance, which results in the large computational complexity. In this study, a partial phase weighting SLM (PPW-SLM) for PAPR reduction in OFDM system is proposed. In the proposed PPW-SLM, partial phase weighting method and the properties of IFFT are employed for simplifying the calculations of IFFTs and obtaining good PAPR reduction performance. Theoretical analysis and simulation results show that, compared with CSLM, the proposed PPW-SLM can obtain a significant computational complexity reduction in similar PAPR reduction performance.

SLM and Clipping Joint Algorithm for PAPR Reduction in OFDM System

As one of the most appealing techniques, selective mapping (SLM) provides an efiective solution for Peakto-average Power Ratio (PAPR) reduction in Orthogonal Frequency Division Multiplexing (OFDM) systems, however, results in large computational complexity simultaneously. As compared to SLM, clipping provides a more simple way towards a better PAPR performance, whereas results in degradation of the Bit Error Rate (BER) performance. In this paper, we proposed a joint algorithm called SLM and Quantization Clipping (SLM-QC) scheme, which combined the conventional SLM technology with a modifled quantization clipping scheme. The proposed scheme achieves a better exploitation of advantages brought about by each technique alone, with the tradeofi between the PAPR performance and the BER performance being well balanced.

PAPR reduction in OFDM systems using peak insertion

A technique for Peak-to-Average Power Ratio (PAPR) reduction of Orthogonal Frequency Division Multiplexing (OFDM) signals by Peak Insertion (PI) is proposed in this paper. PI depends on the duality property of the DFT and PAPR duality of an impulse. A relatively high peak is inserted to the OFDM symbol in the frequency domain such that the PAPR of the transmitted time domain signal is reduced. PAPR reduction up to about 11dB at PAPR CCDF of 10−4 is achievable by PI, but at the expense of increased signal power, which can be reduced by scaling to the desired level without affecting its PAPR. Computer simulation tests show that a tradeoff can easily be made between BER and the PAPR of the transmitted signal to achieve a desired system performance. The PI technique does not require any sort of side information transmission, searching, optimization, and iterative or parallel application of IDFT. PI is faster, simpler, and capable of achieving greater PAPR reduction as compared with other similar techniques which result in transmitted power increase, and therefore, it seems to be suitable to be used for OFDM signal PAPR reduction.

PTS Method with Combined Partitioning Schemes for Improved PAPR Reduction in OFDM System

Although orthogonal frequency division multiplexing (OFDM) is an efficient wireless transmission system, it suffers from a crucial drawback namely high peak-to-average power ratio (PAPR) that limits transmitter power efficiency. Thus, different PAPR reduction algorithms have been introduced. Partial transmit sequence (PTS) is the most attractive solution which can provide good PAPR reduction performance without distortion. In any PTS system, partitioning of the OFDM frame into disjoint sub-blocks is a significant step. Out of the existing partitioning techniques, adjacent partitioning (AP) is a fairly simple partitioning scheme achieving efficient PAPR reduction performance. This paper presents an enhanced PTS approach that combines two PTS partitioning schemes, adjacent and interleaved partitioning, in order to effectively reduce the PAPR of OFDM systems. With an aim of determining the effects of length variability of adjacent partitions, we performed an investigation into the performances of a variable length adjacent partitioning (VL-AP) and fixed length adjacent partitioning in comparison with the enhanced PTS scheme.

Efficient Application of Selected Mapping with Clipping for PAPR Reduction in OFDM Systems

Orthogonal Frequency Division Multiplexing (OFDM) is an inimitable technology in wireless communication. High peak-to-average power ratio (PAPR) is a challenging issue in OFDM system. Large PAPR results in significant distortion in OFDM signal when passed through nonlinear high power amplifier. Selected mapping (SLM) is an efficient technique to reduce PAPR. In this work we efficiently apply SLM technique with clipping to reduce PAPR. And the simulation results show that the proposed techniques have better PAPR reduction performance than conventional Selected Mapping technique and SLM with interleaving.

A Novel Clipping and Filtering Algorithm Based on Noise Cancellation for PAPR Reduction in OFDM Systems

Iterative clipping and filtering is an effective technique to achieve peak-to-average power ratio (PAPR) reduction in orthogonal frequency division multiplexing (OFDM) systems, but requires numerous iterations to minimize the peak regrowth problem. In this paper, a novel clipping and filtering (CF) algorithm based on clipping noise cancellation method is proposed which needs only one iteration to minimize PAPR and also mitigates the effects of in-band and out of band distortion. This method requires three fast fourier transform (FFT)/inverse fast fourier transform IFFT operations while the conventional CF method requires (2K+1) FFT/IFFT operations, where K refers to the number of iterations. The simulation result shows that the QPSK modulated OFDM signal with 1,024 sub-carriers achieves a PAPR reduction of 6 dB in the additive white Gaussian noise channel with optimum bit error rate performance at the receiver.

Optimal phase searching of PTS using modified genetic algorithm for PAPR reduction in OFDM systems

In this paper, a novel genetic algorithm assisted partial transmit sequence (NGA-PTS) is proposed to reduce the peak-to-average power ratio (PAPR) of orthogonal frequency division multiplexing (OFDM). However, the search complexity of the optimum PTS (OPTS) scheme is too large for the typical number of sub-blocks. Therefore, some artificial intelligence methods, such as genetic algorithm technique, and particle swarm optimization, are introduced to reduce the complexity. As traditional GA-PTS (TGA-PTS) technique risks finding a suboptimal solution, how to avoid this disadvantage of TGA-PTS is an interest topic. In order to obtain a better suboptimal solution, a phase factor optimal pair technique and an abandon/introduction new chromosome technique are proposed in GA here. Simulation results show that the proposed scheme achieves a significant improvement over the TGA-PTS scheme in PAPR. Furthermore, by use of the inherent diversity of constellation for each OFDM candidate, in the receiver part, the proposed scheme enables data recovery without any side information. Simulation results show the efficiency of the proposed scheme.