Peak-to-average Power Ratio Reduction In OFDM Systems Research Articles

PAPR Reduction in OFDM System Using Metaheuristic Algorithm

The advancement of technology necessitates the development of more sophisticated modulation strategies for wideband digital communication systems. The requirements for high-speed data transmissions can be effectively met by utilizing orthogonal frequency division multiplexing, which is an effective technique. However, a high peak-to-average power ratio (PAPR) is one of the key limits that OFDM systems face, both in terms of their performance and their power efficiency. The evaluation of the PAPR reduction has become a topic of widespread interest in this present decade due to the relevance it holds in the industrial and scientific communities. The purpose of this study is to show the combination of the bat algorithm with the partial transmit sequence scheme as an effective way for reducing PAPR that also eases the burden of computing work. For the purpose of providing a comparative evaluation of the PAPR reduction performance, a number of simulations using various partial transmit sequence schemes have been carried out. The findings of the simulation show that the BA-PTS scheme has the potential to provide superior PAPR reduction performance while simultaneously reducing the computational load.

Low‐complexity companding function design for PAPR reduction in OFDM systems

In this study, the authors have proposed a low complexity companding function for peak-to-average-power ratio (PAPR) reduction in orthogonal frequency division multiplexing systems. This function transforms the signals into a probability density function with a cumulative distribution function an anti-trigonometric function. By carefully choosing the transform parameters, the bit error rate (BER) performance can be improved significantly during the reduction of PAPR. In addition, the proposed companding function offers design flexibility. Simulation results show that for the same PAPR performance, the proposed companding scheme can offer better BER performance. For example, upon assigning BER = 10−4 in an additive white Gaussian noise channel without a solid-state power amplifier, the minimum required bit energy to noise power spectral ratio (Eb/No) for the proposed companding scheme with c = 0 and A = 1.414 is 11 dB. It is 5, 4.2, and 3 dB lower than exponential companding function, root-based μ-law companding function, and amplitude limiting companding schemes, respectively. Also, their PAPR performance is the same.

PAPR Reduction in OFDM Systems Using Modified SLM with Different Phase Sequences

High Peak-to-average power ratio (PAPR) is one of the main issues in multicarrier modulation systems. PAPR is mainly caused due to the summation of various signals having high amplitude values. Several PAPR reduction techniques were employed, out of which Selective Mapping (SLM) proved to be one of the most effective schemes. Some drawbacks in SLM technique are high computational complexity and phase search complexity. Selection of phase sequences in SLM plays a major role in the reduction of PAPR as well as the computational complexity. Modified SLM was introduced to reduce computational complexity in SLM technique. In this paper, we apply various phase sequences such as Riemann, Centering, Centered Riemann and New Centered to Modified SLM technique and their effect on PAPR reduction are analyzed. From the simulation results, it can be inferred that the modified SLM with New Centered scheme achieves a significant PAPR reduction of the range 8.3–9.3 dB with respect to Conventional OFDM and 3–5.5 dB with respect to Conventional SLM technique. The Modified SLM-New Centered scheme is most suitable for 64-QAM applications as it provides good PAPR reduction performance at lower computational complexity.

A Novel Signal Scrambling Technique for PAPR Reduction in OFDM Systems

OFDM forms the basis of the upcoming next generation technologies so as to achieve higher data rates within a given bandwidth effectively. One of the major issues associated with OFDM is Peak to Average Power Ratio (PAPR) which needs to be minimized to get an efficient performance. The random variation in the signal amplitude of the OFDM signal leads to additional interference in the system and hence affecting the performance of HPA in non-linear region. In this paper, we propose a technique for the reduction of PAPR in OFDM systems with some increased complexity which works for any modulation type and any number of subcarriers. The simulation results show performance improvement with respect to the existing signal scrambling techniques

On the selection of the best companding technique for PAPR reduction in OFDM systems

ABSTRACTOrthogonal frequency division multiplexing (OFDM) is used in high data rate applications due to its ability to cope with frequency-selective channels. However, OFDM suffers from the high peak-to-average power ratio (PAPR) problem, which reduces the power amplifier (PA) efficiency or otherwise degrades bit error rate (BER) and increases out-of-band (OOB) radiation. In the literature, there are various PAPR reduction techniques. Among them companding techniques have small computational complexity, which make them attractive to be used in mobile stations (MS). Generally, companding techniques expand small signals while compressing large signals or compress large signals without affecting small signals. In this paper, different PAPR reduction companding transforms are compared. Results showed that companding transforms that compress large signals without affecting small signals (such as, Log companding and Tanh companding) are better than the others from a BER point of view. Results also showed that the Log companding transform is better than the Tanh transform, in terms of PAPR reduction gain and OOB radiation reduction. So the Log companding transform can be considered as the best practical companding transform among others.

On the PTS Optimization Using the Firefly Algorithm for PAPR Reduction in OFDM Systems

ABSTRACTOrthogonal frequency division multiplexing (OFDM) is currently the most used technique for the high-data-rate transmission. However, OFDM systems have an inherent drawback in that the transmitted signals suffer from a high peak-to-average power ratio (PAPR). Partial transmit sequence (PTS) is generally applied to reduce the PAPR of an OFDM signal in wireless communication systems. Here, the search complexity for optimal phase vector increases exponentially with the number of phase vectors, since it involves an extensive random search over all the combinations of the allowed phase vectors. In this paper, a swarm intelligence algorithm for phase optimization based on the Firefly algorithm (FF) is applied to search the optimal combination of phase vectors. The proposed algorithm provides a superior trade-off between the improved PAPR performance and computational complexity when compared to the PTS scheme for a large number of sub-blocks. Simulation results show that the Firefly-algorithm-based PTS (FF-PTS) algorithm is an efficient method to achieve superior PAPR characteristics for OFDM signals when compared to conventional algorithms with very few parameters to adjust.

PTS based on DisABC algorithm for PAPR reduction in OFDM systems

A novel discrete artificial bee colony algorithm-based partial transmit sequences (DisABC-PTS) scheme is proposed to reduce peak-to-average power ratio (PAPR) of orthogonal frequency division multiplexing signals. Compared to ABC algorithm-based PTS scheme (ABC-PTS) proposed previously, the DisABC-PTS scheme works directly in discrete space, which has a high computational efficiency. Simulation results indicate that DisABC-PTS scheme can obtain lower PAPR than existing PTS schemes and has a low computational complexity.

Modified Gamma Correction Companding for PAPR Reduction in OFDM Systems Considering Solid-State Power Amplifier and Wireless Channels

Orthogonal frequency division multiplexing is a special form of multicarrier modulation and suffers from a very high peak-to-average power ratio (PAPR) that degrades overall performance of the system. In this article, a modified gamma correction companding (MGCC) is proposed that provides a significant reduction in PAPR when compared with existing gamma correction companding and other nonlinear companding methods available in the literature for PAPR reduction. Additionally, with the introduction of $$\gamma $$ and A parameter, the proposed companding can provide more flexibility in PAPR reduction and therefore achieves better trade-offs among PAPR gain, bit error rate (BER) and power spectral density (PSD) levels. MGCC provides an additional immunity from noise by enlarging the small amplitudes of the signal selectively, while subcarriers with the large amplitudes are moderately amplified to reduce PAPR of the signal. Moreover, MGCC improves the BER and PSD performances by minimizing the nonlinear companding distortion. The proposed MGCC improves signal-to-noise ratio (SNR) degradation ( $$\Delta _\mathrm{SNR}$$ ) and total degradation performances by 2.0 and 2.3 dB, respectively, with an input back-off power of 2.5 dB when a practical solid-state power amplifier is considered. Computer simulations reveal that the MGCC can be applied to any modulation scheme and with arbitrary number of subcarriers (N) while it does not increase computational complexity when compared with existing schemes of companding.

A Selected Mapping Technique Using Interleavers for PAPR Reduction in OFDM Systems

In this article, we propose a new selected mapping (SLM) technique using interleavers for reducing high peak-to-average-power ratio (PAPR) in orthogonal frequency division multiplexing systems. The proposed technique can be considered as a modified version of the conventional SLM technique where a set of candidate symbol blocks can be generated from the original symbol block by inserting some pre-known block interleavers between the mapper and the phase rotation multipliers. One of the advantages of this approach is that with very low complex block interleavers the PAPR performance of the SLM scheme can be improved without increasing the number of IFFTs. Simulation results show that the proposed algorithm has better PAPR performance than the conventional SLM for a given number of IFFTs with no additional side information.

Implement PAPR Reduction in OFDM System Using SAS DCT with Companding

OFDM has been adopted as a standard for various high data rate wireless communication systems due to several benefits. One of the major drawbacks in OFDM system is its high Peak-to-Average Power Ratio (PAPR) of its transmitted signals thereby making transmitter amplifier to operate beyond its linear range of operation resulting in signal distortion. In this research work a simple method for reducing Peak-to-Average Power Ratio in OFDM is presented. The method is based on Discrete Cosine Transform (DCT) aided successive addition and subtraction (SAS) of data symbols within a single OFDM frame. Performance of the proposed method is evaluated and compared with the existing techniques. Joint reduction in PAPR by combining SAS preprocessed DCT technique and companding is also presented where system utilizes companding technique to further reduce the PAPR of the OFDM signal. Keywords: OFDM; PAPR; DCT; SAS; CompandingOFDM has been adopted as a standard for various high data rate wireless communication systems due to several benefits. One of the major drawbacks in OFDM system is its high Peak-to-Average Power Ratio (PAPR) of its transmitted signals thereby making transmitter amplifier to operate beyond its linear range of operation resulting in signal distortion. In this research work a simple method for reducing Peak-to-Average Power Ratio in OFDM is presented. The method is based on Discrete Cosine Transform (DCT) aided successive addition and subtraction (SAS) of data symbols within a single OFDM frame. Performance of the proposed method is evaluated and compared with the existing techniques. Joint reduction in PAPR by combining SAS preprocessed DCT technique and companding is also presented where system utilizes companding technique to further reduce the PAPR of the OFDM signal. Keywords: OFDM; PAPR; DCT; SAS; Companding

A modified SLM technique for PAPR reduction in OFDM systems by using a novel phase sequence

ABSTRACTOrthogonal frequency division multiplexing (OFDM) as a basic technique has remarkable influences on communication systems performance. However, the high peak-to-average power ratio (PAPR) of the OFDM signal is its detrimental effect. One of the popular techniques for PAPR reduction is selected mapping (SLM), where an amount of side information (SI) is exchanged undesirably. Swapped SLM (S-SLM) was proposed to reduce the computational complexity of SLM method. In this paper, in order to improve the performance both in terms of PAPR reduction and complexity, we introduce Vandermonde matrix as a novel phase sequence for the S-SLM scheme in OFDM systems, also by using an inter-leaver. In the proposed technique, there is no need to send SI and simulation results show substantial PAPR reduction in comparison with the conventional SLM and S-SLM techniques.

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.

A Low Complexity Tone Reservation Scheme Based on Time-Domain Kernel Matrix for PAPR Reduction in OFDM Systems

The peak-to-average power ratio (PAPR) problem is a main challenge for orthogonal frequency division multiplexing systems. In this paper, the proposed scheme reduces the PAPR with low complexity, by utilizing the time-domain kernel matrix to generate the peak reduction signals. With the time-domain kernel generated only once or offline, there are no IFFT/FFT operations in the peak reduction iterations. Also, we performed simulations and results indicated that the algorithm converges to the threshold in about three iterations, so the hardware complexity and time complexity of this scheme are relatively low to achieve a comparable peak reduction as some other tone reservation schemes.

Invertible Subset LDPC Code for PAPR Reduction in OFDM Systems with Low Complexity

In this paper, we introduce a new family of low-density parity-check (LDPC) codes, called as invertible subset LDPC (IS-LDPC) code, for peak-to-average power ratio (PAPR) reduction in OFDM systems with low complexity. An IS-LDPC code has a number of disjoint invertible subsets, and each invertible subset can be independently inverted to generate other valid codewords of the LDPC code. To construct IS-LDPC codes with good error-correcting performance, we propose a modified progressive edge-growth construction algorithm and verify its effectiveness by analyzing the constructed Tanner graphs. Both theoretical analysis and numerical results show that the IS-LDPC codes exhibit good error-correcting performance and the proposed PAPR reduction scheme based on IS-LDPC codes significantly reduces the PAPR. Compared with the existing coding-based candidate generation schemes, the proposed scheme has a much lower searching complexity when the codeword is transmitted by multiple OFDM symbols. With all mentioned advantages, the proposed PAPR reduction scheme based on IS-LDPC codes could serve as an attractive PAPR reduction solution for future multicarrier communication systems.

PAPR Reduction in OFDM Systems: Polynomial-Based Compressing and Iterative Expanding

In this paper a companding-based scheme is proposed to reduce the Peak-to-average power ratio (PAPR) of an orthogonal frequency division multiplexing system. At the transmitter side, a compressing polynomial function is appended to the inverse discrete Fourier transform block; and at the receiver the transmitted signal is retrieved iteratively through combining the discrete Fourier transform block with a reverse expanding function. In the iterative algorithm the Jacobi's method is used for solving the equations. Also, the general form of the compressing polynomial functions is attained through the use of Daubechies wavelet functions. As an advantage, the proposed method involves less complexity at the transmitter compared to other PAPR reduction methods. Furthermore, it requires less increasing to signal-to-noise ratio for the same bit error rate in comparison with other companding methods. The order of compressing polynomial and the number of iterations for the proposed algorithm at the receiver can be set in accordance with the performance-complexity trade off.

Novel Low-Complexity Partial Transmit Sequences Scheme for PAPR Reduction in OFDM Systems Using Adaptive Differential Evolution Algorithm

A low-complexity partial transmit sequence (PTS) technique for reducing the peak-to-average power ratio (PAPR) of an orthogonal frequency division multiplexing signal is presented. However, the conventional PTS scheme requires an exhaustive searching over all combinations of allowed phase factors. Consequently, the computational complexity increases exponentially with the number of the subblocks. This paper presents a novel approach to the PAPR problem to reduce computational complexity based on the relationship between phase weighing factors and transmitted bit vectors. In this paper, we aim to obtain the desirable PAPR reduction with the low computational complexity. Since the process of searching the optimal phase factors can be categorized as combinatorial optimization with some variables and constraints, we propose a novel scheme, which is based on a stochastic optimization technique called modified differential evolution, to search the optimal combination of phase factors with low complexity. To validate the analytical results, extensive simulations have been conducted, showing that the proposed schemes can achieve significant reduction in computational complexity while keeping good PAPR reduction.

Partial transmit sequence scheme with new phase sequence for PAPR reduction in OFDM systems

One of the effective methods used for reducing peak to average power ratio (PAPR) in OFDM systems is partial transmit sequence (PTS). In the conventional PTS (CPTS) several inverse fast Fourier transform (IFFT) operations and complicated calculation to obtain optimum phase sequence, increase the computational complexity of C-PTS. In this paper, we propose a technique to reduce the number of IFFT operations to half at the expense of a slight PAPR degradation. Simulations are performed with QPSK modulation with OFDM signal and Saleh model power amplifier. The effects of digital predistortion (DPD) to increase the linearity and efficiency of the Saleh model power amplifier (PA) are also examined.

A low complexity partial transmit sequence scheme by use of dummy signals for PAPR reduction in OFDM systems

In this paper a novel technique for reducing the peak to average power ratio (PAPR) in OFDM systems by using the combination of the dummy sequence insertion (DSI) and partial transmit sequence (PTS) is proposed. In DSI increasing the number of dummy sequence decrease the transmission efficiency (TE) and in PTS the complexity increases when the number of subblock increases. Unlike the conventional PTS which needs several inverse fast fourier transform (IFFT) operations, the proposed DSI-PTS technique requires half IFFT operations only, while the PAPR performance is even better. So, it can remarkably reduce the computational complexity. Simulation results are examined with IEEE 802.16-2004 standard. By applying the DSI-PTS method about 0.5 dB reduction in PAPR at complementary cumulative distribution function (CCDF) of 0.01% is achieved compared to the conventional PTS while the complexity is reduced.

Comparisons of SCR and Active-set Methods for PAPR Reduction in OFDM Systems

signal to clipping noise ratio (SCR) and active-set methods are two existing methods for peak-to-average power ratio (PAPR) reduction based on tone reservation. In this paper, the computational complexit ies of these two methods are analyzed and simulation is done for comparing their PAPR-reducing performance . The simulation results show that active-set method requires less computational complexity than that of SCR method while they achieve similar PAPR reduction performance.

NEW PAPR REDUCTION IN OFDM SYSTEMS BY HYBRID ALGORITHM OF PTS AND APPR METHODS

In this paper, we propose a new peak to average power ratio (PAPR) reduction technique by a hybrid algorithm based on a partial transmit sequence (PTS) and adaptive peak power reduction (APPR) methods.