Low Complexity Partial Transmit Sequence Research Articles

A LOW-COMPLEXITY PTS TECHNIQUE–BASED IMPROVED PSO ALGORITHM FOR PAPR REDUCTION IN OFDM SYSTEMS

Partial transmit sequence (PTS) is a potent and distortionless scheme frequently used to lower the high peak-to-average power ratio (PAPR) levels in orthogonal frequency division multiplexing (OFDM) signaling. Although this method effectively reduces the PAPR, its main limitation is the exponential growth in the computational expense caused by the exhaustive search for the optimal complex of rotation factors. This work proposes a suboptimal PTS scheme based on an improved particle swarm optimization (PSO) algorithm. The latter exploits heuristics to find the best-matched weighting factors complex in fewer computations. A comparison against existing techniques ascertains the superior efficiency of the proposed scheme in terms of PAPR mitigation and computational burden.

Low-Complexity PTS Scheme for Improving PAPR Performance of OFDM Systems

Orthogonal frequency division multiplexing (OFDM) has been one of the mainstream technologies in the fields of modern wireless communications. However, its own high peak to average power ratio (PAPR) problem can impair the performance of system, which has greatly restricted its wide applications. Partial transmit sequence (PTS) was proposed for improving the PAPR performance of OFDM systems. But its introduction greatly increases the computational complexity of the system. In this paper, a low-complexity PTS scheme is proposed based on the dominant time-domain samples, and two new metrics for choosing these samples are introduced. In addition, to further reduce the computational complexity, grouping method has been involved in proposed scheme. Simulation results indicate that the proposed low-complexity PTS scheme can provide a perfect PAPR reduction performance with more computational complexity savings.

Low-Complexity Partial Transmit Sequence Methods Using Dominant Time-Domain Samples for Multicarrier Faster-Than-Nyquist Signaling

In Multicarrier faster-than-Nyquist (MFTN) systems, one of the most important problems of MFTN signaling is high peak-to-average power ratio (PAPR). In this paper, partial transmit sequence (PTS) method is adopted to resolve this problem, and we focus on reducing the computational complexity of it. First, the PTS method combined with alternative signal (AS) is introduced to overcome the overlapping structure of MFTN signaling. Then, due to the dominant time-domain samples of MFTN signaling are used, a new metric which can select dominant time-domain samples accurately is proposed. Based on that, two low-complexity PTS methods are proposed. To further reduce the computational complexity, by analyzing the position distribution of sample with peak power, part of the samples are removed from the procedure of calculating metric for selecting dominant time-domain samples. Simulation results confirm that the proposed low-complexity PTS methods can effectively reduce computational complexity without degrading the PAPR reduction performance.

Low-Complexity PTS Scheme for PAPR Reduction in FBMC-OQAM Systems

Most of the peak-to-average power ration (PAPR) reduction techniques, such as partial transmit sequence (PTS) algorithm and selective mapping algorithm, for conventional OFDM systems are not directly applied to filter bank multi-carrier with offset quadrature amplitude modulation (FBMC-OQAM) systems because of the overlapping structure of FBMC-OQAM signals. Furthermore, the complexity of the existing algorithms based on PTS is very high for the FBMC-OQAM systems. In this letter, we propose a low-complexity PTS based on hybrid processing algorithm (H-PTS) to reduce the PAPR values of FBMC-OQAM systems. Firstly, the proposed algorithm processes phase factors of the PTS by double-layer search. As a result, the complexity of searching the optimal phase factors is simplified. Moreover, an efficient algorithm of estimating the PAPR values of the FBMC-OQAM signals is employed to further reduce computational complexity. Simulation results show that, compared with the conventional PTS algorithm and segmental PTS algorithm, the proposed H-PTS algorithm could achieve a better PAPR reduction as well as lower computational complexity.

New PTS Schemes With Adaptive Selection Methods of Dominant Time-Domain Samples in OFDM Systems

In orthogonal frequency division multiplexing (OFDM) systems, high peak-to-average power ratio (PAPR) of OFDM signals is one of the most important problems. As a solution to the PAPR problem in OFDM systems, the partial transmit sequence (PTS) is a fairly suitable scheme due to its PAPR reduction performance and distortionless characteristic. However, high computational complexity is a serious problem in the PTS scheme. In this paper, in an effort to reduce its computational complexity, new PTS schemes are proposed using dominant time-domain samples of OFDM signals. Although the proposed PTS schemes use dominant time-domain samples in a manner similar to several existing low-complexity PTS schemes, we propose more efficient selection methods for dominant time-domain samples. The proposed PTS schemes lower the computational complexity compared to the conventional PTS schemes while achieving the optimal PAPR reduction performance.

A Low Complexity PTS Technique Using Minimal Trellis in OFDM Systems

In this paper, we present a novel algorithm for peak-to-average power ratio (PAPR) reduction of OFDM signals by executing partial transmit sequence (PTS) in minimal trellis of block codes. The proposed method uses a linear code with good minimal trellis to select the transmitted OFDM signal with minimum PAPR and to transmit side information with error correction. The goals of combining strategy of trellis and PTS are twofold: to provide a low complexity PTS for weighting vector search and to highlight error protection capability for side information. Simulation results show that the proposed scheme achieves good PAPR reduction with lower complexity, compared to other PTS approaches.

Low-complexity PTS PAPR reduction scheme for UFMC systems

In this study, a low-computational-complexity partial transmit sequence (PTS) is proposed for reducing peak-to-average power ratios (PAPRs) of universal filtered multi-carriers (UFMCs). First, we analyze the differences in PAPR between a UFMC system and an orthogonal frequency division multiplexing system. Second, we characterize the threshold of the minimum peak power of the UFMC symbol and delete the candidate signal samples with power values below the threshold. This allows for a reduction in the number of time-domain samples that are multiplied by the corresponding phase-rotating vectors; in addition, it can be used for estimating the PAPR. Third, considering the relationship between the phase-weighting sequences, the computational complexity of the candidate signals is simplified. Numerical results show that the proposed PTS scheme achieves nearly the same PAPR reduction as that achieved by the conventional PTS scheme; meanwhile, it has considerably low computational complexity when the probability, $$\beta $$ , of the maximum peak power being more than the possible minimum peak power is greater than or equal to 0.5.

Low-Complexity PTS Schemes Using Dominant Time-Domain Samples in OFDM Systems

Partial transmit sequence (PTS) is a probabilistic peak-to-average power ratio (PAPR) reduction scheme for orthogonal frequency division multiplexing (OFDM) signals, but it requires an exhaustive search for the one with the minimum PAPR over all alternative OFDM signal vectors. In order to reduce such computational complexity, it was proposed that the PAPR value of each alternative OFDM signal vector is approximately estimated by using dominant time-domain samples selected based on a simple metric. In this paper, two new effective metrics for selecting dominant time-domain samples are proposed for low-complexity PTS scheme. For further lowering the computational complexity, two low-complexity PTS schemes are proposed by sorting the dominant time-domain samples in decreasing order of their metric values. Simulation results confirm that compared with the conventional PTS scheme, the proposed PTS schemes show identical PAPR reduction performance with substantially reduced computational complexity.

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

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

N ‐PTS scheme with low complexity for PAPR reduction

Partial transmit sequence (PTS) is a promising technology for peak-to-average power ratio (PAPR) reduction because it introduces no distortion. However, the high computational complexity is the main drawback of PTS scheme. A low-complexity PTS scheme, called N-PTS, is proposed for PAPR reduction. By constructing some sequences, the time-domain signals are obtained by combining the original signal with two circular signals. Thus, only one inverse fast Fourier transform block is required to implement. Analyses and simulation results show that the N-PTS scheme achieves extremely low computational complexity while sacrificing a little bit of performance compared with the conventional PTS.

A novel reduced complexity optimized PTS technique for PAPR reduction in wireless OFDM systems

In this paper, we propose a novel low complexity Partial Transmit Sequence (PTS) technique employing Random phase sequence matrix (RPSM) for peak to average power ratio (PAPR) reduction in orthogonal frequency division multiplexing (OFDM) systems. The main goal of our suggested scheme is to achieve the optimum phase sequence matrix to minimize PAPR and simultaneously reduce the computational complexity by decreasing the number of Inverse Fast Fourier Transform (IFFT) operations required. Lower PAPR reduces the complexity of Digital to Analog converters (DAC) and increases the efficiency of power amplifiers. Analytical expressions for Complementary Cumulative Distribution Function (CCDF), Number of subcarriers, subblocks and Total computational complexity are derived. Simulation results match closely with the analytical results. It is demonstrated that a favorable tradeoff can be achieved between the reduction of PAPR and computational complexity. It is observed that the suggested modified PTS technique outperforms the traditional PTS (T-PTS) technique.

A Comparative Analysis of WiMax System with Partial Transmit Sequence (PTS) and Low Complexity PTS

A Comparative Analysis of WiMax System with Partial Transmit Sequence (PTS) and Low Complexity PTS

Low-Complexity PTS-Based Schemes for PAPR Reduction in SFBC MIMO-OFDM Systems

Multiple-input multiple-output orthogonal frequency division multiplexing (MIMO-OFDM) is an attractive technique for high-data-rate transmission. However, MIMO-OFDM systems have an inherent drawback in that the transmitted signals may suffer from a high peak-to-average power ratio (PAPR). The conventional partial transmit sequences (PTS) scheme can be applied to each transmitting antenna directly to reduce the PAPR of MIMO-OFDM systems, but it has high computational complexity. In this paper, two types of low-complexity PTS schemes are proposed to reduce the PAPR for MIMO-OFDM systems that use space-frequency block coding (SFBC). The two proposed PTS schemes use the sample powers of subblocks to generate cost functions for selecting samples to estimate the peak power of each candidate signal, thus reducing the computational complexity. In addition, for one of the proposed PTS schemes, the similarity of the input signals from the various transmitting antennas is used to further reduce the computational complexity. Simulation results show that, as compared with other related works, the proposed PTS schemes can achieve a reduced PAPR performance and a bit error rate performance close to that of SFBC MIMO-OFDM systems, but at much lower computational cost.

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.

A Low Complexity PTS Scheme Based on Tree for PAPR Reduction

The paper proposes a scheme called T-PTS to reduce the partial transmit sequence (PTS) complexity based on W-way tree. With the nodes in the tree corresponding to phase weighting factors and layers corresponding to subblocks, all the candidates can be calculated by the combination of layers and weighting factors on the paths from the root to the leaves. In each layer, we order the nodes in a 2W period, and set the last W nodes bilateral symmetry with the first W nodes, where only one weighting factor on the paths from root to the neighbor leaves is different. Therefore, all candidate signals can be obtained by adding the difference signal on the last candidate, which can reduce the complexity dramatically. Furthermore, extensive simulations show that the proposed T-PTS does not have performance degradation on the peak-to average power ratio (PAPR).

A New Low-Complexity PTS Scheme Based on Successive Local Search Using Sequences

A new partial transmit sequence (PTS) scheme with low computational complexity is proposed, where two search steps are taken to find a subset of phase rotating vectors showing good peak-to-average power ratio (PAPR) reduction performance. In the first step, sequences with low correlation are used as phase rotating vectors for PTS scheme, which are called the initial phase vectors. In the second step, local search is performed based on the initial phase vectors to find additional phase rotating vectors which show good PAPR reduction performance. Numerical analysis shows that the proposed PTS scheme achieves better PAPR reduction performance with significantly reduced computational complexity than the existing low-complexity PTS schemes.

Low Complexity Partial Transmit Sequence with Complex Gain Memory Predistortion in OFDM Systems

In this paper the peak to average power ratio (PAPR) reduction and digital predistortion effects in orthogonal frequency division multiplexing (OFDM) systems are investigated. By applying a predistortion technique called complex gain memory predistortion (CGMP), power amplifier works at higher power efficiency. The proposed enhanced partial transmit sequence scheme is applied for PAPR reduction and integration with CGMP technique results in increasing in OFDM system efficiency and prolonged battery life. Simulation and results are examined with actual power amplifier and OFDM signal with quadrature phase shift keying (QPSK) modulation.

PAPR Reduction Using Low Complexity PTS to Construct of OFDM Signals Without Side Information

Partial transmit sequence (PTS) is one of the most well-known peak-to-average power ratio (PAPR) reduction techniques proposed for orthogonal frequency-division multiplexing (OFDM) systems. The main drawbacks of the conventional PTS (C-PTS) are high computational complexity and transmission of several side information bits. A new PTS with simple detector is proposed in this paper to deal with these drawbacks of C-PTS. The candidates can be generated through cyclically shifting each sub-block sequence in time domain and combining them in a recursive manner. At the receiver, by utilizing the natural diversity of phase constellation for different candidates, the detector can successfully recover the original signal without side information. Numerical simulation shows that the proposed scheme performs very well in terms of PAPR. The probability of detection failure of the side information demonstrates that the detector could work without any side information with high reliability. The proposed scheme achieves almost the same bit error rate (BER) performance as the C-PTS with perfect side information, under both additive white Gaussian noise (AWGN) channel and Rayleigh fading channel.

Low-Complexity SLM and PTS Schemes for PAPR Reduction in OFDM Systems

One major drawback of orthogonal frequency-division multiplexing is the high peak-to-average power ratio (PAPR) of the output signal. The selected mapping (SLM) and partial transmit sequences (PTS) methods are two promising techniques for PAPR reduction. However, to generate a set of candidate signals, these techniques need a bank of inverse fast Fourier transforms (IFFT's) and thus require high computational complexity. In this paper, we propose two low-complexity multiplication-free conversion processes to replace the IFFT's in the SLM method, where each conversion process for an N-point IFFT involves only 3N complex additions. Using these proposed conversions, we develop several new SLM schemes and a combined SLM & PTS method, in which at least half of the IFFT blocks are reduced. Computer simulation results show that, compared to the conventional methods, these new schemes have approximately the same PAPR reduction performance under the same number of candidate signals for transmission selection.

A Class of Low Complexity PTS Techniques for PAPR Reduction in OFDM Systems

This letter presents a class of low complexity partial transmit sequence (LC-PTS) techniques for reducing the peak-to- average power ratio (PAPR) in orthogonal frequency division multiplexing (OFDM) systems. The basic principle is to analyze and utilize the correlation among the candidate signals generated in PTS, so as to simplify the computational complexity. Furthermore, the proposed technique focuses on simplifying the computation for each candidate signal, instead of reducing the total number of candidate signals such as in (Jayalath and Tellambura, 2000). Thus, it can be easily combined with other simplified techniques. Simulation results show that the new technique can effectively reduce the complexity compared with the conventional PTS scheme.