Peak-to-average Power Ratio Mitigation 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 hybrid SLM for PAPR mitigation for ACO OFDM

The high peak to average power ratio (PAPR) is the main challenge facing asymmetrically clipped optical (ACO) orthogonal frequency division multiplexing (OFDM). We propose a new hybrid technique that incorporates a modified selective mapping (SLM) and companding called low complexity hybrid selective mapping (LCHSLM) for PAPR mitigation in ACO OFDM systems. It is demonstrated through computer simulations that our proposed system significantly reduces the PAPR compared with the conventional SLM or companding alone. In addition, LCHSLM achieves a significant reduction in complexity compared with conventional SLM without bit error rate (BER) degradation.

Joint security enhancement and PAPR mitigation for OFDM-NOMA VLC systems

Security is of crucial importance to visible light communication (VLC) systems. In this paper, we propose and experimentally demonstrate a secure non-orthogonal multiple access (NOMA) VLC system with orthogonal frequency division multiplexing (OFDM) modulation, where the peak-to-average power ratio (PAPR) is also significantly reduced. Based on 2D chaotic map, the public key serves a two-fold purpose: to provide physical-layer security against eavesdropper, and to generate a set of phase-rotated candidate signals in the chaotic selected mapping (SLM) scheme where the signal with lowest PAPR is selected for transmission. The private keys further enhance the security and guarantee the privacy among the legitimate users via chaotic data scrambling. The experiment based on a direct current-biased optical OFDM (DCO-OFDM) VLC system with two legitimate users and one eavesdropper successfully verified the joint security enhancement and PAPR mitigation performance of the proposed scheme for NOMA VLC application.

Peak to average power ratio alleviation by utilizing swarm intelligence along with machine learning for multiple input multiple output‐orthogonal frequency division multiplexing based underwater acoustic communication system

AbstractAn underwater acoustic (UWA) network uses multiple input multiple output‐orthogonal frequency division multiplexing (MIMO‐OFDM) to achieve high data rate with high amplitude that results in terms of augmented peak to average power ratio (PAPR). This significant PAPR deemed as a stumbling block to degrade the performance of MIMO‐OFDM in UWA communication by causing nonlinear distortion within the high‐power amplifier (HPA). While PAPR mitigation techniques have been suggested for the single input single output UWA case, there has been limited research work on controlling the PAPR dilemma in the MIMO‐OFDM UWA case. To address this flaw, this article proposes a modified behavior of the artificial bee colony algorithm at the transmission end, which is further cross‐verified using machine learning techniques. The simulation results show that the proposed technique outperforms current state‐of‐the‐art PAPR diminishing methods, which is further enhanced in accordance with varying neuron counts and population size. Following that, we also analyzed and compared energy efficiency and performance gain of our proposed technique along with various advanced techniques. Furthermore, a desirable ratio between new and trained data was obtained to improve network efficiency by keeping PAPR values low.

New scheme for PAPR reduction in FBMC-OQAM systems based on combining TR and deep clipping techniques

Filter bank multi-carrier with offset quadrature amplitude modulation (FBMC-OQAM) system is a very efficient multicarrier modulation technique for 5G, but it suffers as all multicarriers designs from large peak-to-average power ratio (PAPR). Tone reservation (TR) is a method designed to solve this problem by reserving several subcarriers called tones in the frequency domain to generate a cancellation signal in the time domain to eliminate high peaks. In this paper, we suggest a serial combination of tone reservation (TR) method with an enhanced version of clipping called deep clipping (DC) method (TR&DC) to enhance the peaks (PAPR) mitigation in FBMC-OQAM signal model without significantly impacting the quality of transmission. Numerical results and analysis show that the new TR&DC approach allows better overall performance and offers remarkable gain in term of PAPR mitigation than the TR method, with similar BER performance to TR over additive white gaussian noise channel and Rapp HPA model.

Latency-efficient code-division multiplexing (CDM) based carrier aggregation for 5G NR mobile fronthaul

We propose and experimentally verify a latency-efficient code-division multiplexing (CDM) based carrier aggregation (CA) scheme with simultaneous mitigation of peak-to-average power ratio (PAPR), for the scenario of 5G new radio (NR) mobile fronthaul (MFH). We utilize the least squares approximation (LSA) algorithm to reduce 36% number of iterations for achieving the same PAPR mitigation, in comparison with the traditional CDM based CA scheme. Finally, we experimentally demonstrate the proof-of-concept transmission of 16×100 MHz 5G NR signals mapped with 64 quadrature amplitude modulation (QAM) having the common public radio interface (CPRI) equivalent date rate of 78.6 Gb/s, based on the use of a directly modulated laser (DML). After 10 km standard single mode fiber (SSMF) transmission, we can secure both the latency reduction of CA processing and the PAPR mitigation with almost no penalty of receiver sensitivity.

Performance enhancement of LED-based indoor OFDM-VLC system using digital chaotic scheme

LED based visible light communication (VLC) has become a feasible technology for indoor high-speed access networks. Optical orthogonal frequency division multiplexing (O-OFDM) with high spectrum efficiency is often used to increase the data rate to overcome the limited bandwidth of LEDs. Due to the LED nonlinearity and high peak-to-average-power ratio (PAPR) of OFDM, the indoor broadcasting OFDM-VLC system suffers from not only the performance deterioration, but also the security issue. In this paper, we propose to use digital chaotic sequence pilot-assisted (CSPA) scheme to jointly improve the signal-to-noise-ratio (SNR) performance and the system security. The experimental results indicate that the proposed method can achieve 3 dB PAPR mitigation even up for OFDM 64-QAM signal and 2 dB SNR improvement. Meanwhile, the proposed digital CS offers a key space of ∼10106 for each OFDM symbol to guarantee the secure transmission.

A New Subblock Segmentation Scheme in Partial Transmit Sequence for Reducing PAPR Value in OFDM Systems

Partial transmit sequence (PTS) is considered an efficient algorithm to alleviate the high peak-to-average power ratio (PAPR) in orthogonal frequency division multiplexing (OFDM) systems. The PTS technique is depended on the partitioning the input data sequence into the several subblocks, and then weighting these subblocks with a group of the phase factors. There are three common types of partitioning schemes: interleaving scheme (IL-PTS), adjacent scheme (Ad-PTS), and pseudo-random scheme (PR-PTS). The three conventional partitioning schemes have various performances of the PAPR value and the computational complexity pattern which are considered the main problems of the OFDM system. In this paper, the three ordinary partition schemes are analyzed and discussed depending on the capability of reducing the PAPR value and the computational complexity. Furthermore, new partitioning scheme is introduced in order to improve the PAPR reduction performance. The simulation results indicated that the PR-PTS scheme could achieve the superiority in PAPR mitigation compared with the rest of the schemes at the expense of increasing the computational complexity. Furthermore, the new segmentation scheme improved the PAPR reduction performance better than that the Ad-PTS and IL-PTS schemes.

A novel method for joint- PAPR mitigation in OFDM-based massive MIMO downlink systems

Massive MIMO has gained much attention with the increase in the high speed data communication. The problem of peak-to-average power ratio (PAPR) is considered, the detrimental aspects in OFDM based massive multiple-input multiple-output (MIMO) downlink systems. The previous works done in reduction of PAPR problem using convex optimization are computationally inefficient. We considered Bayesian approach to mitigate PAPR by utilizing the redundant degrees of freedom (DOF) of the transmit array, which effectively reduced the level of PAPR. The performance or numerical results indicate the applied algorithm achieved a good improvement over the existing techniques in terms of the PAPR reduction.

A low PAPR multicarrier and multiple access schemes for VLC

The omnipresence of solid-state illuminating devices like Light Emitting Diodes (LEDs) has driven Visible Light Communication (VLC) to acquire mammoth eminence. However, the limited dynamic range of LEDs leads to deleterious non-linear distortion when employing the high data rate multicarrier modulation technique like optical orthogonal frequency division multiplexing (OOFDM) resulting in high Peak to Average Power Ratio (PAPR). Furthermore, since VLC has profound applicability in a cellular network, there is an urge to investigate different PAPR mitigation techniques. In this paper, Discrete Cosine Transform-Spread-Fast-Optical OFDM (DCT-S-FOOFDM) is proposed and compared with other PAPR reduction schemes like Partial Transmit Sequence (PTS), clipping and filtering techniques. This work focuses on imparting Discrete Fourier Transform (DFT)-spreading for Optical Orthogonal Frequency Division Multiple Access (OOFDMA) and DCT-spreading for Fast Optical Orthogonal Frequency Division Multiple Access (FOOFDMA) system to reduce PAPR. Here, an elaborate mathematical analysis of the time-domain signal is accomplished for Asymmetrically clipped DC biased-Optical-Interleaved FDMA (ADO-IFDMA), Asymmetrically clipped-Optical-Localized FDMA (ACO-LFDMA), Fast-Optical-IFDMA (F-O-IFDMA) and Fast-Optical-LFDMA (F-O-LFDMA). The simulated result analysis emphasizes that PAPR is reduced significantly by employing DCT-Spreading in FOOFDM. Among the multiple access schemes, PAPR reduction in F-O-IFDMA is superior than F-O-LFDMA and outperforms FOOFDMA.

A low PAPR performance with new segmentation schemes of partial transmit sequence for OFDM systems

Despite the fact that OFDM has numerous features, the high peak-to-average power ratio (PAPR) deems one of the challenging disadvantages face by the system in the real applications. The high PAPR limits the OFDM signal efficiency on the transmitter side. Thus many PAPR alleviation approaches have been suggested in the past. Partial transmit sequences (PTS) has been accounted as one of the successful procedures for decreasing the high PAPR; with the consideration that the computational complexity of the PTS method regarded high relatively. Moreover, improving the PAPR mitigation performance of the PTS algorithm relies upon the number of the partitioned subblocks, the number of the phase rotation vectors, and the kind of the segmentation scheme utilized. This article presents new segmentation schemes to enhance the PAPR mitigation execution without further intricacy on the system. Adjacent shifting segmentation scheme (Ad-Sh-PTS) and rows exchange of interleaving segmentation schemes (IL-Ex-PTS) are proposed depending on the two well-known segmentation schemes of adjacent partition PTS (Ad-PTS) and interleaving partition PTS (IL-PTS). The simulation demonstrates that the suggested algorithms can accomplish mitigation in PAPR preferable compared to the traditional schemes, Ad-PTS and IL-PTS schemes.

ISI and PAPR Immune IEEE 802.11p Channels Based on Single-Carrier Frequency Domain Equalizer

Doppler Effect is a prominent obstacle in vehicular networks, which dramatically increase the Bit-Error-Rate (BER). This problem is accompanied with the presence of the Orthogonal Frequency Division Multiplexing (OFDM) systems in which the Doppler shift interrupts the subcarriers orthogonality. Additionally, Inter-Symbol Interference (ISI) and high Peak-to-Average Power Ratio (PAPR) are likely to occur which corrupt the received signal. In this paper, the single-carrier combined with the frequency domain equalizer (SC-FDE) is utilized as an alternative to the OFDM over the IEEE 802.11p uplink vehicular channels. The Minimum Mean Squared Error (MMSE) and Zero-Forcing (ZF) are employed in order to study the impact of these equalization techniques along with the SC-FDE on the propagation medium. In addition, we aim to enhance the BER, improve the transmitted signal quality and achieve ISI and PAPR mitigation. The proposed schemes are investigated and we found that the MMSE outperforms the ZF equalization under different Doppler shift effects and modulations.

Modeling and compensation of transmitter nonlinearity in coherent optical OFDM

We present a comprehensive study of nonlinear distortions from an optical OFDM transmitter. Nonlinearities are introduced by the combination of effects from the digital-to-analog converter (DAC), electrical power amplifier (PA) and optical modulator in the presence of high peak-to-average power ratio (PAPR). We introduce parameters to quantify the transmitter nonlinearity. High input backoff avoids OFDM signal compression from the PA, but incurs high penalties in power efficiency. At low input backoff, common PAPR reduction techniques are not effective in suppressing the PA nonlinear distortion. A bit error distribution investigation shows a technique combining nonlinear predistortion with PAPR mitigation could achieve good power efficiency by allowing low input backoff. We use training symbols to extract the transmitter nonlinear function. We show that piecewise linear interpolation (PLI) leads to an accurate transmitter nonlinearity characterization. We derive a semi-analytical solution for bit error rate (BER) that validates the PLI approximation accurately captures transmitter nonlinearity. The inverse of the PLI estimate of the nonlinear function is used as a predistorter to suppress transmitter nonlinearity. We investigate performance of the proposed scheme by Monte Carlo simulations. Our simulations show that when DAC resolution is more than 4 bits, BER below forward error correction limit of 3.8 × 10(-3) can be achieved by using predistortion with very low input power backoff for electrical PA and optical modulator.

PAPR Analysis and Mitigation Algorithms for Beamforming MIMO OFDM Systems

Beamforming (or precoding) techniques have been widely adopted in modern MIMO OFDM systems. Using beamforming can significantly improve the receive SNR of OFDM systems. However, the combination of transmit signals after beamforming deteriorates the peak-to-average power ratio (PAPR), which has long been considered a major issue of OFDM systems. High PAPR not only complicates the design of the power amplifier, but also increases power consumption. In this paper, we theoretically analyze the PAPR performance of MIMO OFDM systems that adopt either one of the two popular beamforming schemes, i.e. MRT (maximum ratio transmission) and EGT (equal gain transmission). The analysis considers different numbers of channel taps after sampling. The results may provide important reference for practical designs when evaluating the required power amplifiers and power consumption. Moreover, the theoretical results show that MRT OFDM systems generally perform much worse than EGT OFDM systems in terms of PAPR. Furthermore, motivated from the derived results, PAPR reduction algorithms are proposed for both MRT OFDM and EGT OFDM systems. It is worth to mention that for MRT OFDM systems, the proposed algorithm can improve both PAPR and bit error rate; for EGT OFDM systems, the proposed algorithm improves PAPR while it only slightly degrades bit error rate.

PAPR Reduction Scheme with SOCP for MIMO-OFDM Systems

Combination of multiple-input multiple-output (MIMO) with orthogonal frequency division multiplexing (OFDM) has become a promising candidate for high performance wireless communications. However one major disadvantage of MIMO-OFDM systems lies in a prohibitively large peak-to-average power ratio (PAPR) of the transmitted signal on each antenna. In this paper we extend from SISO to MIMO systems a method based on allocating dedicated subcarriers for PAPR mitigation. These subcarriers are located on unused subcarriers of OFDM spectrum under the assumption they all fall under the power mask. This is originally implemented with a SOCP optimization algorithm applied before space time coding scheme. This jointly mitigates PAPR on each MIMO branch scheme. This approach does not degrade the bit-error-rate (BER) and the data bit rate and no side information (SI) transmission is required. Simulation results are presented in the IEEE 802.16 WiMAX standard contexts: an Alamouti space time code with two transmitted antennas and 256 OFDM subcarriers are considered where 56 of which are unused and allocated for PAPR reduction. PAPR gains up to 7dB are obtained depending on mean power increase limitation. Moreover, with a spectrum mask constraint, this method is standard compliant.