Peak-to-average Power Ratio Of Signal Research Articles

Joint PAPR reduction with channel estimation for OFDM-based VLC systems

Abstract This paper presents a new combination of channel estimation (CE) methods and peak-to-average power ratio (PAPR) reduction techniques for orthogonal frequency division multiplexing (OFDM)-based visible light communication (VLC) systems. We first propose iterative clipping and filtering to minimize the PAPR of optical OFDM signals. Then, we introduce a computationally efficient, high-performance channel estimation approach using block-type pilots with modified clipped signals. The proposed method integrates clipping with three distinct CE techniques, resulting in both significant PAPR reduction and enhanced bit error rate (BER) performance. Among the CE methods evaluated, the expectation-maximization (EM) technique provides better BER results compared to other approaches. Simulation results confirm that the combined use of clipping and advanced CE methods leads to notable improvements in PAPR reduction and BER performance for OFDM-based VLC systems.

A novel SLM scheme for peak-to-average power ratio reduction in WOLA-OFDM system

This paper addresses high peak-to-average power ratio (PAPR) issue in the recently invented weighted overlap and add-orthogonal frequency division multiplexing (WOLA-OFDM) system. The selective mapping (SLM), one of the most widely used PAPR reduction schemes in OFDM-based multicarrier transmission strategies, can be used to reduce the PAPR of WOLA-OFDM signals. However, the overlapping of symbol extensions in the WOLA-OFDM transmitter considerably deteriorates the performance of SLM. To overcome this problem, we have developed an efficient SLM scheme named dual symbol optimization-SLM (DSO-SLM) for the WOLA-OFDM system. In this new scheme, instead of reducing the PAPR of adjacent symbols separately as in conventional SLM, each symbol is evaluated together with its overlapping predecessor symbol while searching for the optimal transmission signal with minimized PAPR. With the usage of DSO procedure, it becomes possible to enhance the performance of conventional SLM in the WOLA-OFDM system.

Two-stage collaborative information interaction reliability improvement for the distribution grid

The impulse noise generated by a large volume of power electronics devices imposes a hazardous impact on information interaction reliability in low-voltage distribution grids. In this paper, we propose a two-stage collaborative information interaction reliability improvement algorithm to minimize the bit error rate (BER) of the information interaction under impulse noise. In the first stage, the transmission-side peak-to-average power ratio (PAPR) is reduced based on the adaptive particle swarm optimization (PSO)-enabled partial transmit sequence (PTS). In the second stage, the reception-side dual-signal blanking is proposed based on the transmission-side PAPR and reception-side useful signal power estimation and peak median ratio. The transmission–reception collaborative information interaction reliability improvement is realized through two aspects. First, transmission-side PAPR reduction improves the performance of reception-side signal blanking by making it easier to distinguish useful signals from impulse noise. Second, the transmission-side PAPR is utilized to improve the estimation accuracy of both coarse and precise thresholds in dual-signal blanking. Simulation results show that the proposed algorithm outperforms existing algorithms in both PAPR reduction and BER performances to achieve information interaction reliability improvement effectively.

A mathematical analysis of the PAPR in the NOMA waveform using SLM algorithm for 64-QAM

In Non-Orthogonal Multiple Access (NOMA) technology, a paradigm shift in wireless communication is observed, as it allows numerous users to simultaneously transmit data over the same spectral resources in a non-orthogonal manner. Despite the advancements it brings to the table, NOMA is faced with a notable technical obstacle, that being the elevated Peak-to-Average Power Ratio (PAPR). Elevated PAPR levels can lead to less efficient use of power and a deterioration in the fidelity of the signal. We proposed a Selective Mapping (SLM) as a powerful solution to address this issue. SLM is a PAPR reduction technique that applies controlled phase rotations to the symbols of different users before transmission, aiming to minimize the PAPR of the combined signal. In the context of NOMA, the application of SLM offers several notable advantages. SLM modifies the Power Spectrum Density (PSD), leading to a more uniform and spectrally efficient power distribution over the frequency spectrum. This enhancement in spectral efficiency concurrently lowers the risk of disrupting nearby frequency channels. Moreover, SLM exerts a favorable influence on the Bit Error Rate (BER) in NOMA systems, which contributes to improved transmission accuracy. Utilizing SLM to achieve lower PAPR values significantly diminishes the probability of symbol errors, thus enhancing the dependability. Additionally, it has been observed that the method in question delivers an improvement in PAPR, BER, and PSD with gains of 2.2 dB, 4 dB, and -620 respectively, in comparison to traditional SLM techniques.

PEAK-TO-AVERAGE POWER RATIO OF SPECTRALLY EFFICIENT FDM SIGNALS

The change of the number of subcarriers in SEFDM signal from 5 to 1024 leads to the growth of the PAPR (peak-to-average power ratio) from 4.5 to 9 dB. PAPR of SEFDM signals stays about constant (instability is no more than 5%) while normalized subcarriers frequency spacing increase from 1/2 to 1. It indicates no additional energy loss during the transition from OFDM signals to SEFDM signals, caused by an increase in the PAPR. It is proposed to use a part of the resulting gain in the frequency band to reduce PAPR. The method, based on modification of Tone Insertion method, was developed. Developed method consists in adding additional subcarriers with randomly generated manipulation symbols to the SEFDM signal. SEFDM symbol with minimal PAPR is chosen to be send. According to this method the PAPR can be reduced in average of 1.4 dB. The degree of reduction of the PAPR depends on the size of the channel alphabet of additional subcarriers (changing of the average win is 0.6 dB for BPSK to 1.4 dB for QAM-64) and the number of combinations of symbols of additional subcarriers (1.6 dB for 1000 combinations for QAM-64). According to estimation of the FPGA resources for implementation of PAPR reduction algorithm it is required relatively small resource costs compared to the formation of SEFDM signal without reduction.

Symbol interferometry and companding transform for PAPR reduction of OTFS signal

AbstractThis paper presents methods for reducing the peak‐to‐average power ratio (PAPR) of the orthogonal time frequency space (OTFS) signal. These methods mainly consist of two operations: symbol interferometry (SI) and either ‐law or ‐law companding. SI spreads the data of one OTFS symbol onto all symbols and is implemented using a simple inverse fast Fourier transform operation on each OTFS symbol. During the second operation, the PAPR of the OTFS signal is significantly reduced. For our performance analysis, the complementary cumulative distribution function, probability density function, and bit error rate are illustrated through simulations performed in MATLAB. The performance is also analyzed using a solid‐state power amplifier at the transmitter and compared with OTFS, ‐law‐based OTFS, and SI OTFS systems. The results indicate that the proposed OTFS system achieves a low PAPR.

Improved PAPR Reduction Technique in 5G Systems: Addressing Limitations and Challenges with Computational Techniques

A high peak-to-average power ratio (PAPR) in the Orthogonal Frequency Division Multiplexing (OFDM) system reduces the efficiency of the power amplifier (PA) at the transmitter. This flaw lowers the efficiency of the OFDM system overall and results in excessive energy usage. The OFDM signal is preprocessed to lower its peak power before transmission in order to address this problem. For 4G and 5G waveforms, we investigate several crest-factor reduction (CFR) approaches in this work. We emphasize the importance of processing OFDM signals before transmission in order to address the significant PAPR issue. In-depth analysis of the CFR technique known as "clipping," which is frequently utilized in real-time applications, is conducted. We go over the difficulties brought on by the high PAPR of OFDM signals and how they affect power amplifier effectiveness. We evaluate the suggested PAPR reduction technique's performance in terms of PAPR reduction capability, signal distortion, computational overhead, and bit error rate (BER) using simulation models and MATLAB-based evaluations. We contrast the efficiency of our suggested method with the PAPR reduction strategies currently in use, such as the partial transmit sequence (PTS), selected mapping (SLM), and crest factor reduction (CFR) methods. Additionally, we confirm the suggested method using a hardware testbed, highlighting its usefulness in actual 5G systems. Additionally, we assess the suggested method's ability to lower the cost and complexity of hardware design for 5G systems in order to assess the economic benefits.

Time-Frequency Domain Non-Orthogonal Multiple Access for Power Efficient Communications

We propose a power efficient non-orthogonal multiple access (NOMA) scheme suitable for Internet of Things (IoT) and device-to-device (D2D) communications. OFDM-based power-domain NOMA (PD-NOMA) is one of the promising approaches to achieve simultaneous connections of massive devices. Nevertheless, the problem of high peak-to-average power ratio (PAPR) is a major challenge, since power amplifier (PA) efficiency is a critical factor for IoT and D2D devices consisting of low-cost hardware components. This paper overcomes this problem by introducing time-frequency domain NOMA (TF-NOMA), where OFDM and DFT-spread OFDM (DFT-s-OFDM) are superposed over the time-frequency domain. By utilizing the low PAPR property achieved by DFT-precoding, TF-NOMA can efficiently reduce the PAPR of the downlink signal transmitted by the base station (BS) as well as the uplink signals of the devices located far from BS. As a result, the proposed TF-NOMA can operate with higher PA efficiency than the conventional OFDM-based PD-NOMA. Furthermore, the insertion of DFT-precoding with the aim of PAPR reduction also enhances the error propagation resistance due to the resulting Gaussian mixture signal property. Throughout the mathematical analysis and computer simulations, we demonstrate that TF-NOMA achieves better error rate performance than the conventional PD-NOMA with significant improvement of PA efficiency.

A powerful PTS strategy boosted by a novel discrete crow search algorithm for reducing the PAPR of UFMC signals

Abstract As being one of the main waveform candidates developed for meeting the demands of fifth generation (5G) and beyond telecommunication technologies, universal filtered multicarrier (UFMC) has various appealing features contributing to overcome many obstacles in wireless communication. However, due to the usage of multiple subcarriers, UFMC signals suffer from having high peak-to-average power ratio (PAPR), which has to be kept at low level to prevent the communication quality from being deteriorated. To overcome the problem of high PAPR in the UFMC signals, an advanced version of partial transmit sequence (PTS) was created for PAPR alleviation by integrating an intelligent optimization algorithm in place of its random phase generator. To this end, crow search algorithm (CSA) was utilized. Initially, its novel discrete version called DCSA was developed to make it suitable to be employed in phase sequence optimization, which is a type of combinatorial optimization problem to be solved in discrete space. After the integration of DCSA into the conventional PTS, an advanced PTS variant named DCSA-PTS was created for the UFMC. Optimizing the phase sequences via the DCSA instead of generating them in a random way enhances the performance of PTS scheme. Thanks to the DCSA-based phase optimization, it becomes possible to attain better phase combinations in smaller number of searches. The advantage of using DCSA as a phase optimizer is supported by the simulation results. Due to the superior phase optimization performance of our novel DCSA, the proposed DCSA-PTS strategy clearly outperforms the other schemes considered in this paper.

Multi-antennas PAPR Reduction for FBMC/OQAM System

Background: The filter bank multicarrier (FBMC) with offset quadrature amplitude modulation (OQAM) is a promising future generation of wireless systems. However, like multicarrier modulations (MCM), FBMC/OQAM has a high peak-to-average power ratio (PAPR), which allows the FBMC/OQAM signal to pass through the nonlinear region of the high-power amplifier (HPA) in the time domain and causes in-band and out of band (OOB) distortion. Methods: In this paper, a new method to overcome this problem called multi-antennas PAPR (MAP) reduction is proposed. It consists of using I antennas in transmission and reception to transmit I FBMC/OQAM sub-signals with low PAPR. The complementary cumulative distribution function (CCDF), the bit error rate (BER), and the energy efficiency are used to evaluate the method's performance. Results: The simulation results showed that the new technique can reduce the PAPR of the original signal by more than half, achieve BER comparable to that of the original signal without HPA, and when the input back-off (IBO) equals 3dB, the error vector magnitude (EVM) result can be reduced from 19% to 7%. Conclusion: The PAPR, BER, and EVM of MAP technique are much better than the original system.

Optimized intensity-modulated type PTS-based PAPR reduction scheme for intensity-modulated direct-detection optical OFDM systems.

High peak-to-average power ratio (PAPR) of the signal is a major drawback in optical orthogonal frequency division multiplexing (OFDM) system. In this paper, an intensity-modulated type Partial Transmit Sequences (PTS) based scheme is proposed and applied to the intensity-modulated OFDM (IMDD-OFDM) system. The proposed intensity-modulated type PTS (IM-PTS) scheme ensures that the time-domain signal output by the algorithm is real value. What's more, the complexity of the IM-PTS scheme has been reduced without much performance penalty. A simulation is performed to compare the PAPR of different signal. In the simulation, the PAPR of OFDM signal is reduced from 14.5 dB to 9.4 dB at 10-4 probability. We also compare the simulation results with another algorithm based on the PTS principle. A transmission experiment is conducted in a seven-core fiber IMDD-OFDM system at a rate of 100.8Gbit/s. The Error Vector Magnitude (EVM) of received signal is reduced from 9 to 8 at -9.4dBm received optical power. Furthermore, the experiment result shows that the reduction of complexity has little performance impact. The optimized intensity-modulated type PTS (O-IM-PTS) scheme effectively increases the tolerance of the nonlinear effect of the optical fiber and reduces the requirement for linear operating range of optical device in the transmission system. During the upgrade process of the access network, there is no need to replace the optical device in the communication system. What's more, the complexity of PTS algorithm has been reduced, which lower data processing performance requirements of the devices such as ONU and OLT. As a result, the cost of network upgrades is reduced a lot.

A novel PAPR reduction method for hybrid beamforming transmitter

In orthogonal frequency division multiplexing (OFDM) systems, peak-to-average power ratio (PAPR) is one of the major factors that affect the power efficiency of transmitter. There exist many PAPR reduction methods for the conventional fully digital multiple-input multiple-output (MIMO) systems but there is little discussion on the PAPR reduction for the hybrid beamforming systems. When some output signals of the digital to analogue converter (DAC) are combined by the analogue beamforming network before power amplifier (PA), the one to one mapping between the digital signal and the signal passing through PAs is destroyed. In such hybrid beamforming architectures, the existing methods can only reduce the PAPR of DAC input signal but not PAPR of PA input signal. In this paper, we investigate whether and how we can extend existing PAPR reduction methods to the hybrid beamforming systems. We propose a novel PAPR reduction method, which extends the iteratively clipping and filtering (ICF) to the hybrid beamforming systems. To the best of our knowledge, our proposed algorithm is the first PAPR reduction algorithm dedicated for the hybrid beamforming systems. From the simulation, our proposed algorithm can achieve a smaller PAPR than the improved selective mapping (SLM) algorithm at the cost of minor signal distortion.

Low complexity partition-recombined SLM scheme for reducing PAPR in coherent optical OFDM systems

High peak-to-average power ratio (PAPR) remains the main challenge of coherent optical orthogonal frequency division multiplexing (CO-OFDM) systems. Selective mapping (SLM) is a well-known effective PAPR reduction technique, but it suffers from high computational complexity. To reduce the PAPR of OFDM signals, a low-complexity, partition-recombined SLM (PRSLM) scheme is proposed. The PRSLM scheme can generate more candidate signals than that of the conventional-original SLM (COSLM) scheme. The real and imaginary components of time-domain symbols are first partitioned, and then recombined to generate new candidate signals, which reduces computational complexity significantly. A 40-GBaud single-polarization CO-OFDM transmission system is set up to evaluate the performance of the PRSLM scheme. Simulation results show that the proposed scheme achieves 61.9% reduction in complex multiplication complexity, and 60.3% reduction in addition complexity compared with the COSLM scheme when the FFT size is 128. Furthermore, the proposed scheme achieves a similar PAPR reduction performance to the COSLM scheme without bit error rate degradation. In a nutshell, the PRSLM scheme improves noise tolerance and implementation efficiency of high-speed optical communication as well as alleviates nonlinear impairments.

PAPR Reduction of OFDM with DFT Spreading Method

Future communication systems will demand the transmission of huge amounts of data, therefore will require a highly linear power amplifier. The Orthogonal Frequency Division Multiplexing (OFDM) technique is widely used in multimedia services for providing high data rates and providing high Quality of Service. The transmitter power amplifier's range of operation in a communication system is linear. Signal distortion happens when the input signal's amplitude exceeds the linear range of the transmitter power amplifier. Therefore, the transmitter's input signal has to have a low peak to average power ratio (PAPR). The OFDM system has been recognized as the high rate wireless radio channel transmission. Therefore, it will also be highly beneficial for the high-speed communication system. However, due to the extremely high PAPR issue, using the OFDM system in a communication system is not simple. It results in extremely low power efficiency. Therefore, it is crucial to lower the PAPR in the OFDM system in order to employ it in the communication system. By using a discrete Fourier matrix, the Discrete Fourier Transform spreading strategy may significantly lower the PAPR of an OFDM signal. This paper describes the PAPR reduction approach in OFDM signals and examines the effectiveness of OFDM.

Analysis of Compressing PAPR-Reduced OFDM IQ Samples for Cloud Radio Access Network

A common problem of the virtualized cloud radio access network architecture (C-RAN) is the compression of the time-domain IQ samples before transmission over the fronthaul link. Considering a multicarrier waveform such as OFDM, whose IQ samples follow a quasi-Gaussian distribution, the conventional Gaussian quantizer may be used as the optimal solution to the compression problem. However, since the high peak-to-average power ratio (PAPR) of OFDM signals remains a serious problem, various techniques may be employed to reduce the time-domain fluctuations of the IQ samples in the OFDM, resulting in a change in its distribution. The latter fact makes the Gaussian quantizer suboptimal. The literature lacks a performance analysis of the conventional OFDM-based compression techniques when the PAPR of the OFDM signal is reduced. Therefore, in this paper, we study for the first time the impact of reducing the PAPR of the OFDM signal before compression in the C-RAN architecture through rate-distortion analysis. We consider clipping and tone reservation PAPR reduction algorithms. The former is the simplest PAPR reduction approach, while the latter is one of the most effective algorithms used in broadcasting standards such as DVB-T2 and ATSC 3.0. We first derive the distribution of the PAPR-reduced OFDM IQ samples. This is used to optimize the thresholds and codebook levels of a non-uniform scalar quantizer and the number of quantization bits allocated for each quantized level in the entropy coding stage, along with the MER performance analysis. The simulation results show that the conventional Gaussian-based compression techniques applied to a PAPR-reduced signal is not very robust to the statistical changes in the signal unless the signal distribution at the input of the Gaussian quantizer is not significantly affected. However, a significant gain is obtained when the quantizer is optimized with respect to the true distribution of the PAPR-reduced IQ samples.

Variable length error correcting code for image in OFDM and PAPR reduction

Data <span>transmission in orthogonal frequency division multiplexing (OFDM) system needs source and channel coding, the transmitted data suffers from the bad effect of large peak to average power ratio (PAPR). Source code and channel codes can be joined using different joined codes. Variable length error correcting code (VLEC) is one of these joined codes. VLEC is used in mat lab simulation for image transmission in OFDM system, different VLEC code length is used and compared to find that the PAPR decreased with increasing the code length. Several techniques are used and compared for PAPR reduction. The PAPR of OFDM signal is measured for image coding with VLEC and compared with image coded by Huffman source coding and Bose-Chaudhuri-Hochquenghem (BCH) channel coding, the VLEC code decreases the data transmitted size and keep the same level of PAPR reduction with respect to data coded by Huffman and BCH code when using PAPR reduction methods.</span>

Reducing PAPR of OFDM signals using a tone reservation method based on ell_{infty }-norm minimization

Orthogonal frequency division multiplexing (OFDM) continues to be the most preferred signal-multiplexing scheme for high-speed data communication. However, OFDM signals are known to have the problem of high peak-to-average power ratio (PAPR), especially when the number of subcarriers is large, which leads to nonlinear amplification in the high power amplifier and consequently to bit-error rate degradation and out-of-band radiation. In this paper, we propose a new optimal tone reservation method for reducing high PAPR in OFDM signals in order to avoid nonlinear amplification effects. The method employs Chebyshev-norm minimization to determine peak-reduction coefficients for OFDM signal. Simulation results show that the proposed method can achieve high PAPR reduction at the expense of a small loss in data rate and a slight increase in average transmit power. For example, with 4 out of 64 subcarriers reserved for peak-reduction coefficients, which represents 6.25% data-rate loss, the method can achieve 4.06 dB of PAPR reduction with only a 0.46 dB increase in average transmit power. Similarly, when 8 subcarriers or 12.5% of the total number of subcarriers are reserved, a PAPR reduction of 5.75 dB is achieved with a paltry 0.19 dB rise in transmit power.

Nonlinear companding transforms for reducing the PAPR of OTFS signal

In this paper, two non-linear companding transforms, namely exponential and sine hyperbolic, are proposed to reduce the peak to average power ratio (PAPR) of the orthogonal time frequency space (OTFS) modulation signal. The companding transforms are normalized such that the average power remains the same before and after companding. The resulting transforms have a saturation kind of characteristics for larger amplitudes of a signal while enhancing the smaller amplitudes slightly, which leads to a reduction of PAPR significantly. To validate the companding transforms in the OTFS system, we analyze the results in terms of PAPR, transform gain, attenuation factor, and bit error rate (BER). Also, compared the PAPR and BER performance of OTFS with OFDM, and the existing μ-law and clipping methods in OTFS. The results signify that the proposed companding transforms outperform the existing μ-law and clipping methods for PAPR reduction.

Ciphered BCH Codes for PAPR Reduction in the OFDM in Underwater Acoustic Channels

We propose an effective, low complexity and multifaceted scheme for peak-to-average power ratio (PAPR) reduction in the orthogonal frequency division multiplexing (OFDM) system for underwater acoustic (UWA) channels. In UWA OFDM systems, PAPR reduction is a challenging task due to low bandwidth availability along with computational and power limitations. The proposed scheme takes advantage of XOR ciphering and generates ciphered Bose–Chaudhuri–Hocquenghem (BCH) codes that have low PAPR. This scheme is based upon an algorithm that computes several keys offline, such that when the BCH codes are XOR-ciphered with these keys, it lowers the PAPR of BCH-encoded signals. The subsequent low PAPR modified BCH codes produced using the chosen keys are used in transmission. This technique is ideal for UWA systems as it does not require additional computational power at the transceiver during live transmission. The advantage of the proposed scheme is threefold. First, it reduces the PAPR; second, since it uses BCH codes, the bit error rate (BER) of the system improves; and third, a level of encryption is introduced via XOR ciphering, enabling secure communication. Simulations were performed in a realistic UWA channel, and the results demonstrated that the proposed scheme could indeed achieve all three objectives with minimum computational power.

Minimizing Peak to Average Power Ratio in OFDM System with WHT and Log Companding

Orthogonal Frequency Division Multiplexing (OFDM) suffers the effect of Peak to Average Power Ratio (PAPR) that reduces the strength or power of radio frequency (RF) signal at the transmitter and which also pushes the performance of transmitter amplifier into distortion. In order to minimize the effect of PAPR in OFDM, this paper proposed a system that precodes the OFDM signal using Walsh-Hadamard Transform (WHT) and Log function companding algorithm. Simulations were conducted in MATLAB environment while varying the number of subcarriers, N = 16, 64, 128, 256. simulation results indicated original OFDM revealed high PAPR in transmitted signal for the different number of subcarriers (N) such that for N =16, 64, 128, and 256, resulting in 7.964dB, 8.885 dB, 9.548 dB, and 9.961 dB respectively. With the introduction of WHT-Log companding scheme, the PAPR of OFDM signal was significantly reduced to 4.775 dB, 4.285 dB, 4.517 dB, and 4.602 dB by a percentage improvement of 40%, 51.8%, 52.7%, and 57.8% for N = 16, 64, 128, and 256 respectively. As a result, from the simulation results, the proposed system can be said to have largely reduced PAPR in OFDM system using a scheme with significant computational complexity.