Peak-to-average Power Ratio Reduction Research Articles

Testbed for a Novel Approach to Minimizing the PAPR of 5G Systems

The generalized frequency division multiplexing (GFDM) system has attracted the interest of the research community due to its unique characteristics such as high spectrum efficiency, low latency, and high transmission rate. However, like every multicarrier technique superimposition of a number of subsymbols in the time domain results in a high peak-to-average power ratio (PAPR). In general, the PAPR reduction system in the literature increases the average power while decreasing the PAPR which is not a plausible solution for practical 5G applications. In order to address this issue, we propose an efficient PAPR reduction strategy that maintains the PAPR without increasing the average power. In this method, an optimal orthogonal precoding matrix based on singular value decomposition (SVD) is designed to reduce the system’s average power. Because this optimal precoding matrix cannot successfully reduce the PAPR, we introduce a second technique called peak samples affixing to minimize both the peak and average power. For the proposed method’s assessment, using LabVIEW software and the universal software radio peripheral 2953R (USRP) as hardware, we developed an experimental setup to enable real-time transmission. The received spectral response from USRP authenticated the proposed method by showing a good agreement with simulations.

OTFS modulation and PAPR reduction for IoT-railways

The internet of things (IoT) has been widely considered to be integrated with high-speed railways to improve safety and service. It is important to achieve reliable communication in IoT for railways (IoT-R) under high mobility scenarios and strict energy constraints. Orthogonal time frequency space (OTFS) modulation is a two-dimensional modulation technique that has the potential to overcome the challenges in high Doppler environments. In addition, OTFS can have lower peak-to-average power ratio (PAPR) compared to orthogonal frequency division multiplexing, which is especially important for the application of IoT-R. Therefore, OTFS modulation for IoT-R is investigated in this paper. In order to decrease PAPR of OTFS and promote the application of OTFS modulation in IoT-R, the peak windowing technique is used in this paper. This technique can reduce the PAPR of OTFS by reducing the peak power and does not require multiple iterations. The impacts of different window functions, window sizes and clipping levels on PAPR and bit error rate of OTFS are simulated and discussed. The simulation results show that the peak windowing technique can efficiently reduce the PAPR of OTFS for IoT-R.

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.

Sustainable and Robust Techniques of Wireless Communications for Industry 4.0: Towards Efficient PAPR Reduction Models

This work presents the concerns of reliable, comprehensive, and high-quality communication networks essential in wireless communications for Industry 4.0. These are considered critical requirements of wireless technology for Industry 4.0. For a reliable transmission of digital data over broadband widths and Giga Hertz channels, the corresponding Peak-to-Average-Power Ratio (PAPR) must be under control. Industry standards Multiple-Input Multiple-Output Orthogonal Frequency Division Multiplexing With Offset Quadrature Amplitude Modulation (MIMO-OFDM/OQAM) system has been considered as the modulation technique with less Computational Complexity (CC). It usually produces phase sequence sets with different PAPR, a complex phenomenon to control. For robustness in PAPR control, the technique proposed has a receiver that initially restores the frequency domain rotation signal according to the sequence selection of the transmitter. Then it compares the distance between the reverse rotation sequence and the nearest constellation point to restore the original sequence. The proposed method simulation results can efficiently suppress the PAPR of MIMO-OFDM/OQAM signals. The proposed method is compared with the traditional Selective Mapping (SLM) algorithm. The proposed method reduces the CC, and can obtain the approximate Bit-Error Rate (BER) performance of the conventional SLM method when the sideband side information is known.

A Low-Complexity SLM PAPR Reduction Scheme for OFDMA

In orthogonal frequency division multiplexing (OFDM) systems, selected mapping (SLM) techniques are widely used to minimize the peak to average power ratio (PAPR). The candidate signals are generated in the time domain by linearly mixing the original time-domain transmitted signal with numerous cyclic shift equivalents to reduce the amount of Inverse Fast Fourier Transform (IFFT) operations in typical SLM systems. The weighting factors and number of cyclic shifts, on the other hand, should be carefully chosen to guarantee that the elements of the appropriate frequency domain phase rotation vectors are of equal magnitude. A low-complexity expression is chosen from among these options to create the proposed low-complexity scheme, which only requires one IFFT. In comparison to the existing SLM technique, the new SLM scheme achieves equivalent PAPR reduction performance with significantly less computing complexity. MATLAB tool is used for simulating the proposed work.

Simulation Analysis of Low PAPR FFT-based OFDM Through Nakagami Channel

In response to the inefficiency of power amplifier in conventional Orthogonal Frequency Division Multiplexing (OFDM) system, a low Peak-to-Average Power Ratio (PAPR) scenario can be obtained by implementing several PAPR reduction techniques. Partial Transmit Sequence (PTS) is a well-known instance to provide zero distortion for the system, while clipping is one of the simplest methods but it is sacrificing the error rate performance. In this work, Authors focused on analyzing the implementation of PTS and Palm Date Leaf clipping technique on OFDM system with 16-, 64-, 256-, and 1024-QAM under various Nakagami channel. In addition, the High-Power Amplifier (HPA) was also considered by using Solid State Power Amplifier (SSPA) model. It was found that linear HPA serves as the lower boundary for non-linear HPA, and system under high saturation level performs similarly. In physical properties, high saturation level is equivalent to higher power consumption in amplifier. Thus, optimal level was obtained by considering taking the one with moderate BER performance. After the system’s PAPR was reduced, the optimum saturation level of HPA was found to be 5 dB, 8 dB, 9 dB, and 11 dB for each Quadrature Amplitude Modulation (QAM) under Nakagami channel with m value of 1.5. However, this value was found to be ample for lower m value such as 1 or 0.7. In this case, the system required lower saturation level on the HPA for Nakagami channel with lower m value.

Modified [formula omitted]-law Root Companding for PAPR reduction in GFDM signals

Generalized Frequency Division Multiplexing (GFDM) is a multicarrier modulation technique and able to meet the requirements of next generation wireless systems. But it exhibits high peak to average power ratio (PAPR), which degrades the efficiency of the power amplifier (PA). In this work, modified Root Companding and modified μ-law Root Companding are proposed to reduce PAPR in GFDM signals. The existing methods alter the average power due to expansion of small signals, whereas the proposed method keeps the average power as constant by adjusting both small and large signals. Therefore, the adjustment of dynamic gain in PA is not required. Transform gain and achievable PAPR reduction of the proposed methods are compared by varying companding metrics such as companding root R and companding parameter μ. Also, bit error rate (BER) performance is analysed over AWGN channel and the value of R, μ is chosen such that companding distortion is small. The theoretical PAPR distribution of the proposed methods are derived and validated with Monte-Carlo simulations. The BER performance over multipath fading channel is also analysed. Further, the BER, PAPR and power spectral density performance of the proposed methods are compared with conventional OFDM, GFDM and existing PAPR reduction methods. The computational complexity is also analysed.

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.

A hybrid technique for the PAPR reduction of NOMA waveform

SummaryNon‐orthogonal multiple access (NOMA) is a great contender for future cellular modulation due to its desirable properties like massive connectivity, high data rate transmission, and high spectral efficiency. However, its peak‐to‐average power ratio (PAPR) is significant, which becomes a significant disadvantage for the efficient operability of the NOMA waveform compared to current techniques. Several PAPR reduction algorithms like selective mapping (SLM), partial transmission sequence (PTS), and companding techniques have been proposed to lower the PAPR of multicarrier waveforms (MCWs). PTS reduces the PAPR but has high complexity. On the other hand, SLM has a less complex framework, but its PAPR performance is not as efficient as PTS. Companding methods reduce the PAPR by compressing the signals at the transmitter, which unfortunately reduces the dynamic range of the signal. In this work, we propose a hybrid algorithm (SLM + PTS) with a companding method for the first time for the NOMA waveform, which efficiently reduces the PAPR with low computational complexity. Furthermore, we compare the performances of a host of candidate algorithms like SLM, PTS, hybrid (SLM + PTS), hybrid + A law (SLM–PTS–A law), and hybrid + Mu law (SLM–PTS–Mu law). The results of the experiments show that the hybrid + Mu law did a better job than the existing PAPR reduction algorithms.

Variation Approach-Based Nonlinear Companding Scheme for PAPR Reduction in OFDM Systems

Orthogonal frequency division multiplexing (OFDM) continues to find vast deployment in current and next generation wireless communication systems. However, high peak-to-average power ratio (PAPR) is one of the major drawbacks in the OFDM system. In this paper, we develop a variation approach based nonlinear companding (VANC) scheme to reduce the PAPR in OFDM systems. It aims to find the probability density function (PDF) for OFDM signal amplitudes with low PAPR and low distortion compared with their original Rayleigh distribution. The target PDF is found by solving a variation optimization problem model, which is built to find the lowest PDF distortion with both average signal power and probability conservation constraint. To the best of our knowledge, it is the first time that the variation method is used to find companding function to address the high PAPR problem. We then propose an algorithm with companding operation based on quantized levels. Simulation results validate the performance superiorities of the proposed scheme to that of other typical companding schemes.

Reducing peak to average power ratio (PAPR) for visible light communications (VLC) system using Walsh–Hadamard precoded discrete Hartley transforms

Abstract In visible light communication (VLC), intensity modulation with direct detection (IM/DD) based on DC-biased optical orthogonal frequency division multiplexing (DCO-OFDM) is used to transfer data at a high rate. Because OFDM signals are modulated using IM/DD, the peak of the transmitted signals is scaled up, resulting in a high peak-to-average power ratio (PAPR). In this article, the Walsh–Hadamard transform (WHT) is used as a precoder for discrete Hartley transform (DHT) to decrease the PAPR and the DC bias and achieve a good bit error rate (BER) performance in such a system. PAPR reduction results from the decrease of superposition of the transmitted signals owing to the use of WHT as a precoder. The proposed scheme and conventional DCO-OFDM indoor VLC system based on discrete Hartley transform (DHT) are compared to assure the new system’s benefits and efficiency.

Comparison of PAPR Reduction Using ABC-FF Algorithm and OGWO in MIMO-OFDM

In the transmitted signal, the high peak-to-average power ratio (PAPR) is the real disadvantage of multiple input, multiple output (MIMO) orthogonal frequency division multiplexing (OFDM) systems. Among different PAPR reduction techniques, selected mapping (SLM) is a famous strategy that accomplishes good PAPR reduction performance without signal distortion. Likewise, Partial transmit sequence (PTS) is additionally solitary of the successful techniques to decrease the PAPR in OFDM. Though, result an optimal segment issue in PTS system is measured to exist a critical concern. To progress the existing PAPR reduction techniques, we have incorporated ideal SLM and PTS based PAPR reduction strategy in parallel. By utilizing, the OGWO algorithm; the transmit succession was chosen with least PAPR above all communication antennas. The proposed PAPR reduction approach is applied independently on each transmitted antenna, and so the PAPR can be extremely reduced. Moreover, the OGWO optimization based PAPR reduction technique will provide better performance and it was been promoted as an uncomplicated way for PAPR reduction. The proposed approach will be analyzed with ABC-FF Algorithm PAPR reduction scheme to show the effectiveness

OFDM and MIMO wireless communication performance measurement using enhanced selective mapping based partial transmit sequences

The great spectral efficiency to mitigate multipath fading of OFDM (orthogonal frequency division multiplexing) made more accepted for broadband communication systems with some drawbacks such as high PAPR (Peak-to-Average Power Ratio), ISI (Inter-Symbol Interference) and ICI (Interiv Carrier Interference). High PAPR forces the operations of the HPA amplifier to work beyond its linear region causing in-band distortion as well as out-band noise and are overcome by using an amplifier with a large dynamic range. In this method, OFDM symbols are partitioned into multiple disjoint sub-blocks which are independently rotated in phase by optimum phase weighting factors. The resultant OFDM signal has less PAPR when compared to that of original OFDM signal in wireless communication. To minimize computational complexity, a modified PTS technique is proposed to enhance PAPR reduction and power amplifier efficiency in OFDM and MIMO (multiple inputs, multiple outputs)-OFDM methods through Selective Mapping based PTS (SMPTS) method combined with PAPR reduction methods.

VHDL implementation of circular shifting‐partial transmit sequence in MIMO OFDM systems

SummaryOne of the basic issues in orthogonal frequency‐division multiplexing (OFDM) frameworks is the peak‐to‐average power ratio (PAPR). There are several PAPR reduction methods available. The partial transmit sequence (PTS) technique is considered one of the superior techniques for overcoming this issue. In this study, an efficient VHSIC hardware description language VHDL implementation of the PTS design utilising roundabout circular shifting CS was planned. The proposed structured method was designed as a real‐time prototype circuit over a field programmable gate array (FPGA) utilising the VHDL language. The implementation results of the prototype circuit in terms of the resources used in the FPGA using the Xilinx synthesis tool on the Virtex‐5 board for SISO, 2 × 2 MIMO and 4 × 4 MIMO models for N‐IFFT 64 and 256 points are presented. The structured framework effectively combined to be a compact framework with low intricacy and high speed. Testing of the implemented circuit verified its functionality. A comparison of our proposed CS‐PTS scheme with previously used PTS schemes, such as the subblock scheme, showed that our proposed method is superior in terms of hardware complexity reduction.

A Joint Design of SCMA Codebook and PTS-Based PAPR Reduction for Downlink OFDM Scheme

In this paper, a joint design of sparse code multiple access (SCMA) codebook and peak-to-average power ratio (PAPR) reduction based on the partial transmit sequence (PTS) technique is proposed for the downlink orthogonal frequency division multiplexing (OFDM) scheme. A benchmark scheme is firstly devised based on a direct extension of the conventional PTS-based OFDM scheme. Based on the characteristics of the near-optimal SCMA codebook designs reported in our previous work, a PTS-based SCMA-OFDM design is proposed by carefully determining the rotation angles of the SCMA codebooks, according to the adopted signal sub-constellations. A receiver which does not need the side information is further devised. Considering the phase ambiguity issue of the receiver, the PTS angles have been carefully refined. When compared to both the original scheme that does not consider PAPR reduction techniques and the benchmark scheme, the proposed scheme achieves a significantly enhanced PAPR performance with approximately the same error performance. In addition, a comparable PAPR performance, an improved error performance, and a lower computational complexity can be achieved when compared to the clipping-based SCMA-OFDM scheme reported in the previous literature.

Deep Unfolding Network for PAPR Reduction in Multicarrier OFDM Systems

In this letter, we propose a Deep Unfolding Network called PR-DUN to reduce the peak-to-average power ratio (PAPR), which is a thorny problem in Orthogonal Frequency-Division Multiplexing (OFDM) systems. The proposed multi-layer model is constructed by unrolling an iterative algorithm resulting in layers with trainable parameters, which are optimized to minimize a loss function related to the PAPR value. The deep unfolding model uses the backpropagation algorithm to transfer gradients backwards to adjust parameters. Furthermore, the proposed scheme can accommodate any transmit power constraint, and therefore can control the power increase caused by the auxiliary signal. Simulation results show that the proposed PR-DUN model achieves a larger PAPR reduction and a smaller bit error rate while being less computationally intensive than related solutions.

EVM Mitigation With PAPR and ACLR Constraints in Large-Scale MIMO-OFDM Using TOP-ADMM

Although signal distortion-based peak-to-average power ratio (PAPR) reduction is a feasible candidate for orthogonal frequency division multiplexing (OFDM) to meet standard/regulatory requirements, the error vector magnitude (EVM) stemming from the PAPR reduction has a deleterious impact on the performance of high data-rate achieving multiple-input multiple-output (MIMO) systems. Moreover, these systems must constrain the adjacent channel leakage ratio (ACLR) to comply with regulatory requirements. Several recent works have investigated the mitigation of the EVM seen at the receivers by capitalizing on the excess spatial dimensions inherent in the large-scale MIMO that assume the availability of perfect channel state information (CSI) with spatially uncorrelated wireless channels. Unfortunately, practical systems operate with erroneous CSI and spatially correlated channels. Additionally, most standards support user-specific/CSI-aware beamformed and cell-specific/non-CSI-aware broadcasting channels. Hence, we formulate a robust EVM mitigation problem under channel uncertainty with nonconvex PAPR and ACLR constraints catering to beamforming/broadcasting. To solve this formidable problem, we develop an efficient scheme using our recently proposed three-operator alternating direction method of multipliers (TOP-ADMM) algorithm and benchmark it against two three-operator algorithms previously presented for machine learning purposes. Numerical results show the efficacy of the proposed algorithm under imperfect CSI and spatially correlated channels.

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.

A reduced PAPR hybrid OFDM visible light communication system

Orthogonal frequency division multiplexing (OFDM) is used by visible light communication (VLC) systems. Its main goal is to lessen inter-symbol interference's negative impacts. As a result, a lot of bandwidth and a high data rate are transmitted. Using OFDM-based VLC systems, nonetheless, have a high peak-to-average power ratio (PAPR). This research presents a new VLC system for indoor applications that reduces the PAPR while maintaining an acceptable bit error rate (BER). To achieve this, a hybrid pre-coding technique-based PAPR reduction solution is proposed; Vander-monde like matrix (VLM) combined with Gaussian matrix (GM). This technique takes advantage of both VLM and GM as a two stages for the signal to simultaneously reduce the PAPR and save the BER from damage. According to the results, the proposed solution (VLM in conjunction with GM) lowers the PAPR to 9.5 dB. Our system performs better when compared to other systems like discrete cosine transform (DCT), GM, VLM, DCT&GM, and original OFDM by 27%, 25%, 11%, 20%, and 34%, respectively.

Use of Chaotic Oscillations for Precoding and Synchronization in OFDM

This paper proposes a novel linear precoding method for Orthogonal Frequency Division Multiplexing (OFDM) based on the employment of the chaotic waveforms generated by the fourth-order chaotic oscillator and orthonormalized by the Gram-Schmidt process. The proposed linear precoding method is aimed to increase resilience to the multipath propagation issues and reduce the Peak-to-Average Power Ratio (PAPR) of the transmitted signal. Moreover, the chaotic waveform enables novel timing synchronization methods to be implemented in the receiver. The modelling of baseband Linear Precoded OFDM (LP-OFDM) data transmission system with Rayleigh channel has been performed in Simulink environment to validate the proposed method and to compare the performance to the classic precoding methods, such as Walsh-Hadamard Transform (WHT). Experiments have shown that in a high Signal-to-Noise Ratio (SNR) scenario, the employment of the novel precoding scheme allows reducing Bit Error Ratio (BER) by several dB compared to non-precoded OFDM. The proposed precoding method leads to the reduction of PAPR; however, it is not as efficient as classical precoding schemes, such as WHT. Experimental evidence of synchronization of the chaotic oscillators within 50 samples long time interval is presented.