Low Peak-to-average Power Ratio Research Articles

Signals With Sparse Mutual Interference for Sounding Massive MIMO Channels

In this paper, we propose a set of new sounding reference signals (SRSs) for time-division duplexing (TDD) massive MIMO systems with channel aging. It is analytically shown that the proposed set of SRSs exhibit zero correlation zone (ZCZ) property, which guarantees sparse and marginal interference between the SRSs. Therefore, all SRSs in the set can be transmitted concurrently in a cell with a short SRS period per user to alleviate the channel aging effect. We also analytically derive the peak-to-average power ratio (PAPR) and show how the SRS should be constructed to achieve low PAPR. Finally, simulation results are provided to show that the proposed SRSs result in larger downlink throughput than the 5G New Radio SRSs.

Band-limited dual-frequency multiplexing technique for GNSS signals

Global navigation satellite systems (GNSSs) usually adopt constant-envelope multiplexing (CEM) techniques to deal with the nonlinear characteristic of high-power amplifiers (HPAs) on satellites. However, almost all the existing navigation signal CEM techniques assume that the bandwidth of the transmitter is large enough when compared to that of navigation signals, which often contradicts reality, especially for the multiplexing of wideband navigation signals such as the signals in the Galileo E5 and BDS-3 B2 bands. Consequently, the constant-envelope characteristic deteriorates severely when the composite signal passes through the filter, which leads to nonlinear distortion and low amplification efficiency. Even if the nonlinear distortion can be mitigated by using amplifier linearization techniques, the actual transmitted signal power still suffers from a high peak-to-average power ratio (PAPR) of the composite signal. In order to address this problem, we present a new band-limited, dual-frequency multiplexing technique. The main premise of this method is to consider the impact of the filter on the navigation signals at first and then introduce the band-limited auxiliary signals to reduce the peak power of the composite signal as much as possible, thereby increasing the actual transmission power of the navigation signals. Simulation results demonstrate that the proposed method has lower PAPR and higher amplification efficiency than existing methods. In addition, implementation of the proposed multiplexing technique is still based on a look-up table, which has little change compared with previous CEM methods, and the complexity of signal generation is affordable.

Novel Efficient Multiwavelet-Based Modulation for Downlink NOMA Systems

A new modulation scheme using multiwavelets for downlink non-orthogonal multiple-access (NOMA) transceivers is presented in this work. Multiwavelets leading to remarkable spectral diversity are exploited to modulate/demodulate the superimposed multi-user signals in downlink NOMA systems, where the discrete multiwavelet transform and the inverse discrete multiwavelet transform are invoked in the new demodulator of the user equipment and the new modulator of the base station, respectively. The performance evaluation and the computational-complexity analysis of our proposed new NOMA scheme are also conducted. Simulation results demonstrate that the proposed new scheme can significantly increase the system capacity while dramatically suppressing the peak-to-average-power ratio (PAPR) compared to the conventional OFDM-based NOMA approach. Meanwhile, our new scheme can achieve the same system capacity as the scalar-wavelet-based NOMA approach but with a lower PAPR at little extra cost of computational-complexity. All of these three aforementioned NOMA schemes can result in the identical bit-error-rate under the same signal-to-noise ratio condition.

A Novel DFT-Based Scheme for PAPR Reduction in FBMC/OQAM Systems

In this letter, a novel discrete Fourier transform (DFT)-based scheme is proposed for peak to average power ratio (PAPR) reduction in filter-bank multicarrier with offset quadrature amplitude modulation (FBMC/OQAM) systems. The key idea is the combination of DFT and the concept of block repetition. Different from the conventional DFT-based PAPR reduction method, the output complex-valued signal of the DFT module is directly transmitted in the proposed DFT-based PAPR reduction method, instead of separating and transmitting the real and imaginary parts of the output signal, respectively. The proposed method can provide a solution to the low PAPR without the cost of high complexity, signal distortion or side information. To validate the performance of the proposed method, simulation results are provided in terms of complementary cumulative distribution function (CCDF) and bit error ratio (BER).

A Novel PAPR Reduction Scheme for OFDM Systems Based on Neural Networks

Orthogonal frequency division multiplexing (OFDM) is extensively applied in the downlink of narrowband Internet of Things (NB‐IoT). However, the high peak‐to‐average power ratio (PAPR) of OFDM systems leads to a decrease in transmitter efficiency. Therefore, the researchers proposed the artificial neural network (ANN) based PAPR reduction schemes. However, these schemes have the disadvantages of high complexity or cannot overcome the defects of traditional schemes. In this paper, a novel PAPR reduction scheme based on neural networks (NNs) is proposed for OFDM systems. This scheme establishes a PAPR reduction module based on NN, which is trained using the low PAPR data obtained by the simplified clipping and filtering (SCF) method. To overcome the defect of poor BER performance of the SCF scheme, a recovery module is introduced at the receiver, to recover the distorted signal. To realize the improvement of BER performance and the reduction of PAPR simultaneously, the two modules are jointly trained based on multiobjective optimization. Experimental results based on a 100 MHz OFDM signal show that this scheme can reduce PAPR by 4.5 dB. Meanwhile, the BER of this scheme can be reduced to 0.001 times that of the SCF scheme.

PAPR reduction in OFDM system using combined MCS and DHMT precoding

Orthogonal Frequency Division Multiplexing (OFDM) has become a preferable scheme for most high data rate wireless communication standards. However, the non-linear power amplifier effect experienced in the OFDM system has increases the peak-to-average power ratio (PAPR). This paper proposed a Median Codeword Shift (MCS) as a new solution to alleviate the effect of high PAPR. MCS takes advantage of the codeword structure and bit position changes through the manipulation of the codeword structure and permutation process to achieve a low PAPR value. Additionally, the enhanced version of MCS is also being proposed by merging MCS with the Discrete Hartley matrix transform (DHMT) precoding method to boost the PAPR reduction. Simulation results show that MCS is capable of minimizing PAPR of conventional OFDM with 24% improvement and at the same time outperform Selective Codeword Shift (SCS) with a 0.5 dB gap. A remarkable result was also achieved by MCS-DHMT with a 15.1% improvement without facing any bit error rate (BER) degradation.

PAPR reduction in OFDM system using combined MCS and DHMT precoding

Orthogonal Frequency Division Multiplexing (OFDM) has become a preferable scheme for most high data rate wireless communication standards. However, the non-linear power amplifier effect experienced in the OFDM system has increases the peak-to-average power ratio (PAPR). This paper proposed a Median Codeword Shift (MCS) as a new solution to alleviate the effect of high PAPR. MCS takes advantage of the codeword structure and bit position changes through the manipulation of the codeword structure and permutation process to achieve a low PAPR value. Additionally, the enhanced version of MCS is also being proposed by merging MCS with the Discrete Hartley matrix transform (DHMT) precoding method to boost the PAPR reduction. Simulation results show that MCS is capable of minimizing PAPR of conventional OFDM with 24% improvement and at the same time outperform Selective Codeword Shift (SCS) with a 0.5 dB gap. A remarkable result was also achieved by MCS-DHMT with a 15.1% improvement without facing any bit error rate (BER) degradation.

ASIC Implementation of Low PAPR Multidevice Variable-Rate Architecture for IEEE 802.11ah

The advancement of next-generation systems has led to a rapid increase in day-to-day applications by connecting billions of devices. Mobile networks require a considerable cost to support these billions of devices, and conventional IEEE 802.11 is meant for the usage of small-scale applications. To support long-range applications, IEEE task group-ah has proposed a new standard named IEEE 802.11ah. However, it has challenges like efficient device grouping based on variable sampling rates and power consumption. This standard employs orthogonal frequency-division multiplexing as a multicarrier scheme that suffers from high peak-to-average power ratio (PAPR). Hence, to support multiple devices of variable rates in the physical layer along with low PAPR and acceptable bit error rate, a new framework and an optimized architecture of carrier interferometry-group orthogonal–orthogonal frequency-division multiple access architecture is proposed. The proposed architecture reduces the 16-point inverse fast Fourier transform area by 57.1%, device padding area by 50% along with three extra adders functional area compared with the existing architecture. Furthermore, the proposed architecture is prototyped on Virtex5 field-programmable gate array for on-chip validation, and the hardware parameters are measured in real time. The area-timing complexity of the proposed architecture is estimated and further achieves the lowest area- and power-delay product than the existing architecture. Application-specific integrated circuit implementation is carried out using commercially available 32 - nm technology library, where the postlayout results reported less area utilization and low power consumption.

New Complementary Sets With Low PAPR Property Under Spectral Null Constraints

Complementary set sequences (CSSs) are useful for dealing with the high peak-to-average power ratio (PAPR) problem in orthogonal frequency division multiplexing (OFDM) systems. In practical OFDM transmission, however, certain sub-carriers maybe reserved and/or prohibited to transmit signals, leading to the so-called spectral null constraint (SNC) design problem. For example, the DC sub-carrier is reserved to avoid the offsets in D/A and A/D converter in the LTE systems. While most of the current research focus on the design of low PAPR CSSs to improve the code-rate, few works address the aforementioned SNC in their designs. This motivates us to investigate CSSs with SNC as well as low PAPR property. In this article, we present systematic constructions of CSSs under SNCs and low PAPR. First, we show that mutually orthogonal complementary sets (MOCSs) can be used as seed sequences to generate new CSSs with SNC and low PAPR, and then provide an iterative technique for the construction of MOCSs which can be further used to generate complementary sets (CSs) with low PAPRs and spectral nulls at varying positions in the designed sequences. Next, inspired by a recent idea of Chen, we propose a novel construction of these seed MOCSs with non-power-of-two lengths from generalized Boolean functions.

Application of 5G new radio for satellite links with low peak‐to‐average power ratios

SummaryThe aim of the paper is to consider feasibility of 5G new radio (NR) over satellite links also known as nonterrestrial networks (NTNs). Large propagation delay and Doppler frequency shift are challenges like is high peak‐to‐average power ratio (PAPR) of 5G NR signal because satellite systems would like to operate at very low‐power amplifier back‐off values. This paper provides a brief summary of progress made in initial synchronization and uplink random access process both in the literature and standardization. Furthermore, the paper explains what is the relationship between low PAPR and power amplifier back‐off and the density of reference symbols by showing that 2‐dB back‐off values can be attained using sufficient reference symbol density. Finally, open issues that need clarification are listed. Interestingly, all solutions to these problems do not mean changes in the standard but proper actions from vendors and operators.

Transmit Efficiency Enhancement Using Over-the-Air Beamforming Phased Array for High PAPR Signals

This article presents a new transmitter phased-array architecture for efficiency-boosting of a transmitter–receiver link for high peak-to-average power ratio (PAPR) signals. The phased array architecture utilizes sequential over-the-air combining of weighted power amplifiers (PAs) to increase the system efficiency without any die area nor antenna size penalties. The transmitted signal is decomposed into a low duty-cycle signal comprising only the signal peaks and a low PAPR signal containing the remaining envelope levels. The two signals are transmitted through different chains, each optimized for a different power level, and recombined over the air at the receiver side. A 5-GHz PA with a fast 2-ns ON/OFF switching time was designed in 0.18- $\mu \text{m}$ CMOS process to demonstrate the efficiency boost technique. For a four-element array configuration, efficiency enhancement of $2.3 \times $ is demonstrated using an 80-MHz MSC9 802.11ac signal with 9-dB PAPR. The transmitter achieves efficiencies of 15% and 13% for 80- and 160-MHz signals, respectively, at the error vector magnitude (EVM) of −32 dB.

Low PAPR reference signal transceiver design for 3GPP 5G NR uplink

Low peak-to-average-power ratio (PAPR) transmissions significantly improve the cell coverage as they enable high power transmissions without saturating the power amplifier. To support the low PAPR transmissions, π/2-BPSK-based data and DMRS are introduced in the latest version of 5G NR specifications. In addition to that, the spatial multiplexing support is also extended to π/2-BPSK data transmissions. The DMRS sequences corresponding to these spatial streams (users) are frequency division multiplexed (FDM). However, the spectrum shaping process employed in the generation of π/2-BPSK waveforms is frequency selective and hence results in asymmetric spectrum shaping effect on DMRS sequences, when they are frequency multiplexed. This subsequently results in a non-uniform block error (BLER) and PAPR performances across the spatial users, which in turn may result in inter user interference across the spatial users. In this paper, we propose two transmitter architectures, namely method 1 and method 2, to generate low PAPR π/2-BPSK-based DMRS waveforms. The proposed architectures ensure that the spectrum shaping effect is uniform across all the spatial streams. We corroborate through simulations that the proposed architectures will result in identical block error and PAPR performances across all the spatial streams.

Low-Complexity PAPR Reduction Method for OFDM Systems Based on Real-Valued Neural Networks

High peak-to-average power ratio (PAPR) in orthogonal frequency division multiplexing (OFDM) systems is one of the major drawbacks in wireless transmitters. In this letter, a novel low complexity PAPR reduction method based on the real-valued neural network (NN) is proposed. This method first builds the PAPR reduction module using the real-valued NN to achieve the reduction of PAPR. To reconstruct the transmission signal, the PAPR decompression module is introduced into the receiving end to recover the signal in order to minimize the bit error rate (BER) of the systems. The PAPR reduction module and the PAPR decompression module can be jointly trained offline, therefore, the reduction of PAPR and the minimization of BER can be achieved simultaneously. To reduce the process rate of the PAPR reduction, the trained model uses multiple parallel processing links to achieve the reduction of the PAPR. The extensive simulations indicate that the proposed method outperforms previously available methods in terms of PAPR and BER, while having low complexity.

Low peak-to-average power ratio OFDM-PON system with multiprobabilistic shaping distribution

Higher flexibility and high peak-to-average power ratio (PAPR) are the main challenges for orthogonal frequency division multiplexing passive optical network (OFDM-PON) systems. For this purpose, we propose a low PAPR OFDM-PON system with a dynamic regulatory factor U, which can dynamically adjust the transmission capacity of the system according to the needs of users at optical network units and reduce PAPR at the same time. Dynamic regulatory factor U can assign different probabilistic shaping schemes to different subcarriers, thus improving the system flexibility and adjustability in both the time and frequency domains. Meanwhile, U can flexibly change the number of phase sequence groups in selecting mapping, which is a well-known effective PAPR reduction technique. Simulations of a back-to-back OFDM-PON transmission system with different bit rates are setup to verify the performance of the proposed scheme. It is demonstrated that the proposed scheme achieves effective PAPR reduction performance with considerably lower computational complexity and outstanding bit error performance. More importantly, our proposed OFDM-PON system can be flexible and adjustable in acquiring different and dynamic access bit rates, which suggests a prospective solution for the next-generation PON.

SSB Pruned DFT-Spread FBMC Signal With Low PAPR in Direct-Detection PONs

Filter bank multi-carrier (FBMC) using offset quadrature amplitude modulation (OQAM) has recently attracted increasing interests for the next-generation high-speed optical transmission systems, due to the salient FBMC modulation advantages in terms of high spectrum efficiency by completely removing the cyclic prefix. However, high peak-to-average power ratio (PAPR) still plays a key role of constraining the performance of FBMC systems. In this paper, we investigate a single sideband (SSB) pruned discrete Fourier transform (DFT)-spread FBMC for direct-detection (DD) passive optical network systems (PONs). It is demonstrated that the PAPR of the SSB pruned DFT-spread FBMC signal with the overlapping factor of 1.56 outperforms the conventional FBMC signal and the simple DFT-spread FBMC signal by ∼2 dB and 1 dB at the complementary cumulative distribution function (CCDF) of 1 × 10−3, respectively. Finally, by using the pruned DFT-spread FBMC with low PAPR, the aggregate data rate of 50-Gbit/s can be achieved after 50-km single mode fiber (SMF) transmission below the 7% hard decision forward-error correction (HD-FEC) threshold in the DD PONs.

ECCM Schemes against Deception Jamming Using OFDM Radar with Low Global PAPR.

In this paper, a type of effective electronic counter-countermeasures (ECCM) technique for suppressing the high-power deception jamming using an orthogonal frequency division multiplexing (OFDM) radar is proposed. Concerning the velocity deception jamming, the initial phases of the pulses transmitted in a coherent processing interval (CPI) are designed to minimize the jamming power within a specific range, forming a notch around the jamming in the Doppler spectrum. For the purpose of suppressing the range deception jamming and the joint range-velocity deception jamming, the phase codes of the subcarriers belonging to the OFDM pulses are optimized to minimize the jamming power, distributing some specific bands in the range and the range-velocity domain, respectively. According to Parseval’s theorem, the phase encoding, acting as the coding manner of the OFDM subcarriers can ensure that the energy of each OFDM symbol stays the same. It is worth noticing that the phase codes of the OFDM subcarriers can influence the peak-to-average power ratio (PAPR). Thus, an optimization problem is formulated to optimize the phase codes of the subcarriers under the constraint of global PAPR, which can regulate the PAPRs of multiple OFDM symbols at the same time. The proposed problem is non-convex; therefore, it is a huge challenge to tackle. Then we present a method named by the phase-only alternating direction method multipliers (POADMM) to solve the aforementioned optimization problem. Some necessary simulation results are provided to demonstrate the effectiveness of the proposed radar signaling strategy

High Data Rate Discrete-Cosine-Spreading Aided M-Ary Differential Chaos Shift Keying Scheme With Low PAPR

Traditional differential chaos shift keying (DCSK) systems have low spectrum efficiency since half of time slots are used to transmit the reference chaotic signals. Our objective is to utilize the orthogonality of chaotic vectors and orthogonal cosine functions to construct a high data rate M-ary modulation scheme while providing improved reliability over wireless channels. In this brief, we propose a discrete-cosine-spreading (DCS) aided M-ary DCSK scheme. In our design, we first utilize the Gram-Schmidt algorithm to generate orthogonal chaotic basis vectors, then the linear combination of these vectors is used for M-ary modulations to improve the data rate. In order to suppress the interferences between modulated signals and reduce the peak to average power ratio (PAPR) induced by the overlapping of linear combinations, subsequently we apply discrete cosine codes to spread the modulated symbols. The resultant symbols are respectively transmitted over the quadrature and inphase channels. Furthermore, we derive the theoretical bit error rate (BER) expression over additive white Gaussian noise (AWGN) channel and multipath Rayleigh channels, then we analyze the computational complexity. Simulation results validate the theoretical derivations, and demonstrate that compared with the benchmark schemes, the proposed scheme could achieve higher data rate with the improved bandwidth efficiency, better BER performances over multipath fading channels, and lower PAPR.

Generation of Orthogonal Sequence Sets for M-ary Spread Spectrum Communications with OFDM Modulation

The number of orthogonal sequences is a key point of M-ary spread spectrum (MSS) communication system since more sequences mean higher data rate. When orthogonal frequency division multiplexing (OFDM) modulation is used into MSS system, the additional low peak-to-average power ratio (PAPR) property is required due to high power efficiency. Based on the segmentation-shift operation, multiple orthogonal sequence sets with the same size and sequence length are generated in this paper. By combining these orthogonal sequence sets, the number of the generated orthogonal sequences is very large. For any two orthogonal sequence sets, there exists good cross-correlation performance between them at zero shift. In addition to large set size and good correlation property, the generated multiple orthogonal sequence sets possess low PAPR, which is very suitable for OFDM modulation. The generation algorithm of multiple orthogonal sequence sets is provided in this paper, and the corresponding simulation results show the effectiveness of the provide method.

Multiple transmit antennas for low PAPR spatial modulation in SC-FDMA: single vs. multiple streams

The main reason for the selection of single-carrier frequency division multiple access (SC-FDMA) modulation technique in mobile high data rate communications lays in its low value of peak-to-average power ratio (PAPR). If spatial modulation, a multiple-input multiple-output technique that achieves bitrate increase, is applied to the SC-FDMA system in its conventional form, the PAPR level is increased. Hence, based on previously mentioned, in this paper, we provide the general design criteria for low PAPR spatial modulation (LPSM) implemented in SC-FDMA systems with multiple transmit antennas. The straightforward generalization of LPSM is derived and it is shown that it requires the number of transmit antennas to be doubled in order to add another bit in the spatial component. Based on that, the alternative generalized technique with higher number of spatial bits is proposed. As these techniques present single-stream generalizations, the approach with multiple-streams is proposed as well. After PAPR and performance comparisons, it is concluded that single-stream techniques outperform multiple-stream techniques in the cases of low overall data rate, whereas multiple-stream approach is better in high overall data rate scenarios. All proposed techniques maintain low PAPR level on all transmit antennas.

Cognitive radio technology with reduced PAPR and complexity for IoT-based OFDM networks

The principle target of an International Mobile Telecommunication (IMT) is to build a platform to advance the improvement of technology used in 5G and to inspire the support with the MNCs and organizations. The journey of 5th Generation initiated with 1G technology and has provided a massive improvement in today’s world. 5G technology on IMT provides the target to achieve ultra-high data rate, connectivity, reliability, lower latency, and lower data traffic. The usage of Orthogonal Frequency-Division Multiplexing (OFDM) system in 4G technology causes high Peak-to-Average Power Ratio (PAPR), complexity, and out-of-band radiation. To avoid these parameters, Filtered (F)-OFDM is exploited in 5G technology. The design becomes complex by the division of spectrum into non-contiguous spectrum fragments. So, resource block F-OFDM system using Internet of Things is proposed to convert non-contiguous spectrum into contiguous spectrum but the complexity remains the same. The proposed work of this paper is IoT-based RB-F-OFDM system along with inverse fast Walsh-Hadamard and Fourier transform to decrease the complexity and also, adaptive filter is exploited for retaining the actual (regular) grid to avoid signal information required for specifying a particular subband in the spectrum. Also, to enhance the quality of service, spectrum efficiency and cognitive radio system are used along with these techniques. Simulation result shows that proposed RB-Adaptive Filtered (AF)-OFDM provides low PAPR, high signal-to-interference ratio, and low bit error rate performance. The proposed RB-AF-OFDM system has the benefits of both RB-F-O FDM and adaptive F-OFDM so it further reduces the PAPR and complexity to the considerable value which is around 2.5.