dB Peak-to-average Power Ratio Research Articles

A novel piecewise nonlinear companding scaling scheme for FBMC PAPR reduction

The performance of offset quadrature amplitude modulation filter bank multi carrier (OQAM-FBMC) has been noticed to be affected by a high peak-to-average power ratio (PAPR). High PAPR causes the transmit power amplifier to become saturated, improving the bit error rate (BER) and causing out of band (OOB) distortions. In this paper, the PAPR of FBMC systems can be reduced by using shifting and scaling the trigonometric companding technique associated with a reduced BER performance and the power spectral density (PSD) with low OOB distortions. The characteristics of low peak signals are not changed by this companding scheme, while the characteristics of high peak signals are transformed into scaling piecewise nonlinear trigonometric functions. By tuning the parameters the suggested technique maintains the average signal power level unchanged. The theoretical analysis of the proposed scheme is also studied and also compared with the simulation results. The performance of the trigonometric companding scheme is also analysed with the μ-law and A-law existing companding methods and the suggested method obtaining 3 dB and 3.2 dB PAPR improvement respectively. The proposed technique determined to be better in terms of BER performance and spectrum efficiency.

Spread spectrum OFDM-IM with X-transform

This paper proposes a developed index modulated spread spectrum orthogonal frequency division multiplexing (OFDM) that is based on X-transform (IM-XOFDM-SS). The presented OFDM sends information not only by M-ary data symbols but also by indexes bits that used to select the spreading code from a known set, and applies the X-transform for baseband processing. A theoretical analysis for upper bound bit-error rate (BER) over Rayleigh fading channels is derived for the proposed scheme. Simulations results show that our proposed scheme outperforms the competitive benchmark systems in terms of BER, peak-to-average power ratio (PAPR) and computational complexity. It achieves, at 10−4 BER, about 22 dB and 21 dB SNR gain when spectral efficiency is SE=1 bps/Hz. Additionally, it gains about 5.5 dB PAPR reduction in comparison to IM-OFDM-SS scheme that is based on FFT for baseband processing.

A Novel PAPR Reduction Scheme Based on Joint Traditional Algorithm and Machine Learning for CO-OFDM Systems

The high peak-to-average power ratio (PAPR) deteriorates the performance of coherent optical orthogonal frequency division multiplexing (CO-OFDM) systems. Machine learning (ML) has evolved into a powerful technology to reduce PAPR with its flexible learning ability. We propose a joint scheme which adopts iterative partial transmission sequence (IPTS) scheme cascading a feedforward neural network (FNN) trained on iterative <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\pmb {\mu }$ </tex-math></inline-formula> -law companding and filtering (IMCF) algorithm. The proposed scheme greatly reduces the complexity of partial transmission sequence (PTS) scheme, which has excellent PAPR reduction effect and BER performance. Our method achieves a 5.03 dB PAPR reduction for <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$10\pmb {^{-4}}\,\,\pmb {CCDF}$ </tex-math></inline-formula> and an additional transmission distance of 200 km SMF for <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$10\pmb {^{-3}}\,\,\pmb {BER}$ </tex-math></inline-formula> , compared with the original OFDM signal. Meanwhile, the computational complexity of proposed scheme is reduced by 32.4%, compared with IPTS cascading IMCF (IPTS-IMCF) scheme.

PAPR-Degraded Secure OFDM-WDM-PON Based on Chaotic Set-Partitioned SLM

This letter proposes and experimentally demonstrates an orthogonal frequency division multiplexing wavelength division multiplexing passive optical network (OFDM-WDM-PON) system based on novel chaotic set-partitioned selective mapping (SP-SLM) scheme. With the implementation of a three-dimensional chaotic system, peak-to-average power ratio (PAPR) reduction and chaotic encryption are simultaneously realized on the process of OFDM signal modulation, so as to enhance the system performance in the presence of PAPR, bit error rate (BER), fiber nonlinear tolerance and security. The experimental results show that, when compared with original OFDM signal, the OFDM signal with SP-SLM can achieve 4 dB PAPR reduction at the complementary cumulative distribution function value of <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$10^{-4}$ </tex-math></inline-formula> , as well as a 1.1 dB gain in receiver sensitivity at a BER of <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$10^{-3}$ </tex-math></inline-formula> . For fiber nonlinear tolerance, the optimal launch fiber power of OFDM signal with SP-SLM is 10 dBm, which is better than 9 dBm of original OFDM signal under the same received optical power of −16 dBm. Furthermore, the key space of the proposed scheme can reach up to <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$10^{98}$ </tex-math></inline-formula> , which is large enough to effectively protect against illegal attackers.

A new PAPR and BER enhancement technique based on lifting wavelet transform and selected mapping method for the next generation waveforms

Orthogonal frequency division multiplexing (OFDM) is widely used in many digital communication systems because of its immunity to inter-symbol interference, high spectral efficiency and capability of handling multipath. Walsh-Hadamard transform (WHT) and discrete wavelet transform (DWT) have also been suggested in order to enhance the performances of multi-carrier wireless communication systems. In general, high peak-to-average power ratio (PAPR) is one of the biggest disadvantages of these systems and OFDM also has this disadvantage. Many techniques such as amplitude clipping and filtering, encoding, interleaving, tone reservation (TR), tone addition (TI), partial transmission sequence (PTS), and selected mapping (SLM) techniques have been proposed to reduce the high PAPR. Without any modification these techniques are useless due to the related symbol addition process. For this reason, we developed a new technique composed of Lifting wavelet transform (LWT) and SLM method in order to decrease the PAPR in multi-carrier systems. The performance of this new LWT-SLM scheme is measured by applying it to zero tail (ZT) discrete Fourier transform-spread OFDM (ZT DFT-s OFDM) and unique word OFDM (UW OFDM) waveforms, which are promising next generation waveforms. Simulation results show that, the ZT DFT-s OFDM system obtains the 3.3 dB PAPR gain and 0.8 dB better bit error rate (BER) performance compared to classical OFDM with proposed scheme without sacrificing BER performance.

PAPR reduction using twin symbol hybrid optimization-based PTS and multi-chaotic-DFT sequence-based encryption in CP-OFDM system

Orthogonal frequency division multiplexing (OFDM) is considered as one of the most significant transmission methodologies of the recent past. Moreover, it permits easy demodulation and modulation. To find the new OFDM-based waveform to be used in fifth generation which is one of the foremost open issues for wireless networks of the next generation. In addition, the OFDM is affected by the maximum Peak-to-Average Power Ratio (PAPR). In order to minimize these problems, this paper proposed a Twin Symbol Hybrid Optimization used as a basis of the Partial Transmit Sequence (TSHO-PTS) method of Cyclic Prefix-OFDM (CP-OFDM). This CP-OFDM achieves the requirements of 5G telecommunication standards. Moreover, the exhaustive searching for optimal phase factors might increase the computational cost of PTS. To beat this problem, a hybrid version of slap swarm optimization (SSO) and Bald Eagle Search (BES) algorithm is introduced to investigate the phase factor optimally by the PTS method. Digital chaotic sequences are used to ensure the physical layer security during the data transmission scheme for the Discrete Fourier Transform Spread OFDM (DFT-S-OFDM) subcarrier allocation. The simulation takes place in the MATLAB platform, and the performances are evaluated by several performance metrics like Complementary cumulative distribution function (CCDF), Bit Error Rate (BER), and computational complexity. The performance of the proposed model is compared with various existing approaches and previous works. From the implemented results, the proposed strategy achieved less (5 dB) PAPR, minimum (10–8) BER, less processing time (0.18 s) than the existing schemes, and hence the complexity also very low (7%) than others.

Gaussian orthogonal matrix transform approach for PAPR reduction of optical OFDM signals

Optical orthogonal frequency division multiplexing (O-OFDM) has been widely adopted as a high-speed data transmission technique in visible light communication systems. This technique usually suffers from high peak-to-average-power ratio (PAPR). In this paper, a new PAPR reduction technique is proposed for O-OFDM signals. At the transmitter, a matrix transformation with the Gaussian elements is applied to the time-domain O-OFDM signal and at the receiver, the inverse matrix is used to recover the original signal. We show that the Gaussian orthogonal matrices can reconstruct the original signals without degrading the bit error rate (BER) performance. Gram-Schmidt technique is used to orthogonalize the Gaussian matrices. Computer simulations are conducted for 16-QAM baseband modulated symbols and about 3 dB PAPR reduction gain is achieved by the proposed approach compared with conventional O-OFDM.

Blind Algorithm Development for Peak to Average Power Ratio Reduction in OFDM Systems under Frequency Selective Channels

One major drawback of orthogonal frequency division multiplexing (OFDM) system is peak to average power ratio (PAPR). This effect causes high power amplifier (HPA) to introduce intermodulation and out of band radiation as the signal goes through, thus degrades the performance of OFDM systems. This paper proposes blind algorithms which takes advantage of signal transformation technique and signal distortion technique. Simulation results show that at complementary cumulative distribution function (CCDF) level of 10-3 , the proposed algorithm achieved 3.2 dB PAPR improvement compared to discrete Fourier transform with interleaved frequency division multiple access (DFT-IFDMA) based algorithm. The bit error rate (BER) performance has degraded by 2 dB compared to the original OFDM signal with no distortion under frequency selective channel (FCS) at BER of 10-4 . These presented results, mark this algorithm as a better candidate for PAPR reduction algorithm in long term evolution (LTE) network. Under AWGN channels, the proposed algorithm performs better both in low and high signal power values. Under frequency selective channels, the existing and proposed algorithm converges after 10 dB of signal to noise power values. The low BER transmissions at low signal power values signify energy efficiency, ideal for portable wireless devices with limited battery power.

Partial Pre-Emphasis for Pluggable 400 G Short-Reach Coherent Systems

Pre-emphasis filters are used to pre-compensate for the transmitter frequency response of coherent systems to mitigate receiver noise enhancement. This is particularly essential for low-cost, low-power coherent transceivers due to having an extremely bandlimited transmitter. However, the pre-emphasis filter also increases the signal peak-to-average power ratio (PAPR), thus posing a higher effective number of bits (ENoB) requirement for the arbitrary waveform generator (AWG). In this paper, we first numerically study the PAPR impact of partial pre-emphasis filters. We show that with partial pre-emphasis, an ENoB reduction from 5 to 4.5 bits is attainable at the same signal-to-noise ratio (SNR) out of the AWG. Next, we experimentally investigate the overall performance penalty of partial pre-emphasis in a 50 Gbaud 16QAM coherent system. A manageable Q factor penalty of around 0.5 dB is found for both single-polarization and dual-polarization systems with a 0.8 dB PAPR reduction.

Adaptive Uniform Entropy Loading for SSB-DMT Systems

In this paper, we proposed a simple uniform entropy loading (UEL) algorithm to adaptively load the same entropy for all the subcarriers according to the channel state information. Thanks to the signal-to-noise ratio (SNR) equalization effect of precoding, only one distribution matcher is used for UEL, maximally reducing the complexity of entropy loading. The proposed algorithm is based on the relationship between the optimal information bits per symbol (IBPS) and SNR for probabilistically shaped quadrature amplitude modulation (PS QAM) under the constraint of normalized generalized mutual information (NGMI) considering the implementation of constant composition distribution matching (CCDM) and off-the-shelf forward error correction (FEC) code. Different from generalized mutual information (GMI), IBPS intuitively represents practical performance. Besides, the relationship between IBPS and SNR for conventional QAM and time domain hybrid QAM (TDHQ) are also calculated to perform the well-known bit power loading (BPL) algorithm, Levin-Campello (LC) algorithm, and TDHQ assisted adaptive loading (AL) algorithm, respectively. Based on theoretical analysis, to our best knowledge, we first found that precoding procedure adopted by TDHQ assisted AL and UEL scheme degrades Shannon capacity compared to water-filling algorithm, the upper limit of BPL algorithms. However, benefiting from shaping gain of PS QAM, the proposed UEL algorithm achieves higher net data rate (NDR) and lower peak-to-average power ratio (PAPR) than the LC algorithm, which is demonstrated by the simulations and experiments in single sideband discrete multi-tone (SSB-DMT) systems. According to the experimental results, up to 3.2% NDR improvement and 0.82 dB PAPR reduction are realized by the UEL algorithm compared to the LC algorithm. The UEL algorithm also outperforms TDHQ assisted AL algorithm by the average NDR gain of up to 8.0%. The simple and effective advantages make the proposed UEL scheme suitable for the short-to-medium reach optical fiber communication systems.

Constant-Envelope Space-Time Shift Keying

From the power amplifier's perspective, the peak-to-average power ratio (PAPR) is of essential importance, especially for both single-RF and reduced-RF multiple-input multiple-output (MIMO) single-carrier schemes. In this context, many of the diversity-oriented index modulation schemes—including the full-RF space-time shift keying (STSK) and the single-RF asynchronous STSK (ASTSK) that invoke randomized signals—exhibit eroded energy-efficiency. To circumvent this problem, we propose a holistic signal construction approach for single-RF, reduced-RF, and full-RF MIMO setups, which always achieve both perfect 0 dB PAPR transmission and inter-channel interference (ICI) free signal detection. More explicitly, first of all , we conceive a new family of single-RF constant-envelope ASTSK (CE-ASTSK), which is capable of substantially outperforming conventional spatial modulation (SM) in both Rayleigh fading and Ricean fading associated with increasing line-of-sight (LoS) power. Second , we propose the new full-RF CE-STSK concept, which is capable of outperforming the orthogonal space-time block codes (STBCs) without either increasing PAPR or imposing ICI. This is particularly beneficial because the conventional linear dispersion code (LDC) approaches always compromise the orthogonality of STBC and hence impose ICI. Third , we also conceive the reduced-RF versions of CE-STSK, which outperform both generalized spatial modulation (GSM) and space-time block coded spatial modulation (STBC-SM). Finally , the proposed schemes are intrinsically amalgamated with turbo detection assisted channel coding, which further confirms the superiority of CE-ASTSK and CE-STSK over SM and STBC in the single-RF and full-RF modes, respectively.

Modified SLM scheme of FBMC signal in satellite communications

In this study, a segment-selected mapping (SSLM) scheme is proposed to reduce the peak-to-average power ratio (PAPR) of the filter bank multi-carrier (FBMC) signal in satellite communications. The standard selected mapping (SLM) scheme is suggested to reduce the PAPR of the traditional multi-carrier signals. However, it cannot be directly applied to the FBMC signal due to the overlapping nature of the FBMC signal. In the proposed method, each symbol in the FBMC signal is divided into several segments to solve the overlapping problem. Each segment is regarded as an independent unit, and rotates a suitable phase to minimise the PAPR in the frequency domain. The authors simulated the FBMC signal in the satellite communications by introducing the influence of the high power amplifiers and the Doppler frequency shift. The simulation results from complementary cumulative distribution function of the PAPR show that the proposed scheme can achieve about 0.3 dB PAPR performance compared to the existing dispersive SLM scheme, with lower complexity.

PAPR Reduction of TDCS Based on Chirp Noise Sequence

This letter proposes a transform domain communication system (TDCS) based on chirp noise sequence to deal with its high peak to average power ratio (PAPR). The optimal chirp noise sequence is obtained by the selective mapping to improve PAPR reduction of the proposed TDCS waveform with low complexity. Compared with other PAPR reduction algorithms, such as magnitude weighting selection and complementary peak reducing signal, the proposed TDCS based on optimal chirp noise sequence has about 1.5 dB PAPR reduction gain without extra bit error rate loss.

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.

Design of Highly Linear Broadband Continuous Mode GaN MMIC Power Amplifiers for 5G

In this paper, we present a design approach for broadband harmonic-tuned monolithic microwave integrated circuit (MMIC) power amplifiers (PAs). Two harmonic matching networks are proposed for the realization of continuous class-B and class-F modes in an integrated PA. A design procedure is developed for integrated PAs using these matching networks to achieve high linearity, broadband operation, and compact chip area, in the presence of parasitic components and the physical limitations of the MMIC process. Two proof-of-concept fully integrated PAs are implemented in a 0.25-μm GaN-on-SiC process. Output power of 34.2-36.4 dBm with 40% to 49% power-added efficiency (PAE) is achieved in 4.2-7.0 GHz (51.6% fractional bandwidth), from the continuous class-B PA with only 1.5-mm 2 chip area. Furthermore, the continuous class-F PA achieves 36.2 dBm output power and 52% PAE at 5.0 GHz. The PAs are also characterized using QAM signals with wide bandwidth, in order to evaluate their performance for 5G wireless applications. For a 64-QAM signal with 100-MHz bandwidth and 8 dB peak-to-average power ratio (PAPR), the continuous class-B PA achieves 29.3 dBm average output power, 28% average PAE, and -25 dB (5.5%) error vector magnitude (EVM). The continuous class-F PA, tested using a 200 MHz 256 QAM signal with 8.5 dB PAPR, provides an average output power of 28.5 dBm, average PAE of 27%, and -28 dB (4%) EVM, without any pre-distortion.

A Class-G Voltage-Mode Doherty Power Amplifier

This paper presents the combination of two back-off efficiency enhancement techniques, the voltage-mode Doherty and the class-G switched-capacitor power amplifier (PA), to achieve efficiency peaking at both 6 and 12 dB back off without introducing the mode-switching glitches present in previous architectures. The proposed technique enables transmission of high peak-to-average-power ratio (PAPR) signals with high efficiency while maintaining excellent linearity. The PA is fabricated in 45-nm CMOS SOI with integrated balun for power combining and matching. At 3.5 GHz a saturated output power of 25.3 dBm is measured with 30.4%/25.3%/17.4% power added efficiency (PAE) at 0/6/12 dB back off. With memoryless, non-adaptive linearization, the PA achieves 19.2% PAE with −35.8 dB error vector magnitude (EVM) while transmitting a 40 MHz 256-QAM 10.1 dB PAPR 802.11ac modulation. Significant efficiency improvement compared to class-B and EVM better than −34 dB is maintained over more than 1 GHz bandwidth.

Coding Efficiency and Bandwidth Enhancement in Polar Delta-Sigma Modulator Transmitter Using Quantization Noise Reduction and Parallel Processing Techniques

This paper introduces an architecture to enhance coding efficiency (CE) and bandwidth of the delta-sigma modulator (DSM) transmitters. In this architecture a low-pass envelope DSM (LPEDSM) is used instead of the traditional Cartesian low-pass DSM (LPDSM) to reduce the quantization noise and to improve the coding efficiency. The simulation results show that for an uplink long-term evolution (LTE) signal with 1.92[Formula: see text]MHz bandwidth, 7.8[Formula: see text]dB peak-to-average power ratio (PAPR), and an oversampling ratio (OSR) of 32, the CE for the polar LPEDSM transmitter is equal to 41.72% in comparison to 9.7% CE for the Cartesian LPDSM transmitter. In the next step, the CE and bandwidth of the transmitter are improved at the same time by using the quantization noise reduction technique in the polar LPEDSM transmitter with parallel baseband. By using this combined technique in the four-branch transmitter baseband part for an uplink LTE signal with 7.68[Formula: see text]MHz bandwidth, 7.8[Formula: see text]dB PAPR, and an OSR of 32, the CE is improved from 42.59% to 55.86% with 40[Formula: see text]dB signal-to-noise-and-distortion ratio (SNDR) while the clock speed is only 61.44[Formula: see text]MHz which is four times lower than the clock speed requirement of the conventional transmitter baseband part to achieve the same SNDR.

Performance Analysis of Layered ACO-OFDM

Layered asymmetrically clipped optical orthogonal frequency division multiplexing (LACO-OFDM) has been proposed for improving the spectral efficiency of conventional asymmetrically clipped optical OFDM. Multiple base layers that are orthogonal in the frequency domain are sequentially superimposed to form LACO-OFDM, where each superimposed layer fills the empty subcarriers left by the previous layer. As our contribution, the bit error ratio (BER) considering the effect of thermal noise, clipping distortion, inter-layer interference, and the bit rate difference between layers is analysed in this paper. Since the BER performance of LACO-OFDM is closely related to its peak-to-average power ratio (PAPR) distribution, we also provide the analytical expression of the PAPR distribution in this paper, which quantifies how the number of layers in LACO-OFDM reduces the PAPR. As a further advance, we propose a tone-injection aided PAPR reduction design for LACO-OFDM, which in turn improves the BER performance. Simulations are provided for verifying both the analytical BER performance and the PAPR distribution of LACO-OFDM. The results show that the expressions derived match well with the simulations. Furthermore, the PAPR reduction method proposed attains a 5 dB PAPR reduction at the $10^{-3}$ probability-point of the complementary cumulative distribution function, as well as a better BER performance than the original LACO-OFDM scheme.

Algorithm for reducing PAPR of Multicode CDMA using Reed–Muller codes

A new algorithm for reducing peak-to-average power ratio (PAPR) of multicode code division multiple access (MC-CDMA) systems under binary PSK modulation is presented. The algorithm is based on Reed-Muller (RM) codes that are modified by finding a suitable binary sequence that minimises the PAPR of the MC-CDMA. Three types of RM codes are investigated: namely, zero order, first order and second order. Simulation studies conducted show that the proposed algorithm achieves transmitter power savings of up to 6 dB. Zero-order and first-order codes exhibit 0 dB PAPR, while several others maintain a constant and low PAPR as compared with the original MC-CDMA systems.

A 65% efficient envelope tracking radio‐frequency power amplifier for orthogonal frequency division multiplex

A high-efficiency radio-frequency (RF) power amplifier (PA) is described for high peak-to-average power ratio (PAPR) orthogonal frequency division multiplexed signals. Envelope tracking is used, where the supply voltage of an RF amplifier is modulated in harmony with the envelope of the RF signal. The envelope modulator is a split-frequency design composed of a switched mode power supply (SMPS) for the low-frequency content, and a hybrid amplifier for the high-frequency part. The hybrid amplifier combines digital switching with a linear amplifier in a transformer coupled push-pull structure. For verification, a 7 dB PAPR 3 MHz bandwidth 3rd generation partnership project long-term evolution (LTE) signal is used. When amplifying the AC component of the LTE envelope signal, 56.2% efficiency is achieved by the hybrid amplifier at 4.6 W output power into a 10 Ω load. Combined with a 94.4% efficient SMPS, the modulator can produce 23.4 W at 83% efficiency. This is combined with an 80.3% efficient 300 MHz RF PA. Together they achieved 65.6% DC-to-RF efficiency at 18.2 W RF output power. The measured PAPR at the amplifier output was 6.5 dB.