Peak-to Average Power Research Articles

Implementation of particle swarm optimization based ICF technique to reduce the PAPR of ACO-OFDM

Abstract Orthogonal frequency division multiplexing (OFDM) is advantageous in terms of the spectral efficiency it offers. However, in OFDM, the bandwidth-efficient multicarrier modulation (MM) is limited by the peak-to-average power (PAPR) problem. Iterative clipping and filtering (ICF) method has been used in this work to address such issue. The ICF is regarded as a practical scheme that has become widely accepted and used due to the fact that it is characterized by low computational complexity. This method is also easily implemented, characterized by non-expansion of bandwidth, and it does not require the support to the receiver side during implementation. Nevertheless, the significant of this work is on further improvement where the method involves the iterative clipping of the same signals with a fixed clipping threshold (CT) in every clipping operation. Particle swarm optimization based ICF-OFDM, which is proposed in this research work, literally finds the most suitable clipping ratio, that eventually solves the problem of output power instability. Subsequently, the proposed method is implemented with asymmetrical clipped optical OFDM (ACO-OFDM) to validate the proposed method through the use of Matlab simulation. The PAPR reduction of the proposed method is then compared with the PAPR of the Hartley transform (DHT)-based ACO-OFDM and the traditional ACO-OFDM and DCO-OFDM. The best BER performance has been investigated via two modulation index. Results indicate that our method outperforms the counterparts in term of PAPR reduction and BER performance.

Low-complexity amplitude-division irregular QAM formats for short-reach unamplified coherent optical systems.

A low-complexity scheme is proposed to realize irregular uniform quadrature amplitude modulation (QAM) formats with Gray mapping, which are named amplitude-division irregular QAM (AD-Ir-QAM) formats. Compared to conventional probabilistic shaping (PS) with the Maxwell-Boltzmann (MB) distribution (PS-MB), irregular QAM formats show a smaller peak-to-average power (PAPR) and achieve a better performance in systems with the peak-power constraint. Compared with irregular QAM formats realized by PS (PS-Ir-QAM), AD-Ir-QAM formats realize a more flexible rate adaptation and have a lower implementation complexity. Experimental results obtained in an unamplified coherent optical system show that, at a generalized mutual information (GMI) of 4.5 bits/2D-symbol, AD-Ir-100QAM achieves gains of 2.1 and 0.5 dB in the power budget over PS-MB-100QAM and PS-Ir-100QAM, respectively.

Peak to average power ratio reduction techniques based on chirp selection for single and multi‐user orthogonal chirp division multiplexing system

AbstractThis article deals with peak to average power (PAPR) reduction in a single and multi‐user orthogonal chirp division multiplexing (OCDM) context. Two methods for PAPR reduction based on the selection of the frequency variation (up or down) of the chirps are first presented in a single user system. The first technique consists in considering two OCDM signals generated with up and down chirps, respectively, and selecting the one offering lowest PAPR. The second PAPR reduction method is based on usual clipping, and in that case the chirp selection aims to reduce the clipping noise. An adapted receiver is presented, based on the maximum likelihood estimation of the frequency variation (up or down) of the chirp. Then, a general procedure for multi‐user OCDM transmission is introduced, where a sub‐band of the available bandwidth is dedicated to each user, whose frequency of the chirps varies within this sub‐band. Next, the PAPR reduction techniques are generalised to this multi‐user OCDM system. Moreover, a performance analysis of the first PAPR reduction method is developed, and it is shown through simulations that theoretical and numerical results match for both Nyquist rate and oversampled signals. It is also shown that the chirp selection reduces the clipping noise, and improves the bit error rate performance compared with clipping only.

Implementation of FBMCbased Massive MIMOusing Space Time Block Coding

In wireless communication multipath propagation of signal will cause major drawbacks like Intersymbol interference (ISI), Delay spread, Doppler Spread and Intercarrier interference. These drawbacks are efficiently handled by using OFDM technology with Cyclic Prefix, but at the cost of High PAPR increasing the non-linear behaviour of Power Amplifier thereby increases BER and inband distortion, high out of band emissions and loss of spectral efficiency.To reduce the PAPR several PAPR reduction techniques have been proposed over the last few decades but at high complexity. Due to above drawbacks, OFDM technology is not able to provide the requirements of next generation wireless communication and thereby making it un-favourable for 5G communications. To overcome above drawbacks of OFDM, I used a, Filter Bank multicarrier (FBMC), 5G candidate waveform and proposed a method for reducing PAPR, Out-of-band emissions and latency with improving spectral efficiency. I developed a novel precoding method based on a pruned Discrete Fourier Transform (pDFT) in combination with Poly Phase Network (PPN) architecture. The proposed technique has the same peak-to average power ratio as OFDM but does not require a cyclic-prefix and has much lower out-of-band emissions. Furthermore, my method restores complex orthogonality and the ramp-up and ramp-down period of FBMC is dramatically decreased, allowing low latency transmissions. PPN is processed after pDFT, which transforms the received data into ISI-free data.

PAPR Reduction of NOMA Using Vandermonde Matrix-Particle Transmission Sequence

Non-Orthogonal Multiple Access (NOMA) is an ideal choice for 5G waveforms due to their characteristics such as high data rate, massive device connectivity, high spectral access, and effective frequency selective fading. Thus, it permits gigantic connectivity. The spectrum overlaps with NOMA, which consents several operators to segment the spectrum at the same frequency. These features make NOMA more suitable for use beyond 5G. Peak to Average Power (PAPR) is a major problem in Multi-Carrier Techniques (MCT) like NOMA and it also degrades the performance of the amplifier. The Partial Transmission Sequence (PTS) is a superior algorithm for moderating the PAPR. However, it also increases the complexity of the structure. The PAPR is reduced in NOMA by multiplying the NOMA signal with optimised phase vectors (P). The phase vectors are generated by using the Vandermonde Matrix (VM). In this work, we proposed a VM-PTS algorithm for the NOMA system, and the number of computations to search the optimal phase vectors for NOMA high PAPR signal is less as compared with existing PTS. The outcomes demonstrate that the performance of the recommended PTS in terms of PAPR, Bit Error Rate (BER), and complexity is better than the conventional PTS (C-PTS).

Power Domain Multiplexing Waveform for 5G Wireless Networks

Power domain non-orthogonal multiple access combined with a universal filtered multi-carrier (NOMA-UFMC) has the potential to cope with fifth generation (5G) unprecedented challenges. NOMA employs power-domain multiplexing to support several users, whereas UFMC is robust to timing and frequency misalignments. Unfortunately, NOMA-UFMC waveform has a high peak-to-average power (PAPR) issue that creates a negative affect due to multicarrier modulations, rendering it is inefficient for the impending 5G mobile and wireless networks. Therefore, this article seeks to presents a discrete Hartley transform (DHT) pre-coding-based NOMA enabled universal filter multicarrier (UFMC) (DHT-NOMA-UFMC) waveform design for lowering the high PAPR. Additionally, DHT precoding also takes frequency advantage variations in the multipath wireless channel to get significant bit error rate (BER) gain. In the recommended arrangement, the throughput of the system is improved by multiplexing the users in the power domain and permitting the users with good and bad channel conditions to concurrently access the apportioned resources. The simulation outcomes divulge that the projected algorithm accomplished a gain of 5.8 dB as related to the conventional framework. Hence, it is established that the proposed DHT-NOMA-UFMC outperforms the existing NOMA-UFMC waveform. The key benefit of the proposed method over the other waveforms proposed for 5G is content gain due to the power domain multiplexing at the transmitting side. Thus, a huge count of mobile devices could be supported under specific restrictions. DHT-NOMA-UFMC can be regarded as the most effective applications for 5G Mobile and Wireless Networks. However, the main drawback of the proposed method is that the Fourier peak and phase signal is not easily estimated.

Generalized Expression and Design Method of Modified Load Networks for Doherty Power Amplifier With Extended Back-Off Range

This paper presents a generalized expression of the modified load networks (MLNs) for Doherty power amplifiers (DPAs) with an extended output power back-off (OBO) range. Based on the analysis using this new expression, a new circuit structure generally applicable to any combination of the multiple MLNs is proposed. The load network has a simple structure including impedance matching circuits and offset lines for the carrier and peaking amplifiers. A design procedure for the proposed load network is presented. A DPA using any optimized combination of the multiple MLNs can be easily designed using the proposed load network. For verification, a GaN-HEMT symmetrical DPA based on a combination of the virtual open-stub (VOS) and out-phased current combining (OCC) methods was designed and implemented for the frequency band of 3.4 - 3.7 GHz. The reversed uneven power splitting method is adopted in the design for higher power gain. Using the 5G New Radio (NR) signal with a peak-to average power ratio (PAPR) of 7.9 dB and a signal bandwidth of 100 MHz, the proposed DPA exhibited DE of 55.3 - 60.9% with a power gain of 11.9 - 12.7 dB at an average output power of 33.7 dBm. An adjacent channel leakage power ratio (ACLR) of -42.6 - -44.8 dBc was achieved at the average power level by using a digital predistortion (DPD) technique across the band.

Investigations into Balancing Peak-to-Average Power Ratio and Mean Power Extraction for a Two-Body Point-Absorber Wave Energy Converter

The power harnessed by wave energy converters (WECs) in oceans is highly variable and, therefore, has a high peak-to-average power (PTAP) ratio. To minimize the cost of a WEC power take off (PTO) system, it is desirable to reduce the PTAP ratio while maximizing the mean power extracted by WECs. The important issue of how PTAP ratio reduction measures (such as adding an inertia element) can affect the mean power extracted in a reference model has not been thoroughly addressed in the literature. To investigate this correlation, this study focuses on the integration of the U.S. Department of Energy’s Reference Model 3, a two-body point absorber, with a slider-crank WEC for linear-to-rotational conversion. In the first phase of this study, a full-scale numerical model was developed that predicts how PTO system parameters, along with an advanced control algorithm, can potentially affect the proposed WEC’s PTAP ratio as well as the mean power extracted. In the second phase, an appropriate scaled-down model was developed, and extracted power results were successfully validated against the full-scale model. Finally, numerical and hardware-in-the-loop (HIL) simulations based on the scaled-down model were designed and conducted to optimize or make trade-offs between the operational performance and PTAP ratio. The initial results with numerical and HIL simulations reveal that gear ratio, crank radius, and generator parameters substantially impact the PTAP ratio and mean power extracted.

A comprehensive study on the role of advanced technologies in 5G based smart hospital

In the present scenario, orthogonal frequency division multiplexing (OFDM) waveform technique is playing a significant part in smart hospitals. Still, its impact is not effective in smart hospitals due to the numerous limitations such as loss of bandwidth due to the use of guard band, spectrum leakage, high peak to average power (PAPR), high detection delay, and thus along. Right now, fifth-generation (5G) employment is becoming regularized around the world and the state-of-the-art radio system is expected to meet all the demands of smart hospitals. High spectrum access, massive capacity, high throughput, and low PAPR are the requirements of smart healthcare hospitals. The digital hospital has seen tremendous progression in bandwidth requirements. From transmitting medical images to wearable devices, networks must operate at maximum speeds to safeguard patient care. The selection of competent transmission technologies will play an important role in the regularization of digital hospitals equipped with 5G. In the projected work, we focus on the implementation of novel waveforms such as Non-orthogonal multiple access (NOMA), Universal filter multi-carrier (UFMC), and filter bank multi-carrier (FBMC) system. Several parameters such as power spectrum density, bit error rate, capacity, and PAPR of advanced waveforms and OFDM methods are analyzed and studied.

Performance Evaluation of MRMED Algorithm by Monitoring BER

In this research work, we have developed a communication system (transmitter / receiver) to control peak to average power (PAPR) with small bit error rate (BER) for a 4G system called multicode code division multiple access (MCCDMA). Proposed communication system works on modified Reed Muller encoded data (MRMED) string. In MRMED data is first encoded with Reed Muller (RM) code. Thereafter, encoded RM message is XORed with optimal binary string, which results lower Peak to Average Power ratio (PAPR). A well-known fact is that, bit error rate (BER) is the best performance measurement tool for a communication system. To check the integrity of our communication system, we have run the simulation for monitoring BER using MRMED sequence. Simulation work conducted, with multipath Rayleigh fading, Minimum Shift Keying (MSK) modulation and several orders of RM codes. Our results show that implementing MRMED sequences of the suggested MCCDMA communication structure, returns noticeable lower BER. For instance, in case of RM(1,4), that has error improvement proficiency of 3 (three) errors , returns BER = 8.2x10−5 adopting MSK, at SNR = 12dB. Similarly, for RM(2,3), which has error improvement efficiency of 0 error and shows distinct BER of 4.9x10−4 at 12dB (SNR).In addition to using simulation for checking BER performance of our communication system, we have also shown in our results that, as the error improvement capability of different RM codes surges, correspondingly we get a lower BER.

Performance Analysis of OFDM With Peak Cancellation Under EVM and ACLR Restrictions

This paper presents performance analysis of an adaptive peak cancellation method to reduce the high peak-toaverage power ratio (PAPR) for OFDM systems, while keeping the out-of-band (OoB) power leakage as well as an in-band distortion power below the pre-determined level. In this work, the increase of adjacent leakage power ratio (ACLR) and error vector magnitude (EVM) are estimated recursively using the detected peak amplitude. We present analytical framework for OFDM-based systems with theoretical bit error rate (BER) representations and detection of optimum peak threshold based on predefined EVM and ACLR requirements. Moreover, the optimum peak detection threshold is selected based on the oretical design to maintain the predefined distortion level. Thus, their degradations are automatically restricted below the pre-defined levels which correspond to target OoB radiation. We also discuss the practical design of peak-cancellation (PC) signal with target OoB radiation and in-band distortion through optimizing the windowing size of the PC signal. Numerical results show the improvements with respect to both achievable bit error rate (BER) and PAPR with the PC method in eigen-beam space division multiplexing (E-SDM) systems under restriction of OoB power radiation. It can also be seen that the theoretical BER shows good agreements with simulation results.

Research on optical 32QAM-OFDM-PON access scheme with different numbers of sub-carriers using DMT modulation

An optical 32QAM-OFDM-PON system with different numbers of sub-carriers using discrete multitone (DMT) modulation and demodulation is designed and demonstrated by experiment. Electron-optic generation, directly photoelectric detection, and electrical self-mixing reception of 32QAM-OFDM downstream signals are achieved. 5Gb/s 32QAM-OFDM downlink signals with different numbers of sub-carriers are successfully transmitted over 42 km SMF-28. Peak-to average power ratio (PAPR) characteristic, computational complexity and bit error rate (BER) performance are analyzed. The results show that the sub-carriers numbers of 32QAM-OFDM downlink signals should be carefully selected according to the actual requirements, if spectral efficiency, PAPR characteristic, computational complexity and receiver sensitivity are considered.

Adaptive SOICAF Algorithm for PAPR Mitigation in OFDM Systems

Orthogonal frequency division multiplexing (OFDM) technology widely used in wireless communications applications for its high data rate. The major limitation of OFDM is the peak-to-average power (PAPR) problem. Several techniques were applied to mitigate PAPR in OFDM application systems. One of the schemes used for PAPR mitigation is Iterative clipping and filtering (ICAF). It uses the same or identical signals for recursive clipping with a constant threshold level for distinct levels of iterations. This scheme drives signal processing blocks like Fast-Fourier transform (FFT)/inverse FFT (IFFT) blocks the number of times to achieve the required level of PAPR, thereby consumes the average system power and takes more computational time. For further improvement, a new adaptive algorithm to mitigate PAPR in OFDM systems proposed. The proposed adaptive algorithm Lagrange multiplier optimization. Results after simulation justify that depending on the threshold value, PAPR reduction achieved with a slight degradation in BER compared with other existing techniques. BER remains same for low threshold level value, but for high threshold level values it is little bit degraded. Over all PAPR reduction, it performs better by 4 dB when compared to the other schemes. In the case of BER tradeoffs, the complexity of the design and computational speed of resources usage minimized. By carefully selecting the clipping threshold, we can achieve same BER with good reduction in PAPR.

PAPR Reduction Using Iterative Clipping/Filtering and ADMM Approaches for OFDM-Based Mixed-Numerology Systems

Mixed-numerology transmission is proposed to support a variety of communication scenarios with diverse requirements. However, as the orthogonal frequency division multiplexing (OFDM) remains as the basic waveform, the peak-to average power ratio (PAPR) problem is still cumbersome. In this paper, based on the iterative clipping and filtering (ICF) and optimization methods, we investigate the PAPR reduction in the mixed-numerology systems. We first illustrate that the direct extension of classical ICF brings about the accumulation of inter-numerology interference (INI) due to the repeated execution. By exploiting the clipping noise rather than the clipped signal, the noise-shaped ICF (NS-ICF) method is then proposed without increasing the INI. Next, we address the in-band distortion minimization problem subject to the PAPR constraint. By reformulation, the resulting model is separable in both the objective function and the constraints, and well suited for the alternating direction method of multipliers (ADMM) approach. The ADMM-based algorithms are then developed to split the original problem into several subproblems which can be easily solved with closed-form solutions. Furthermore, the applications of the proposed PAPR reduction methods combined with filtering and windowing techniques are also shown to be effective.

Combined Envelope Scaling with Modified SLM Method for PAPR Reduction in OFDM-Based VLC Systems

Abstract Orthogonal frequency-division multiplexing technique (OFDM) has been adopted widely as a modulation technique for radio frequency (RF) and optical communication systems such as visible-light communication (VLC) due to its high spectral efficiency and low-complexity implementation. VLC-OFDM is recommended in 5 G mobile communication. However, VLC-OFDM suffer from the high peak to-average power ratio (PAPR). In this paper, a modified selective mapping (MSLM) method is applied to the proposed system followed by a new envelope scaling process for further reductions in PAPR of VLC-OFDM system. Simulation results show that the proposed method reduces the PAPR by about 6.8 and 1.7 dB comparing with the original signal and the traditional SLM with a number of rotation vector U = 8, respectively.

Linear and Non-Linear Companding Transformation Reducing PAPR in OFDM Signals

An important disadvantage of Orthogonal Frequency Division Multiplexing (OFDM) signals is high peakto-average power ratio (PAPR), causing genuine debasement popular execution when a nonlinear power amplifier (PA) is utilized. A notable technique to diminish power ratio deprived of confinements on framework parameters is Companding Transform (CT), for example, the sum of subcarriers, outline organization, and gathering type. Another nonlinear companding change, the utilization of hyperbolic transfer sigmoid function capacity is proposed for PAPR decrease in this paper. The proposed methodology extends the little flag and packs the pinnacle flag in the time zone at the same time without changing the average power. Results dependent on MATLAB demonstrate that the proposed methodology increases additional pinnacle decrease and improves the BER (bit error ratio)execution.

Peak Average Power Ratio Reduction Technique For Better Performance With Multi Input Multi Output

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 various novel PAPR reduction schemes to show the effectiveness.

A Compact Ka/Q Dual-Band GaAs MMIC Doherty Power Amplifier With Simplified Offset Lines for 5G Applications

In this paper, a Ka/Q dual-band Doherty power amplifier (DPA) with simplified offset lines is implemented in a 0.1-μm gallium arsenide (GaAs) process. It is found that the dual-band transmission lines (TLs) employed in the sub-6-GHz dual-band DPA are not suitable to be used as the offset lines in millimeter-wave (mm-wave) dual-band DPAs due to their large sizes and insert losses. An in-depth analysis reveals that the phase requirement of the offset lines can be relaxed, and the DPA exhibits a reasonable performance in a certain phase-shift range. A novel design method is proposed to realize offset lines using simple TLs, which can satisfy the phase-shift ranges in dual bands by choosing a proper electrical length. To enhance the gain of the DPA, a reversed uneven power splitter is adopted to deliver more power to the main power amplifier (PA). The fabricated DPA achieves an output power of 25.4/25.2 dBm, a peak power-added efficiency (PAE) of 33%/25%, and a 6-dB back-off PAE of 22%/17% at 29/46 GHz, respectively, with a compact size of 2.2 1.4 mm2. Applying a 20-MHZ 64-quadraticamplitude modulation (QAM) signal with a 7.7-dB peak-toaverage power ratio (PAPR), the measured average output power, PAE, and error vector magnitude (EVM) at 29/46 GHz are 18.4/19 dBm, 17%/15%, and 1.5%/1.1% after linearization, respectively. To the best of our knowledge, the proposed DPA is the first demonstration of mm-wave dual-band DPAs that do not require any additional switching or reconfiguration.

A New Approach to Iterative Clipping and Filtering PAPR Reduction Scheme for OFDM Systems

While achieving reduced/good peak-to-average power (PAPR) in orthogonal frequency division multiplexing (OFDM) systems is attractive, this must not be performed at the expense of the transmitted signal with over-reduced signal power, as it leads to degraded bit error ratio (BER). We introduce a uniform distribution approach to solving the PAPR reduction problem of OFDM signals and then use Lagrange multiplier (LM) optimization to minimize the number of iterations involved in an adaptive fashion. Due to the nonlinear attenuation of the PAPR reduction scheme, we compensate the output signal using a correlation factor that minimizes the error floor in the in-band distortion of the clipped signal using the minimum mean square error method so as to improve the BER performance. Three different methods are introduced each enabling PAPR reduction by clipping followed by filtering with no direct dependence on a clipping ratio parameter. We find that our approach significantly reduces the PAPR of the OFDM signals (especially with LM optimization) better than the conventional adaptive iterative clipping and filtering operating without LM optimization. Based on our proposed methods, we additionally outline two simple steps for achieving perfect PAPR reduction (i.e., 0 dB). We also evaluate the performance of the three new models over high power amplifier (HPA) for completeness; the HPA is found to induce negligible BER degradation effects on the processed signal compared with the unprocessed signal.

Performance enhanced DDO-OFDM system with adaptively partitioned precoding and single sideband modulation.

As a promising solution for short-to-medium transmission systems, direct detection optical orthogonal frequency division multiplexing (DDO-OFDM) or discrete multi-tone (DMT) has been intensively investigated in last decade. Benefitting from the advantages of peak-to-average power (PAPR) reduction and signal-to-noise ratio (SNR) equalization, precoding techniques are widely applied to enhance the performance of DDO-OFDM systems. However, the conventional method of partitioning precoding sets limits the ability of precoding schemes to optimize the SNR variation and the allocation of modulation formats. Thus, the precoding transmission systems are hard to reach the capacity that traditional bit-power loading (BPL) techniques, like the Levin-Campello (LC) algorithm, can achieve. In this paper, we investigate the principle of SNR variation for precoded DDO-OFDM systems and theoretically demonstrate that the SNR equalization effect of precoding techniques is actually determined by the noise equalization process. Based on this fact, we propose an adaptively partitioned precoding (APP) algorithm to unlock the ability to control the SNR of each subcarrier. As demonstrated by the simulation and experimental results, the proposed APP algorithm achieves the transmission capacity as high as the LC algorithm and has nearly 1 dB PAPR reduction. Besides, the look-up table (LUT) operation ensures low complexity of the proposed APP algorithm compared with LC algorithm. To avoid severe chromatic dispersion (CD) induced spectral fading, single sideband (SSB) modulation is also implemented. We find that SSB modulation can reach the capacity of double sideband (DSB) modulation in optical back-to-back (OB2B) configuration by optimizing the modulation index. Therefore, the APP based SSB-DDO-OFDM scheme can sufficiently enhance the performance of cost-sensitive short-to-medium reach optical fiber communication systems.