Peak-to-average Power Ratio Of Orthogonal Frequency Division Multiplexing Signal Research Articles

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

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

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

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

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

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

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

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

PAPR Reduction in OFDM Systems Using Hybrid Zadoff-Chu Transform Precoding and Partial Transmit Sequence

Orthogonal Frequency Division Multiplexing (OFDM) is a multicarrier modulation (MCM) scheme that plays a significant role in digital wireless communication. As a result of its high data rate capability and immunity to multipath fading effect, among others, OFDM remains an ideal technology for 5G communication systems and beyond. Unfortunately, a major drawback of this technology is the high peak-to-average power ratio (PAPR). Nevertheless, many techniques for reducing PAPR have been proposed in the past to address this problem. However, all the techniques previously used have limitations such as high computational complexity, data rate loss, high signal distortion, increase in bandwidth, increase in transmit power, and memory requirements. In this paper, a hybrid technique that combines Zadoff-Chu Transform (ZCT) precoding and Partial Transmit Sequence (PTS) for reducing high PAPR in OFDM signals is presented. To reduce the data rate loss and computational complexity in PTS when a large subblock is used, a Zadoff-Chu precoding is applied to OFDM symbols to precode the symbol before applying PTS with a fewer number of subblocks. An OFDM model was developed where ZCT and PTS techniques were implemented. The performance of the hybrid model was analyzed using Power Spectral Density (PSD), Complementary Cumulative Distribution Function (CCDF), and Bit Error Rate (BER). The simulation result indicates that the hybrid ZCT-PTS provides a better result than using either Zadoff-Chu precoding technique or Partial Transmit Sequence technique separately. A PAPR of 4.2 dB and BER of 3dB is achieved for hybrid ZCT-PTS. The hybrid technique provides a better system performance when compared with Conventional OFDM systems.

An efficient and improved PTS algorithm for PAPR reduction in OFDM system

ABSTRACT In this research, an improved PTS algorithm is projected for diminishing peak to average power ratio (PAPR) of well accepted and effective orthogonal frequency division multiplexing (OFDM) system. OFDM is also considered as trustworthy method for several wireless communication applications and obtained a lot of research interests but unfortunately, one of the most important concern is very high PAPR in OFDM signals, which deteriorates system performance thus this is the most important drawback. To address this problem, a novel partial transmit sequence (PTS) algorithm is projected based upon centering phase sequences matrix (PTS-CPSM-Algo). These phase sequences are used for optimization of data so that minimum PAPR can be obtained. This algorithm obtains significant reduction in PAPR which leads to the enhancement in performance of OFDM system. From the developed analysis and simulation results, supremacy can be clearly seen for proposed PTS-CPSM-Algo over already existing OFDM system, selected mapping (SLM) and partial transmit sequence (PTS).

A Novel Clipping-Based Method to Reduce Peak-To-Average Power Ratio of OFDM Signals

Orthogonal frequency division multiplexing (OFDM) is a widely used technology for wireless broadband communications. However, it also suffers from some drawbacks. One of the critical limitations is the problem of high peak-to-average power ratio (PAPR), which causes distortions of some nonlinear components such as power amplifiers. A number of techniques have been proposed to reduce the PAPR of OFDM signals, among which the clipping-based methods have gained a lot of attention due to the effective PAPR reduction and simplicity of implementation. This paper proposes a novel clipping-based method to reduce the PAPR of OFDM signals. Based on the recently proposed clipping noise compression (CNC) method, the proposed scheme introduces a preset normalization factor to replace the calculation of average amplitude of clipping noise in the original CNC method during compression processing. Comparative simulations were carried out, and the results exhibit that the proposed method achieves better bit-error-ratio performance with equal level of PAPR reduction compared to the original CNC method.

PAPR reduction in OFDM system for DVB-S2

<p>A special form of multicarrier modulation is Orthogonal Frequency Division Multiplexing (OFDM) which is offer high spectral efficiency for high speed data transmission through multipath fading channels. Many advantages can be achieved by using OFDM in addition to spectral efficiency like its robustness against intersymbol interference and multipath effect. One of a major drawback of OFDM is high Peak-to-Average Power Ratio (PAPR) of the transmitted signal which leads to a distortion in the power amplifier and causes decreasing the efficiency of power amplifier. To reduce PAPR of OFDM signal many of promising solutions have been proposed and implemented. In this paper, a joint Low Density Parity Check code (LDPC), Discrete Cosine Transform (DCT) and μ-law companding is proposed to reduce PAPR of OFDM signal at transmitter. Comparison of these PAPR reduction techniques is done based on CCDF performance of the system.</p>

A Hybrid Approach to Reduce the PAPR of OFDM Signals Using Clipping and Companding

Orthogonal frequency division multiplexing (OFDM) is an important technology that has been widely used in broadband wireless communications. However OFDM has some drawbacks, one of which is the high peak-to-average power ratio (PAPR) problem. Many techniques for reducing PAPR thus have been proposed in the literatures, where clipping and companding are effective techniques and have gained a lot of research interest. Based on the study of clipping and companding, this paper proposes a hybrid approach to reduce the PAPR of OFDM signals. An iterative clipping and filtering (ICF) technique and an enhanced nonlinear companding (ENC) scheme are used as the typical clipping and companding techniques in this paper. The results of the analysis show that the computational complexity of the proposed method is slightly higher than that of ENC, but much lower than that of ICF. And the simulation results show that the proposed method has better performance on PAPR reduction and bit error rate (BER) in contrast to ICF. On the other hand, compared to ENC with equal PAPR reduction, the proposed method still achieves better performance on BER.

Performance analysis of CE-OFDM-CPM Modulation using MIMO system over wireless channels

Orthogonal Frequency-Division Multiplexing (OFDM) is a multicarrier modulation that has expanded attractiveness and is used for wireless communication system. However one key weakness of OFDM signal is the high Peak-to-Average Power Ratio (PAPR). The high PAPR of OFDM signal cause nonlinear distortions by the power amplifier, which in turn affects negatively the OFDM transmission signal. These nonlinearities in amplifiers cause both Inter-Symbol Interference (ISI) and inter-carrier interference (ICI) in the system. A “power back-off” is required to prevent spectral broadening and performance degradation from inter-modulation distortion. To overcome this problem we propose Constant Envelope OFDM (CE-OFDM) which provides a good solution to the high PAPR issue in OFDM. OFDM signal is transformed, by way of Phase Modulation (PM), to a constant envelope signal, thereby alleviating the need for a power back-off and allowing for the most efficient power amplifier operation possible. In this paper the implementation of Maximum-Likelihood Sequence Estimation (MLSE) channel equalization in CE-OFDM-PM is proposed, a performance gain comparison and evaluation over fast fading channels well be presented and discussed. At the same time, Multiple-Input Multiple-Output (MIMO) system is found to provide better performance over wireless channels by providing communication links with substantial diversity and capacity. Likewise for MIMO system, simulation results are given in terms of BER (Bit Error Rate) to show the performance gain of the Alamouti code and of the proposed receiver. The simulation results show that the Minimum Mean Square Error (MMSE) is the best one to avoid ISI.

A novel hybrid genetic algorithm to reduce the peak-to-average power ratio of OFDM signals

Orthogonal frequency division multiplexing (OFDM) is an effective approach for high rate data transmission in telecommunication systems. The high peak-to-average power ratio (PAPR) is one of the main drawbacks of the OFDM systems. Partial transmit sequence (PTS) is an efficient method to decrease the PAPR of OFDM signals. But, the PTS technique needs an exhaustive search over all combinations of phase rotation factors and the computational complexity grows exponentially with the number of sub-blocks. To reduce the search complexity, we introduce a novel hybrid genetic algorithm (HGA) in the PTS technique. The important aspect of the proposed method is the choice of salient phase factors to reduce the high PAPR. The proposed HGA-PTS approach incorporates novel local search operations that are designed and embedded in the genetic algorithm to explore the optimum phase factors. Numerical simulations are performed for 16-QAM modulated symbols and the obtained results show that the HGA-PTS significantly reduces both the PAPR and search complexity.

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.

A Clipping-Noise Compression Method to Reduce PAPR of OFDM Signals

Iterative clipping and filtering (ICF) is widely employed in the orthogonal frequency-division multiplexing (OFDM) systems to reduce the peak-to-average power ratio (PAPR). However, the conventional ICF-based methods usually involve numerous transformations between the frequency domain and the time domain and run into numbers of iteration. This letter proposes a clipping-noise compression method, in which the transmitted OFDM signal is modified in the time domain by clipping and noise compression. The computational complexity is greatly reduced owing to the fact that only one fast Fourier transform is needed in the approach. Furthermore, the proposed method exhibits better PAPR reduction and bit error rate (BER) performance in the simulations compared with the conventional ICF-based methods.

Complexity reduction of PTS technique to reduce PAPR of OFDM signal used in a wireless communication system

A new partial transmit sequence (new-PTS) scheme is illustrated in this study. The target behind it is to reduce the peak-to-average power ratio (PAPR) in an orthogonal frequency division multiplexing (OFDM) system. Despite its competitive attributes, the PTS technique is considered computationally expensive due to multiple inverse fast Fourier transforms (IFFT) and the need of a thorough investigation to find the optimal phase factor. The primary concern, thus, is to eliminate the IFFT blocks. In the present study, a remarkable strategy has been followed, mainly relying on analysing the available data in the random access memory. Additionally, the least PAPR value is calculated and its corresponding address is precisely determined; such an address is the side information to be sent to recover the users' original data at the OFDM receiver. Moreover, the effectiveness of the so-called complexity reduction of the new-PTS method is pointed out in order to limit the number of searches that are required to acquire the best PAPR performance, which significantly reduces the computational complexity overhead. Consequently, the numerical analysis and comparative study show the overall high performance, which the proposed PTS scheme offers in respect to both the bit error rate and PAPR reduction.

Low-Complexity Blind Selected Mapping Scheme for Peak-to-Average Power Ratio Reduction in Orthogonal Frequency-Division Multiplexing Systems

Orthogonal frequency-division multiplexing (OFDM) is an attractive multicarrier technique for the simplicity of equalization and high data throughput. However, the transmitted OFDM signal has a very high peak-to-average power ratio (PAPR), which severely degrades the performance of practical OFDM systems and reduces the efficiency of high-power amplifiers (HPA). The selected mapping (SLM) scheme is an effective PAPR reduction method of OFDM signals. However, this approach usually requires side information (SI) transmission, which increases the difficulty of the hardware implementation with high complexity and reduces the data transmission rate. In this paper, based on designing phase rotation vectors in the time domain, a novel blind SLM method with low complexity is proposed to reduce the PAPR of OFDM signals. At the transmitter, the proposed method properly designs the phase rotation vectors in the time domain, which can be considered as an equivalent wireless channel without SI transmission. At the receiver, the effect of phase rotation vectors can be removed by the conventional channel estimation method, and the data demodulation processing can be easily performed by the frequency domain equalization. Simulation results show that the proposed scheme can achieve low complexity in PAPR reduction and has great robustness in bit error rate (BER) performance compared to the other low-complexity SLM PAPR schemes.

Low complexity reconfigurable complex filters for PAPR reduction of OFDM signals: analysis, design and FPGA implementation

In this study, the authors analyse the reconfigurable filtering techniques based on the tone reservation (TR) set and data bearing subcarriers in the time domain and frequency domain to reduce the peak-to-average power ratio (PAPR) of orthogonal frequency division multiplexing (OFDM) signals. The hardware architecture of these filters is proposed and mapped onto Xilinx Artix-7 field programmable gate array (FPGA) with 16-bit fixed-point representation to achieve a trade-off between numerical accuracy and hardware resource utilisation. The simulation results of the proposed methods and experimental results on FPGA for 16-quadrature amplitude modulation (QAM) and 64-QAM modulation are presented. These results show that the PAPR of OFDM signals is significantly reduced (about 7 dB) after 2–4 iterations. Performance comparison of the proposed methods with some typical methods of PAPR reduction, such as clipping-and-filtering and TR techniques, is presented.

Modified switching DE algorithm to facilitate reduction of PAPR in OFDM systems

Partial Transmit Sequence (PTS) currently can be regarded as an extremely attractive and popular method which allows the achievement of very good Peak to Average Power Ratio (PAPR) reduction for signals that have undergone Orthogonal Frequency Division Multiplexing (OFDM), while also is being a technique which does not distort the signals being processed. In this method, a comprehensive search is conducted taking into account all possible combinations of phase-factors that can occur, leading to an increasing complexity of computation with respect to increasing in sub-blocks. The current paper outlines a novel low complexity sub-optimal PTS technique with its basis in an altered implementation of Differential Evolution (DE) algorithm shortly MBLX-DE which significantly diminishes the PAPR of OFDM signals. More specifically SWDE_Sucess_MBLX (Switched parameter Differential Evolution with success based mutation and modified blending crossover) algorithm (Ghosh et al., 2017) is modified in an efficient way and has been implemented for the PTS scheme. The proposed algorithm introduces modifications in three stages of SWDE_Sucess_MBLX like population central tendency based mutation scheme is incorporated along with the success based mutation, a random selection between two cross-over strategies with blending rate concept and threshold-based selection. A theoretical performance study with general formulas of the proposed scheme is presented and a comparative analysis is done with existing algorithms. Extensive simulation results demonstrate that our proposed method can substantially outperform against the currently best-known algorithms in the context of reduction of PAPR as well as performance in terms of complexity of the computations to be performed.

Root-Based Nonlinear Companding Technique for Reducing PAPR of Precoded OFDM Signals

Orthogonal frequency division multiplexing (OFDM) signals are characteristically independent and identically distributed Gaussian random variables that follow Rayleigh distribution. The signals also exhibit high peak-to-average power ratio (PAPR) problem due to the infinitesimal amplitude component distributed above the mean of the Rayleigh distribution plot. Since the amplitudes are nonlinearly and non-monotonically increasing, applying roots to the amplitude distribution is shown in this paper to change the probability density function (PDF) and thus reduces the PAPR. We exemplify these by imposing this constraint on standard $\mu $ -law companding (MC) technique in reducing PAPR of OFDM signals, which is known to expand the amplitudes of low power signals only without impacting the higher amplitude signals. This limits the PAPR reduction performance of the MC scheme. Since companding involves simultaneously compressing/expanding high/low amplitude OFDM signals, respectively, in this paper, we refer to the new method as a root-based MC (RMC) scheme that simultaneously expands and compresses OFDM signal amplitudes unlike MC. In addition, we express a second transform independent of the MC model. The results of the two proposed schemes outperform four other widely used companding techniques [MC, log-based modified (LMC), hyperbolic arc-sine companding (HASC) and exponential companding (EC)]. Besides these, we precode the OFDM signals using discrete Hartley transform (DHT) in order to further reduce the PAPR limits achieved by RMC by distorting the phase. While preserving the BER, DHT-precoded RMC outperforms all the four other companding schemes (MC, EC, HASC, LMC) in terms of PAPR.

Hybrid STBC-PTS with enhanced artificial bee colony algorithm for PAPR reduction in MIMO-OFDM system

Peak-to-average power ratio (PAPR) is found to be a significant role in multiple input, multiple output (MIMO) orthogonal frequency division multiplexing (OFDM) systems. Partial transmit sequence (PTS) is one of the effective methods to reduce the PAPR in OFDM signals. However, finding an optimum phase factor in PTS scheme is considered to be a significant issue. In order to overcome this problem, we use orthogonal initialization method to identify the initial population for enhanced Artificial Bee Colony (ABC) algorithm. In addition, PTS technique uses exhaustive search method to find the better combination of phase factors. This would also increase the computational complexity of the system. In order to overcome this issue, a newly suboptimal method is also used in the enhanced ABC algorithm. Finally, we have combined the space time block coding (STBC) and the PTS based enhanced ABC algorithm to reduce the PAPR and bit error rate (BER). The orthogonal initialization method and suboptimal method in ABC algorithm greatly reduces the PAPR and BER in the OFDM system. MATLAB software is used to run this simulation.

DFT-spread combined with clipping method to reduce the PAPR in VLC-OFDM system

Orthogonal frequency division multiplexing (OFDM) is an attractive technique to realize high data rate in light emitting diodes (LEDs)-based visible light communication (VLC). However, high peak-to-average power ratio (PAPR) of OFDM makes VLC-OFDM very sensitive to the nonlinearity of LEDs. In this paper, the discrete Fourier transform-spread (DFT-spread) combined with clipping method is proposed to reduce the PAPR of OFDM signal in VLC system. Combining simulation with experiment, a performance comparison is made among conventional OFDM, DFT-spread-OFDM, and clipped DFT-spread-OFDM with different clipping ratios (CRs) in a single LED-based VLC system. The experimental results show that the proposed clipped DFT-spread-OFDM method can effectively improve the system performance compared with the other two methods. At the optimum signal peak-to-peak (PTP) value, by using the clipped DFT-spread-OFDM scheme with CR at 8 dB, the bit error rate (BER) of the system can be reduced from 0.003 7 to 0.000 287.1