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One of major drawbacks of Orthogonal Frequency Division Multiplexing (OFDM) is the high Peak-to-Average Power Ratio (PAPR) of the transmit signal. Due to the non-linear characteristics of the power amplifier (PA), significant out-of- band and in-band distortions occur when high peak signals exceed the saturation level of the PA. In this paper we pr...
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... verify the proposed PAPR reduction technique, we tested it in the IEEE 802.11a, IEEE802.16e (WiMax) and DVB systems. Here we show the results of a WLAN IEEE 802.11a system. We employed 5 of the unused tones to reduce the PAPR. 16 QAM modulation was employed. Fig. 4 illustrates the complementary cumulative distribution function (CCDF) plot, in which a decrease in PAPR of up to 4 dB is obtained by employing the new technique in an IEEE802.11a system. On average 4 iterations are required so that an optimum solution can be obtained. Simulations were carried out involving PAPR reduction with use of ...
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Citations
... Many researchers introduced such techniques and classified PAPR into several classes. In terrestrial communication, clipping is the easiest way to mitigate PAPR [20][21][22][23]. Moreover, reconstruction of the lost clipped signal, iterative clipping, and filtering have been introduced [24][25][26]. ...
Underwater Acoustic (UWA) communication networks are commonly formed by associating various independent UWA vehicles and transceivers connected to the bottom of the sea with battery-operated power modems. Orthogonal Frequency Division Multiplexing (OFDM) is one of the most vital innovations for UWA communications, having improved data rates and the ability to transform fading channels into flat fading. Moreover, OFDM is more robust on Inter-Symbol and Inter-Carrier Interferences (ISI and ICI respectively). However, OFDM technology suffers from a high Peak to Average Power Ratio (PAPR), resulting in nonlinear distortions and higher Bit Error Rates (BERs). Saving power of battery deployed modems is an important necessity for sustainable underwater communications. This paper studies PAPR in UWA OFDM communications, employing Selective Mapping (SLM) as a tool to mitigate PAPR. The proposed SLM with the oversampling factor method proves to be less complex and more efficient. Simulation results indicate that SLM is a promising PAPR reduction method for UWA OFDM communications reducing BER.
... The high PAPR in auto-encoders based communication system is because of normalized layer in the architecture of auto-encoders, in which unit average power is the requirement and also approximately Gaussian distribution. The maximum transmitted signal is, therefore, closely related to the expansion of a Gaussian distribution tail resulting in a high maximum transmitted power [20][21][22][23][24]. Adding PAPR with loss function is the only proposed solution for the reduction of PAPR in auto-encoder based end to end communication system [25,26]. ...
The need of fast, reliable and the accuracy in communication networks is increasing day by day. The intelligent networks have left their
beneficial impact in underwater acoustic (UWA) orthogonal frequency divisional multiplexing (OFDM) communication system. In the UWA communication
network the OFDM technology is employed to get a reliable and robust communication. For obtaining better performance of bit error rate (BER) and
significant gain in the system, the deep learning auto-encoders are utilized in deep neural networks (DNN). Considering several benefits of autoencoders in the OFDM system it goes through a high peak to average power ratio (PAPR) that makes power amplifier (PA) operating in the nonlinear region.
So, to maintain the operation of power amplifier working in the linear region, this paper proposes a deep learning-based PAPR mitigation method termed as
T-AE, PAPR method. Firstly, the PAPR is reduced with a novel T-AE layer in the auto-encoder; secondly, the proposed method makes the PA operate in
the linear region. Finally, to prove the feasibility of the proposed method the simulation is performed which verifies the superiority of our proposed method
with the efficient performance of BER as compared to traditional OFDM systems.
... Though, few methods [42][43] also use pilot tones and unused subcarrier to reduce the PAPR without increasing BER but result in a slight broadening of the original spectrum. ...
In this thesis, channel Estimation techniques have been
summarized according to their performance index in terms of Bit error rate and
implementation complexity, furthermore a comparison of performance is made with the
estimators simulated using soft computing method, namely Artificial Neural Networks.
Channel Estimation techniques are further extended to OFDM based Long Term
Evolution(LTE). Followed by introducing analytical expression and performance
comparison for OFDM based systems in presence of channel estimation error and
Carrier Frequency Offset.
... The SLM technology effectively enhances the performance of the PAPR reduction without any of the signal being distorted. However, it has a higher computational complexity [8]. The block diagram of SLM technique is shown in Fig. 1. ...
Peak-to-average power ratio (PAPR) is a major drawback for multicarrier system such as orthogonal frequency division multiplexing (OFDM). Due to increase in PAPR of OFDM signal the power amplifier causes non-linear distortion. In this paper we have proposed a PAPR reduction scheme for OFDM system by modification in conventional selective mapping (SLM) technique with Hadamard transform (HT). Furthermore, the Complementary Cumulative Distribution Function (CCDF) of the PAPR for both the conventional and the Modified SLM are measured and compared.
... However, this is much less than for clipping before interpolation. [15,17] The clipping noise is added at the transmitter rather than the receiver. In fading channels this means that in general the clipping noise will cause less degradation in bit error rate than noise added in the channel since the clipping noise fades along with the signal. ...
... In [17] and [18], the use of unused subcarriers in addition to data subcarriers for CF-based PAPR reduction was proposed, which is similar to the tone reservation method. The PAPR reduction signal at the unused subcarriers is generated by repeating the CF operation. ...
This paper presents a new adaptive peak-to-average power ratio (PAPR) reduction method based on clipping and filtering (CF) for precoded orthogonal frequency division multiplexing (OFDM)-multipleinput multiple-output (MIMO) transmission. While the conventional CF method adds roughly the same interference power to each of the transmission streams, the proposed method suppresses the addition of interference power to the streams with good channel conditions. Since the sum capacity is dominated by the capacity of the streams under good channel conditions and the interference caused by the PAPR reduction process severely degrades the achievable capacity for these streams, the proposed method significantly improves the achievable sum capacity compared to the conventional CF method for a given PAPR. Simulation results show the capacity gain by using the proposed method compared to the conventional method. Copyright © 2013 The Institute of Electronics, Information and Communication Engineers.
... Reference [135] develops an ef cient computational algorithm for this case. Reference [136] exploits the use of unused subcarriers as well as the phase information of pilot subcarriers in OFDM systems to reduce the PAPR. This scheme is extended in [137] to include the use of phase information of frequency domain signal to further reduce PAPR. ...
The objective of this survey is to provide the readers and practitioners in the industry with a broader understanding of the high peak-to-average power ratio (PAPR) problem in orthogonal frequency division multiplexing (OFDM) systems and generate a taxonomy of the available solutions to mitigate the problem. Beginning with a description of OFDM systems, the survey describes the most commonly encountered impediment of OFDM systems, the PAPR problem and consequent impact on power amplifiers leading to nonlinear distortion. The survey clearly defines the metrics based on which the performance of PAPR reduction schemes can be evaluated. A taxonomy of PAPR reduction schemes classifies them into signal distortion, multiple signaling and probabilistic, and coding techniques with further classification within each category. We also provide complexity analyses for a few PAPR reduction methods to demonstrate the differences in complexity requirements between different methods. Moreover, the paper provides insights into the transmitted power constraint by showing the possibility of satisfying the constraint without added complexity by the use of companding transforms with suitably chosen companding parameters. The rapid growth in multimedia-based applications has triggered an insatiable thirst for high data rates and hence increased demand on OFDM-based wireless systems that can support high data rates and high mobility. As the data rates and mobility supported by the OFDM system increase, the number of subcarriers also increases, which in turn leads to high PAPR. As future OFDM-based systems may push the number of subcarriers up to meet the higher data rates and mobility demands, there will be also a need to mitigate the high PAPR that arises, which will likely spur new research activities. The authors believe that this survey will serve as a valuable pedagogical resource for understanding the current research contributions in the area of PAPR reduction in OFDM systems, the - ifferent techniques that are available for designers and their trade-offs towards developing more efficient and practical solutions, especially for future research in PAPR reduction schemes for high data rate OFDM systems.
... Distribution shaping is the second approach for PAPR reduction. Examples of this family of approaches include block coding [7], data permutation, Partial Transmit Sequence (PTS) [8], Selected Mapping (SLM) [9], Tone Reservation [10], [11] and Tone Injection [12]. The key idea common to these methods is to modify the distribution of frequency domain OFDM data so as to reduce the probability of large magnitudes of time domain OFDM symbols. ...
... Thus, clipping may still be needed. Moreover, some of these methods require very complicated computations such as linear programming [10], [11] making them impractical for low power, real time embedded mobile communications. ...
A novel Peak to Average Power Ratio (PAPR) reduction method leveraging the rare occurrence of large magnitude Orthogonal Frequency Division Multiplexing (OFDM) symbols is proposed. A distinct innovation of this approach is the exploitation of the sparseness structure of a bit-plane binary number representation of time domain OFDM symbols. By encoding the sparsely populated non-zero entries in the binary bit plane matrix, the dynamic range of OFDM symbols to be transmitted can be significantly reduced without increasing bit error rate. Smaller dynamic range of OFDM symbols implies reduced PAPR, and hence better performance. This method incurs no data rate reduction penalty which may occur when side information must be transmitted via some data subcarriers. Simulation results reveal that this proposed new method out-performs current PAPR reduction methods by wide margins.
... Previously we proposed an efficient PAPR reduction technique for SISO-OFDM system which exploits the use of a small number of the unused subcarriers present in the transmission band [2]. This approach can effectively reduce the PAPR by 2 to 4 dB. ...
... For instance, in a WiMAX system with 256 IFFT/FFT size, 192 tones are data subcarriers, 8 tones are pilot subcarriers and 56 are null subcarriers, while in a LTE system with IFFT/FFT size of 2048, the number of used subcarriers are 1201 and 847 subcarriers are unused tones. In [2], a solution was proposed to use some of these unused subcarriers to reduce the PAPR of OFDM signals. The idea is to absorb the distortion caused by PAPR reduction by setting small values on some of the unused tones. ...
Orthogonal frequency division multiplexing based multiple input multiple output techniques (MIMO-OFDM) tend to achieve high data rate transmission targets for 4G wireless communication systems. However, due to its inherent drawback of high peak-to-average power ratio (PAPR), the OFDM based transmission may severely affect the power efficiency of RF power amplifiers. In this paper, we propose a simple approach to reduce the PAPR of MIMO-OFDM signals based on the use of unused subcarriers. In order to avoid processing the signals at each transmitter separately, a peak cancelling signal is only generated at one antenna and then employed to all the others with only simple modifications. Simulation has shown that by using this proposed approach, a minimum 2 dB reduction in PAPR can be achieved for all transmit signals. Since the generation of the peak cancellation signal for each transmitter separately is avoid, the overall cost of the system can be significantly reduced.
... Some subcarriers are set to zero and are not used for data transmission. In the literature, solutions have been proposed to use some of these unused tones to reduce the PAPR of OFDM signals [19]- [21]. The idea is to absorb the distortion caused by PAPR reduction by setting small values on some of the unused tones instead of spreading the distortion on all data carriers or out-of-band frequencies. ...
... If not, the hole punching procedure is performed again, and Steps 1)-3) are repeated. Fig. 13 shows the block diagram of this procedure, and further details can be found from [21]. Since only a small number of unused tones can be employed, if we restore the original carrier data directly, then the distortion on the unused tones grows rapidly as the number of iterations increases in order to create a clear vector hole. ...
In order to combat high peak-to-average power ratio and poor power efficiency, drain modulated polar transmitter architectures have been proposed for orthogonal frequency-division multiplexing (OFDM) systems. However, this type of power amplifier architecture suffers from poor linearity in the low amplitude region, which often causes significant distortion to the system. In this paper, we propose a novel technique to introduce a vector hole into the constellation diagram of the OFDM signal, called vector hole punching, so that the envelope of the signal will avoid the origin region, thereby preventing the amplitude of the signal approaching zero, which dramatically improves the linearity of the system. This is achieved through a technique based on a combination of direct clipping, circle-tangent shifting, and the use of unused tones. Test results show a clear vector hole can be created by employing this technique that only slightly broadens the original spectrum and maintains a very low error vector magnitude.
