scholarly journals Clipping Noise Compensation with Neural Networks in OFDM Systems

Signals ◽  
2020 ◽  
Vol 1 (1) ◽  
pp. 100-109
Author(s):  
Tzu-Hsien Sang ◽  
You-Cheng Xu
Keyword(s):  
Neural Network ◽  
Orthogonal Frequency Division Multiplexing ◽  
Frequency Division ◽  
Ofdm Systems ◽  
Inverse Discrete Fourier Transform ◽  
Noise Compensation ◽  
The Neural Network ◽  
Frequency Domains ◽  
Iterative Procedures ◽  
Ofdm Signals

The application of deep learning (DL) to solve physical layer issues has emerged as a prominent topic. In this paper, the mitigation of clipping effects for orthogonal frequency division multiplexing (OFDM) systems with the help of a Neural Network (NN) is investigated. Unlike conventional clipping recovery algorithms, which involve costly iterative procedures, the DL-based method learns to directly reconstruct the clipped part of the signal while the unclipped part is protected. Furthermore, an interpretation of the learned weight matrices of the neural network is presented. It is observed that parts of the network, in effect, implement transformations very similar to the (Inverse) Discrete Fourier Transform (DFT/IDFT) to provide information in both the time and frequency domains. The simulation results show that the proposed method outperforms existing algorithms for recovering clipped OFDM signals in terms of both mean square error (MSE) and Bit Error Rate (BER).

Generalized Trapezoidal Companding Technique for PAPR Reduction in OFDM Systems

2018 ◽  
Vol 0 (0) ◽  
Author(s):  
Saruti Gupta ◽  
Ashish Goel
Keyword(s):  
Bit Error Rate ◽  
Orthogonal Frequency Division Multiplexing ◽  
Average Power ◽  
Frequency Division ◽  
Performance Parameters ◽  
Ofdm Systems ◽  
Ofdm System ◽  
Ofdm Signal ◽  
Specific Degree ◽  
Ofdm Signals

Abstract The main drawback in the performance of the Orthogonal Frequency Division Multiplexing (OFDM) system is the higher Peak-to-Average Power Ratio (PAPR) of the OFDM signals at the transmitter side. Companding is a well-known technique useful for reducing PAPR in the OFDM signal. This paper proposes a new nonlinear companding scheme that transforms the magnitude of Rayleigh distributed OFDM signal of specific degree into trapezoidal distribution. Additional design parameter is used in the proposed companding scheme to make the companding function more flexible. In the designed OFDM system the companding function has more degree of freedom which improves the PAPR and bit error rate (BER) parameters of the designed system. It has been demonstrated that the designed companding scheme provides more flexibility to accomplish an optimum trade-off between the performance parameters PAPR and BER of the designed OFDM system.

scholarly journals An Algorithm Combining Synchronization and Channel Estimation for OFDM Systems

2009 ◽  
Author(s):  
Pham Hong Lien ◽  
Nguyen Duy Lai
Keyword(s):  
Channel Estimation ◽  
Orthogonal Frequency Division Multiplexing ◽  
Carrier Frequency Offset ◽  
Multipath Fading ◽  
Frequency Offset ◽  
Frequency Division ◽  
Ofdm Systems ◽  
Clock Frequency ◽  
Close Relationship ◽  
Ofdm Signals

OFDM (Orthogonal Frequency Division Multiplexing) is more and more popular in applications of digital communications because of the effective spectrum and less impacts  of multipath fading. However, beside these advantages, OFDM signals are destroyed easily by errors such as CFO (Carrier Frequency Offset), SFO (Sampling Clock Frequency Offset). Thus, it’s necessaryto have robustly offset algorithms to overcome these disadvantages. Studies about OFDM we just examined channel estimation with assumptions that synchronization is perfect, and vice versa. However, they have a close relationship, channel estimation can be restricted if synchronization is bad, and vice versa. This paper presents an algorithm combining synchronization and channel estimation in OFDM systems. The algorithm is compared with other proposed algorithms by simulation. The simulation result of the algorithm combining synchronization and channel estimation is close to that of ideal conditions: perfect channel estimation and synchronization.

scholarly journals Deep neural network for orthogonal frequency division multiplexing systems without cyclic prefix transmission

2018 ◽  
Vol 189 ◽  
pp. 04016
Author(s):  
Viet-Hung Nguyen ◽  
Minh-Tuan Nguyen ◽  
Yong-Hwa Kim
Keyword(s):  
Neural Network ◽  
Orthogonal Frequency Division Multiplexing ◽  
Deep Neural Network ◽  
Cyclic Prefix ◽  
Wireless Transmission ◽  
Frequency Division Multiplexing ◽  
Frequency Division ◽  
Ofdm System ◽  
New Approach ◽  
Multiplexing Systems

Orthogonal frequency division multiplexing (OFDM) is widely used in wired or wireless transmission systems. In the structure of OFDM, a cycle prefix (CP) has been exploited to avoid the effects of inter-symbol interference (ISI) and inter-carrier interference (ICI). This paper proposes a new approach to transmit the signals without CP transmission. Using the deep neural network, the proposed OFDM system transmits data without the CP. Simulation results show that the proposed scheme can estimate the CP at the receiver and overcome the effect of ISI.

scholarly journals Investigation and Suppression of RF Leakage Power in Front End Wireless Devices

2021 ◽  
Author(s):  
Kanchana Devi A ◽  
Bhuvaneswari B
Keyword(s):  
Orthogonal Frequency Division Multiplexing ◽  
Frequency Division ◽  
Ofdm Systems ◽  
Wireless Devices ◽  
Modulation And Demodulation ◽  
Front End ◽  
High Spectral Efficiency ◽  
Power Leakage ◽  
System Frequency ◽  
Isolation Performance

In this modern Communication Wireless System, Frequency Division Duplex (FDD) is mostly used. Duplex is a device to separate Transmitter and Receiver signals. Transmitter or Power leakage causes from limited isolation performance of the duplexer. Various Techniques of Modulation using Orthogonal Frequency Division Multiplexing (OFDM) provided better solution to cancel this leakage. The OFDM provides high spectral efficiency, lower multi-path distortion and to eliminate inter symbol interference (ISI). Fast Fourier Transform implemented modulation and demodulation functions more efficiently. Using simulation result of the various parameters are analysed. In addition, Comparison of the table between Bit rate error value, Signal strength throughput, Power consumption and Mean square error values obtained in the OFDM systems.

scholarly journals AN EFFICIENT METHOD FOR PAPR REDUCTION IN OFDM SYSTEMS WITH REDUCED COMPLEXITY

2013 ◽  
pp. 96-100
Author(s):  
PRITANJALI KUMARI ◽  
US TRIAR
Keyword(s):  
Orthogonal Frequency Division Multiplexing ◽  
Average Power ◽  
High Peak ◽  
Papr Reduction ◽  
Power Calculation ◽  
Frequency Division Multiplexing ◽  
Power Ratio ◽  
Frequency Division ◽  
Ofdm Systems ◽  
Reduced Complexity

Orthogonal Frequency Division Multiplexing (OFDM), widely used in digital wireless communication, has a major drawback of high Peak to Average Power Ratio (PAPR). A reduced complexity partial transmit sequence (PTS) scheme has been proposed to solve high peak to average power ratio (PAPR) of orthogonal frequency division multiplexing (OFDM) system. In the proposed PTS scheme, a function is generated by summing the power of time domain samples at time ‘n’ in each sub blocks, known as “Hn”.Only those samples, having Hn greater than or equal to a preset threshold value (αT) are used for peak power calculation during the process of selecting a candidate signal with the lowest PAPR for transmission. As compared to conventional PTS scheme, the proposed scheme achieves almost the same PAPR reduction performance with much lower computational complexity.

scholarly journals Analysis of the Consecutive Mean Excision Algorithms

2010 ◽  
Vol 2010 ◽  
pp. 1-13 ◽  
Author(s):  
Johanna Vartiainen ◽  
Janne Lehtomäki ◽  
Harri Saarnisaari ◽  
Markku Juntti
Keyword(s):  
Signal Detection ◽  
Computer Simulations ◽  
Orthogonal Frequency Division Multiplexing ◽  
Cognitive Radios ◽  
Diagnostic Methods ◽  
Frequency Division ◽  
Analysis Framework ◽  
Narrowband Signal ◽  
Ofdm Signals ◽  
Theoretical Performance

The backward and forward consecutive mean excision (CME/FCME) algorithms are diagnostic methods for outlier (signal) detection. Since they are computationally simple, they have applications for both narrowband signal detection in cognitive radios and interference suppression. In this paper, a theoretical performance analysis framework of the CME algorithms is presented. The analysis provides simple tests of the detectability of the signals based on their shape in the considered domain (e.g., spectrum). As a consequence, results can be used to quickly check whether the CME/FCME algorithms are usable for a given problem or not without the need to resort to time consuming computer simulations. The computer simulations for random and orthogonal frequency division multiplexing (OFDM) signals show that the presented analysis is able to predict the detectability of signals well.

scholarly journals Palm Date Leaf Clipping: A New Method to Reduce PAPR in OFDM Systems

Information ◽  
2020 ◽  
Vol 11 (4) ◽  
pp. 190 ◽  
Author(s):  
Brahim Bakkas ◽  
Reda Benkhouya ◽  
Idriss Chana ◽  
Hussain Ben-Azza
Keyword(s):  
Communication Systems ◽  
Orthogonal Frequency Division Multiplexing ◽  
High Speed ◽  
Average Power ◽  
Papr Reduction ◽  
Frequency Division ◽  
Ofdm Systems ◽  
Leaf Clipping ◽  
Hyperbolic Cosine ◽  
Transmitted Signal

Orthogonal frequency division multiplexing (OFDM) is the key technology used in high-speed communication systems. One of the major drawbacks of OFDM systems is the high peak-to-average power ratio (PAPR) of the transmitted signal. The transmitted signal with a high PAPR requires a very large linear range of the Power Amplifier (PA) on the transmitter side. In this paper, we propose and study a new clipping method named Palm Clipping (Palm date leaf) based on hyperbolic cosine. To evaluate and analyze its performance in terms of the PAPR and Bit Error Rate (BER), we performed some computer simulations by varying the Clipping Ratio (CR) and modulation schemes. The obtained results show that it is possible to achieve a gain of between 7 and 9 dB in terms of PAPR reduction depending on the type of modulation. In addition, comparison with several techniques in terms of PAPR and BER shows that our method is a strong alternative that can be adopted as a PAPR reduction technique for OFDM-based communication systems.

Carrier Modulation Technology Based on Orthogonal Frequency Division Multiplexing

2013 ◽  
Vol 774-776 ◽  
pp. 1671-1676
Author(s):  
Chen Wu Li ◽  
Jian Zhang ◽  
Qin Xie ◽  
Xiao Hong Zhang
Keyword(s):  
Fourier Transform ◽  
Discrete Fourier Transform ◽  
Orthogonal Frequency Division Multiplexing ◽  
Low Voltage ◽  
Power Line ◽  
Power Line Communication ◽  
Frequency Division Multiplexing ◽  
Frequency Division ◽  
Family Network ◽  
Inverse Discrete Fourier Transform

This paper first analyzes the transmission characteristics of low-voltage power line channels with the focus on the study of carrier modulation technology regarding the power line communication part, then proposes the orthogonal frequency division multiplexing technology that serves for the digital communication of family network power line communication gateways, analyzes the OFDM system principle, actulizes OFDM modulation and demodulation through discrete Fourier transform (DFT) and inverse discrete Fourier transform (IDFT), and build the OFDM simulation model. Finally, a specific plan of using power lines as the family network transmission media is proposed.

scholarly journals NOMA for Multinumerology OFDM Systems

2018 ◽  
Vol 2018 ◽  
pp. 1-9 ◽  
Author(s):  
Ayman T. Abusabah ◽  
Huseyin Arslan
Keyword(s):  
Orthogonal Frequency Division Multiplexing ◽  
Multiple Access ◽  
Frequency Division ◽  
Ofdm Systems ◽  
Superposition Coding ◽  
Promising Technique ◽  
Successive Interference Cancelation ◽  
Power Domain ◽  
Multiple Access Schemes ◽  
Spectrally Efficient

Nonorthogonal multiple access (NOMA) is a promising technique which outperforms the traditional multiple access schemes in many aspects. It uses superposition coding (SC) to share the available resources among the users and adopts successive interference cancelation (SIC) for multiuser detection (MUD). Detection is performed in power domain where fairness can be supported through appropriate power allocation. Since power domain NOMA utilizes SC at the transmitter and SIC at the receiver, users cannot achieve equal rates and experience higher interference. In this paper, a novel NOMA scheme is proposed for multinumerology orthogonal frequency division multiplexing system, that is, different subcarrier spacings. The scheme uses the nature of mixed numerology systems to reduce the constraints associated with the MUD operation. This scheme not only enhances the fairness among the users but improves the bit error rate performance as well. Although the proposed scheme is less spectrally efficient than conventional NOMA schemes, it is still more spectrally efficient than orthogonal multiple access schemes.

scholarly journals PAPR Reduction of OFDM Signals by Novel Global Harmony Search in PTS Scheme

2012 ◽  
Vol 2012 ◽  
pp. 1-7 ◽  
Author(s):  
Hojjat Salehinejad ◽  
Siamak Talebi
Keyword(s):  
Smart Grids ◽  
Orthogonal Frequency Division Multiplexing ◽  
Signal Transmission ◽  
Harmony Search ◽  
Average Power ◽  
Wind Farms ◽  
Papr Reduction ◽  
Power Ratio ◽  
Frequency Division ◽  
Ofdm Signals

The orthogonal frequency division multiplexing (OFDM) modulation technique is one of the key strategies for multiuser signal transmission especially in smart grids and wind farms. This paper introduces an approach for peak-to-average power ratio (PAPR) reduction of such signals based on novel global harmony search (NGHS) and partial transmit sequence (PTS) schemes. In PTS technique, the data block to be transmitted is partitioned into disjoint subblocks, which are combined using phase factors to minimize PAPR. The PTS requires an exhaustive search over all combinations of allowed phase factors. Therefore, with respect to the fast implementation and simplicity of NGHS technique, we could achieve significant reduction of PAPR.

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