scholarly journals A Novel Noise Suppression Channel Estimation Method Based on Adaptive Weighted Averaging for OFDM Systems

Symmetry ◽  
2019 ◽  
Vol 11 (8) ◽  
pp. 997 ◽  
Author(s):  
Zhang ◽  
Zhou ◽  
Wang
Keyword(s):  
Fourier Transform ◽  
Channel Estimation ◽  
Fast Fourier Transform ◽  
Orthogonal Frequency Division Multiplexing ◽  
Noise Suppression ◽  
Estimation Method ◽  
Weighted Averaging ◽  
Doppler Spread ◽  
Estimation Methods ◽  
Ofdm Systems

Orthogonal frequency division multiplexing (OFDM) systems have inherent symmetric properties, such as coding and decoding, constellation mapping and demapping, inverse fast Fourier transform (IFFT) and fast Fourier transform (FFT) operations corresponding to multi-carrier modulation and demodulation, and channel estimation is a necessary module to resist channel fading in the OFDM system. However, the noise in the channel will significantly affect the accuracy of channel estimation, which further affects the recovery quality of the final received signals. Therefore, this paper proposes an efficient noise suppression channel estimation method for OFDM systems based on adaptive weighted averaging. The basic idea of the proposed method is averaging the last few channel coefficients obtained from coarse estimation to suppress the noise effect, while the average frame number is adaptively adjusted by combining Doppler spread and signal-to-noise ratio (SNR) information. Meanwhile, to better combat the negative effect brought by Doppler spread and inter-carrier interference (ICI), the proposed method introduces a weighting factor to correct the weighted value of each frame in the averaging process. Simulation results show that the proposed channel estimation method is effective and provides better performance compared with other conventional channel estimation methods.

A MMSE Channel Estimation Method in QC-LDPC Coded OFDM Systems

2014 ◽  
Vol 989-994 ◽  
pp. 3759-3762 ◽  
Author(s):  
Gulomjon Sangirov ◽  
Yong Qing Fu ◽  
Ye Fang
Keyword(s):  
Channel Estimation ◽  
Orthogonal Frequency Division Multiplexing ◽  
Wireless Channels ◽  
Minimum Mean Square Error ◽  
Estimation Method ◽  
Coherent Detection ◽  
Estimation Methods ◽  
Ofdm Systems ◽  
Computationally Efficient ◽  
Coded Ofdm

An orthogonal frequency division multiplexing (OFDM) is one of the effective techniques used in wireless communications. In OFDM systems, channel impairments due to multipath dispersive wireless channels can cause deep fades in wireless channels. The OFDM receiver also requires an accurate and computationally efficient channel state information when coherent detection is involved. Therefore, it needs a good robust estimation method of the channel in wireless communication for OFDM systems. And one of these channel estimation methods is minimum mean square error (MMSE) channel estimation. MMSE channel estimation one most used method in OFDM systems. In this work we enhanced robustness of MMSE channel estimation by using it in base of quasi-cyclic low density parity check (QC-LDPC) coded OFDM system.

scholarly journals Channel estimation of OFDM in C-band communication systems under different distribution conditions

2021 ◽  
Vol 23 (3) ◽  
pp. 1778
Author(s):  
Heba Abdul-Jaleel Al-Asady ◽  
Hassan Falah Fakhruldeen ◽  
Mustafa Qahtan Alsudani
Keyword(s):  
Fourier Transform ◽  
Channel Estimation ◽  
Fast Fourier Transform ◽  
Communication Systems ◽  
Orthogonal Frequency Division Multiplexing ◽  
Frequency Division Multiplexing ◽  
Frequency Division ◽  
Ofdm System ◽  
High Data ◽  
High Efficient

<p>Orthogonal frequency division multiplexing (OFDM) is a transmission system that uses multiple orthogonal carriers that are sent out at the same time. OFDM is a technique for mobile and wireless communication that has high-efficient frequency utilization, high data-rate transmission, simple and efficient implementation using the fast Fourier transform (FFT) and the inverse fast Fourier transform (IFFT), and reduces inter symbol interference (ISI) by inserting cyclic prefix (CP). One of the most important approaches in an OFDM system is channel estimation. In this paper, the orthogonal frequency division multiplexing system with the Rayleigh channel module is analyzed for different areas. The proposed approach used large numbers of subcarriers to transmit the signals over 64-QAM modulation with pilot add channel estimation. The accuracy of the OFDM system is shown in the measuring of the relationships of peak power to the noise ratio and bit error rate.</p>

scholarly journals A Comprehensive Review on Channel Estimation in OFDM System

2019 ◽  
Vol 5 (3) ◽  
pp. 6 ◽  
Author(s):  
Neha Dubey ◽  
Ankit Pandit
Keyword(s):  
Channel Estimation ◽  
Mean Square Error ◽  
Orthogonal Frequency Division Multiplexing ◽  
Transmission Rate ◽  
Minimum Mean Square Error ◽  
Estimation Method ◽  
Least Square ◽  
Estimation Methods ◽  
Mean Square ◽  
Mimo Ofdm

In wireless communication, orthogonal frequency division multiplexing (OFDM) plays a major role because of its high transmission rate. Channel estimation and tracking have many different techniques available in OFDM systems. Among them, the most important techniques are least square (LS) and minimum mean square error (MMSE). In least square channel estimation method, the process is simple but the major drawback is it has very high mean square error. Whereas, the performance of MMSE is superior to LS in low SNR, its main problem is it has high computational complexity. If the error is reduced to a very low value, then an exact signal will be received. In this paper an extensive review on different channel estimation methods used in MIMO-OFDM like pilot based, least square (LS) and minimum mean square error method (MMSE) and least minimum mean square error (LMMSE) methods and also other channel estimation methods used in MIMO-OFDM are discussed.

scholarly journals Adaptive Blind Channel Estimation for MIMO-OFDM Systems Based on PARAFAC

2020 ◽  
Vol 2020 ◽  
pp. 1-17
Author(s):  
Ruo-Nan Yang ◽  
Wei-Tao Zhang ◽  
Shun-Tian Lou
Keyword(s):  
Channel Estimation ◽  
Cost Function ◽  
Orthogonal Frequency Division Multiplexing ◽  
Weighted Least Squares ◽  
Estimation Method ◽  
Blind Channel Estimation ◽  
Ofdm Systems ◽  
Blind Channel ◽  
Mimo Ofdm ◽  
The Cost

In order to track the changing channel in multiple-input multiple-output orthogonal frequency division multiplexing (MIMO-OFDM) systems, it is prior to estimate channel impulse response adaptively. In this paper, we proposed an adaptive blind channel estimation method based on parallel factor analysis (PARAFAC). We used an exponential window to weight the past observations; thus, the cost function can be constructed via a weighted least squares criterion. The minimization of the cost function is equivalent to the decomposition of third-order tensor which consists of the weighted OFDM data symbols. To reduce the computational load, we adopt a recursive singular value decomposition method for tensor decomposition; then, the channel parameters can be estimated adaptively. Simulation results validate the effectiveness of the proposed algorithm under diverse signalling conditions.

scholarly journals Iterative Channel Estimation Scheme for the WLAN Systems with the Multiple-Antenna Receivers

2012 ◽  
Vol 6-7 ◽  
pp. 871-875
Author(s):  
Zi Wei Zheng
Keyword(s):  
Fourier Transform ◽  
Channel Estimation ◽  
Fast Fourier Transform ◽  
Orthogonal Frequency Division Multiplexing ◽  
Multipath Fading ◽  
Spectrum Efficiency ◽  
Frequency Division Multiplexing ◽  
Multiple Antenna ◽  
Frequency Division ◽  
Estimation Scheme

Alleviate the multipath delay spread and suitable for broadband transmission efficiency, orthogonal frequency division multiplexing wireless local area network (WLAN) is widely used to assist inverse fast Fourier transform and fast Fourier transform operation domain. Orthogonal frequency division multiplexing is a blow to the broadcast channel multipath fading and high data throughput, transmission, wireless fading channel method, which is widely used to support high performance bandwidth-efficient wireless multimedia services. Several times in the transmitter and receiver antenna technology allows data transfer rate and spectrum efficiency and the use of multiple transmit antennas and multiple receive antennas through spatial processing. High-precision channel estimation scheme is very important wideband multi-carrier orthogonal frequency complex WLAN systems use multiple antenna receiver based division of labor and the overall multi-carrier orthogonal frequency multiplexing division of performance-based WLAN system is to crucial antenna to receive the symbol error rate. In this article, the iterative channel estimation scheme proposed multi-carrier orthogonal frequency division multiplexed using multiple antennas receiver-based WLAN system.

scholarly journals Iterative Channel Estimation for the Chinese Digital Television Terrestrial Broadcasting Systems with the Multiple-Antenna Receivers

2012 ◽  
Vol 6-7 ◽  
pp. 439-444
Author(s):  
Zi Wei Zheng
Keyword(s):  
Fourier Transform ◽  
Channel Estimation ◽  
Fast Fourier Transform ◽  
Orthogonal Frequency Division Multiplexing ◽  
Multipath Fading ◽  
Wireless Channel ◽  
Digital Television ◽  
Frequency Division Multiplexing ◽  
Multiple Antenna ◽  
Frequency Division

Orthogonal frequency division multiplexing is an effective against multipath fading and high data throughput wireless channel transmission technology. Assistance with the inverse fast Fourier transform and fast Fourier transform operation, orthogonal frequency division multiplexing modulation and demodulation operations of the system convenient and convenient hardware implementation, orthogonal frequency division multiplexing, so in the modern digital television terrestrial broadcasting the system is widely used to support high performance bandwidth-efficient multimedia services. Broadband multi-carrier orthogonal frequency division multiplexing with multi-antenna and multi-antenna receiving system, to increase the diversity gain and improve the capacity of the system in different multipath fading channel. Accurate channel estimation in a simple channel equalization and decoding of broadband multi-carrier orthogonal frequency division multiple-antenna receiver and channel estimation accuracy and multiplexing system is very important, is the key to the performance of the overall broadband multi-carrier orthogonal frequency division multiplexing system in the multi-antenna receiver bit error rate. In this paper, iterative channel estimation to plan for digital terrestrial television broadcasting broadband multi-carrier orthogonal frequency division multiple antenna receiver multiplexing system proposal.

An Improved Channel Estimation Method in OFDM System

2013 ◽  
Vol 347-350 ◽  
pp. 1646-1652
Author(s):  
Shun Xian Li
Keyword(s):  
Channel Estimation ◽  
Orthogonal Frequency Division Multiplexing ◽  
Fourier Coefficients ◽  
Estimation Method ◽  
Ofdm Systems ◽  
Basis Expansion ◽  
Basis Expansion Model ◽  
Inverse Reconstruction ◽  
Expansion Model ◽  
Symbol Duration

In this paper, we will focus on channel estimation (CE) in orthogonal frequency-division multiplexing (OFDM) systems. The time-varying (TV) channelsare modeled by a basis expansion model (BEM). Due to the time-variation, the channel matrix in the frequency domain is no longer diagonal, but approximately banded.We use a pilot-aided algorithm for estimation of rapidly varying wireless channels in OFDM systems. Theperforms is goodwhen the channels vary on the scale of a single OFDM symbol duration, which occurs in mobile communication scenarios such as WiMAX, WAVE, and DVB-T.We recover Fourier coefficients of the channel taps by the pilot information.We then estimate the BEM coefficients of the channel taps from their respective Fourier coefficients using a recently developed inverse reconstruction method.We compare some BEM models in inverse methodsto find out the best ones in certain conditions.

scholarly journals Wireless channel estimation in OFDM systems based on collaborative filtering techniques

2019 ◽  
Vol 70 (3) ◽  
pp. 244-252
Author(s):  
Velimir Švedek ◽  
Adrian Satja Kurdija ◽  
Željko Ilić
Keyword(s):  
Channel Estimation ◽  
Collaborative Filtering ◽  
Orthogonal Frequency Division Multiplexing ◽  
Predictive Accuracy ◽  
Spline Interpolation ◽  
Estimation Algorithm ◽  
Wireless Channel ◽  
Estimation Methods ◽  
Ofdm Systems ◽  
Interpolation Methods

Abstract In this paper, a new channel estimation algorithm in Orthogonal Frequency Division Multiplexing (OFDM) systems is proposed. The proposed algorithm is suitable for cases with low density of pilot sub-carriers, where standard interpolation methods (linear, second order and cubic spline interpolation) are inaccurate. The algorithm improves the interpolation methods by employing memory based collaborative filtering (CF) techniques which are less sensitive to the number and location of the pilot subcarriers. CF algorithms are usually used in the context of recommender systems (e-commerce) for predictions of the unknown user-item ratings based on known values of similar users. The advantage of CF is the ability to e ciently produce quality predictions with highly sparse data. Computer simulations are used to verify the proposed channel estimation algorithm and demonstrate that the proposed algorithm improves predictive accuracy metrics, such as Root Mean Squared Error (RMSE), compared to usual estimation methods.

scholarly journals Channel Estimation methods with low complexity for 3GPP/LTE

2014 ◽  
Vol Volume 18, 2014 ◽  
Author(s):  
Moussa Diallo ◽  
Maryline Helard
Keyword(s):  
Channel Estimation ◽  
Estimation Method ◽  
Low Complexity ◽  
Estimation Methods ◽  
Ofdm Systems ◽  
Border Effect ◽  
Noise Component ◽  
System Parameters ◽  
Truncated Svd ◽  
Truncation Threshold

International audience OFDM based pilots channel estimation methods with processing into the transform domain appear attractive owing to their capacity to highly reduce the noise component effect. However, in current OFDM systems, null subcarriers are placed at the edge of the spectrum in order to assure isolation from interfering signals in neighboring frequency bands; and the presence of these null carriers may lead, if not taken into account, to serious degradation of the estimated channel responses due to the “border effect” phenomenon. In this paper an improved algorithm based on truncated SVD is proposed in order to correctly support the case of null carriers at border spectrum. A method for optimizing the truncation threshold whatever the system parameters is also proposed. To make the truncated SVD channel estimation method applicable to any SISO or MIMO OFDM system and whatever the system parameters, a complexity reduction algorithm based on the distribution of the power in the transfer matrix (based on DFT or DCT) is proposed. Les techniques d’estimation de canal, basée sur des symboles pilotes, par passage dansun domaine de tranfert sont très attractives pour les systèmes de télécommunications utilisant l’OFDM.Cependant, elles montrent des limites pour les systèmes de télécommunications, où un ensemble desous-porteuses de garde, est inséré sur les bords du spectre dans le but d’éviter tout recouvrementspectral avec d’autres applications utilisant des bandes voisines. Ces sous-porteuses de gardeont selon leur nombre tendance à dégrader fortement les performances de ces estimateurs. Nousproposons, dans un premier temps, une optimisation qui permet d’améliorer considérablement lesperformances de ces estimateurs quels que soit le nombre de porteuses de garde. Dans un secondtemps, pour de rendre l’estimateur proposé attractif pour les constructeurs, nous avons proposé unetechnique permettant de réduire leur complexité de réalisation de manière notable.

scholarly journals Channel Estimation Based on Statistical Frames and Confidence Level in OFDM Systems

2018 ◽  
Vol 8 (9) ◽  
pp. 1607 ◽  
Author(s):  
Xiao Zhou ◽  
Chengyou Wang ◽  
Ruiguang Tang ◽  
Mingtong Zhang
Keyword(s):  
Channel Estimation ◽  
Mean Square Error ◽  
Confidence Level ◽  
Orthogonal Frequency Division Multiplexing ◽  
Minimum Mean Square Error ◽  
Estimation Method ◽  
Least Square ◽  
Estimation Methods ◽  
Mean Square ◽  
Inverse Operation

Channel estimation is an important module for improving the performance of the orthogonal frequency division multiplexing (OFDM) system. The pilot-based least square (LS) algorithm can improve the channel estimation accuracy and the symbol error rate (SER) performance of the communication system. In pilot-based channel estimation, a certain number of pilots are inserted at fixed intervals between OFDM symbols to estimate the initial channel information, and channel estimation results can be obtained by one-dimensional linear interpolation. The minimum mean square error (MMSE) and linear minimum mean square error (LMMSE) algorithms involve the inverse operation of the channel matrix. If the number of subcarriers increases, the dimension of the matrix becomes large. Therefore, the inverse operation is more complex. To overcome the disadvantages of the conventional channel estimation methods, this paper proposes a novel OFDM channel estimation method based on statistical frames and the confidence level. The noise variance in the estimated channel impulse response (CIR) can be largely reduced under statistical frames and the confidence level; therefore, it reduces the computational complexity and improves the accuracy of channel estimation. Simulation results verify the effectiveness of the proposed channel estimation method based on the confidence level in time-varying dynamic wireless channels.

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