scholarly journals Sparse Channel Estimation for DCO-OFDM VLC Systems in the Presence of Clipping Noise

2021 ◽  
Author(s):  
Ekin Basak Bektas ◽  
Erdal Panayirci
Keyword(s):  
Channel Estimation ◽  
Time Domain ◽  
Orthogonal Frequency Division Multiplexing ◽  
Channel Model ◽  
Estimation Algorithm ◽  
Visible Light Communications ◽  
Ofdm Systems ◽  
Noise Mitigation ◽  
The Time Domain ◽  
Sparse Channel

Abstract In this paper, a new iterative channel estimation algorithm is proposed that exploits channel sparsity in the time domain for DC-biased optical orthogonal frequency division multiplexing OFDM (DCO-OFDM) systems in indoor visible light communications (VLC) in the presence of a clipping noise. A path-based channel model is used, in which the channel is described by a limited number of paths, each characterized by a delay and channel gain. Making use of the pilot symbols, overall sparse channel tap delays and path gains were initially estimated by the compressed sensing approach, in the form of the Orthogonal Matching Pursuit (OMP) and the least-squares (LS) algorithms, respectively. Then a computationally efficient and novel iterative channel estimation algorithm is developed that estimates the clipping noise in the time-domain and compensated for its effect in the frequency-domain. Computer simulation results show that the algorithm converges in maximum two iterations and that yields excellent mean square error (MSE) and bit error rate (BER) performance, outperforming those channel estimation algorithms, which do not have the clipping noise mitigation capability.

scholarly journals Adaptive Prediction of Channels with Sparse Features in OFDM Systems

2013 ◽  
Vol 2013 ◽  
pp. 1-5 ◽  
Author(s):  
Changwei Lv ◽  
Shujuan Hou ◽  
Wenbo Mei
Keyword(s):  
Time Domain ◽  
Orthogonal Frequency Division Multiplexing ◽  
Channel Model ◽  
Prediction Method ◽  
Frequency Domain Method ◽  
Ofdm Systems ◽  
Physical Channel ◽  
The Time Domain ◽  
Sparse Features ◽  
Sparse Channel

A time domain channel prediction method exploiting features of sparse channel is proposed for orthogonal frequency division multiplexing (OFDM) systems. The proposed predictor operates in the time domain on each channel tap and separates the negligible taps from significant channel taps before performing prediction. We also compare the proposed prediction method with the classical frequency domain method realized at each OFDM subcarrier and demonstrate that our method increases the prediction accuracy and reduces the computational complexity. Simulations on the physical channel model verify the performance of the proposed method.

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 Pilot Design for Sparse Channel Estimation in Orthogonal Frequency Division Multiplexing Systems

2018 ◽  
Vol 2 ◽  
pp. 60-68 ◽  
Author(s):  
P. Vimala ◽  
G. Yamuna
Keyword(s):  
Channel Estimation ◽  
Compressive Sensing ◽  
Fading Channel ◽  
Orthogonal Frequency Division Multiplexing ◽  
Wide Band ◽  
Frequency Division Multiplexing ◽  
Frequency Division ◽  
Ofdm Systems ◽  
Sparse Channel Estimation ◽  
Sparse Channel

Orthogonal Frequency Division Multiplexing (OFDM) is a well-known technique used in modern wide band wireless communication systems. Coherent OFDM systems achieve its advantages over a multipath fading channel, if channel impulse response is estimated precisely at the receiver. Pilot-aided channel estimation in wide band OFDM systems adopts the recently explored compressive sensing technique to decrease the transmission overhead of pilot subcarriers, since it exploits the inherent sparsity of the wireless fading channel. The accuracy of compressive sensing techniques in sparse channel estimation is based on the location of pilots among OFDM subcarriers. A sufficient condition for the optimal pilot selection from Sylow subgroups is derived. A Sylow subgroup does not exist for most practical OFDM systems. Therefore, a deterministic pilot search algorithm is described to select pilot locations based on minimizing coherence, along with minimum variance. Simulation results reveal the effectiveness of the proposed algorithm in terms of bit error rate, compared to the existing solutions.

scholarly journals Sparse DFT Based Channel Estimation In OFDM Systems

2020 ◽  
Vol 3 (2) ◽  
pp. 1-10
Author(s):  
Maryam K. Abboud ◽  
Bayan M. Sabbar
Keyword(s):  
Channel Estimation ◽  
Communication Systems ◽  
Orthogonal Frequency Division Multiplexing ◽  
Channel Model ◽  
Doppler Frequency ◽  
Mobile Systems ◽  
Vehicle Speed ◽  
Ofdm Systems ◽  
Estimation Algorithms ◽  
Doppler Frequency Shifts

Channel estimation is an essential part of Orthogonal Frequency Division Multiplexing (OFDM) communication systems. In this paper, two Discrete Fourier Transform (DFT) improvement algorithms are proposed and compared where the 1st one exploits channel sparsity concept while the other considers significant channel coefficients only. In the proposed algorithms; Enhanced and Sparse DFT (E-DFT and S-DFT), different number of significant channel components is selected either by a threshold determining procedure such as in    E-DFT, or through determining channel sparsity level such as in S-DFT. In the presence of Doppler frequency shifts, the Inter Symbol Interference (ISI) effect on channel coefficients is successfully reduced using the proposed estimation algorithms. Vehicular A-ITU channel model is considered with a relatively high vehicle speed up to 68 Km/h in order to test the suitability of the proposed algorithms for mobile systems. E-DFT and S-DFT improves conventional as well as previous DFT improvement methods (I-DFT) suggested by [7], [8], [9], [15]. For 64 subcarriers, S-DFT outperforms E-DFT and I-DFT by about 3dB at a BER of 0.01 with a mobility reaches 45 Km/h, and by about 0.4dB and 2.5dB at a BER of 0.02 with a mobility reaches 68Km/h.

Zero Taps Detection-Based Sparse Channel Estimation Method for OFDM Systems

2014 ◽  
Vol 513-517 ◽  
pp. 2577-2580
Author(s):  
Xue Jiao Zheng ◽  
Jian Jiao
Keyword(s):  
Channel Estimation ◽  
Estimation Method ◽  
Estimation Algorithm ◽  
Ofdm Systems ◽  
Detection Problem ◽  
Sparse Channel Estimation ◽  
Precise Evaluation ◽  
Moderate Complexity ◽  
Sparse Channel

The channel whose impulse response contains a large number of zero taps is sparse. Exploiting the sparsity of the channel, the estimation problem can be converted into an on-off keying (OOK) detection problem. Therefore, a sparse channel estimation algorithm was proposed. First, with an initial estimate, posed a detection problem by casting the determination of non-zero taps into an OOK communication problem; then took precise evaluation against the established non-zero taps position. In the simulation, the proposed algorithm was compared to the standard LSE via simulations in terms of MSE and BER. The results show that, the proposed algorithm can provide the best performance while maintaining moderate complexity.

Sign in / Sign up

Export Citation Format

Share Document