scholarly journals An Improved Channel Estimation Algorithm Based on WD-DDA in OFDM System

2021 ◽  
Vol 2021 ◽  
pp. 1-9
Author(s):  
Dan Wang ◽  
Zhiqiang Mei ◽  
Jiamin Liang ◽  
Jinzhi Liu
Keyword(s):  
Channel Estimation ◽  
Orthogonal Frequency Division Multiplexing ◽  
Signal To Noise Ratio ◽  
Estimation Algorithm ◽  
Transform Domain ◽  
Ofdm System ◽  
Low Snr ◽  
Estimation Algorithms ◽  
Residual Noise ◽  
First Time

Channel estimation is the key technology to ensure reliable transmission in orthogonal frequency division multiplexing (OFDM) system. In order to improve the accuracy of the channel estimation algorithm in a low signal-to-noise ratio (SNR) channel environment, in this paper, we proposed an improved channel estimation algorithm based on the transform domain. The improved algorithm with wavelet denoising (WD) and distance decision analysis (DDA) to perform secondary denoising on the channel estimation algorithm based on the transform domain is proposed. First, after the least-squares (LS) algorithm, WD is used to denoise for the first time, then the DDA is used to further suppress the residual noise in the transform domain, and the important channel taps are screened out. Simulation results show that the proposed algorithm can improve the detection performance of existing channel estimation algorithms based on transform domain in low SNR.

Channel Estimation Based on Interpolation in OFDM System

2010 ◽  
Vol 439-440 ◽  
pp. 794-798
Author(s):  
Yue Hua Cui ◽  
Shuang Ye ◽  
Qiu Rui Wu ◽  
Jian Hua Liu ◽  
Yan Dai
Keyword(s):  
Channel Estimation ◽  
Orthogonal Frequency Division Multiplexing ◽  
Estimation Algorithm ◽  
Linear Interpolation ◽  
High Rate ◽  
Transform Domain ◽  
Rate Data ◽  
Ofdm System ◽  
High Spectral Efficiency ◽  
Low Pass

OFDM（Orthogonal Frequency Division Multiplexing）is a new modulation technology, which can reduce multi-pass interference efficiently. It splits a high-rate data stream into a number of lower-rate data streams which can be transmitted simultaneously over a number of subcarriers. It brings high spectral efficiency. In this paper, we first introduce the channel estimation algorithm based on comb-pilot in OFDM system, and emphasis on analysis and comparison of the three kinds of interpolation methods: linear interpolation, low-pass interpolation and transform-domain interpolation. We use MATLAB to carry out the system simulation, and its results indicate that: The performance of low-pass interpolation is the best ,but it’s hard to carry out; transform-domain interpolation’s performance and complexity are both between above two methods.

scholarly journals Pilot-Based Time Domain SNR Estimation for Broadcasting OFDM Systems

2018 ◽  
Vol 2018 ◽  
pp. 1-8
Author(s):  
Abid Muhammad Khan ◽  
Varun Jeoti ◽  
Muhammad Zaka Ur Rehman ◽  
Muhammad Taha Jilani ◽  
Omer Chugtai ◽  
...  
Keyword(s):  
Time Domain ◽  
Orthogonal Frequency Division Multiplexing ◽  
Signal To Noise Ratio ◽  
Ofdm Systems ◽  
Ofdm System ◽  
Significant Saving ◽  
Snr Estimation ◽  
Channel Changes ◽  
Low Snr ◽  
Estimation Scheme

The estimation of signal-to-noise ratio (SNR) is a major issue in wireless orthogonal frequency-division multiplexing (OFDM) system. In OFDM system, each frame starts with a preamble symbol that facilitates the SNR estimation. However, the performance of preamble-based SNR estimation schemes worsens in the fast-changing environment where channel changes symbol to symbol. Accordingly, in this paper, we propose a novel pilot-based SNR estimation scheme that optimally exploits the pilot subcarriers that are inserted in each data symbol of the OFDM frame. The proposed scheme computes the circular correlation between the received signal and the comb-type pilot sequence to obtain the SNR. The simulation results are compared with the conventional preamble-based Zadoff-Chu sequence SNR estimator. The results indicate that the proposed scheme generates near-ideal accuracy; especially in low SNR regimes, in terms of the normalized mean square error (NMSE). Moreover, this scheme offers a significant saving of computation over a conventional time domain SNR estimator.

scholarly journals Application of a Channel Estimation Algorithm to Spectrum Sensing in a Cognitive Radio Context

2014 ◽  
Vol 2014 ◽  
pp. 1-13 ◽  
Author(s):  
Vincent Savaux ◽  
Moïse Djoko-Kouam ◽  
Yves Louët ◽  
Alexandre Skrzypczak
Keyword(s):  
Channel Estimation ◽  
Spectrum Sensing ◽  
Orthogonal Frequency Division Multiplexing ◽  
Variance Estimation ◽  
Minimum Mean Square Error ◽  
Estimation Algorithm ◽  
Joint Estimation ◽  
Noise Variance ◽  
Low Snr ◽  
Mean Square Error Criterion

This paper deals with spectrum sensing in an orthogonal frequency division multiplexing (OFDM) context, allowing an opportunistic user to detect a vacant spectrum resource in a licensed band. The proposed method is based on an iterative algorithm used for the joint estimation of noise variance and frequency selective channel. It can be seen as a second-order detector, since it is performed by means of the minimum mean square error criterion. The main advantage of the proposed algorithm is its capability to perform spectrum sensing, noise variance estimation, and channel estimation in the presence of a signal. Furthermore, the sensing duration is limited to only one OFDM symbol. We theoretically show the convergence of the algorithm, and we derive its analytical detection and false alarm probabilities. Furthermore, we show that the detector is very efficient, even for low SNR values, and is robust against a channel uncertainty.

Comparison of various channel equalization techniques in OFDM system using different digital modulations

2016 ◽  
Vol 3 (3) ◽  
pp. 634 ◽  
Author(s):  
Pratima Manhas ◽  
M.K. Soni
Keyword(s):  
Fading Channels ◽  
Orthogonal Frequency Division Multiplexing ◽  
Signal To Noise Ratio ◽  
Multipath Fading ◽  
Ofdm System ◽  
Multipath Fading Channels ◽  
Estimation Algorithms ◽  
High Data ◽  
Data Rates ◽  
High Data Rates

<p>The nature of future wireless applications requires high data rates and for this OFDM technique is used. OFDM stands for orthogonal frequency division multiplexing and is a type of multi-carrier transmission where all the subcarriers are orthogonal to each other. At high data rates, the channel distortion to the data is very important and it is somewhat impossible to recover the transmitted data with a simple receiver. So a complex receiver structure is needed which uses computationally expensive equalization and channel estimation algorithms to estimate the channel. These estimations can be used within the received data to recover the originally transmitted data. OFDM can simplify the equalization problem by changing the frequency-selective channel into a flat channel. The radio channels in mobile radio systems are usually multipath fading channels that results in intersymbol interference (ISI) in the received signal. To remove ISI from the signal, many kind of equalizers can be used. The need for equalizers arises from the fact that the channel has amplitude and phase dispersion which results in the interference of the transmitted signals with one another which is known as ISI .So, to solve this problem equalizers are designed. Equalizer is intend to work in such a way that Bit Error Rate (BER) should be low and Signal-to-Noise Ratio (SNR) should be high. An equalizer within a receiver compensates for the average range of expected channel amplitude and delay characteristics. This paper deals with the various equalization techniques (LMS, RLS and CMA) used for OFDM system .A comparative analysis of different equalization technique in terms of BER is done using MATLAB Simulink.</p>

An Improved SVD-LMMSE Channel Estimation Algorithm of LTE System

2013 ◽  
Vol 756-759 ◽  
pp. 862-866
Author(s):  
Yang Zhou ◽  
Hong Cheng Dong ◽  
Xiao Wen Li
Keyword(s):  
Channel Estimation ◽  
Orthogonal Frequency Division Multiplexing ◽  
Minimum Mean Square Error ◽  
Multiple Input Multiple Output ◽  
Estimation Algorithm ◽  
Least Square ◽  
Superior Performance ◽  
Estimation Algorithms ◽  
Dct Transform ◽  
Value Decomposition

This paper first introduces the MIMO-OFDM (Multiple Input Multiple Output-Orthogonal Frequency Division Multiplexing) system model, and then studies several classical channel estimation algorithms: LS (Least Square) algorithm, LMMSE (Liner Minimum Mean-Square Error) algorithms and SVD-LMMSE (Singular value decomposition) algorithm. Finally, based on the DCT transform domain channel estimation, the original SVD-LMMSE algorithm has been improved. Theoretical analysis and simulation results show that: The improved SVD-LMMSE algorithm not only can reduce the complexity of the implementation, but also has more superior performance.

scholarly journals Optimization of Iterative Channel State Estimation Algorithms in SCMA System

2018 ◽  
pp. 23-34
Author(s):  
V. P. Klimentyev ◽  
A. B. Sergienko
Keyword(s):  
Channel Estimation ◽  
State Estimation ◽  
Spectral Efficiency ◽  
Signal To Noise Ratio ◽  
Iterative Algorithms ◽  
Channel State ◽  
Computational Costs ◽  
Channel State Estimation ◽  
Low Snr ◽  
Estimation Algorithms

Optimization of iterative algorithms for channel state estimation in a sparse coding multiple-access system (SCMA) is performed to reduce computational costs of the receiver. It is shown that when a signal-to-noise ratio (SNR) does not exceed 10 dB, one iteration of the algorithm is sufficient, and an increase in the number of iterations does not lead to an increase in spectral efficiency. Simulation demonstrates a possibility of a reasonable choice of the total number of decoder iterations and their distribution between different stages of the channel estimation. For an uncoded system, iterative re-estimation of the channel is proposed, as well as ways to reduce computational costs during its calculation. In the coded system, at a low SNR the achieved spectral efficiency values are approximately similar to those with pilot-only channel estimation. The article provides recommendations for the placement of data symbols and pilot signals in re-source blocks to increase the system spectral efficiency.

An improved least square channel estimation algorithm for coherent optical OFDM system

Optik ◽  
2013 ◽  
Vol 124 (23) ◽  
pp. 5937-5940 ◽  
Author(s):  
S. Zhang ◽  
C.L. Bai ◽  
Q.L. Luo ◽  
L. Huang ◽  
F.F. He
Keyword(s):  
Channel Estimation ◽  
Estimation Algorithm ◽  
Least Square ◽  
Ofdm System ◽  
Square Channel ◽  
Optical Ofdm

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>

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