A Low-Complexity Time-Domain MMSE Channel Estimator for Space-Time/Frequency Block-Coded OFDM Systems (original) (raw)
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International Journal of Engineering Research and Technology (IJERT), 2016
https://www.ijert.org/comparative-performance-study-of-ls-and-mmse-channel-estimation-over-time-varying-channel-in-ofdm-system https://www.ijert.org/research/comparative-performance-study-of-ls-and-mmse-channel-estimation-over-time-varying-channel-in-ofdm-system-IJERTV5IS031192.pdf Orthogonal Frequency Division Multiplexing (OFDM) has been recently applied widely in wireless communication systems, due to high data rate, transmission capability with high bandwidth efficiency and its robustness to multipath delay. Channel estimation is an essential problem at the receiver, where the wireless channel is usually frequency selective and time varying. The estimation of channel at pilot subcarriers is based on Least Square (LS), Minimum Mean Square Error (MMSE) while interpolation is done using linear interpolation. For performance evaluation of LS and MMSE channel estimators in OFDM system, the previous works use the block type pilot arrangement, where the pilot tones are transmitted into all subcarriers but at specific period which is suitable for frequency selective fading. In order to keep track of the time-varying channel characteristic, the pilot tones symbols must be placed as the coherence time which causes data reduction. Aiming at this disadvantage, we propose to use the comb-type pilot arrangement where the pilot tones are transmitted at each time to track the rapid variation of the channel. The Clarke' model is used to perform the time varying channel and 16-QAM as the modulation scheme. The performance of the algorithms is measured in terms of Mean Square Error (MSE) and Symbol Error Rate (SER). Simulation results reveal that MMSE estimator provides better performance to track the time-varying channel .
On Channel Estimation in OFDM Systems
The use of multi-amplitude signaling schemes in wireless OFDM systems requires the tracking of the fading radio channel. This paper addresses channel estimation based on time-domain channel statistics. Using a general model for a slowly fading channel, we present the MMSE and LS estimators and a method for modifications compromising between complexity and performance. The symbol error rate for a 16-QAM system is presented by means of simulation results. Depending upon estimator complexity, up to 4 dB in SNR can be gained over the LS estimator.
LS and MMSE Estimation with Different Fading Channels for OFDM System
In wireless communication system, the multipath channels introduce frequency selectivity and time varying properties in OFDM symbols which causes Inter-Carrier Interference (ICI) within symbols. For mitigation of such impairments caused by the fading channels, channel estimation is imperative. In present work, two main block-type pilot symbols assisted Least Square (LS) and Minimum Mean Square Error (MMSE) channel estimation techniques for two fading channel models, Rayleigh and Rician are implemented. The bit error rate characteristic performance for both estimators is compared for slow fading channel models with different symbol mapping techniques. The results show that the MMSE estimator has good performance for both Rayleigh and Rician channels as compared to LS estimator. However, MMSE estimator has higher complexity than that of LS.
MIMO-OFDM WIRELESS COMMUNICATION SYSTEM PERFORMANCE ANALYSIS FOR CHANNEL ESTIMATION
IRJET, 2023
This study proposes a hybrid Wiener filter-based pilot-based low-complexity channel estimator for use in the LTE-A downlink using cell-specific reference signals (C-RS) and user equipment reference signals (UE-RS). Sub-optimally, the suggested system only needs 8.8 and 74.5 percent as many calculations as the optimum system and other sub-optimum systems, respectively. In addition, a Fast Fourier Transform (FFT)-based CE technique is developed, which requires less computing power. End-to-end LTE-A system throughput validation of the reported pilot-based system demonstrates the feasibility of the proposed system. Next, we provide a novel blind CE method for SIMO and MIMO systems that makes use of a hybrid OFDM symbol structure. It is shown that the created system achieves comparable performance to a pilotbased system with an equivalent level of complexity and improved spectrum efficiency, provided that a sufficient number of receive antennas are used. Last but not least, we offer alternative Resource Grid (RG) configurations that support the blind-based CE method designed for MIMO-OFDM systems, with the goal of enhancing MSE performance while reducing the number of necessary receive antennas. From the standpoint of the investigated blind-based CE scheme, the results reveal that the suggested RG configurations give better MSE performance than the LTE-A RG configuration.
Reduced-Complexity Recursive MMSE Channel Estimator for the Wireless OFDM Systems
2008 IEEE Wireless Communications and Networking Conference, 2008
An accurate estimate of the channel frequency response (CFR) needed for OFDM equalisation can be obtained using the linear minimum mean square error (MMSE) algorithm. However, for an optimal operation such an estimator requires real-time inversion of the CFR correlation matrix that is found to be impractical due to considerable increase of the receiver's complexity. In this article, we develop the ways of design of the MMSE channel estimator yielding near-optimum performance and being computationally efficient at the same time. The proposed technique is based on the transform-domain processing and tracking of the correlation of the channel impulse response (CIR) observation. The former feature allows reducing the size of the correlation matrix, whereas the latter one leads to a design form with no matrix inversions. Simulations show that the developed algorithm achieves performance close to the optimal MMSE estimator and is particularly beneficial for both the sample-spaced and the non-sample-spaced sparse multipath channels.
Advanced Channel Estimation for MIMO-OFDM in Realistic Channel Conditions
2007 IEEE International Conference on Communications, 2007
An advanced decision-directed channel estimation scheme is proposed, which is suitable for employment in a wide range of multi-antenna multi-carrier systems as well as for communications over the entire range of practical channel conditions. In particular, we consider a MIMO-OFDM system operating in a mobile wireless multipath channel, which exhibits frequency-selective Rayleigh fading and is characterized by a time-variant power delay profile. Both the mean square error as well as the bit error rate performances achieved by the proposed system are documented. Specifically, we report a virtually errorfree performance of a rate 1 2 turbo-coded 8x8-QPSK-OFDM system, exhibiting an effective throughput of 8•2• 1 2 =8bits/sec/Hz, while having a pilot overhead of only 10%, at an SNR of 10dB and an OFDM-symbol-normalized Doppler frequency of 0.003, which corresponds to the mobile terminal speed of about 65 km/h.
Time-Domain Channel Estimation Scheme for OFDM over Fast Fading Channels
Wireless Communications and Mobile Computing, 2022
In high-mobility scenarios, the time variation of mobile radio channels leads to a loss of orthogonality among subcarriers in orthogonal frequency division multiplexing (OFDM) systems, resulting in intercarrier interference (ICI) and performance deterioration. Conventional channel estimation schemes are usually based on pilot tones, which are distributed in each OFDM symbol to estimate the channel variation. Hence, the channel estimator itself suffers from ICI. In this study, a new estimation scheme, which does not suffer from ICI, is proposed to estimate the channel variation within OFDM symbols. The main idea is to zero-pad (ZP) the OFDM symbol in the time domain. Then, in the middle of the ZP interval, an impulse signal is inserted as a pilot sample, which is used to estimate the channel at the pilot signal in the OFDM symbol. Finally, a linear model is used to estimate the channel variation over an OFDM symbol. Additionally, we derive the mean squared error (MSE) of the proposed...
A Low-Complexity KL Expansion-Based Channel Estimator for OFDM Systems
EURASIP Journal on Wireless Communications and Networking, 2005
This paper first proposes a computationally efficient, pilot-aided linear minimum mean square error (MMSE) batch channel estimation algorithm for OFDM systems in unknown wireless fading channels. The proposed approach employs a convenient representation of the discrete multipath fading channel based on the Karhunen-Loeve (KL) orthogonal expansion and finds MMSE estimates of the uncorrelated KL series expansion coefficients. Based on such an expansion, no matrix inversion is required in the proposed MMSE estimator. Moreover, optimal rank reduction is achieved by exploiting the optimal truncation property of the KL expansion resulting in a smaller computational load on the estimation algorithm. The performance of the proposed approach is studied through analytical and experimental results. We then consider the stochastic Cramér-Rao bound and derive the closedform expression for the random KL coefficients and consequently exploit the performance of the MMSE channel estimator based on the evaluation of minimum Bayesian MSE. We also analyze the effect of a modelling mismatch on the estimator performance. To further reduce the complexity, we extend the batch linear MMSE to the sequential linear MMSE estimator. With the fast convergence property and the simple structure, the sequential linear MMSE estimator provides an attractive alternative to the implementation of channel estimator.
Improved Channel Estimation and Removal of Fading for MIMO-OFDM Systems
Irish Interdisciplinary Journal of Science & Research (IIJSR) Volume 7, Issue 1, Pages 46-52, January-March 2023, 2023
Many inference algorithms develop the time-domain connection of the direct by employ a Kalman filter base on a first-order (or sometimes second-order) estimate of the time-varying channel amid a norm based on link toning (CM), or on the Minimization of Asymptotic Variance (MAV). To decrease the complexity of the high-dimensional RW-KF for combined opinion of the multi-path multifaceted amplitudes, we suggest using an inferior dimensional RW-KF that estimate the compound amplitude of each path separately. We demonstrate that this amounts to a simplification of the joint multi-path Kalman increase formulation through the Woodbury’s identities. Hence, this innovative algorithm consists of a superposition of self-determining single-path single-carrier KFs, which be optimized in our earlier studies. This examination allow us to settle in the optimization to the authentic multi-path multi-carrier scenario, to afford logical formulas for the mean-square error presentation and the best tuning of the future estimator in a straight line as a function of the physical parameter of the canal (Doppler frequency, signal-to-noise-ratio, power delay profile). These logical formula are known for the first-, second-, and third-order RW models used in the KF. The future per-path KF is exposed to be as well-organized as the accurate KF (i.e., the joint multi-path KF), and outperforms the autoregressive-model-based KFs future in the literature.