Robust channel estimation for OFDM systems with rapid dispersive fading channels

Li, Y.; Cimini, Leonard J.; Sollenberger, N.R.

doi:10.1109/26.701317

Cited by 990 publications

(519 citation statements)

References 13 publications

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“…The design of the optimal (MMSE) interpolator requires knowledge of the 2-D correlation function of the channel, i.e., of the powerdelay profile and the Doppler spectrum. Since this information is not easily available at the receiver, the design problem becomes that of finding the most robust estimator with respect to a mismatch in the channel correlation [15].…”

Section: Introductionmentioning

confidence: 99%

Pilot-Based Channel Estimation for OFDM Systems by Tracking the Delay-Subspace

Simeone

Bar-Ness

Spagnolini

2004

IEEE Trans. Wireless Commun.

186

133

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Abstract-In orthogonal frequency division multiplexing (OFDM) systems over fast-varying fading channels, channel estimation and tracking is generally carried out by transmitting known pilot symbols in given positions of the frequency-time grid. The traditional approach consists of two steps. First, the least-squares (LS) estimate is obtained over the pilot subcarriers. Then, this preliminary estimate is interpolated/smoothed over the entire frequency-time grid. In this paper, we propose to add an intermediate step, whose purpose is to increase the accuracy of the estimate over the pilot subcarriers. The presented techniques are based on the observation that the wireless radio channel can be parametrized as a combination of paths, each characterized by a delay and a complex amplitude. The amplitudes show fast temporal variations due to the mobility of terminals while the delays (and their associated delay-subspace) are almost constant over a large number of OFDM symbols. We propose to track the delay-subspace by a subspace tracking algorithm and the amplitudes by the least mean square algorithm (or modifications of the latter). The approach can be extended to multiple input multiple output OFDM or multicarrier code-division multiple-access systems. Analytical results and simulations prove the relevant benefits of the novel structure.Index Terms-Channel estimation, fading radio channel, multiple input multiple output (MIMO), orthogonal frequency-division multiplexing (OFDM), subspace tracking.

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Section: Introductionmentioning

confidence: 99%

Pilot-Based Channel Estimation for OFDM Systems by Tracking the Delay-Subspace

Simeone

Bar-Ness

Spagnolini

2004

IEEE Trans. Wireless Commun.

186

133

View full text Add to dashboard Cite

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“…In fact, by assuming a wide-sense stationary uncorrelated scattering (WSSUS) channel model, the TD correlation between symbols is dependent on the Doppler spread and the FD correlation between subcarriers is dependent on the delay spread [41]. Existing wideband systems that rely on OFDM and SC-FDMA already exploit time and frequency correlation to estimate the channel coefficients.…”

Section: Exploiting Correlation In Multipath Wireless Channelsmentioning

confidence: 99%

Implicit vs. Explicit Approximate Matrix Inversion for Wideband Massive MU-MIMO Data Detection

Yin

et al. 2017

J Sign Process Syst

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Massive multi-user (MU) MIMO wireless technology promises improved spectral efficiency compared to that of traditional cellular systems. While datadetection algorithms that rely on linear equalization achieve near-optimal error-rate performance for massive MU-MIMO systems, they require the solution to large linear systems at high throughput and low latency, which results in excessively high receiver complexity. In this paper, we investigate a variety of exact and approximate equalization schemes that solve the system of linear equations either explicitly (requiring the computation of a matrix inverse) or implicitly (by directly computing the solution vector). We analyze the associated performance/complexity trade-offs, and we show that for small base-station (BS)-to-user-antenna ratios, exact and implicit data detection using the Cholesky decomposition achieves near-optimal performance at low complexity. In contrast, implicit data detection using approximate equalization methods results in the best trade-off for large BS-to-user-antenna ratios. By combining the advantages of exact, approximate, implicit, and explicit matrix inversion, we develop a new frequencyadaptive equalizer (FADE), which outperforms existing data-detection methods in terms of performance and complexity for wideband massive MU-MIMO systems.

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“…Finally, our simulation results show how these methods would improve the performance in a highly time-variant environment with high delay spread. A model reduction approach for OFDM channel estimation under high mobility conditions [5] deals with the orthogonal frequency-division multiplexing (OFDM) which combines the advantages of high performance and relatively low implementation complexity. However, for reliable coherent detection of the input signal, the OFDM receiver needs accurate channel information.…”

Section: Introductionmentioning

confidence: 99%

Analysis of Iterative Channel Algorithm for MIMO OFDM systems using Doppler Spread

V¹

2017

IJERT

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Abstract-Multiple-input multiple-output (MIMO) orthogonal frequency division multiplexing (OFDM) system operating in high mobility scenarios, channel estimation becomes a challenging issue, due to fast channel variation and severe intercarrier interference (ICI). This paper proposes a novel pilotaided iterative receiver, based on pilot symbols and iterative softestimate of data symbols and parallel interference cancellation (PIC) scheme coupled with decision statistical combining (DSC) is used to cancel the ICI and to improve the data symbols detection. These data symbols are then utilized to refine the channel estimation further, iteratively. The simulation results of both methods are compared and values obtained depict that the PIC-DSC method improve channel estimation and its BER/SNR value remains stable. Keywords-MIMO; OFDM; DSC;PIC; BER. I. INTRODUCTIONIn a high mobility environment, the wireless channel is time variant and frequency selective causing the symbol transmission to be impaired by the Doppler spread. The Doppler spread destroys the orthogonality and creates intercarrier interference (ICI) between OFDM sub-carriers. In addition, the channel changes significantly within one OFDM symbol. Standard channel estimation methods that assume the wireless channels to be invariant within one OFDM symbol, or apply a block-type pilot placement, cannot be used in such a high mobility system. In estimation of the time domain channel coefficients is performed by using pilot tones and by linear interpolation of the time domain channel estimates. The authors use a comb-type pilot tones placement. In least-square (LS) and minimum-mean-square-error (MMSE) channel estimation methods, together with various linear interpolation methods such as linear, second order, low pass, spline-cubic and time domain interpolation are investigated. The authors extend the channel estimation method in [1] to take into account ICI and use a comb-type pilot placement instead of a block-type pilot placement. None of these schemes however, utilize data symbols in the channel estimation process.Recently, high mobility transmission has been considered as one of the important key features of LTE standard. This standard needs to provide support for high mobility users that move at speeds up to 350 Km/h. When users are highly mobile, the multipath wireless channel becomes time-variant and frequency-selective within one OFDM Symbol. The Doppler spread, caused by mobility, destroys the orthogonality and creates inter-carrier interference (ICI) between OFDM subcarriers. As a consequence, the existing channel estimation methods that assume an invariant

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Robust channel estimation for OFDM systems with rapid dispersive fading channels

Cited by 990 publications

References 13 publications

Pilot-Based Channel Estimation for OFDM Systems by Tracking the Delay-Subspace

Pilot-Based Channel Estimation for OFDM Systems by Tracking the Delay-Subspace

Implicit vs. Explicit Approximate Matrix Inversion for Wideband Massive MU-MIMO Data Detection

Analysis of Iterative Channel Algorithm for MIMO OFDM systems using Doppler Spread

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