Iterative channel estimation and decoding with product codes in multicarrier systems

Necker

2003

IEEE Commun. Lett.

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Section: A One-dimensional App Channel Estimationmentioning

confidence: 99%

“…whereby the FIR £lter coef£cients u f,i are calculated with the Wiener-Hopf equation based on the frequency auto-correlation function R f ;k [2]. m f is the prediction order.…”

Section: A One-dimensional App Channel Estimationmentioning

confidence: 99%

Section: A One-dimensional App Channel Estimationmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

See 3 more Smart Citations

Totally blind APP channel estimation for mobile OFDM systems

Necker

2003

IEEE Commun. Lett.

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A comparative study of iterative channel estimators for mobile ofdm systems

IEEE Trans. Wireless Commun.

Jelting

Speidel

2003

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In this letter, we investigate two iterative channel estimators for mobile orthogonal-frequency division multiplexing. The first estimator is based on iterative filtering and decoding whereas the second one uses an a posteriori probability (APP) algorithm. The first method consists of two cascaded one-dimensional Wiener filters, which interpolate the unknown time-varying two-dimensional frequency response in between the known pilot symbols. As will be shown, the performance can be increased by feeding back the likelihood values at the output of the APP-decoder to iteratively compute an improved estimate of the channel frequency response. The second method applies two APP estimators, one for the frequency and the other one for the time direction. The two estimators are embedded in an iterative loop similar to the turbo decoding principle. As will be shown in detail, this iterative estimator is superior and its performance is independent of whether the chosen time-frequency pilot grid satisfies the two-dimensional sampling theorem or not. The bit-error rate as a function of the signal-to-noise ratio is used as a performance measure. In addition, the convergence of the iterative decoding loop is studied with the extrinsic information transfer chart.

Totally blind APP channel estimation with higher order modulation schemes

2003 IEEE 58th Vehicular Technology Conference. VTC 2003-Fall (IEEE Cat. No.03CH37484)

Necker

2003

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Abstract-A new two-dimensional blind channel estimation scheme for coherent detection of OFDM signals in a mobile environment is presented. The channel estimation is based on the A Posteriori Probability (APP) calculation algorithm. The time-variant channel transfer function is completely recovered without phase ambiguity with no need for any pilot or reference symbols. The two-dimensional channel estimation is performed by applying a concatenation of two one-dimensional APP estimators for frequency and time direction in combination with an iterative estimation and decoding loop. The phase ambiguity problem is solved by using higher order modulation schemes with asymmetrical arrangement. The proposed approach maximizes the spectral efficiency by avoiding any reference or pilot symbols and minimizes the BER by using coherent demodulation. We investigate the performance of our algorithm with respect to the BER and study the convergence of the iterative estimation and decoding loop using Extrinsic Information Transfer (EXIT) charts.