In this article, doubly selective channel estimation is considered for 1amplify-and-forward-based relay networks. The complex exponential basis expansion model is chosen to describe the time-varying channel, from which the infinite channel parameters are mapped onto finite ones. Since direct estimation of these coefficients encounters high computational complexity and large spectral cost, we develop an efficient estimator that only targets at useful channel parameters that could guarantee the later data detection. The training sequence design that can minimize the channel estimation mean-square error is also proposed. Finally, numerical results are provided to corroborate the study.
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