Adaptive frequency-domain biased estimation algorithms with automatic adjustment of shrinkage factors

In this work, we propose adaptive frequency-domain biased estimation algorithms with mechanisms to automatically adjust the shrink age factors. The proposed estimation algorithms improve the performance of the conventional least squares (LS) estimator in terms of mean-squared error (MSE), while requiring a very modest in crease in complexity. An extension of the Cramer-Rao Lower Bound (CRLB) is computed in order to serve as a performance benchmark for the MSE performance of the biased estimators. We consider an application of the proposed algorithms to single-carrier frequency domain equalization (SC-FDE) of direct-sequence ultra-wideband (DS-UWB) systems, in which the channel estimation is performed by the proposed algorithms. The simulation results show that the proposed algorithms significantly outperform existing methods.