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arXiv · 1610.03260

Channel Training for Analog FDD Repeaters: Optimal Estimators and Cramér-Rao Bounds

Stefan Wesemann·Thomas L. Marzetta
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Abstract

For frequency division duplex channels, a simple pilot loop-back procedure has been proposed that allows the estimation of the UL & DL channels at an antenna array without relying on any digital signal processing at the terminal side. For this scheme, we derive the maximum likelihood (ML) estimators for the UL & DL channel subspaces, formulate the corresponding Cramér-Rao bounds and show the asymptotic efficiency of both (SVD-based) estimators by means of Monte Carlo simulations. In addition, we illustrate how to compute the underlying (rank-1) SVD with quadratic time complexity by employing the power iteration method. To enable power control for the data transmission, knowledge of the channel gains is needed. Assuming that the UL & DL channels have on average the same gain, we formulate the ML estimator for the channel norm, and illustrate its robustness against strong noise by means of simulations.

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Stefan Wesemann, Thomas L. Marzetta. 2017-04-04. Channel Training for Analog FDD Repeaters: Optimal Estimators and Cramér-Rao Bounds. https://doi.org/10.1109/tsp.2017.2749210

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