Channel Training for Analog FDD Repeaters: Optimal Estimators and Cram\'er-Rao Bounds
| Autor: | Wesemann, Stefan, Marzetta, Thomas L. |
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| Rok vydání: | 2016 |
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| Druh dokumentu: | Working Paper |
| DOI: | 10.1109/TSP.2017.2749210 |
| Popis: | 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 Cram\'er-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. Comment: Submitted to IEEE Transactions on Signal Processing, 12 pages, 7 figures |
| Databáze: | arXiv |
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