Low-complexity channel estimation for the UHF MIMO-RFID systems with optimal training

The issue of channel estimation is investigated for the UHF MIMO-RFID systems over pinhole channel. A training sequences aided linear minimum mean square error (LMMSE) channel estimation is proposed for the whole pinhole channel at the reader. Based on the mean square error (MSE) criterion, the MSE bound and the optimal training scheme with this bound are derived. By exploiting the optimal training scheme, an optimal low-rank LMMSE channel estimator is proposed to reduce the computational complexity via singular value decomposition (SVD). Furthermore, the Chu sequence is employed as the optimal training sequence to implement with easy realization and reduce computational complexity at the reader. Simulation results demonstated the effectiveness of the proposed low-complexity channel estimation method and the superiority of the derived optimal training scheme for the MIMO-RFID systems.