A hybrid channel estimator for MIMO-OFDM system with per-subcarrier transmit antenna selection

A novel hybrid channel estimator that gives robust performance with respect to the error in antenna-to-subcarrier assignment (ATSA) for spatially correlated MIMO-OFDM system with per-subcarrier transmit antenna, is proposed. In practice, the antenna selection information is transmitted through a binary symmetric control channel with a crossover probability. Though minimum mean-square error (MMSE) estimator performs well at low signal to noise ratio (SNR), in the presence of antenna selection error it introduces irreducible error at high SNR. In this paper, we have proved that relaxed MMSE estimator overcomes the performance degradation at high SNR, with less computational complexity. The proposed hybrid estimator combines the benefit of MMSE at low SNR and relaxed MMSE estimator at high SNR. Further, an analytical expression for SNR threshold at which the hybrid estimator is to be switched from MMSE to relaxed MMSE is also derived. The simulation results show that the proposed hybrid estimator gives robust performance, irrespective of the ATSA error and power delay profile of the channel.