Pilot-symbol aided channel estimation by Wiener filtering for OFDM systems with multiple transmit antennas

We address pilot-symbol aided channel estimation (PACE) for OFDM based systems employing multiple transmit antennas. Two approaches are investigated: first, all N_T transmit antennas use all available pilot symbols simultaneously, resulting in N_T superimposed signals; second, a subset of available pilots is allocated for each transmit antenna exclusively. The Wiener filter and the corresponding mean square error (MSE) are derived. By applying the sampling theorem, the minimum pilot overhead required to estimate the channel of N_T superimposed waveforms is analyzed.