Channel estimation for space time coded OFDM systems in non-sample-spaced multipath channels

Space-time (ST) coded OFDM has been proved to be an effective and promising technique for future wideband wireless data access. As the multiple transmit antennas transmit signals act as co-channel interference to each other, the channel estimation for ST-coded OFDM systems is different from the single transmit antenna scenario. Channel estimation can be achieved by estimating the channel impulse response based upon a discrete Fourier transform (DFT). However, in a multipath channel with non-sample-spaced time delays, this approach will cause power leakage and result in an error floor. In this paper, based on the use of IPIC DLL (interpath interference cancellation delay locked loop), we propose a least square (LS) and minimum mean square error (MMSE) channel estimators for ST-coded OFDM with non-sample-spaced multipath time delays. It is shown that the proposed channel estimators can eliminate the error floor substantially and perform quite close to the case with ideal channel state information.