In this paper, we propose an efficient channel estimation technique for orthogonal frequency-division multiplexing (OFDM) systems with transmitter diversity. The proposed technique estimates uniquely all channel frequency responses needed in space-time coded OFDM systems using "comb-type" training symbols. The computational complexity of the proposed technique is reduced dramatically, compared with the previous minimum mean-squared error (MMSE) technique, due to the processing made all in the frequency-domain. Also, several other techniques for mitigating random noise effect and tracking channel variation are discussed to further improve the performance of the proposed approach. The performances of the proposed approach are demonstrated by computer simulation for mobile wireless channels.

In this letter, a two-dimensional pilot-symbol aided (2-D PSA) channel estimation technique for coherent orthogonal frequency-division multiplexing (OFDM) systems with transmitter diversity is proposed. The 2-D PSA channel estimator and the corresponding orthogonality condition between the sets of pilot symbols are derived under minimum mean-square error (MMSE) criterion for OFDM systems with transmitter diversity. The proposed estimator is shown to be accurate and effective for tracking variations of channels between multiple transmitter antennas and receiver antennas.