Abstract: In the multiple antenna OFDM systems,the non-orthogonal training sequences are usually used as the channel training sequences,which would lead to the matrix inversion operation with great complexity during the channel estimation process．So,the training symbols in multi-user CDMA uplinks was used for time channel training symbols in the multiple antenna OFDM systems,and the multiple antenna spatial channels could be evaluated according to the classical Steiner channel estimation algorithm．In fact,the training symbol matrix in transmit antenna is one circular matrix,which could be diagonalized by discrete Fourier transformation at receiver antenna,and the matrix inversion operation could also be avoided．Furthermore,based on the initial estimation results of Steiner algorithm,one could obtain the direction of arrival (DoA) for incidence waves at different multiple receiver antenna．These DoA information is further used to improve the Steiner algorithm．Numerical results show that the improved Steiner algorithm with DoA could obtain 0.5dB SNR improvement with QPSK modulation and 2dB SNR improvement with 16QAM modulation,when compared to that of original Steiner method.

Key words: Multiple antenna,OFDM,Channel estimation,Direction of arrival