1. In an orthogonal frequency division multiplexing (OFDM) multiple-input multiple-output (MIMO) wireless communication system where both a transmitter and a receiver include a plurality of antennas, a method for optimizing channel estimation in the OFDM wireless communication system, the method comprising: generating a plurality of training sequences without performing inverse fast Fourier transform (IFFT) from a basic code M 0 by linearly shifting the basic code M 0 , the length of the basic code M 0 and each shift W between two training sequences are chosen such that each shift W is greater than a maximum delay spread of a wireless communication channel; concatenating the training sequences with OFDM symbols; transmitting the training sequences and the OFDM symbols with a plurality of transmit antennas, each transmit antenna transmitting a different training sequence simultaneously; receiving the training sequences and the OFDM symbols with a plurality of receive antennas; and processing the training sequences to obtain a channel response estimate.