Optimal pilot design for MIMO-OFDM system channel estimation in time domain

In this paper, we propose a least squares (LS) channel estimation scheme in time domain for MIMO-OFDM systems based on pilot tones. The basic idea is that time-domain signals generated by pilots of transmitter and receiver are used to estimate the time-domain channel responses. Optimal pilot sequences (OPS) with regard to (w.r.t) the mean square error (MSE) of LS channel estimation are also presented; It is shown that the OPS are equipowered, equispaced, and position orthogonal. The maximum guard bandwidth (MGB) w.r.t MSE is introduced, as virtual subcarriers are not used for transmission. If the guard bandwidth of MIMO-OFDM system is less than or equal to the MGB, the OPS can be avoided from the guard band by adjusting initial position of OPS. Through simulations, it is shown that the OPS derived in this paper outperform conventional OPS in terms of MGB and MSE.