Efficient Training Sequence for Joint Carrier Frequency Offset and Channel Estimation for MIMO-OFDM Systems

Combining orthogonal frequency division multiplexing (OFDM) and multiple input and multiple output (MIMO) technologies enables high spectral efficiency data transmission over frequency selective fading channels. However, carrier frequency offset (CFO) and channel estimation become more complex for MIMO-OFDM systems. In this paper, we propose a class of efficient shift-orthogonal training sequences to assist joint CFO and channel estimation. We show that with the proposed training sequence, the CFO estimation touches Cramer- Rao bound (CRB) at practical SNR values. Such sequences are efficient as the overhead used for channel estimation can be significantly reduced compared to using conventional training sequence designs. We also derive a tight lower bound on the MSE of the channel estimation in the presence of the residual CFO.