Abstract—In this paper, we study the joint estimation of inphase

and quadrature-phase (I/Q) imbalance, carrier frequency

offset (CFO), and channel response for multiple-input multipleoutput

(MIMO) orthogonal frequency division multiplexing

(OFDM) systems using training sequences. A new concept called

channel residual energy (CRE) is introduced. We show that by

minimizing the CRE, we can jointly estimate the I/Q imbalance

and CFO without knowing the channel response. The proposed

method needs only one OFDM block for training and the training

symbols can be arbitrary. Moreover when the training block

consists of two repeated sequences, a low complexity two-step

approach is proposed to solve the joint estimation problem.

Simulation results show that the mean-squared error (MSE) of

the proposed method is close to the Cramer-Rao bound (CRB).

Index Terms—MIMO OFDM, CFO, I/Q imbalance, channel

estimation.