Reduced-complexity baseband compensation of joint Tx/Rx I/Q imbalance in mobile MIMO-OFDM

Direct-conversion multiple-input multiple-output orthogonal frequency division multiplexing (MIMO-OFDM) transceivers enjoy high data rates and reliability at practical implementation complexity. However, analog front-end impairments such as I/Q imbalance and high mobility requirements of next-generation broadband wireless standards result in performance-limiting inter-carrier interference (ICI). In this paper, we study the effects of ICI due to these impairments for OFDM with space frequency block codes and spatial multiplexing, derive a generalized linear model and propose a non-iterative reduced-complexity digital baseband joint compensation scheme. Furthermore, we present a pilot scheme for joint estimation of the channel and the I/Q imbalance parameters and evaluate its performance through simulations. Our proposed scheme is effective in estimating and compensating for frequency-independent and frequency-dependent transmit and receive I/Q imbalances even in the presence of a residual frequency offset.