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

Abstract

Abstract-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 nextgeneration broadband wireless standards result in performancelimiting 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 frequencydependent transmit and receive I/Q imbalances even in the presence of a residual frequency offset.

Performance and Compensation of I/Q Imbalance in Differential STBC-OFDM

“…where S k (n) is the 2 × 2 STBC transmitted data matrix corresponding to the (2k + 1)-th, (2k + 2)-th OFDM symbols of the k-th data block at the n-th subcarrier defined in Eq. (8). Similarly, S k+1 (n) and U k+1 (n) are the 2 × 2 STBC transmitted data matrix and information matrix, respectively, corresponding to the (2 (k + 1) + 1)-th and (2 (k + 1) + 2)th OFDM symbols of the (k + 1)-th data block at the n-th subcarrier.…”

Training Symbol Design for Channel Estimation and IQ Imbalance Compensation in OFDM Systems

“…Since I/Q imbalance problem is originated from the unavoidable differences in the relative amplitudes and phases of the physical analog I and Q signal paths, the effects of I/Q imbalances in OFDM systems cannot be rectified by increasing signal power, thus, to obtain better quality of the high rate communications systems, efficient channel estimation and I/Q imbalance compensation techniques are crucial [4], [5].…”

“…In the literature, training symbol designs for channel estimation and I/Q imbalance compensation for OFDM systems have been predominantly developed ( see [2], [4]- [6] and the references there in). However, there is no existing method that optimally select phase information of the training (or pilot) symbols to reduce the peak to average power ratio (PAPR) effect.…”

Modelling and compensation of frequency-dependent I/Q imbalance in multiple beamforming OFDM transceivers

“…[1] and references there in. Extensions to MIMO diversity and spatial multiplexing scenarios for quasi-static and fast timevarying channels were reported in [2] and [3], respectively. In [4], the effects of I/Q imbalance on MIMO beamforming systems have been investigated however they assume a flat-fading channel and frequency-independent I/Q imbalance at the receive side only.…”