Compensation of cascaded radio impairments in MIMO-OFDM systems with direct-conversion architecture

Direct-conversion radio architecture is a low-cost, small-size design for the analog front-end subsystem in a wireless communication transceiver. This architecture, however, induces radio impairments such as I-Q imbalance and dc offset that, along with frequency offset, incur severe degradation in communication performance. This paper aims to improve the performance of estimation and compensation for cascaded transmitter and receiver radio impairments in the MIMO-OFDM (multiple-input, multiple-output orthogonal frequency-division multiplexing) systems. First, a novel two-stage compensation scheme is proposed which is applicable to a general form of MIMO operations with any number of transmit and receive antennas. Second, with a periodic training, an improved low-complexity joint estimation and compensation algorithm for radio impairments is proposed. Numerical results show the superiority of proposed method over the existing ones in bit error rate (BER) performance and training overhead.