Joint Estimation of Transmitter and Receiver IQ Imbalance With ML Detection for Alamouti OFDM Systems
OFDM systems are susceptible to receiver impairments such as IQ imbalance and phase noise. These impairments can severely degrade the achievable effective signalto-noise ratio at the receiver. In this paper, we propose a joint compensation scheme to mitigate the effects of the IQ imbalance and phase noise in multiple-input multiple-output (MIMO) OFDM systems. For ease of notation, a system with one transmit and two receive antennas is used to illustrate how to exploit the structure of MIMO transceivers to efficiently compensate for such impairments. We exploit the fact that the two received signals suffer from the same phase noise distortion, making it possible to achieve better compensation results than the single-input single-output case. The pilot tones in OFDM symbols are exploited to aid data recovery, and the data symbols are jointly estimated with the phase noise components that are parameterized by using the principle component analysis technique. The sensitivity of OFDM receivers to the analog impairments is significantly lowered, which helps simplify the RF and analog circuitry design in terms of implementation cost, power consumption, and silicon fabrication yield.