Novel IQ imbalance estimation for wideband MIMO OFDM systems with CFO

This paper deals with IQ imbalance in wideband MIMO OFDM systems. In systems with a large bandwidth, the IQ imbalance will be frequency-dependent and hence can not be described by a single parameter. Furthermore if there is a carrier-frequency offset (CFO), the IQ imbalance estimation in a MIMO system with multiple channels becomes a challenging task. However the CFO introduces a time-varying component to the received signal which we exploit to estimate the model parameters using a carefully designed training sequence. This approach derives the TX and RX IQ imbalance separately in an accurate fashion. We verify this by simulations and also show the estimated IQ imbalance in a hardware prototype we have built.