A novel approach to estimate I/Q imbalance, CFO and channel response for MIMO OFDM systems

Systems using Orthogonal Frequency Division Multiplexing (OFDM) suffer with carrier frequency offset (CFO), in phase and quadrature phase imbalance (I/Q) due to which there will be large performance degradation. The CFO, I/Q imbalance are caused due to mismatch of carrier frequency at the transmitter and local oscillator frequency at the receiver. This paper presents a novel approach for joint estimation of I/Q imbalance, CFO and Channel Estimation for Multiple-Input Multiple-Output (MIMO) OFDM systems. A new energy parameter called φ is introduced, and from this parameter φ we can jointly estimate CFO, I/Q imbalance irrespective of channel estimation. The proposed method uses an optimal training block with one or two training sequences. For estimation of two repeated sequences, a two-step approach is proposed. From the simulation results we show that the Mean-Square Error (MSE) of this method is close to Cramer-Rao Bound (CRB).