Pilot Designs with Guard Bands for Channel Estimation of MIMO OFDM Systems with Frequency-Dependent I/Q Imbalances

All practical OFDM systems insert null guard bands to facilitate easy filter implementation and emission spectrum control. The null guard bands introduce a constraint for optimal pilot designs in MIMO OFDM systems. Semiconductor downscaling and the use of high modulation order have signified the importance of pilot designs for OFDM systems in the presence of I/Q imbalances, but existing designs have not addressed the use of guard bands, the overhead efficiency, the estimation optimality, and general applicability in pilot data multiplexed format and/or MIMO setup. This paper proposes a pilot design for channel estimation of MIMO OFDM systems with guard bands and both transmit and receive frequency-dependent I/Q imbalances, which overcomes the limitations of the existing designs. Simulation and numerical results corroborate better performance, overhead advantage and applicability in pilot-data-multiplexed MIMO setup of the proposed design over the existing MIMO OFDM pilot design with I/Q imbalances.