Transmit Beamforming for MIMO Dual Functional Radar-Communication With IQI

Multiple-input-multiple-output (MIMO) dual-func- tional radar communication (DFRC) provides a solution to the severe spectrum scarcity challenge. MIMO systems may be prone to the hardware impairments (HWI). Considering I/Q-imbalance (IQI), the most common type of HWI, we study the optimal transmit beamforming design for MIMO DFRC. Both radar-centric and communication-centric scenarios are investigated. For the radar-centric design, the radar beampattern and communciations user signal-to-interference-plus-noise ratio (SINR) with IQI are derived. Then, the radar beampattern is optimized by using the semidefinite relaxation (SDR) method. For the communication-centric design, the achievable rate with IQI is derived. Then, the transmit beamforming is optimized with the constraint on the MIMO radar receive signal-to-noise ratio (SNR). Moreover, the computational complexity is analyzed. Numerical results verify that IQI amplitude mismatch, IQI phase mismatch and the IQI mitigation error can significantly degrade the system's overall performance. Also, for the communication-centric scenario, IQI phase mismatch at the CUs is much more important than that at the BS.