Joint MMSE and CRB-Based Robust Beamforming Design for Monostatic ISAC Systems With Channel Uncertainty

In this paper, we contribute to the beamforming design problem with imperfect channel state information in a monostatic integrated sensing and communication (ISAC) system. We propose a robust waveform design framework tailored for monostatic ISAC systems, incorporating a channel random error vector to account for imperfections in the communication channels, and addressing clutter interference in radar sensing received waveforms. Next, we derive expressions for target estimation performance via utilizing the minimum mean squared error criterion and the Cramer-Rao bound, which serve as objective functions for our beamforming design. Additionally, we introduce signal-to-interference-plus-noise ratio outage probability constraints and power constraints, formulating two different beamforming optimization problems. Utilizing semi-definite programming techniques, we reformulate these optimization problems into convex optimization problems and resolve them via a convex toolbox. Finally, our simulation results achieves 45% sensing gain and 37% communication gain at an SINR threshold of 20 dB compared with the baseline.