Abstract
Future wireless communication systems are envisioned to share radio frequency spectrum with radars in order to meet the growing spectrum demands. In this paper, we address the problem of target detection by radars that project waveform onto the null space of interference channel in order to mitigate interference to cellular systems. We consider a multiple-input multiple-output (MIMO) radar and an MIMO cellular communication system with X base stations (BSs). We consider two spectrum sharing scenarios. In the first scenario, the degrees of freedom (DoF) available at the radar are not sufficient enough to simultaneously detect target and mitigate interference to X BSs. For this case, we select one BS among X BSs for waveform projection on the basis of guaranteeing minimum waveform degradation. For the second case, the radar has sufficient DoF to simultaneously detect target and mitigate interference to all X BSs. We study target detection capabilities of null-space projected (NSP) waveform and compare it with the orthogonal waveform. We derive the generalized likelihood ratio test for target detection and derive detector statistic for NSP and orthogonal waveform. The target detection performance for both waveforms is studied theoretically and via Monte Carlo simulations.