Multi-Metric Waveform Optimization for Multiple-Input Single-Output Joint Communication and Radar Sensing

Joint communication and radar sensing (JCAS) integrates the two functions into one system, sharing one transmitted signal. In this paper, we investigate JCAS waveform optimization in communication-centric systems, where a base station (BS) detects radar targets and communicates with mobile users simultaneously. Different from existing works, we study multi-metric optimizations for a practical low-cost system and establish their connections. To relax the requirement of full-duplex technology, we add a single receive antenna for sensing at the BS, which is synchronized with and spatially separated from the JCAS transmit array. We first optimize precoders for communications and radar, individually. Then, we formulate a JCAS waveform optimization problem that constrains either mutual information (MI) or Cramér-Rao bound (CRB) of radar and maximizes the relaxed signal-to-interference-plus-noise rate (SINR) of communications. Exploiting the geometric characteristic of the relaxed SINR, we provide a closed-form solution under certain conditions and propose a numerical iteration algorithm that works in all situations. We also disclose the connections between optimizations with constraining MI and CRB, using numerical results. Finally, simulation results are provided and validate the proposed optimization solutions.