A Precoding OFDM MIMO Radar Coexisting With a Communication System

A novel orthogonal frequency-division multiplexing (OFDM) multiple-input multiple-output (MIMO) radar is proposed in this paper in a scenario of coexisting with a communication system. For the purpose of avoiding interference to communication while maintaining MIMO radar's capabilities, such as measuring signal's direction of departure (DOD), a collocated antenna array is divided into several overlapped subarrays. Mutually OFDM waveforms exploiting an orthogonal space-time block code are transmitted through these subarrays to obtain waveform diversity, which can be separated at the radar receiver. A MUSIC-like DOD estimation algorithm and the Cramér-Rao bound of DOD are proposed for overlapped subarrays' configuration in order to evaluate performance of the beamforming strategy. The beamformer is designed using an optimization technique at cost of maximizing the input SNR of radar while keeping communication rate constant. Due to nonconvexity of the optimization problem, a two-step optimization algorithm is proposed. Simulation experiments validate theoretical analysis of the proposed precoding radar. Experiments also show robustness of the precoding scheme and the ability of balancing the input SNR of radar and the communication rate.