Simultaneous Multi-Beam Sweeping for mmWave Massive MIMO Integrated Sensing and Communication

Efficient beamforming is critical for multiple-input multiple-output (MIMO) integrated sensing and communication (ISAC) systems. In this paper, we focus on a millimeter wave (mmWave) massive MIMO ISAC system, where a mono-static MIMO ISAC node equipped with large transmit and receive antenna arrays wishes to sense a target while concurrently serving a communication user equipment (UE). We propose a cost-effective analog beamforming method, where double-beam codebooks are designed for both the ISAC transmitter and receiver based on sub-array methods. The proposed double-beam codebook can formulate double beams flexibly and it includes the conventional single-beam codebook as a special case. For sensing and communication purposes, the ISAC transmitter needs to direct signals towards the sensing target and communication UE concurrently, and the ISAC receiver requires to formulate receive beams to effectively receive the echoes reflected from the sensing target. To achieve this goal, we further propose the novel simultaneous beam sweeping schemes to search the optimal transmit and receive beams of ISAC, where both simultaneous single-beam and double-beam sweeping schemes are proposed that can achieve different balances between the beamforming gain and required time overhead for beam sweeping. The simulation results demonstrate the effectiveness of the proposed double-beam codebook design and beam sweeping schemes compared to the conventional benchmarks.