Simultaneous Beam Sweeping for Multi-Beam Integrated Sensing and Communication

Effective beamforming is essential for multi-antenna based integrated sensing and communication (ISAC), where multiple beams are usually required to concurrently direct signal power towards both the communication user equipment (UE) and the sensing target. This paper studies millimeter wave (mmWave) ISAC system, where an ISAC node with large antenna arrays wishes to simultaneously communicate with an UE and sense a target using the cost-effective analog beamforming. We first propose a subarray-based double-beam codebook design, which includes the conventional single-beam codebook as a special case. With the proposed codebook design, for all possible combinations of the UE and target directions, signal power can be effectively directed towards them concurrently, as long as the beam is appropriately selected. To this end, we further propose a novel beam sweeping protocol, for which the beam searching processes for communication and sensing are carried out simultaneously, with either single-beam or double-beam sweeping that achieves different balances between the required sweeping time and beamforming gain. Simulation results are provided to show the effectiveness of the proposed codebook design and simultaneous beam sweeping methods.