Cooperative ISAC with Rotatable Antenna for the Low-Altitude Economy

Integrated sensing and communication (ISAC) is envisioned as a promising technology to empower the emerging low-altitude economy (LAE). However, current networks primarily serve terrestrial users, resulting in insufficient low-altitude coverage. Furthermore, standalone ISAC systems exhibit restricted sensing ranges, as fixed antenna orientations suffer from significant gain loss at large angles. In view of this, we propose cooperative ISAC enabled by rotatable antenna (RA) technology. RA aligns its boresight with target directions through antenna rotation, effectively mitigating gain loss at large angles. This compact and low-complexity design provides robust coverage and high-precision sensing, making it well-suited for deployment in the LAE. Specifically, multiple RA-equipped base stations (BSs) employ coordinated beamforming to provide robust connectivity for authorized unmanned aerial vehicles (UAVs), while concurrently monitoring distributed critical locations within the target airspace for potential intrusions. To implement this scheme, we maximize the system sum-rate subject to various practical constraints by jointly optimizing BS-UAV associations, transmit beamforming, RA orientation, and UAV trajectories. This nonconvex problem is addressed by an efficient alternating optimization (AO) algorithm that integrates semidefinite relaxation (SDR) and successive convex approximation (SCA). Finally, numerical results demonstrate that the proposed RA-enhanced ISAC system outperforms baselines in line-of-sight (LoS)-dominated, large-angle low-altitude scenarios.