Shifting the ISAC Trade-Off With Fluid Antenna Systems

As an emerging reconfigurable antenna technology, fluid antenna system (FAS) has the capability of improving both sensing and communication (S&C) performance by switching the antenna position over the available ports. This increased spatial degree-of-freedom (DoF) by FAS can be translated into enlarging the trade-off region for integrated sensing and communication (ISAC). In this letter, we propose a signal model for FAS-enabled ISAC and jointly optimize the transmit beamforming and port selection of FAS. In particular, our objective is to minimize the transmit power, while satisfying both communication and sensing requirements. To tackle this, an efficient iterative algorithm based on sparse optimization, convex approximation, and a penalty approach is developed. Our simulation results illustrate that the proposed scheme can attain 33% reductions in the transmit power with guaranteed S&C performance, showing the great potential of FAS for striking a balance between S&C in ISAC systems.