  As an emerging antenna technology, a fluid antenna system (FAS) enhances
spatial diversity to improve both sensing and communication performance by
shifting the active antennas among available ports. In this letter, we study
the potential of shifting the integrated sensing and communication (ISAC)
trade-off with FAS. We propose the model for FAS-enabled ISAC and jointly
optimize the transmit beamforming and port selection of FAS. In particular, we
aim to minimize the transmit power, while satisfying both communication and
sensing requirements. An efficient iterative algorithm based on sparse
optimization, convex approximation, and a penalty approach is developed. The
simulation results show that the proposed scheme can attain 33% reductions in
transmit power with guaranteed sensing and communication performance, showing
the great potential of the fluid antenna for striking a flexible tradeoff
between sensing and communication in ISAC systems.
