Movable-Signal Multiple Access (MSMA) for Pinching-Antenna-Assisted ISAC

Abstract

Pinching-antenna systems (PASS) can reshape an integrated sensing and communication (ISAC) channel through radiating-point placement, but one carrier state generally cannot simultaneously condition a multiuser channel and coherently combine a target echo. This letter studies movable-signal multiple access (MSMA) for this mismatch. The data streams share one block-frozen communication state and are separated by joint feed precoding, whereas a coded sensing reference occupies a second block-frozen state over the same PASS geometry. An attenuation-aware guided-plus-spherical channel model is developed with an explicit point-target coefficient and finite receive-filter overlap between the two state components. For the resulting target-dependent disturbance covariance, an exact conditional Fisher-information matrix and Cramér–Rao lower bound are derived, followed by a local curvature law that relates state resolution to PASS-induced delay variance. A three-block method screens finite state pairs, jointly selects structured precoding directions and allocates stream powers, and updates ordered pinching positions. Every reported iterate is feasible for the original SINR and power constraints and is accepted only when the exact sensing objective does not decrease. Numerical results show the gain over fixed-carrier, single-state, and fixed-geometry designs.