2D Movable Antenna Assisted ISAC: Joint Beamforming and Antenna Position Optimization

Abstract

This paper studies a two-dimensional (2D) movable-antenna (MA) assisted integrated sensing and communications (ISAC) system. The base station serves multiple single-antenna users and senses one point target using a reconfigurable 2D MA array. The considered design exploits antenna-position adaptation and transmit beamforming to improve the sensing signal-to-noise ratio (SNR) under user signal-to-interference-plus-noise ratio (SINR), power-budget, antenna-region, and minimum-spacing constraints. Different from conventional fixed-array ISAC designs, the considered model explicitly characterizes the two-dimensional MA coordinates in both the multiuser communication channels and the round-trip sensing channel, which enables joint exploitation of beam-domain and geometry-domain degrees of freedom. The resulting problem is nonconvex because the beamforming vectors and MA coordinates are coupled in both the sensing objective and the communication constraints. An alternating optimization (AO) method is developed, where the beamforming subproblem is handled by semidefinite relaxation (SDR) and Gaussian randomization, while the MA-position subproblem is solved by a second-order successive convex approximation (SCA) procedure with inner approximations for the SINR and minimum-spacing constraints. Simulation results show that the proposed MA design provides higher sensing SNR than fixed-array, antenna-selection, and random-position benchmarks while maintaining the required communication quality.