Transmit Beamforming Optimization for SDMA Enabled NOMA-ISAC

This paper investigates a spatial division multiple access (SDMA) enabled non-orthogonal multiple access (NOMA) integrated sensing and communications (ISAC) framework. A dual-functional base station serves multiple communication users via SDMA and transmits a superimposed NOMA-ISAC signal for radar sensing. A transmit beamforming optimization problem is formulated to maximize the sensing signal-to-interference-plus-noise ratio (SINR). To address the non-convexity, a two-level iterative algorithm based on the Dinkelbach method and semidefinite relaxation (SDR) is proposed. Numerical results show the performance gain of combining SDMA into the NOMA-ISAC system and the trade-off between sensing and communications.