Hybrid NOMA Empowered Integrated Sensing and Communications

Abstract

A novel concept of hybrid non-orthogonal multiple access (HNOMA) empowered integrated sensing and communications (ISAC) is proposed, where the additional sensing-to-communication (S2C) interference can be mitigated via successive interference cancellation (SIC) in an adaptive manner. A transmit power minimization problem is formulated to jointly optimize the beamforming vectors and SIC options, subject to the dual functionality requirements. To address this non-convex mixed integer problem, we first investigate the ideal case where the additional S2C interference can be unconditionally eliminated. It reveals that the required number of dedicated sensing beams is no more than one. By exploring this insight, we propose a hybrid-NOMA ISAC (HNOMA-ISAC) scheme, where the binary SIC option of each CU is determined via the optimal solution of the ideal case. The remaining beamforming design problem is solved via semidefinite relaxation (SDR). Simulation results reveal that the proposed HNOMA-ISAC scheme achieves the identical sensing performance as the conventional ISAC scheme while maintaining much lower transmission energy consumption.