Joint User Grouping and Power Allocation for Uplink NOMA-ISAC Systems

This study considers non-orthogonal multiple access (NOMA) inspired integrated sensing and communication (ISAC) systems. In particular, it presents a novel approach that jointly optimizes power allocation (PA) and user grouping (UG) in the uplink of NOMA-based ISAC. The proposed optimization is a mixed-integer non-linear programming (MINLP) problem, which is a non-convex and non-deterministic polynomial time-hard. To solve the formulated problem, an outer approximation (OA) technique is employed to transform the original MINLP problem into a mixed-integer linear programming (MILP) problem and a non-linear programming (NLP) one. The performance of the optimized PA and UG approach is evaluated through extensive simulations, which examine the impact of the radar signal and the maximum power limit for each user equipment. Additionally, the performance of the radar system is assessed using the radar channel estimation and probability of detection. Compared to benchmark techniques, it is shown that the proposed scheme produces higher achievable communication sum rates while satisfying the performance requirements of the radar system.