Power Source Allocation for RIS-Aided Integrating Sensing, Communication, and Power Transfer Communication Systems Based on NOMA

The integration of sensing, communication, and power transfer (ISCPT) has emerged as a promising paradigm for energy- and spectrum-efficient 6G networks. Recent studies have revealed that sensing accuracy, achievable rate, and harvested energy inherently exhibit conflicting design requirements and form a nontrivial trade-off region. However, existing integrated sensing and communication (ISAC) and simultaneous wireless information and power transfer (SWIPT) schemes typically optimize at most two of these functionalities and lack a unified resource-allocation framework that can flexibly balance all three under stringent power budgets. Motivated by this gap, we consider a reconfigurable intelligent surface (RIS)-aided ISCPT system that employs non-orthogonal multiple access (NOMA) to support multi-user connectivity. In the proposed design, the RIS reshapes the wireless propagation environment in an energy-efficient manner to enhance both sensing and power transfer, while NOMA provides power-domain multiplexing to improve spectral efficiency and user scalability. We formulate a total transmit power minimization problem by jointly optimizing the base-station beamforming, RIS phase shifts, power splitting (PS) ratios, and NOMA decoding order under quality-of-service (QoS), Cramér–Rao-bound-based sensing accuracy, and energy-harvesting constraints. The resulting problem is highly non-convex due to the coupling among the design variables. To solve it efficiently, we develop a block coordinate descent (BCD)-based algorithm that leverages semidefinite relaxation (SDR), successive convex approximation (SCA), and the alternating direction method of multipliers (ADMM). Simulation results verify that the proposed RIS-aided NOMA-ISCPT framework significantly reduces the base-station transmit power while achieving favorable trade-offs among communication reliability, sensing precision, and energy-transfer efficiency.