Robust resource allocation for HRIS-assisted NOMA WPCN under short-packet transmission

To improve the quality-of-service in short-packet transmissions and further reduce the transmission energy consumption of the hybrid base station (HBS), this paper proposes a hybrid reconfigurable intelligent surface (HRIS)-assisted non-orthogonal multiple access (NOMA) wireless powered communication network (WPCN) framework that supports short-packet communication under imperfect channel state information (CSI). Aiming to minimize the transmission energy consumption of the HBS, we formulate a joint optimization problem under a norm-bounded CSI model and a nonlinear energy harvesting (EH) model. Specifically, we optimize the network time allocation, HBS precoding and receive beamforming, wireless-powered devices’ (WPDs’) transmit power and packet length, as well as the HRIS mode selection and beamforming to simultaneously support wireless energy transfer (WET) and wireless information transfer (WIT). Owing to the strong coupling among optimization variables and the presence of integer constraints, the resulting formulation takes the form of a mixed-integer non-convex optimization problem, rendering direct solution intractable. Accordingly, a low-complexity suboptimal alternating optimization (AO) algorithm is devised, integrating the S-procedure, Schur’s complement, successive convex approximation (SCA), and the penalty approach. Numerical results verify the robustness and effectiveness of the proposed algorithm, demonstrating its superiority in lowering the HBS transmission energy.