Transmissive RIS-Empowered LEO-Satellite Communications With Hybrid-NOMA Under Residual Hardware Impairments

This manuscript introduces an efficient resource allocation framework for a transmissive reconfigurable intelligent surface (T-RIS) assisted Low Earth Orbit (LEO) satellite non-orthogonal multiple access (NOMA) system under residual hardware impairments (RHIs) resulting from imperfect transceiver hardware design. In particular, the goal is to maximize the sum rate of the considered multi-cluster based T-RIS assisted LEO-satellite NOMA network. This is achieved by optimizing the power-allocation of users, time-allocation for each cluster, and transmit passive beamforming of T-RIS node, while adhering to quality-of-service (QoS), time-allocation, and power-budget constraints. Moreover, the presented optimization algorithm tackles the considered highly non-convex problem in three steps. Firstly, the power-allocation of NOMA users is computed by exploiting Lagrange duality and sub-gradient methods. Secondly, the time-allocation for each cluster is determined based on the interior point method by exploiting Mosek-assisted CVX toolbox. Thirdly, the computation of passive beamforming employs semi-definite programming (SDP) and successive convex approximation (SCA) techniques, where a rank-1 solution is achieved by incorporating the Gaussian randomization method. Finally, numerical simulations affirm the effectiveness of the proposed optimization strategy, highlighting its superior performance in comparison to benchmark techniques. Notably, it proves to be highly effective in achieving fast convergence with only a few iterations.