Resource Allocation in STAR-RIS-Aided Networks: OMA and NOMA

Simultaneously transmitting and reflecting reconfigurable intelligent surface (STAR-RIS) is a promising technology that aids in achieving full-space coverage on both sides of the surface, by splitting incident signal into transmitted reflected signals. This paper investigates resource allocation problem STAR-RIS-assisted multi-carrier communication networks. To maximize system sum-rate, joint optimization comprising channel assignment, power allocation, transmission reflection beamforming at STAR-RIS for orthogonal multiple access (OMA) first formulated. solve this challenging problem, we propose assignment scheme utilizing matching theory then invoke alternating optimization-based method to optimize policy vectors iteratively. Furthermore, sum-rate maximization non-orthogonal (NOMA) with flexible decoding orders investigated. efficiently it, location-based algorithm determine sub-channel where user are grouped sub-channel. Based transmission-and-reflection strategy, three-step approach proposed, which involves orders, beamforming-coefficient vectors, employing semidefinite programming, convex upper bound approximation, geometry respectively. Numerical results unveil that: 1) For OMA, general design includes same-side user-pairing preferable, whereas NOMA, proposed transmission-and-reflection can achieve comparable performance exhaustive search-based algorithm. 2) The STAR-RIS-aided NOMA network significantly outperforms networks conventional RISs OMA.