2- Layer Hierarchical RSMA for STAR RIS Assisted Cell-edge Communications

This paper analyzes a simultaneous transmitting and reflecting (STAR) reconfigurable intelligent surfaces (RIS) assisted communication system where a base station communicates with cell-edge users through two-level hierarchical rate splitting multiple access (RSMA) protocol. The rectangular geometry of the STAR RIS and the proximity of RIS atoms result in spatial correlation within the RIS channels. The analysis focuses on evaluating the outage probability (OP) for two operational modes of STAR RIS: energy splitting (ES) and mode switching (MS). The findings provide valuable insights into the design of RSMA and RIS parameters which are crucial for implementation of these systems.