On the Throughput of RSMA-ALOHA for Vortex Wave Communications

In this letter, we propose an uplink rate splitting multiple access (RSMA)-assisted slotted ALOHA (RSMA-ALOHA) for vortex wave (VW) communications, referred to as VW-RSMA-ALOHA. In VW-RSMA-ALOHA, we perform cross-layer optimization of the physical (PHY) and medium access control (MAC) layers by integrating RSMA-based orbital angular momentum (OAM) mode transmission with the slotted ALOHA protocol. Machine-type devices transmit packet as OAM mode using a single uniform circular array (UCA) antenna, while the access point receives all OAM modes from multiple users using concentric UCAs. Theoretical bounds are derived from VW-RSMA-ALOHA throughput, and the results demonstrate that this proposed method enhances the RA throughput in uplink VW communications.