RSMA-Aided Coded Random Access With Priority Access for 6G Massive Heterogeneous IoT

In Internet-of-Things (IoT), several types of random access (RA) protocols have generated significant interest to address the constantly growing access requirements of IoT devices. Considering high traffic loads in a sixth-generation (6G) massive heterogeneous IoT network, this article studies contention-based RA based on a slotted ALOHA with priority access (PA) protocol empowered by uncoordinated uplink rate-splitting multiple access (RSMA), referred to as PA-RSMA-ALOHA. However, prior research created the preconfigured received power model assuming ideal conditions, such as perfect channel state information (CSI) and perfect successive cancellation interference (SIC). Performance degradation may result from the inability to fully remove the decoded signal due to the disregard for imperfect SIC and CSI. This article examines PA-RSMA-ALOHA under imperfect CSI and imperfect CSI. Moreover, an irregular repetition slotted ALOHA (IRSA) protocol is proposed to enhance the throughput by exploiting diversity burst in a medium access control frame, referred to as PA-RSMA-IRSA. First, the bound on the throughput of PA-RSMA-ALOHA with imperfect CSI and SIC is derived using a collision model and Poisson distribution. Next, the effect of packet diversity burst and SIC in PA-RSMA-IRSA is derived to present asymptotic throughput using density evolution graph-based decoding. Finally, simulation results verify the superiority of the proposed PA-RSMA-IRSA over the benchmark RAs.