Joint User Scheduling, Power Allocation, and Rate Control for MC-RSMA in URLLC Services

This paper investigates the resource management problem in multi-carrier rate-splitting multiple access (MC-RSMA) systems with imperfect channel state information (CSI) and successive interference cancellation (SIC) for ultra-reliable and low-latency communications (URLLC) applications. Effective throughput (ET) is employed as the key performance metric in this study to explore the trade-off between the decoding error probability and achievable rate. A mixed-integer non-convex problem is formulated to jointly optimize power allocation, rate control, and user grouping. To tackle this challenge, the achievable ET is approximated using a lower bound, and a decomposition approach is developed to decouple the optimization variables. Specifically, for a given user grouping scheme, an iteration-based concave-convex programming (CCCP) method and an iteration-free lower-bound approximation (LBA) method are proposed for power allocation and rate control. Furthermore, a greedy search-based scheme and a minimum correlation user grouping (MCUG) scheme are designed for the user grouping problem. Simulation results verify the effectiveness of the CCCP and LBA methods in power allocation and rate control and the MCUG method in user grouping when compared to the greedy and random methods. Besides, the superiority of RSMA for URLLC services is demonstrated when compared to spatial division multiple access.