  Rate splitting multiple access (RSMA) and non-orthogonal multiple access
(NOMA) are the key enabling multiple access techniques to enable massive
connectivity. However, it is unclear whether RSMA would consistently outperform
NOMA from a system sum-rate perspective, users' fairness, as well as
convergence and feasibility of the resource allocation solutions. This paper
investigates the weighted sum-rate maximization problem to optimize power and
rate allocations in a hybrid RSMA-NOMA network. In the hybrid RSMA-NOMA, by
optimally allocating the maximum power budget to each scheme, the BS operates
on NOMA and RSMA in two orthogonal channels, allowing users to simultaneously
receive signals on both RSMA and NOMA. Based on the successive convex
approximation (SCA) approach, we jointly optimize the power allocation of users
in NOMA and RSMA, the rate allocation of users in RSMA, and the power budget
allocation for NOMA and RSMA considering successive interference cancellation
(SIC) constraints. Numerical results demonstrate the trade-offs that hybrid
RSMA-NOMA access offers in terms of system sum rate, fairness, convergence, and
feasibility of the solutions.
