RSMA Precoding Design Based on Interference Nulling and Sum Rate Upper Bound

The main contribution of this paper is providing low complexity precoding design for RSMA with low complexity streams. We consider hierarchical streams and interference nulling to simplify choosing streams and precoding design, respectively. The paper mainly revolves around precoding design to maximize sum rate. Particularly, we formulate a convex problem for the upper bound of sum rate maximization problem and examine the cases where the upper bound problem has the same solution as the sum rate maximization problem. In addition, we propose a two-stage algorithm to design precoding based on interference nulling and signal-to-noise ratio maximization.