RSMA Enhanced RIS-FD-UAV-aided Short Packet Communications under Imperfect SIC

Abstract

In this work, we consider a hybrid aerial full-duplex (FD) relaying consisting of a reconfigurable intelligent surface (RIS) mounted over an FD unmanned aerial vehicle (UAV) relay operating in decode and forward mode to assist the information transfer between the base station and multiple users. For better spectral efficiency and low latency, we investigate the use of rate splitting multiple access (RSMA) with finite blocklength codes in such networks and focus on joint optimization of 3D coordinates of the UAV/RIS and phase shift matrix at the RIS under imperfect successive interference cancellation (SIC) at each user and residual-self interference (RSI) at UAV. We formulate the weighted sum-rate maximization problem. We adopt an alternating optimization (AO) approach to deal with the non-convex nature of the problem and propose an algorithm based on the Riemannian conjugate gradient and the sequential-search-based methods to get the optimal phase shift and UAV/RIS position, respectively. We present Monte Carlo simulation-based results to show the effectiveness of the proposed algorithm. Simulation result shows that, with the imperfection of around 5%-10% in SIC, RSMA provides approximately 7%-16% higher average weighted sum rate compared to non-orthogonal multiple access (NOMA).