Abstract
This paper develops a distributed algorithm for user association of a rate-splitting multiple access (RSMA) network in the millimeter wave (mmWave) directional beamforming environment. In the RSMA network, hybrid multiple access (HMA) is employed based on beamforming techniques with mmWave transmission so that non-orthogonal and orthogonal multiple access users are allowed to coexist, but all users are not necessarily accessible to each other. Thus, a basic NOMA pairing principle of grouping the largest rate-gap users may not be the best strategy for the user-resource allocation, and the identification of the optimal pairing gives rise to a significant computation complexity. To handle this, a novel distributed solution is developed based on the message-passing framework among locally accessible users for the objective of maximizing the global network sum-throughput utility. To provide the optimality and the convergence of the developed algorithm, a theoretical analysis is conducted along with numerical results evidencing the superiority over existing schemes.