On Data Rate Maximization Using Hybrid Rate-Splitting/NOMA Network Diamond Relaying

It has been shown that diamond relaying networks offer higher multiplexing gain than conventional cooperative networks. In diamond relaying networks, a relay-pair cooperates to deliver two messages to the destination within only two-time slots using non-orthogonal multiple access (NOMA). It was recently shown that rate-splitting multiple access (RSMA) has superior performance over NOMA. In this paper, the benefits of using rate-splitting in the diamond relaying model is explored for improving the achievable sum data rate. A hybrid rate-splitting/NOMA diamond relaying system model is proposed. The system's sum data rate can be maximized by optimizing the power allocation coefficients for both the rate-splitting and the NOMA phases. Our results show that the proposed hybrid model outperforms the conventional full NOMA diamond relaying systems.