Sum Rate Analysis of Downlink NOMA over α-F Fading Channels

In this paper, our focus is towards resource allocation in a multiuser downlink non-orthogonal multiple access (NOMA) system. In the power-domain NOMA, where multiple access is realized by assigning different power levels to the clustered users, a certain degree of advantage of NOMA depends on clustering of users and power levels allocated to them. This study proposes a new power allocation algorithm, based on sum rate as performance criterion, which is applied for the clusters defined by High-High/High-Low pairing scheme. The proposed algorithm takes into account fairness between clustered users from the acquired users' rate point of view. It provides better sum rate performance of NOMA compared to OMA, but also a low gap between the individual rates of paired users. The detailed numerical and independent simulation results for the downlink NOMA over general alpha- F fading channels are shown.