Objective: In this paper, decode-and-forward (DF) mode is deployed in the relay selection
(RS) scheme to provide better performance in cooperative downlink non-orthogonal multiple access
(NOMA) networks. In particular, evaluation regarding the impact of the number of multiple relays
on outage performance is presented.
Methods: As main parameter affecting cooperative NOMA performance, we consider the scenario
of the fixed power allocations and the varying number of relays. In addition, the expressions of outage
probabilities are the main metric to examine separated NOMA users. By matching related results
between simulation and analytical methods, the exactness of derived formula can be verified.
Results: The intuitive main results show that in such cooperative NOMA networks, the higher the
number of relays equipped, the better the system performance can be achieved.