  In this contribution, the optimization of power proportion allocated for each
user in the downlink (DL) non-orthogonal multiple access (NOMA) systems have
been developed. Successive interference cancellation (SIC) technique recovers
users' signal with high difference between channel gains, in order to find the
lowest optimum power proportion {required to guarantee} an equal data rate for
all active users. Following the same approach, the optimum power proportion for
each user and also the minimum total power to achieve the same rate for all
users (maximum fairness) were obtained as a design goal. Moreover, the same
design methodology was developed seeking to maximize the NOMA system energy
efficiency (EE). It was possible to find the {maximum EE point} and the
respective power distribution among the users for a certain circuitry power
consumption. For all NOMA users in which the optimal operation point for EE
maximization was parameterized, it was possible to find the total power, power
ratio and the equal rate values. As a result, one can find the tradeoff point
between EE and sum rate for each system scenario, as well as the best resource
efficiency operation point. By considering the same rate for all users, the
system attains maximum fairness among the users.
