  In this paper, we investigate energy-efficient (EE) power allocation (PA) for
a special downlink scenario of the massive multiple-input multiple-output
(MIMO) systems. We consider a minimum power required for each user to ensure
that the quality of service (QoS) for each user is satisfied. In this method, a
comparison between the sum of minimum power required by users and the maximum
transmission power is done to determine whether maximizing EE is possible or
not. If the sum of the minimum power required by users is less than the maximum
transmission power, we maximize EE. Otherwise, the number of admitted users in
a cluster is maximized. In both cases, the simulation results show that the
proposed algorithm has better performance than similar algorithms.
