  In this paper, an underlay cognitive radio (CR) multicast network, consisting
of a cognitive base station (CBS) and multiple multicast groups of secondary
users (SUs), is considered. All SUs, belonging to a particular multicast group,
are served by the CBS using a common primary user (PU) channel. The goal is to
maximize the energy efficiency (EE) of the system, through dynamic adaptation
of target rate and transmit power for each multicast group, under the PUs'
individual interference constraints. The optimization problem formulated for
this is proved to be non quasi-concave with respect to the joint variation of
the CBS's transmit power and target rate. An efficient iterative algorithm for
EE maximization is proposed along with its complexity analysis. Simulation
results illustrate the performance gain of our proposed scheme.
