  This paper studies the joint design of user grouping, scheduling (or
admission control) and precoding to optimize energy efficiency (EE) for
multigroup multicast scenarios in single-cell multiuser MISO downlink channels.
Noticing that the existing definition of EE fails to account for group sizes, a
new metric called multicast energy efficiency (MEE) is proposed. In this
context, the joint design is considered for the maximization of MEE, EE, and
scheduled users. Firstly, with the help of binary variables (associated with
grouping and scheduling) the joint design problem is formulated as a
mixed-Boolean fractional programming problem such that it facilitates the joint
update of grouping, scheduling and precoding variables. Further, several novel
optimization formulations are proposed to reveal the hidden difference of
convex/ concave structure in the objective and associated constraints.
Thereafter, we propose a convex-concave procedure framework based iterative
algorithm for each optimization criteria where grouping, scheduling, and
precoding variables are updated jointly in each iteration. Finally, we compare
the performance of the three design criteria concerning three performance
metrics namely MEE, EE, and scheduled users through Monte-Carlo simulations.
These simulations establish the need for MEE and the improvement from the
system optimization.
