  The demand of massive access to the same multimedia content at the same time
is one major challenge for next-generation cellular networks in densely-packed
urban areas. The content-aware multicast transmission strategies provide
promising solutions to such use cases involving many mobile users trying to
fetch the same data. In this work, we consider multigroup multicast
transmission with a common message (e.g., multimedia content), in which
different multicast groups are interested along with their private multicast
messages. We further assume that a relay helps the cellular base station (BS)
disseminate multicast content to the users experiencing high path loss and/or
blockage. We propose superposition and concatenated coding schemes, denoted by
SC and CC, respectively, to transmit the common and private multicast messages.
In order to maximize max-min fair (MMF) rates, we design a novel low-complexity
alternating-optimization algorithm to compute transmit and relay precoders. We
also propose rate-splitting (RS) alternatives of SC and CC schemes together
with an iterative algorithm to derive dedicated transmit and relay precoders so
as to maximize MMF rates. We rigorously evaluate the performance of the
proposed transmission schemes and precoders, and verify the superiority of
RS-based schemes in overloaded scenarios without any saturation with increasing
signal-to-noise ratio.
