  Multicast services, whereby a common valuable message needs to reach a whole
population of user equipments (UEs), are gaining attention on account of new
applications such as vehicular networks. As it proves challenging to guarantee
decodability by every UE in a large population, service reliability is indeed
the Achilles' heel of multicast transmissions. To circumvent this problem, a
two-phase protocol capitalizing on device-to-device (D2D) links between UEs has
been proposed, which overcomes the vanishing behavior of the multicast rate. In
this paper, we revisit such D2D-aided protocol in the new light of precoding
capabilities at the base station (BS). We obtain an enhanced scheme that aims
at selecting a subset of UEs who cooperate to spread the common message across
the rest of the network via D2D retransmissions. With the objective of
maximizing the multicast rate under some outage constraint, we propose an
algorithm with provable convergence that jointly identifies the most pertinent
relaying UEs and optimizes the precoding strategy at the BS.
