  Limited bandwidth resources and higher energy efficiency requirements
motivate incorporating multicast and broadcast transmission into the
next-generation cellular network architectures, particularly for multimedia
streaming applications. Layered division multiplexing (LDM), a form of NOMA,
can potentially improve unicast throughput and broadcast coverage with respect
to traditional orthogonal frequency division multiplexing (FDM) or time
division multiplexing (TDM), by simultaneously using the same frequency and
time resources for multiple unicast or broadcast transmissions. In this paper,
the performance of LDM-based unicast and broadcast transmission in a cellular
network is studied by assuming a single frequency network (SFN) operation for
the broadcast layer, while allowing arbitrarily clustered cooperation among the
base stations (BSs) for the transmission of unicast data streams. Beamforming
and power allocation between unicast and broadcast layers, the so-called
injection level in the LDM literature, are optimized with the aim of minimizing
the sum-power under constraints on the user-specific unicast rates and on the
common broadcast rate. The effects of imperfect channel coding and imperfect
CSI are also studied to gain insights into robust implementation in practical
systems. The non-convex optimization problem is tackled by means of successive
convex approximation (SCA) techniques. Performance upper bounds are also
presented by means of the $\rm{S}$-procedure followed by semidefinite
relaxation (SDR). Finally, a dual decomposition-based solution is proposed to
facilitate an efficient distributed implementation of LDM where the optimal
unicast beamforming vectors can be obtained locally by the cooperating BSs.
Numerical results are presented, which show the tightness of the proposed
bounds and hence the near-optimality of the proposed solutions.
