  We study downlink beamforming in a single-cell network with a multi-antenna
base station serving cache-enabled users. Assuming a library of files with a
common rate, we formulate the minimum transmit power with proactive caching and
coded delivery as a non-convex optimization problem. While this multiple
multicast problem can be efficiently solved by successive convex approximation
(SCA), the complexity of the problem grows exponentially with the number of
subfiles delivered to each user in each time slot, which itself grows
exponentially with the number of users. We introduce a low-complexity
alternative through time-sharing that limits the number of subfiles received by
a user in each time slot. We then consider the joint design of beamforming and
content delivery with sparsity constraints to limit the number of subfiles
received by a user in each time slot. Numerical simulations show that the
low-complexity scheme has only a small performance gap to that obtained by
solving the joint problem with sparsity constraints, and outperforms
state-of-the-art results at all signal-to-noise ratio (SNR) and rate values
with a sufficient number of transmit antennas. A lower bound on the achievable
degrees-of-freedom (DoF) of the low-complexity scheme is derived to
characterize its performance in the high SNR regime.
