  In this paper, we propose a novel joint caching and massive multiple-input
multiple-output (MIMO) transmission scheme, referred to as cache-aided massive
MIMO, for advanced downlink cellular communications. In addition to reaping the
conventional advantages of caching and massive MIMO, the proposed scheme also
exploits the side information provided by cached files for interference
cancellation at the receivers. This interference cancellation increases the
degrees of freedom available for precoding design. In addition, the power freed
by the cache-enabled offloading can benefit the transmissions to the users
requesting non-cached files. The resulting performance gains are not possible
if caching and massive MIMO are designed separately. We analyze the performance
of cache-aided massive MIMO for cache-dependent maximum-ratio transmission
(MRT), zero-forcing (ZF) precoding, and regularized zero-forcing (RZF)
precoding. Lower bounds on the ergodic achievable rates are derived in closed
form for MRT and ZF precoding. The ergodic achievable rate of RZF precoding is
obtained for the case when the numbers of transmit antennas and users are large
but their ratio is fixed. Compared to conventional massive MIMO, the proposed
cache-aided massive MIMO scheme achieves a significantly higher ergodic rate
especially when the number of users approaches the number of transmit antennas.
