  Presence of multiple antennas on both sides of a communication channel
promises significant improvements in system throughput and power efficiency. In
effect, a new class of large multiple-input multiple-output (MIMO)
communication systems has recently emerged and attracted both scientific and
industrial attention. To analyze these systems in realistic scenarios, one has
to include such aspects as co-channel interference, multiple access and spatial
correlation. In this paper, we study the properties of correlated MIMO
multiple-access channels in the presence of external interference. Using the
replica method from statistical physics, we derive the ergodic sum-rate of the
communication for arbitrary signal constellations when the numbers of antennas
at both ends of the channel grow large. Based on these asymptotic expressions,
we also address the problem of sum-rate maximization using statistical channel
information and linear precoding. The numerical results demonstrate that when
the interfering terminals use discrete constellations, the resulting
interference becomes easier to handle compared to Gaussian signals. Thus, it
may be possible to accommodate more interfering transmitter-receiver pairs
within the same area as compared to the case of Gaussian signals. In addition,
we demonstrate numerically for the Gaussian and QPSK signaling schemes that it
is possible to design precoder matrices that significantly improve the
achievable rates at low-to-mid range of signal-to-noise ratios when compared to
isotropic precoding.
