  This paper studies the ergodic rate performance of regularized zero-forcing
(RZF) precoding in the downlink of a multi-user multiple-input single-output
(MISO) system, where the channel between the base station (BS) and each user is
modeled by the double scattering model. This non-Gaussian channel model is a
function of both the antenna correlation and the structure of scattering in the
propagation environment. This paper makes the preliminary contribution of
deriving the minimum-mean-square-error (MMSE) channel estimate for this model.
Then under the assumption that the users are divided into groups of common
correlation matrices, this paper derives deterministic approximations of the
signal-to-interference-plus-noise ratio (SINR) and the ergodic rate, which are
almost surely tight in the limit that the number of BS antennas, the number of
users and the number of scatterers in each group grow infinitely large. The
derived results are expressed in a closed-form for the special case of
multi-keyhole channels. Simulation results confirm the close match provided by
the asymptotic analysis for moderate system dimensions. We show that the
maximum number of users that can be supported simultaneously, while realizing
large-scale MIMO gains, is equal to the number of scatterers.
