Exploiting Spatial Channel Covariance for Hybrid
Precoding in Massive MIMO Systems
Authors: Sungwoo Park, Jeonghun Park, A. Y. Panah, Robert W. Heath, Jr.
IEEE Transactions on Signal Processing, vol. 65, no. 14, pp. 3818 - 3832, Jul. 2017.
We propose a new hybrid precoding technique for
massive multi-input multi-output (MIMO) systems using spatial
channel covariance matrices in the analog precoder design. Applying
a regularized zero-forcing precoder for the baseband precoding
matrix, we find an unconstrained analog precoder that maximizes
signal-to-leakage-plus-noise ratio (SLNR) while ignoring analog
phase shifter constraints. Subsequently, we develop a technique to
design a constrained analog precoder that mimics the obtained unconstrained
analog precoder under phase shifter constraints. The
main idea is to adopt an additional baseband precoding matrix,
which we call a compensation matrix. We analyze the SLNR loss
due to the proposed hybrid precoding compared to fully digital precoding,
and determine which factors have a significant impact on
this loss. In the simulations, we show that if the channel is spatially
correlated and the number of users is smaller than the number
of RF chains, the SLNR loss becomes negligible compared to fully
digital precoding. The main benefit of our method stems from the
use of spatial channel matrices in such a way that not only is each
user's desired signal considered, but also the inter-user interference
is incorporated in the analog precoder design.