  We focus on a two-receiver Multiple-Input-Multiple-Output (MIMO) Broadcast
Channel (BC) and Interference Channel (IC) with an arbitrary number of antennas
at each node. We assume an imperfect knowledge of local Channel State
Information at the Transmitters (CSIT), whose error decays with the
Signal-to-Noise-Ratio. With such configuration, we characterize the achievable
Degrees-of-Freedom (DoF) regions in both BC and IC, by proposing a
Rate-Splitting approach, which divides each receiver's message into a common
part and a private part. Compared to the RS scheme designed for the symmetric
MIMO case, this scheme is suitable for the general asymmetric deployment with
an arbitrary number of antennas at each node. In BC, the proposed block 1)
employs an unequal power allocation to the private messages of the two
receivers, 2) exploits the benefit of having an extra spatial dimension at one
receiver, and 3) is carried out with a Space-Time transmission. These features
enable the scheme to yield a greater DoF region than trivially extending the
scheme designed for the symmetric case. In IC, we modify the scheme proposed
for the BC case by applying a linear transformation to the channel matrices.
Such a linear transformation allows us to identify the signal space where the
two transmitted signals interfere with each other and propose a proper power
allocation policy. The achievable DoF regions are shown to be optimal for some
antenna configurations.
