Recently, the Degrees-of-Freedom (DoF) region of
multiple-input-single-output (MISO) networks with imperfect
channel state information at the transmitter (CSIT) has at-
tracted significant attention. An achievable scheme, known
as Rate-Splitting (RS), integrates common-message-multicasting
and private-message-unicasting. In this paper, focusing on the
general
K
-cell MISO IC with an arbitrary CSIT quality of each
interfering link, we firstly identify the DoF region achieved by
RS. Secondly, we introduce a novel scheme, so called Topological
RS (TRS), whose novelties compared to RS lie in a multi-layer
structure and in transmitting multiple common messages to be
decoded by groups of users rather than all users. The design
of TRS is motivated by a novel interpretation of the
K
-cell IC
with imperfect CSIT as a weighted sum of a series of partially
connected networks. We show that the DoF region achieved
by TRS yields the best known result so far, and we find the
maximal sum DoF via hypergraph fractional packing. Lastly,
for a realistic scenario where each user is connected to three
dominant transmitters, we identify the sufficient condition where
TRS strictly outperforms conventional schemes, and show that
TRS is optimal for some CSIT qualities.