  Future wireless networks, in particular, 5G and beyond, are anticipated to
deploy dense Low Earth Orbit (LEO) satellites to provide global coverage and
broadband connectivity. However, the limited frequency band and the coexistence
of multiple constellations bring new challenges for interference management. In
this paper, we propose a robust multilayer interference management scheme for
spectrum sharing in heterogeneous satellite networks with statistical channel
state information (CSI) at the transmitter (CSIT) and receivers (CSIR). In the
proposed scheme, Rate-Splitting Multiple Access (RSMA), as a general and
powerful framework for interference management and multiple access strategies,
is implemented distributedly at GEO and LEO satellites, coined Distributed-RSMA
(D-RSMA). By doing so, D-RSMA aims to mitigate the interference and boost the
user fairness of the overall multilayer satellite system. Specifically, we
study the problem of jointly optimizing the GEO/LEO precoders and message
splits to maximize the minimum rate among User Terminals (UTs) subject to a
transmit power constraint at all satellites. A robust algorithm is proposed to
solve the original non-convex optimization problem. Numerical results
demonstrate the effectiveness and robustness towards network load and CSI
uncertainty of our proposed D-RSMA scheme. Benefiting from the interference
management capability, D-RSMA provides significant max-min fairness performance
gains compared to several benchmark schemes.
