  In this paper, a novel transmissive reconfigurable intelligent surface (TRIS)
transceiver empowered integrated sensing and communications (ISAC) system is
proposed for future multi-demand terminals. To address interference management,
we implement rate-splitting multiple access (RSMA), where the common stream is
independently designed for the sensing service. We introduce the sensing
quality of service (QoS) criteria based on this structure and construct an
optimization problem with the sensing QoS criteria as the objective function to
optimize the sensing stream precoding matrix and the communication stream
precoding matrix. Due to the coupling of optimization variables, the formulated
problem is a non-convex optimization problem that cannot be solved directly. To
tackle the above-mentioned challenging problem, alternating optimization (AO)
is utilized to decouple the optimization variables. Specifically, the problem
is decoupled into three subproblems about the sensing stream precoding matrix,
the communication stream precoding matrix, and the auxiliary variables, which
is solved alternatively through AO until the convergence is reached. For
solving the problem, successive convex approximation (SCA) is applied to deal
with the sum-rate threshold constraints on communications, and
difference-of-convex (DC) programming is utilized to solve rank-one non-convex
constraints. Numerical simulation results verify the superiority of the
proposed scheme in terms of improving the communication and sensing QoS.
