In this paper, we propose a rate-splitting design and characterize the
sum-degrees-of-freedom (DoF) for the K-user multiple-input-single-output
(MISO) broadcast channel with mixed channel state information at the
transmitter (CSIT) and order-(Kβ1) messages, where mixed CSIT refers to the
delayed and imperfect-current CSIT, and order-(Kβ1) message refers to the
message desired by Kβ1 users simultaneously. In particular, for the sum-DoF
lower bound, we propose a rate-splitting scheme embedding with retrospective
interference alignment. In addition, we propose a matching sum-DoF upper bound
via genie signalings and extremal inequality. Opposed to existing works for
K=2, our results show that the sum-DoF is saturated with CSIT quality when
CSIT quality thresholds are satisfied for K>2.Comment: This work has been accepted by VTC2023-Fal