  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-(K-1) messages, where mixed CSIT refers to the delayed and
imperfect-current CSIT, and order-(K-1) message refers to the message desired
by K-1 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.
