  The robust beamforming problem in multiple-input single-output (MISO)
downlink networks of simultaneous wireless information and power transfer
(SWIPT) is studied in this paper. Adopting the time switching fashion to
perform energy harvesting and information decoding respectively, we aim at
maximizing the sum rate under imperfect channel state information (CSI) and the
chance constraints of users' harvested energy. In view of the fact that the
constraints for minimal harvested energy is not necessary to meet from time to
time, this paper adopts chance constraint to model it and uses the Bernstein
inequality to transform it into deterministic constraints equivalently.
Recognizing the maximum sum rate problem of imperfect CSI as nonconvex problem,
we transform it into finding the expectation of minimum mean square error
(MMSE) equivalently in this paper, and an alternative optimization (AO)
algorithm is proposed to decompose the optimization problem into two
sub-problems: the transmit beamformer design and the division of switching
time. The simulation results show the performance gains compared to non-robust
state of the art schemes.
