  This paper investigates simultaneous wireless information and power transfer
(SWIPT) for multiuser multiple-input-single-output (MISO) secrecy channel.
First, transmit beamfoming without artificial noise (AN) design is considered,
where two secrecy rate optimization frameworks (i.e., secrecy rate maximization
and harvested energy maximization) are investigated. These two optimization
problems are not convex, and cannot be solved directly. For secrecy rate
maximization problem, we employ bisection method to optimize the associated
power minimization problem, and first-order Taylor series expansion is consider
to approximate the energy harvesting (EH) constraint and the harvested energy
maximization problem. Moreover, we extend our proposed algorithm to the
associated robust schemes by incorporating with channel uncertainties, where
two-level method is proposed for the harvested energy maximization problem.
Then, transmit beamforming with AN design is studied for the same secrecy rate
maximization problem, which are reformulated into semidefinite programming
(SDP) based on one-dimensional search and successive convex approximation
(SCA), respectively. Moreover, tightness analysis of rank relaxation is
provided to show the optimal transmit covariance matrix exactly returns
rank-one. Simulation results is provided to validate the performance of the
proposed algorithm.
