  This letter investigates the artificial noise aided beamforming design for
secure simultaneous wireless information and power transfer (SWIPT) in a
two-tier downlink heterogeneous network, where one femtocell is overlaid with
one macrocell in co-channel deployment. Each energy receiver (ER) in femtocell
can be considered as a potential eaves- dropper for messages intended for
information receiver (IR). Our objective is to maximize the secrecy rate at IR
subject to the signal-to-interference-plus noise ratio (SINR) requirements of
macro users (MUs), transmit power constraint and energy harvesting constraint.
Due to the non-convexity of the formulated problem, it cannot be solved
directly. Thus, we propose a novel reformulation by using first-order Taylor
expansion and successive convex approximation (SCA) techniques. Furthermore, an
SCA-based algorithm with low complexity is proposed to arrive at provably
convergent solution. Finally, numerical results evaluate the performance of the
proposed algorithm.
