Adaptive secure wireless information and power transfer in delay-constrained multiuser multi-input single-output networks

We focus on the achievable time-averaged secrecy rate-harvested energy region in delay-constrained wireless powered multi-input single-output (MISO) network, where a multi-antenna buffer-aided access point (AP) is supposed to deliver confidential message to multiple single-antenna users. When a user is scheduled for receiving messages from the AP, other users are assumed to be potential eavesdroppers and can harvest energy from their received radio signal. To this end, the time-averaged secrecy rate-energy region maximization problem was formulated subject to constraints on average queuing delay and average power consumption. On this basis, a delay-aware adaptive secure transmission (DAAST) scheme is presented to enhance the achieved time-averaged secrecy rate-energy region effectively by jointly optimizing the confidential information and artificial noise signal beams, the user scheduling, and the flow control, while strictly guaranteeing the average queuing delay requirements of all users. Numerical results demonstrate that, by fully exploiting the potential of data buffers, the DAAST scheme is an asymptotically optimal scheme, which can arbitrarily approach the optimal solution.