Optimal design for power beacon assisted wireless communication networks with integrated services

In this paper, we consider the optimal design for a wireless-powered communication system, where an energy constrained transmitter harvests energy from a dedicated power beacon (PB). From the service integration perspective, two sorts of service messages are combined and served simultaneously, i.e., a multicast message intended for both receivers and a confidential message intended for receiver 1 but needing to be kept perfectly secret from receiver 2. Our design objective is to maximize the achievable secrecy rate region by jointly optimizing the transmit covariance matrices for the multicast message and confidential message, as well as the transfer time ratio recorded at the transmitter, subject to the multicast service and the transmit power constraints. The formulated secrecy rate region maximization (SRRM) problem is a non-convex vector maximization problem. To address it, we reformulate the SRRM problem into a scalar optimization problem. Furthermore, we propose a two-layer optimal algorithm to find all the Pareto optimal points. Numerical results are finally provided to demonstrate the effectiveness of our proposed scheme in improving the secrecy rate region.