Joint time switching and power allocation for secure multicarrier decode-and-forward relay systems with wireless information and power transfer

Abstract

Secure communication is critical in wireless networks due to the openness of the wireless transmission medium. In this paper, we study the secure communication in a multicarrier orthogonal frequency division multiplexing (OFDM) decode-and-forward (DF) relay network with an energy-constrained relay node which operates with a time-switching (TS) protocol. By jointly designing TS ratios of energy harvesting (EH) and information-decoding (ID) at the relay, TS ratio of signal forwarding from relay to destination and power allocation (PA) over all subcarriers at source and relay, we aim at maximizing the achievable secrecy rate of the DF relay network subject to a maximum transmit power constraint at source and an EH constraint at relay. The formulated optimization problem is a non-convex problem. We decouple it into a convex problem and a non-convex problem, where the non-convex problem can be solved by a constrained concave convex procedure (CCCP) based iterative algorithm to achieve a local optimum. Simulation results verify that our proposed joint TS and PA scheme achieves nearly global optimal resource allocation and outperforms the existing resource allocation scheme.