Physical Layer Security under Accumulated Harvested Energy from RF Source

In this paper, we have studied the accumulation of harvested energy, at decode and forward (DF) relays over several frames, which is used by the relays to forward the signal in a particular frame in presence of a passive eavesdropper. The source broadcasts the information signal to DF relays in the broadcasting phase. Each relay is assisted with two omnidirectional antennas, while the source and the destination is assisted with a single omnidirectional antenna. The selected relay uses the signal received from one antenna to harvest energy, while it uses the received signal from another antenna to decode the message. At the relay, the harvested energy in each frame of communication might not be sufficient to forward the signal, which requires accumulation of energy. The accumulated energy over several frames becomes sufficient to forward the signal to the destination in a particular frame through a single antenna in the relaying phase, while the eavesdropper tries to eavesdrop the relayed information signal. We evaluate the secrecy outage probability in the proposed network to secure the information signal at the physical layer when the selected relay transmits using accumulated harvested energy. The secrecy performance increases with an increase in transmit power of the source, and the number of the frames used for energy accumulation. A closed-form expression on secrecy outage probability under accumulation of harvested energy is developed which is verified by MATLAB based simulation.