Abstract:

A physical layer security transmission scheme is studied in a twohop relay system, which is composed of a source node, a relay node, a destination node and some eavesdroppers. The relay node is equipped with multiple antennas and the others just one. The eavesdroppers’ positions and their channel state information are unknown, so the destination node sends artificial noise to protect the information transmitted in the first and second hop. The relay node works in a simultaneous wireless information and power transfer (SWIPT) mode, and harvests energy from the received signal and artificial noise in the first hop. The harvested energy is used to forward the signals in the second hop. In the first hop, the antennas of relay are divided into two groups, one receiving and combining signals, and the other converting the received signal into energy. In the second hop, the relay node uses all antennas to forward 〖JP2〗signals. Because the eavesdroppers’ channel state information cannot be obtained,the strategy of antenna grouping and signal beamforming vector are optimized through the maximization of the rate of the destination node. A low complexity antenna grouping strategy is given. The simulation results show that an appreciable secrecy rate can be achieved, and it is higher than that when the power splitting strategy is used.