A Physical Layer Security Transmission Mechanism of Relay System Based on Joint Channel Characteristics

Motivated by the problem of untrusted relays,this paper proposes a physical layer security transmission mechanism of relay system based on joint channel characteristics.First of all,we combine the two channels before and after the relay into one,and get the joint channel characteristics.Then in the null space of the channel characteristics,the artificial noise is added to make the internal wire-tappers get none of the information.Simulation results show that when the artificial noise lies in the null space of the legitimate receiver's channel,secrecy capacity of the cooperative relay system can be improved and the bit-error ratio of the legitimate receiver is much smaller than untrusted relays.The trend of the secrecy capacity,changed by increasing relay number,relates to the distribution of eavesdroppers.