| The research of the next generation wireless communication network is underway.The problem of information secrecy transmission has been closely watched.The physical layer security technology uses its own characteristics of the physical channel to achieve secret transmission means has received the unprecedented attention.The artificial noise jamming technology can effectively improve the system's security capacity under the fading channel.Currently,the collaborative interference model is mostly assumption that the relay is credible.However,in the actual communication,the safety of the relay often cannot be guaranteed.So,the study of untrusted relay will have the extremely vital significance.In this paper,we consider stability and safety as the target,and applies the full duplex technology and energy harvesting technology respectively.The main work of this paper is as follows:(1)First,We propose a jam-then-harvest protocol for dual-hop cooperative networks with an untrusted relay,where an external friendly jammer help keep information secret from the un-trusted relay by transmitting a priori jamming signal for the destination.In particular,the wireless powered jammer scavenges energy from the received forwarded signal and recovers its initial energy to perform jamming in next time slot.We analytically derive the exact expressions of the probability of non-zero secrecy rate for the proposed jam-then-harvest protocol.For performance comparison,cooperative jamming with the constant power supply is provided as a benchmark.Numerical results show that the proposed protocol can achieve the secure communication but also harvest the enough energy without a loss of performance in the low jamming power region,and the stability of the system is guaranteed.(2)Finally,the above untrusted relay node research results are extended to fullduplex mode,and a un-trusted relay node transmission strategy based on the source node's artificial noise interference was proposed.First of all,numerical results vertify that the full duplex un-trusted relay system can realize secret communication only when transmitting artificial noise.Then we deduce the mathematical expressions of the secrecy capacity and compare with half-duplex model.The simulation results show that the performance of the full-duplex system is better than that of the half-duplex system even if there is residual self-interference. |
