Research On Wireless Secure Communication With Untrusted Node

Due to the open and broadcast nature of wireless mediums,secure communication between the source and the destination has always been an important challenge.Utilizing the randomness of wireless channels rather than cryptography,positive secrecy capacity can be achieved at the physical layer.Compared to the traditional security encryption authentication technology,physical layer security has a big advantage.Therefore,physical layer secure transmission technology has attracted widespread attention in academia.Most of the secure communication researches at the physical layer are based on the wiretap channels.In the system model,there exists an extra eavesdropper who threatens the security of the system.However,in practice,there may be nodes in the system as potential eavesdroppers.In recent research,people begin to pay attention to the security of channel models with untrustworthy nodes.This paper is also based on this type of model to carry out research work.First,we study a two-user MIMO Gaussian interference channel with confidential messages.The two users do not trust each other and the transmitted messages need to be kept secret to the unintended receiver.We derive the exact secure degrees of freedom(s.d.o.f.)of the system,in which each node equipped with arbitrary number of antennas.The proofs of outer bounds and corresponding achievability schemes are given.The case of single antenna or symmetric multi-antenna,is a special case of our system model.The previous conclusions also verify the accuracy of the secure degrees of freedom.Second,it is known that cooperative communication can enhance coverage and improve system performance.But there are often untrustworthy nodes act as helpers.Therefore,in this paper,the channel model with untrusted relay combines with the cognitive network is considered.Using the destination beamforming cooperative jamming schemes,positive secrecy rate is available.To maximize the secrecy rate,an optimal power allocation scheme is proposed.Finally,we consider a cognitive relay network system with multiple untrusted relays.In the process of signal transmission,two relays are selected at a time slot t.And the inter-relay interference is treated as cooperative jamming to ensure the security of the messages.In this paper,two relay selection schemes are provided and the corresponding expressions of the secrecy outage probability are derived.Then,based on the simulation results,the security performance of the system is analyzed.