Research Of Physical Layer Security Based On Buffer-aided Relay Selection Of Cognitive Radio Network

With the widespread use of wireless communication networks,security of network has become an increasingly important research topic.Wireless networks are vulnerable to eavesdropping attack due to the open and broadcast nature of wireless transmission.Conventional security in wireless networks has been focused on higher layers using cryptographic methods,which require private key exchange and introduces additional complexities and redundancy.Physical layer security,which ensures secure communication by taking advantage of the physical characteristics of wireless channels,has attracted increasing attention.In order to improve the performance of the network,relay is widely used in wireless netwoks because of its convenient implementation and wide applicability.For a data packet transmission,conventional unbuffered relay must determine the best transmitting and receiving links concurrently and adopt the same relay.In contrast,buffer-aided relay can incorporate the instantaneous strength of the wireless links as well as the status of the finite relay buffers to improve diversity gains,transmission efficiency and security performance in cooperative wireless network.In order to improve the utilization of bandwidth resources and solve spectrum scarcity problem in wireless network,cognitive radio network has drawn much attention as an application of wireless networks.This paper studies the buffer-aided relay in cognitive radio networks and proposed a new buffer-aided relay selection scheme,aiming at solving the defects of conventional unbuffered relay,which can not take full advantage of the physical characteristics of wireless channels.From the perspective of physical layer security,this paper use buffer-aided relay as well as Markov state transition matrix to solve the security problem of cognitive radio networks.The proposed scheme can significantly reduces the secrecy outage probability and improves the network security performance.Different from general wireless network,aiming at the characteristics of cognitive radio networks,this paper considers the mutual interference between primary users and secondary users,establishes the buffer-aided relay state throught the number of relays and the size 'of the buffer,constructs Markov state transition matrix to represent the state transition process of relays.From the perspective of secrecy outage probability,a new relay selection scheme is proposed based on the constrction of the model and mathematical derivation.Through simulation results and comparison with the traditional unbuffered relay used in practice,the superioriy of the proposed scheme is verified.On this basis,the influence of the number of relays and the size of buffer on secrecy outage probability of network is studied,and the conclusion that the change of the number of relays is more significant for the decrease of secrecy outage probability of network is obtained.Finally,through the simulation results data,the correctness of the conclusion is demonstrated.