Research On Physical Layer Security Based On Swipt Cooperative Network

In wireless communication networks,the unauthorized third party eavesdropping users can usually use the broadcast characteristics of wireless channels to intercept valuable confidential information,resulting in the failure of secure transmission of confidential information.The existing communication systems usually use upper layer encryption technology to ensure the secure transmission of information.However,with the increasing computational ability of the eavesdroppers,the traditional encryption technology may be difficult to ensure secure transmission.The physical layer security technology is different from the encryption technology on the upper layer,which starts from the bottom layer of the communication system--the physical layer to ensure the transmission security of information.On the other hand,with the large number of applications of various wireless devices,the energy consumption in communication network is increasing rapidly.In the actual wireless network,most communication devices are loaded with batteries that have limited energy storage,which seriously limits the lifetime of the wireless network.As an effective means to reduce network energy consumption,simultaneous wireless information and power transfer(SWIPT)technology can not only prolong the life time of the network,but also ensure the sustainable operation of the communication network under the condition of low cost.Motivated by this,physical layer security in SWIPT cooperative network is studied in this thesis.1.This thesis first designs a relay selection strategy based on SWIPT cooperative network with multiple relays.Since the proposed strategy not only considers the network characteristics of the energy transmission,but also considers the impact of the main channel and the eavesdropper channel on the network's security,the strategy can optimize the security performance of the network.In order to comprehensively evaluate the security performance of the network under the proposed strategy,this thesis analyzes two key performance metrics: secrecy outage probability and ergodic secrecy capacity for two different transmission modes.On the one hand,the closed-form expression of secrecy outage probability is obtained,and the secrecy diversity gain is derived by its asymptotic solution.The results confirm that the performance of secrecy diversity based on the selection scheme can be optimal.On the other hand,the closed-form expression for the lower bound of the ergodic secrecy capacity is obtained.The numerical results show that the relevant theoretical analysis is correct and the influence of other parameters on network's security is further discussed.2.This thesis also explores the physical layer security in multi-relay SWIPT network with cooperative interference.When the relay in SWIPT cooperative network can not only serve as a conventional relay to transmit confidential information to the target user,but also act as a cooperative jammer to send the interference signal to the eavesdropper,the cooperative interference technology can be used to improve SWIPT network's security.Considering that there are multiple destinations in the actual network,this thesis proposes a heuristic relay-jammer selection and user scheduling strategy to increase secrecy capacity and improve SWIPT network's security.In order to evaluate the security performance of SWIPT network under the proposed heuristic strategy,the exact closed-form expression of secrecy outage probability and the closed-form expression for the lower bound of the ergodic secrecy capacity are obtained.Finally,the heuristic strategy proposed in this thesis is compared with the existing strategies.The comparison results show that the heuristic strategy proposed in this paper can significantly improve the security performance of SWIPT network and outperform other strategies.