Research On Security Performance Of Cooperative Communication System In Eavesdropping Environment

High-speed railways bring great convenience to people to travel,but at the same time the rapid movement of trains also puts higher and higher requirements on wireless communication systems.The important issues in high-speed railway communications have been raised,including users’ high-speed transmission requirements for mobile communications and shortage of frequency resources.These problems are effectively solved by the advantages of cooperative communication technology in combating signal fading,expanding signal coverage and increasing channel capacity.Meanwhile,with the large-scale application of cooperative communication,high throughput and high reliability have become the basic goals of mobile communication systems,and its information security has become more and more important.Thus,it is of great significance to study the security performance of cooperative communication systems in the eavesdropping environment.In this thesis,the security performance of relay cooperative communication in the eavesdropping environment is studied.Firstly,for the full-duplex relay cooperative system,under imperfect channel state information,two relay selection schemes are proposed: optimal relay selection and partial relay selection.By deriving the signal-to-interference-noise ratio of the relay node and the signal-to-noise ratio of the destination node,the expression of the secrecy outage probability of the system is derived.According to the derived expressions,these parameters affecting the security performance of the system are analyzed,including the channel state information estimation error,the number of relays,the signal-to-noise ratio of the eavesdropper,and the residual self-interference caused by the full duplex system model.The simulation results show that the optimal relay selection scheme is better than the partial relay selection scheme under imperfect channel state information.At the same time,the full duplex system is superior to the traditional half duplex system under the low average signal-to-noise ratio of residual self-interference.On the contrary,the traditional half duplex system is superior to the full duplex system under the high average signal-to-noise ratio of residual self-interference.Secondly,considering the requirements of green communication,the security performance of wireless carrying relay cooperative systems is studied.By deriving the expressions of secrecy outage probability,interception probability,and security throughput of two relay energy harvesting protocols,the parameters that affect the security performance of the system are analyzed,including the number of relays,transmit signal-to-noise ratio,time switching factor and power splitting factor.The simulation results show that as the power splitting factor increases,the secrecy outage probability of the system will first decrease and then increase,and the interception probability of the system will increase.As the increase of the time switching factor,the secrecy outage probability of the system will gradually decrease.Finally,considering the existence of eavesdroppers,the security performance of massive MIMO relay cooperative systems is studied.The additive quantization noise model is used to process the quantization process,the maximum ratio combining technology is used at the destination base station,and the expression of the system’s secrecy spectral efficiency is derived.The power consumption model of the relay system is constructed,and the trade-off relationship between secrecy energy efficiency and secrecy spectral efficiency is obtained.The simulation results show that the greater the number of eavesdroppers’ antennas,the stronger the eavesdropping ability and the less the secrecy spectral efficiency of system.At the same time,by slightly reducing the secrecy spectral efficiency,the system can obtain relatively high secrecy energy efficiency,which compromises the two performances of the system.