Performance Research Of Multi-User Multi-Hop Network For Secure Transmission And Cache Assistance

Multi-user and multi-hop wireless network is an important form of multi-user parallel transmission in modern wireless communication,which can effectively improve the transmission quality and coverage of the system.As the density of communication users continues to increase,the security and interference problems of the network are also receiving more and more attention.Based on the background of multi-user multi-hop network,this paper analyzes the network performance under different system models.We propose strategies to ensure the security of transmission,reduce interference and improve system capacity of multi-user multi-hop network.The main research contents include the following aspects:First,this paper studies the safety capacity and other performances of multi-antenna half-duplex multi-user multi-hop network.Current research shows that the physical layer security of multi-user systems is more complex than point-to-point communication.Based on the previous research,this paper will further explore the security performance of the more complex multi-antenna multi-hop eavesdropping system.Firstly,the instantaneous secrecy capacity of the model is calculated utilizing information theory,convex optimization and other theories.Secondly,considering the time-varying characteristics of the channel,the ergodic secrecy capacity of the model is obtained,and the factors which influence the ergodic secrecy capacity are analyzed.Then we provide the strategies improving the safety capacity of our system,and finally the simulation results are given to verify the theoretical analysis.Second,the parallelization performance of cache-assisted single chain multihop network is studied.Different from the existing work,we utilize the scheme of cache assisted transmission to prove that cache can indeed reduce the interference of the network,and the multi-user multi-hop network is transformed into a special partially connected interference channel network.Then the upper bound on the degrees of freedom of the network is derived by information theory and other theories.In addition,the more backward the user is in the multi-hop link,the more interference the user will suffer.Thus,we give an achievable scheme which allocates equal-difference signal space for users.Third,the cache-assisted cooperative relay network and its performance are studied.Based on the cooperative relay scenario,the cache capability of relay is considered,and the cache scheme and transmission scheme are designed jointly.It is observed that cache can reduce the number of hops in actual communication.Then the system model is developed and we derive the outage probability.Finally our numerical results demonstrate significant outage performance gains over traditional relaying without caching.We also provide the simulations which show the influence of other factors on outage probability.Finally,we summarize the whole paper and look forward to the future research work.