Research On Two-Way AF Relay Technology Based On Massive MIMO

With the fast development of wireless communication,the problem of spectrum resources' shortage has become more and more prominent,and it's imminent to improve the efficiency of the spectrum for the full use of spectrum resources.In this regard,the introduction of massive MIMO and relay technology can solve this problem well.With hundreds of antennas at the base station,massive MIMO is one of the core technologies of 5G,which provides excellent performance gains in terms of bandwidth,transmit power,and spectral efficiency.In addition,for massive MIMO systems,large-scale antenna arrays can sufficiently reduce transmission power,decrease inter-user interference,average fading and improve system security.The cooperative communication can obtain spatial diversity gain and improve the spectral efficiency.It can also improve the security of the system by using the beamforming and precoding algorithm.Therefore,massive MIMO technology and relay technology have been widely studied.This thesis has analyzed the performance of relay technology based on massive MIMO,and optimized the overall performance of the system through the research on relay location and power allocation scheme.In this thesis,security optimization of multi-pair two-way relay system based on massive MIMO has been first studied.A creative and meaningful security scenario has been discussed.That is,the users are both legitimate users and eavesdroppers,and the paired users communicate with each other with the help of the two-way relay which is based on massive MIMO,and then this thesis optimized the power allocation scheme among the users and the relay to achieve the maximum system security sum rate.The simulation results showed that the proposed optimal power allocation scheme based on geometric programming is superior to the traditional equal power allocation scheme,and the number of user pairs and SNR are the factors which affect the security sum rate of the network.Furthermore,considering some environmental factors such as obstacles between users,or the ground relay has failed to meet the needs of assisting communications,the mobile two-way relay which is above the ground can cross the obstacles to facilitate communications in these circumstances has been used.Then according to the new channel characteristics,the channel model was established by combining with suburban and dense urban,and this thesis maximized the system capacity to meet the communication needs of these two cities through the optimization of the location and power allocation of the mobile relay.The simulation results showed that the designed optimal location scheme based on geometric programming is superior to the traditional scheme that the mobile relay is located at the equidistant midpoint of two communication nodes,and the optimal power allocation scheme based on geometric programming is superior to the traditional equal power allocation scheme,in addition,the system sum rate is almost not affected by the height of the mobile relay.