Research On Performance Improvement Of Multiple Access Technology Based On Time Reversal

With the rapid development of wireless communication,people are no longer satisfied with the current fourth generation mobile communication network(4G).The fifth generation mobile communication network(5G)as the development direction of future wireless communication,also faces higher requirements.In order to meet the development needs of 5G dense mass access and large capacity,it is imperative to study novel multi-access technology.Currently,Space Division Multiple Access(SDMA)and Non-Orthogonal Multiple Access(NOMA)are two emerging multiple access technologies,which are receiving more and more attention.Compared with the traditional multiple access method,SDMA and NOMA break through the limitations of time domain and frequency domain,and achieve simultaneous transmission of multiple signals at the same frequency,which can significantly improve spectrum efficiency and support more concurrent users to transmit at the same time.It is found that time reversal technology can automatically collect the signals' energy scattered on every multipath,and these energy coherently superimpose at the desired user to achieve simultaneous focusing of signals in the temporal and spatial.Therefore,TR technology not only has the potential to achieve multiple access,but also has the advantage of improving system energy efficiency.In summary,this thesis considers the application of TR technology in the field of new multiple access technology to further improve system reliability,increase the amount of equipment access,and improve energy supply.The main innovative work content is:Firstly,the nonorthogonality of channel can cause multiple access interference(MAI)in traditional time-reversal division multiple access(TRDMA)communication system.In order to deal with the above issue,a pseudo-noise code time-reversal division multiple access communication(PN-TRDMA)based on spread spectrum communication is proposed.This method uses Spread spectrum technology to further differentiate the signal by assigning orthogonal pseudo-random codes to different users.Simulation results show that PN-TRDMA can effectively reduce MAI and improve system bit error rate performance.Secondly,for the disadvantage that cooperative NOMA system consider user as relay to forwarding information needs to consume extra short-distance communication resources.This strategy considers that relay users use time reversal simultaneous wireless information and power transfer to detect and collect energy of the signals simultaneously,and use the collected energy for relay forwarding.The simulation results show that this strategy can further improve the reception reliability of weak users on the one hand,and improve the enthusiasm and fairness of relay users by optimizing system energy efficiency on the other hand.It is of great significance to the cooperative NOMA application scenario.