Research On Energy Efficiency Optimization Technology Of MIMO-NOMA System

With the development of mobile communication technology and people's pursuit of a high standard of living,new services and applications are emerging,which has been pretty convenient to people's life.However,the sudden increase in data traffic and the connection of massive mobile devices have put pressure on the new generation of 5G communication technology.Therefore,how to improve spectrum efficiency and achieve large-scale connection of devices have become a research hotspot in the entire academic circle and information industry.Non-orthogonal Multiple Access(NOMA),as a candidate access technology for 5G,uses power multiplexing to non-orthogonally superimpose and transmits information of multiple users on the same resource block and transmits it at the transmitter.At the same time,Serial Interference Cancellation(SIC)technology is used to distinguish the data of each user at the receiver.In this way,the spectrum utilization rate can be improved and the device can be connected on a large scale.In addition,the introduction of Multiple-Input Multiple-Output(MIMO)technology can significantly improve the system speed without increasing bandwidth and transmitting power.Therefore,the combination of the two technologies can better achieve the large connections and high data rates of emerging wireless applications.In order to further improve the system performance,a cooperative communication technology that can expand the network coverage and overcome the channel barrier was applied to systems.The main research work of this paper was divided into the following two parts:(1)A user grouping algorithm based on channel correlation and channel gain difference and a power allocation algorithm based on distance were designed for MIMO-NOMA systems.The user grouping algorithm divided users into a strong user group and a weak user group firstly,and then paired the two users according to the channel correlation and the channel gain difference.After grouping,the interference among groups was eliminated by Zero-Forcing Beam-Forming(ZFBF)technology.In order to further reduce intra-group interference and increase the overall system rate,an intra-group power allocation algorithm was proposed,where the allocated power was proportional to the square of the distance from the user to the base station.This method can obtain a closed-form solution,so the complexity was low.Experimental results showed that the proposed algorithm can further improve the total rate of the MIMO-NOMA systems.(2)A hybrid NOMA / full-duplex scheme was designed to improve the energy efficiency of the MIMO-NOMA systems.Firstly,a downlink network model of MIMO-NOMA systems for cooperative communication was proposed.Secondly,the outage probability and rate of systemsin non-cooperative NOMA,half-duplex,and full-duplex modes were analyzed.Finally,based on this,a hybrid NOMA / full-duplex mode was proposed.When there is no direct transmission path from a base station to a remote user or the quality of the direct transmission path is poor,a full-duplex mode can be used for cooperative transmission;when a direct transmission path is available,non-cooperative NOMA is used for transmission,and analyzing the outage probability and rate of the scheme.Theoretical analysis and simulation results showed that the mixed use of NOMA / full-duplex can effectively improve the performance of remote users while avoiding the loss of near users to a certain extent,improving the performance of systems,and improving users' fairness effectively.