Research On Transmission Scheme Of NOMA Multi-Antenna Systems

As candidate technologies of 5G,Non-Orthogonal Multiple Access(NOMA)and Multiple-Input Multiple-Output(MIMO)can actualize the signal multiplexing,respectively,in the power and space domain,and the system performance can be improved effectively.For further improvement in the spectrum efficiency and capacity of the system,NOMA can be combined with MIMO.Some key technologies of MIMO-NOMA,such as signal detection,user clustering and power allocation,are studied in this thesis.The main works of this thesis are expressed as follows:Firstly,the advantages,chances and challenges of MIMO-NOMA are analyzed.The problems about signal detection in MIMO-NOMA systems are studied,and Bit Error Ratio(BER)of various signal detection algorithms are achieved through the simulation.Secondly,in terms of the problems about user clustering in the MIMO-NOMA downlink communication system,a low-complexity user clustering algorithm is proposed for the lowly correlated scenarios after considering both the correlations and the channel difference of users.In order to reduce the computational complexity,candidate users are divided into two groups in advance.Then,the users with higher channel correlations are paired preferentially,and the remaining users are paired in terms of the channel difference.The simulation results show that the proposed algorithm outperforms the conventional user clustering algorithm in terms of performance and computational complexity.Thirdly,in terms of the problems about power allocation in the MIMO-NOMA downlink communication system,the performance,advantages and disadvantages of several classical power allocation schemes are analyzed.The objective function is established to maximize the capacity of the system while ensuring the users' minimum rates.Through solving the objective function by the Karush-Kuhn-Tucker(KKT)conditions,the power allocation factors are achieved,and according to them,two power allocation schemes are proposed.The simulation results show that the proposed schemes can ensure NOMA users' Quality of Service(Qo S)and improve the system capacity at the same time.