Study On User Grouping And Power Allocation For MIMO-NOMA Systems Based On Spatial Modulation

Non-orthogonal multiple access(NOMA)technology allows users to utilize different power domain resources at the same time,frequency or code domain.In this way,NOMA technology can improve spectral efficiency and user fairness.In addition,spatial modulation(SM)technology in multiple-input multiple-output(MIMO)systems can also improve spectral efficiency.Therefore,MIMO-NOMA systems based on spatial modulation,namely SMN systems,can meet the urgent requirements of 5G communication systems,including spectrum utilization,cost,and connectivity.In this thesis,a user grouping scheme is proposed based on the effective channel gain,where users are grouped according to their effective channel gains.In this way,users in a group have stronger channel differences.Additionally,a two-user power allocation scheme is proposed based on the extreme value problem,where the power allocation coefficient is determined by solving the extreme points of this problem.The results show that significant performance can be achieved by proposed schemes in SMN systems.Due to the only one chosen transmit antenna,the performance improvement of SMN systems is limited.To solve this problem,MIMO-NOMA systems based on generalized spatial modulation(GSM)are designed,namely GSMN system.In addition,a user grouping scheme is proposed based on the min-cut problem.In this way,users with weaker mutual gains can be divided into different groups so that all users in a group have relatively stronger mutual gains.Furthermore,a power allocation scheme is considered based on the sum-rate maximization.Compared with the SMN system,the proposed GSMN system can improve system performance while maintaining appropriate user fairness.Additionally,the proposed schemes are beneficial to the performance improvement of the GSMN system.To further improve spectral efficiency,MIMO-NOMA systems based on quadrature spatial modulation(QSM)are designed,namely QSMN systems,where amplitude-phase modulation(APM)symbols are divided into real and imaginary components.In this way,there is no interference between these two components.Additionally,a user grouping scheme is proposed by considering channel conditions,user locations,and channel correlations.Furthermore,a power allocation scheme is designed to meet users' minimum rate requirements.In this way,users can remove intra-group interference.Simulation results reveal that the proposed QSMN system has better performance in terms of spectral efficiency and user fairness.