Research On Power Allocation Algorithm For Non-orthogonal Multiple Access System With SIC

Mobile communication,has now developed to the fourth generation from the 80 s of last century,experienced evolution process of time division multiple access,frequency division multiple access,code division multiple access and orthogonal frequency multiple access.With the development of science and technology,more and more terminals will be connected to the communication network,in order to meet the needs of future multi-user access,the technology non-orthogonal multiple access(NOMA)was born.This thesis is focus on the power allocation algorithm for non-orthogonal multiple access system with Successive Interference Canceller.The main work is as follows:Firstly,the mathematical model of non-orthogonal multiple access system is given.With the two users as an example,it is proved that advantage of the non-orthogonal multiple access technology on improving spectrum efficiency.For the successive interference cancellation technique,one of the key technologies,two algorithms are proposed: Zero Forcing-Successive Interference Canceller algorithm and Minimum Error Square Successive Interference Canceller algorithm.And then this thesis analyzes and compares between with the two algorithms..Secondly,this thesis studies the power allocation which is the key technology of the transmitter.For the power allocation on a sub-channel,a tree-based search algorithm for incremental power assignment is proposed.The algorithm needs to know the channel gain of each user's signal on the sub-channel,then assigns the users to the tree model,and according to the given power metric and throughput metric for searching and filtering layer by layer.In order to ensure the fairness of the throughput among users,the algorithm sets the maximizing geometric mean user throughput as the objective function.Then the algorithm is compared with the exhaustive search power allocation algorithm,the simulation results show that its computational complexity is not hige.Finally,compared with the existing power allocation algorithms,the simulation results show that the algorithm is effective.Finally,a multiuser grouping algorithm is proposed for the grouping of sub-channels in the cell.In non-orthogonal multiple access systems,the non-orthogonal users need to satisfice certain intervalic power,in order to ensure that the receivercorrects the signal more correctly,so the proposed algorithm arranges and groups the cell users according to channel gain to ensure that there are certain intervalic channel gain and power among users in each sub-channel.In order to reduce the computational complexity,there set the candidate user groups,only select the user from each group of candidates when selecting each time.The fractional power allocation algorithm is used to allocate the initial power.In addition,the weighted throughput product is seted as the objective function for selecting the user groups.Finally,the algorithm is compared with the existing grouping algorithms,the simulation results show that the algorithm is validated by combining the proposed power allocation algorithm.