Research On The Resource Allocation Schemes In Multi-user Group NOMA Systems

Due to the soaring equipments and the scanty spectrum resources,Mobile Communication Networks are facing great challenges in the large-scale connection and spectrum resource utilization,which developed Non-orthogonal Multiple Access(NOMA)technology.In the NOMA,multi-users are divided into several groups at the transmitter end,and the users in the same group share the same orthogonal resource and their signals are distinguished by different powers,then the receiver performs the Successive Interference Cancellation(SIC)technique to extract the signals required by the users.As the focuese of this thesis,User Grouping(UG),Power Allocation(PA)and the receiver's user signal detection are the most critical parts of the NOMA system,and the research contents and innovations are as follows:1.A Hill Climbing Algorithm(HCA)based user grouping scheme is proposed to solve the problem that the optimal Full Space Search(FSS)user grouping scheme is too complex to be applied in practice.The result of the Channel State Sort(CSS)user grouping scheme is used as the initial solution of the HCA to replace user pairs,which can improve in the capacity of the NOMA system.When the transmit power is 30 d Bm,the capacity of HCA-UG scheme is about 2.06%higher than that of the CSS-UG scheme,although the capacity loss of 4.76%compared with the FSS-UG scheme,the computational complexity is lower.The HCA-UG scheme can meet the practical needs of NOMA systems with lower complexity.2.A joint power allocation scheme is proposed,which divides the PA into two stages.In stage 1,the subband power is allocated by the iterative water-filling algorithm through the equivalent channel gain.In stage 2,power is allocated to the users on the subbands according to three performance requirements,namely SC maximization with weights,SC maximization with Quality of Service(Qo S)constraints and maximization of fairness.When the transmit power is 30 d Bm,if PA is performed in the subband with the criterion of maximizing SC with weights and maximizing SC with Qo S restrictions,respectively,the SC is about 59.98%and 59.40%higher than that of the OMA system;if the power is allocated in the subband with the criterion of maximizing fairness,the achievable minimum user rate is higher than that of the OMA system.The proposed PA scheme can meet different performance requirements and has more flexible performance.3.In this thesis,the zero-forcing and minimum mean square error signal detection algorithm is combined with the SIC receiver,and the proposed UG and PA schemes are applied to the NOMA system receiver.Compared with the UG scheme,the PA scheme has more influence on the BER of the NOMA system.e.g.when the BER is 10^-1,The signal-to-noise ratio difference between ?_fp?=0.4 and?_fp?=0.2is about 7 d B.Meanwhile,based on the BER performance of the traditional UG and PA schemes,the BER of the proposed UG and PA schemes are within the acceptable range,which proves the feasibility of the proposed scheme.