Research On Interleaving And Power Allocation Technology For IDMA-NOMA System

Compared with orthogonal multiple access technology,Non-Orthogonal Multiple Access(NOMA)technology has larger system capacity,higher data transmission rate and stronger access capability,which can meet the requirements of the 6th Generation(6G)mobile communication system.It can meet the performance requirements of the sixth generation(6G)mobile communication system,and has attracted extensive attention from academic and industrial circles at home and abroad.Interleave Division Multiple Access(IDMA)technology and power domain NOMA technology based on orthogonal frequency division multiplexing access technology,as typical NOMA technologies,are cascaded to establish an IDMA-NOMA system,which can make full use of the code domain,interleaving domain,power domain and time-frequency domain resources.In order to obtain a lower-complexity,higher-fairness and higher-energy-efficient IDMANOMA system,this thesis proposes an IDMA-NOMA system interleaving algorithm,a fairness-based power allocation algorithm and an optimal energy-efficient power allocation algorithm.The main research contents of the thesis include:(1)Research on the interleaving algorithm of IDMA-NOMA system.In the IDMANOMA system,the effective design of the interleaver,the interleaving and deinterleaving algorithms directly affect the complexity of the iterative multi-user detection algorithm.Aiming at this problem,research is carried out from four aspects: 1)In order to meet the performances such as interleaver distance and correlation,the Lyapunov exponent of the Logistic chaotic system is used to determine the quantized bit length of the fixed-point Logistic sequence in the chaotic state firstly;balance degree and crosscorrelation threshold are used to determine the starting position and the initial value of the fixed-point Logistic sequence,and finally the Logistic interleaving sequence is generated and applied to(de-)interleaving process.2)In order to further reduce the time delay in the fixed-point Logistic sequence generation process,a Field Programmable Gate Array(FPGA)generation algorithm with arbitrary quantized bit length is proposed.The algorithm firstly uses the look-up table method to construct an asymmetric basic multiplier,then uses the shift-add method to calculate the total multiplier,and finally bipolarizes the Logistic sequence.3)In order to reduce the storage space and computational complexity of the(de-)interleaving algorithms in the multi-user detection process,the bipolarized Logistic sequence and the sequence are correspondingly multiplied to complete the(de-)interleaving process.4)In order to facilitate FPGA to calculate the average value of transmitted data in the process of multi-user detection,the piecewise polynomial method is used for fitting,and on the premise of ensuring the fitting accuracy,the problem of out-of-bounds in the fixed-point multiplication process can also be avoided.Simulation results show that the proposed scheme can obtain better bit error rate performance.(2)Research on the fairness-based power allocation algorithm.In IDMA-NOMA system,efficient power allocation to the base station center and edge users can not only improve the system energy-efficient of the users,but also reflect the fairness among users.Therefore,related research is carried out from two aspects: 1)In order to reflect the user fairness,based on the number of sub-carrier multiplexing users,the users are initially grouped and the power coefficients are initialized with the fractional power allocation algorithm;taking the Geometric Mean Weighted System Capacity(GMWSC)as the target,the optimal user grouping combination of the current user group and the adjacent user group is searched in turn,and the power coefficients are allocated to the grouped users.2)In order to further reduce the complexity of the user power allocation algorithm,when the user is stationary or moving at a low-speed,in the vicinity of the user’s optimal power coefficients at the previous moment,with the weighted system capacity as the goal,by adjusting the power allocation step-size and correction-granularity,find the current user optimal power coefficients.Simulation results demonstrate that the proposed scheme can effectively reduce the complexity of power allocation algorithm.Compared with fractional power allocation algorithm,the capacity performance of GMWSC is improved by about 2.3%.(3)Research on the optimal energy-efficient power allocation algorithm of IDMANOMA system.In the Cognitive Radio(CR)network,the primary/secondary users adopt the IDMA-NOMA technology,which can improve the spectral efficiency.In order to prolong the standby time of the secondary users of CR network,for the uplink spectrum sharing model,with the effective range of power consumption rate,system capacity,minimum communication quality of secondary users and Successive Interference Cancellation(SIC)effectiveness as constraints,an optimal energy-efficient power allocation model is established and solved.The solution includes two optimization problems of inner subcarrier power allocation and outer energy-efficiency optimization.For the inner subcarrier power allocation problem,based on the minimum communication quality of the secondary user and the SIC effectiveness,the difference-convex approach is used to maximize the subcarrier capacity.For the outer power energy-efficiency optimization problem,the Dinkelbach approach is used to maximize the system energyefficient.Simulation results demonstrate that the proposed scheme has faster convergence speed,and the system energy-efficient performance is improved by about 11% compared with the fractional power allocation algorithm.