基于NOMA系统的用户分组和功率分配策略

针对非正交多址接入（NOMA）系统的最优用户分组和功率分配方案的高复杂度问题，提出一种改进的用户分组和功率分配策略。首先，对用户进行分组，由信道增益值确定每个子信道的第一个用户，再由贪婪匹配方法分配剩余用户；然后，对用户的功率进行分配，将该功率分配问题分成子信道间和子信道内两部分，对于子信道间采用线性注水算法分配功率，对于子信道内则采用所提的迭代功率分配算法分配功率；最后，构造拉格朗日函数以实现在最大发射功率以及保证每个用户最低数据速率的约束下系统吞吐量的最大化。仿真结果表明，在多用户的情况下，与线性注水的分数阶功率分配（LWF-FTPA）算法和等分数阶功率分配（EQ-FTPA）算法相比，系统吞吐量分别提高了8%和20%，所提策略优于传统算法。

User grouping and power allocation strategy based on NOMA system

An improved user grouping and power allocation strategy was proposed for high complexity problem of optimal user grouping and power allocation schemes for Non-Orthogonal Multiple Access (NOMA) systems. Firstly, the users were grouped, the first user of each subchannel was determined by channel gain value, and the remaining users were allocated by greedy matching method. Then, the power of user was allocated, and the power allocation problem was divided into two parts: inter-subchannel and intra-subchannel. The power was allocated by the linear water-filling algorithm for inter-subchannels, and the power was allocated by the proposed iterative power allocation algorithm for intra-subchannels. Finally, a Lagrangian function was constructed to maximize the throughput of system under the constraints of maximizing transmit power and guaranteeing the minimum data rate for each user. The simulation results show that in the case of multiple users, compared with the LWF-FTPA (Linear WaterFilling-Fractional Transmit Power Allocation) algorithm and EQ-FTPA (EQual-Fractional Transmit Power Allocation) algorithm, the proposed strategy has system throughput increased by 8% and 20% respectively, indicating that the strategy is better than traditional algorithms.