基于NOMA的D2D辅助中继系统性能分析与优化

Performance Analysis and Optimization of D2D Cooperative Relay System Based on NOMA

本文针对两阶段NOMA(Non-Orthogonal Multiple Access)-D2D(Device-to-Device)辅助中继场景提出了一种功率优化算法,推导分析了各用户的中断概率。构建了以最大化系统各态历经容量为目标的优化问题,由于一、二两阶段通信用户的差异性,重点优化了对提升系统容量起决定作用的第一阶段功率分配因子,分析证明了原优化问题存在极值点,并利用凸函数性质获得了优化的功率分配因子,并且进一步推导分析了各个用户的中断概率。仿真结果表明,理论推导的中断概率值与仿真结果完全一致,证明了推导的正确性,本文提出的功率优化算法能显著提高系统容量,且降低了中断概率。例如当SNR为35 dB时,本文算法可以提高约17.6%的系统容量,而作为辅助中继用户的中断概率大约降低了81.3%。

In this paper,a power optimization algorithm is proposed for the two-stage NOMA(Non-Orthogonal Multiple Access)-D2D(Device-to-Device)cooperative relay scene,and the outage probability of each user is deduced and analyzed.An optimization problem aiming at maximizing the ergodic capacity of the system is constructed,due to the difference of communication users in the first and second stages,the power distribution factor in the first stage which plays a decisive role in improving system capacity is optimized.The extreme point of the original optimization problem is proved,the optimal power distribution factor is obtained by using the property of convex function,and the outage probability of each user is further deduced and analyzed.The simulation results show that the theoretical outage probability value is completely consistent with the simulation results,which proves the correctness of the derivation.The power optimization algorithm proposed in this paper can significantly improve the system capacity and reduce the outage probability.For example,when SNR is 35 dB,the algorithm in this paper can improve about 17.6%of the system capacity,while the outage probability of cooperative relay user is reduced by about 81.3%.