协作NOMA系统中的一种新型节能功率分配方案

在传统的协作非正交多址（CNOMA, Cooperative Non Orthogonal Multiple Access)系统中，通常需要向弱用户分配更多的功率，分配给强用户的功率不超过总功率的一半。同时，强用户还需在协作阶段承担中继通信的任务。上述功率分配方式必将给强用户带来一定的负担。为了在满足弱用户服务质量的情况下，进一步提高强用户的中断性能，本文提出一种基于中继和无线携能通信（SWIPT, Simultaneous Wireless Information and Power Transfer）的新型功率分配方案。该方案使用能量收集设备收集能量，通过最大化系统和速率寻求无线携能通信的最优功率分割因子，从而获得系统中断概率的闭式表达。考虑到优化问题的性质，本文提出了一种在功率分配固定的情况下，通过单调优化求解无线携能通信功率分割因子的算法。仿真结果表明，与CNOMA系统的传统功率分配方案相比，本文所提方案能够在不损失弱用户中断性能的前提下，有效提升强用户的中断概率，系统和速率总体提高了近 20%。 

A Novel Energy-saving Power Allocation Strategy in Cooperative NOMA System

In conventional cooperative NOMA (CNOMA) system, more power is allocated to weak users, and the power allocated to strong users is less than half of the total power. Meanwhile, strong users need to act as relays in cooperative communication. Above power allocation strategy will bring some burden to strong users. In order to balance the performance of strong and weak users in CNOMA system, a new power allocation strategy based on relay communication and simultaneous wireless information and power transfer (SWIPT) is proposed in this paper. Energy harvesting equipment is used to collect energy. The optimal power splitting factor of SWIPT and the closed expression of the system outage probability are derived through maximizing the sum rate. Considering the nature of the optimization problem, a monotonic optimization algorithm is proposed to solve the power splitting factor of SWIPT under the condition of the fixed power allocation. Simulation results show that without losing the performance of weak users, the outage probability of strong users is improved compared with conventional power allocation strategy, and the overall sum-rate increases by nearly 20% compared with conventional power allocation strategy in CNOMA system.