协同双小区下行协作NOMA-SWIPT中断性能分析
Outage Performance Analysis of Cooperative NOMA-SWIPT in Coordinated Downlink Dual-Cell Systems
-
摘要: 本文研究了在毫微微蜂窝网络(femtocell network, FN)中,协同双小区系统的非正交多址接入(non-orthogonal multiple access, NOMA)与无线携能通信(simultaneous wireless information and power transfer, SWIPT)下行协作通信的中断性能,提出了一种边缘用户在邻基站及源基站随机中心用户共同协作的下行接入方案。所提方案共分为两个时隙:第一时隙内由两基站向所有用户广播叠加信号,提供中继服务的中心用户对其所接收的叠加信号逐级解码并收集能量。第二时隙,中心用户将其第一时隙内所收集的能量作为额外功率资源,在优先保证自身通信质量的前提下对成功解码的边缘用户信息进行再编码转发。基于空间均质泊松点过程(Poisson point process, PPP)中心用户的位置模型,推导了中心用户与边缘用户平均中断概率的表达式,进行了蒙特卡罗仿真验证,同时分析了各仿真参数(中心用户分布半径、用户阈值速率、路径损耗指数等)与中心用户、边缘用户平均中断概率的关系。结果表明:所提方案可以改善边缘用户的下行接入中断性能和系统吞吐量。Abstract: This study investigated the outage performance of cooperative downlink communications with non-orthogonal multiple access (NOMA) and simultaneous wireless information and power transfer (SWIPT) in the coordinated dual-cell systems of a femtocell network (FN). A downlink scheme was developed for edge users with the aid of an adjacent base station and random center user of the source base station. After ensuring the priority of their own communication quality, center users provide a relaying service by harvesting energy based on the power domain NOMA-SWIPT protocol. This scheme is divided into two time slots. In the first time slot, two base stations broadcast the superimposed signal to all users, and the center users acting as relay devices decode the signal and energy harvest. In the second time slot, the center users use the energy collected in the first time slot as an additional power resource to encode and forward the edge user information, while prioritizing their own requirements. Based on the center users’ location model in a spatial homogeneous Poisson point process (PPP), the average outage probabilities for both the center users and edge users were derived and validated using Monte Carlo simulations. The relationships between some simulation paraments (the distribution radius of center users, threshold rate of users, path loss exponent, etc.) and the average outage probabilities for center users and edge users were analyzed. The results showed that the proposed scheme could improve the downlink outage performance of edge users, along with the system downlink throughput.