一种混合协作NOMA系统的缓冲辅助中继选择方案

A buffer-aided relay selection scheme for hybrid cooperative NOMA system

为了提高系统的中断性能及分集增益,研究了一种混合协作非正交多址接入(non-orthogonal multiple access,NOMA)系统。系统包含一个基站、K-1个配有缓冲器的中继、一个配有缓冲器的近端用户和一个远端用户。其中,基站与近端用户可通过直传方式进行通信或由中继协作通信,而与远端用户通过近端用户或中继进行协作通信。针对该混合协作NOMA系统,提出了一种缓冲辅助中继选择方案,能够基于信道状态信息和缓冲器状态,选择近端用户或最佳中继进行协作传输。推导了系统中断概率和平均包裹时延的闭式表达式,给出了高信噪比下的分集增益。证明了当最大缓冲单元数不小于3时,所提方案能达到满分集增益2 K。仿真结果表明,相对于基准方案,所提方案在系统中断概率与时延之间可以实现更好的折中。

In order to improve the outage performance and diversity gain,we studied a hybrid cooperative non-orthogonal multiple access(NOMA)system.The system consists of a base station,K-1 relays with buffer,a near user with buffer and a far user.The base station and the near user can communicate through direct transmission or with the help of relays,while the far user can communicate with the help of the near user or relays.For the hybrid cooperative NOMA system,a buffer-aided relay selection scheme is proposed to select the near user or the best relay for cooperative transmission based on channel state information and buffer states.The closed-form expressions of system outage probability and average package delay are derived,and the diversity gain under high signal-to-noise ratio is given.It is proved that the proposed scheme can achieve full diversity gain 2 K when the maximum number of buffer units is not less than 3.Finally,simulation results show that the proposed scheme can achieve a better tradeoff between system outage probability and delay compared with benchmark schemes.