不完美串行干扰消除下多RIS辅助的NOMA系统中断性能

Outage performance of multi-RIS-assisted NOMA system with imperfect serial interference cancellation

考虑到实际通信应用中不能实现完美的串行干扰消除(SIC,serialinterferencecancellation),研究了不完美SIC情况下多个智能反射面(RIS,reconfigurableintelligentsurface)辅助的非正交多址接入(NOMA,non-orthogonal multiple access)系统的中断性能和吞吐量。联合考虑直射链路和反射链路,利用Gamma分布近似表征多RIS辅助NOMA系统的信道系数,推导出用户中断概率的近似闭合表达式,并通过Monte-Carlo仿真进行验证,分析系统中断性能与不完美SIC、RIS个数及反射单元数等因素的关系。仿真结果表明,与单RIS辅助的NOMA系统和传统NOMA系统相比,在给定中断概率要求下,多RIS辅助系统所需的信噪比(SNR,signal-to-noise ratio)降低了14.2 dBm,说明了采用多个RIS可以有效地提升用户的中断性能和系统吞吐量,从而补偿不完美SIC带来的性能损失。

Considering the practical communication environments,the outage performance and the throughput were investigated for multiple reconfigurable intelligent surfaces(RIS)assisted non-orthogonal multiple access(NOMA)system with imperfect serial interference cancellation(SIC).The channel coefficients of the RIS-assisted NOMA system including the direct and the reflecting paths were approximated by Gamma distribution.An approximate closed-form expressions of outage probability were derived and validated through Monte Carlo simulations.The study investigated the relationship between the outage performance and system parameters,including the impact of imperfect SIC,the number of RIS and the number of reflecting units.The simulation results demonstrate that,compared with the single RIS-assisted NOMA and the traditional NOMA system,the multi-RIS-assisted system achieves a 14.2 dBm gain in signal-to-noise ratio(SNR)for a given outage probability.Thus,employing multiple RISs can improve the outage performance and the system throughput effectively,thereby compensating for the performance degradation caused by imperfect SIC.