智能反射面辅助的STBC-NOMA系统性能分析

Performance Analysis on Intelligent Reflecting Surfaces Assisted STBC-NOMA Systems

智能反射面(Intelligent Reflecting Surface,IRS)技术以其低成本、灵活部署、易于融合其他关键技术的优势吸引了无线通信学术界和工业界的极大关注.传统的空时分组码(Space-Time Block Coding,STBC)与非正交多址接入(Non-Orthogonal Multiple Access,NOMA)方案的巧妙结合(STBC-NOMA)已被证明能够有效地提高系统的鲁棒性和吞吐量.鉴于此,本文提出一种新的IRS辅助的STBC-NOMA系统的传输框架(IRS-STBC-NOMA). IRS辅助系统给远近不同的两个用户传输信号.采用两个分割的IRS实现STBC传输并利用IRS的相移设计实现发射信号控制,分别推导了所提出传输框架下每个用户的中断概率和遍历速率的闭合表达式;基于所得的分析表达式,给出了渐近或单调的理论分析,之后通过蒙特卡洛仿真进行了对比验证.与现有的STBC-NOMA方案相比,所提IRS-STBC-NOMA方案的中断性能和遍历速率均获得显著提升.

Intelligent reflecting surface(IRS)technology has attracted a great deal of attention from both academia and industry in wireless communications for its low cost,flexible deployment,and ease of integration with other key tech⁃nologies.An ingenious combination of traditional space-time block coding(STBC)and non-orthogonal multiple access(NOMA)schemes(STBC-NOMA)has been proven to be effective in improving system robustness and throughput.In view of this,this paper proposes a novel transmission framework for IRS-assisted STBC-NOMA system,named IRS-STBCNOMA,which transmits signals to two users with different distances with the assistance of IRS.We consider two segment⁃ed IRSs for STBC transmission and utilize the phase shift design of IRS to control transmit signals.We derive the outage probability and ergodic rate for each user under the proposed transmission framework,respectively.Based on the obtained analytical expressions,an asymptotic or monotonic theoretical analysis is offered,followed by a comparative verification through Monte Carlo simulations.Compared with the existing STBC-NOMA scheme,the proposed IRS-STBC-NOMA scheme achieves significant improvement in both outage performance and ergodic rate.