不完美CSI下RIS辅助无线系统的性能分析

Performance analysis of RIS-assisted wireless systems under imperfect CSI

  • 摘要: 针对智能反射面(reconfigurable intelligent surface,RIS)不具备复杂的感知和信号处理能力,使得信道状态信息(channel state information,CSI)估计存在误差的情况,构建了不完美Nakagami-m衰落信道下的RIS辅助端到端的无线通信系统模型,分析了此模型下系统的中断概率(outage probability,OP)和各态历经容量(ergodic capacity,EC). 首先基于矩匹配法推导了端到端信干噪比(signal to interference plus noise ratio,SINR)的累积分布函数(cumulative distribution function,CDF),然后基于此CDF导出了OP与EC的解析闭合表达式,最后推导了高SINR条件下OP与EC的近似表达式. 仿真实验结果表明:解析结果与蒙特卡罗仿真数据高度吻合,且在高SINR情况下与近似曲线逼近;完美CSI的OP值会随着SINR增大而持续降低,而不完美CSI会出现地板现象,且相关系数 \rho 越小,OP值越大;通过增加RIS的反射元件数量可有效减少信道估计误差带来的性能损失.

     

    Abstract: Addressing the issue that reconfigurable intelligent surface (RIS) did not possess complex sensing and signal processing capabilities, leading to errors in channel state information (CSI) estimation, this paper established a RIS-assisted end-to-end wireless communication system model under Nakagami-m fading channels under imperfect CSI. The outage probability (OP) and ergodic capacity (EC) of the system were analyzed within this framework. Initially, the end-to-end signal-to-interference-plus-noise ratio (SINR) was calculated, and then its cumulative distribution function (CDF) was derived based on the moment matching method. Subsequently, analytical closed-form expressions for OP and EC were derived based on CDF. Finally, approximate expressions for OP and EC under high SINR were formulated. Simulation results revealed a high degree of consistency between analytical results and Monte Carlo simulation data, particularly approaching the approximate curves at high SINR. The OP with perfect CSI continued to decrease as the SINR increased, while the OP with imperfect CSI exhibited a floor phenomenon, and the smaller the correlation coefficient (ρ), the larger the OP value. By increasing the number of reflecting elements in the RIS, the performance degradation caused by channel estimation errors can be effectively reduced.

     

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