Performance analysis of RIS-assisted wireless systems under imperfect CSI

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.