MSE Minimization for RIS-Assisted Wireless Networks with Phase Error and Phase-Dependent Amplitude Response
Sin-Yu Huang, Jia-You Lin, Chih-Yu Wang, Ren‐Hung Hwang · 2024
Reconfigurable intelligent surfaces (RIS) is a promising technique to improve communication quality by adjusting the phase shift value of the passive reflected elements equipped on RIS. However, the phase shift value controlled by RIS may suffer from inevitable errors brought by hardware impairment and interference during transmission, which might lead to performance degradation. On the other hand, the assumption of uniform amplitude response made by most literature is not practical due to the imperfect reflection efficiency of the material. To jointly address these two issues, we consider a practical amplitude model that is a function of phase shift value and the phase shift value in our system is imposed an additional error following the Von-Mises distribution. To find the optimal solution that minimizes the average mean square error (MSE) of the received signal, we proposed a gradient descent method (GDM)-based phase shift algorithm that iteratively follows the gradient flow until converges. The numerical result is presented to show the superiority of our proposed algorithm over other existing algorithms.