Outage Probability and BER Performance of RIS-Assisted Links under Imperfect CSI

Abstract

Reconfigurable intelligent surfaces (RIS) offer significant improvements in coverage, capacity, and reliability, making them a key technology for future wireless communication networks. This study examines a RIS-assisted single-input single-output (SISO) communication system with imperfect channel state information (CSI) using quadrature phase shift keying (QPSK) modulation, with a blocked direct transmitter-receiver link. The RIS adjusts phase shifts according to estimated channels, and the broadcast signals are received by the receiver with maximum likelihood (ML) and the proposed maximum a posteriori (MAP) method. The performance metrics of the communication system are evaluated for various RIS sizes with imperfect CSI. The results show that the reliability of the communication system increases with the number of elements of the RIS, reducing the outage probability and enhancing outage capacity. Additionally, the MAP method reduces the BER when compared to the ML method due to the use of prior symbol probability information of the transmitted symbol.