On the Effect of RIS Phase Quantization on Communications System Performances

The past wireless communication systems were designed taking the channel as an uncontrollable element and optimizing the system around this element. However, recently Reconfigurable Intelligent Surfaces (RISs) have gained a significant interest as a way to control the wireless propagation environment and improve the communication system performances. However, to achieve optimal performances, a continuous-phase RIS is required. But, the practical realization of RISs makes it very difficult to obtain a RIS with more than few phase states. Therefore, the required RIS phase must be quantized to these available states. In this paper, we investigate the effect of RIS phase quantization on the wireless system performances in terms of RIS beamforming capabilities, received signal level, and channel estimation accuracy compared to a continuous-phase RIS. We demonstrate that starting from 2-bit quantization very good performances can be achieved.