RIS-Assisted Cooperative Transmission System with Adaptive Reflection Scheme

Reconfigurable Intelligent Surface (RIS) is one of the most promising technologies for future wireless communications. To solve the multiplicative fading effect of traditional passive RIS (PRIS), a hybrid active-passive RIS (HRIS) collaborative transmission system is proposed in this paper. The hybrid RIS can change its reflection mode adaptively according to the channel transmission environment, not only adjusting the phase of the incident signal, but also amplifying the incident signal. For the proposed system model, an approximate closed expression for the outage probability (OP) of the system is obtained using the compound Simpson formula, as well as the correctness of the derived theoretical equation is verified by Monte Carlo simulation. Simulation results show that HRIS can effectively reduce the outage probability of the system compared to PRIS and active RIS (ARIS) which uses the decode-and-forward (DF) protocol.