Dynamic Semi-Passive RIS-Assisted URLLC Communication with Finite Blocklength

Distinct from the conventional paradigms of fully passive and fully active RIS configurations, a novel semi-passive RIS composed of partially active reflecting elements and passive elements which can leverage combined advantages is proposed in this paper, Specifically, we investigate a semi-passive RIS assisted URLLC system from the energy efficient maximization perspective. In addition, efficient alternating optimization, successive convex approximation, and successive refinement algorithms are developed to jointly optimizing the transmit precoding matrices and dynamic RIS beamforming matrix. Numerical analysis shows that the proposed RIS system significantly outperforms traditional RIS and non-RIS systems. Moreover, semi-passive RIS with only few active elements can achieve superior energy efficiency compared to passive RIS even with infinite blocklength. This highlights the potential of semi-passive RIS to reduce latency, enhance reliability, and improve energy efficiency.