Active RIS-Assisted Communication with Dynamic Sub-Connections.

To address the “multiplicative fading effect” challenge associated with passive reconfigurable intelligent surfaces (RIS), active RIS has emerged. However, current active RIS implementations can be power-intensive due to active components. To tackle this, we introduce the dynamic sub-connected architecture for active RIS. Unlike typical sub-connected architectures, this approach uses control switches between RIS elements and a shared power amplifier. By allocating more power to high-gain elements, it enhances overall energy efficiency (EE). We've also developed an EE maximization framework and joint beamforming strategy for both active RIS architectures, validated through simulations as an efficient active RIS solution.