In this study, we develop an active reconfigurable intelligent surface (RIS)-assisted multiple-input multiple-output orthogonal frequency division multiplexing (MIMO-OFDM) prototype compliant with the 5G New Radio standard at 3.5~GHz. The experimental results clearly indicate that active RIS plays a vital role in enhancing MIMO performance, surpassing passive RIS. Furthermore, when considering factors such as complexity, energy consumption, and performance, the comparative evaluation between passive RIS and active RIS reinforces the critical role of active RIS in MIMO systems. These findings underscore the practical significance of active RIS in improving MIMO gain in 5G scenarios.

翻译：本研究开发了一个工作在3.5~GHz、符合5G新空口标准的主动式可重构智能表面(RIS)辅助多输入多输出正交频分复用(MIMO-OFDM)原型系统。实验结果表明，主动RIS在增强MIMO性能方面起到关键作用，其效果优于无源RIS。此外，在综合考虑复杂度、能耗和性能等因素时，对无源RIS和主动RIS的比较评估进一步证实了主动RIS在MIMO系统中的关键作用。这些发现凸显了主动RIS在5G场景中提升MIMO增益的实际意义。