We introduce a phase hopping scheme for reconfigurable intelligent surfaces (RISs) in which the phases of the individual RIS elements are randomly varied with each transmitted symbol. This effectively converts slow fading into fast fading. We show how this can be leveraged to significantly improve the outage performance especially for small outage probabilities without channel state information (CSI) at the transmitter and RIS. Furthermore, the same result can be accomplished even if only two possible phase values are available. Since we do not require perfect CSI at the transmitter or RIS, the proposed scheme has no additional communication overhead for adjusting the phases. This enables robust ultra-reliable communications with a reduced effort for channel estimation.

翻译：我们引入了可重新配置智能表面(RIS)的阶段性跳跃计划, 各个RIS元素的阶段随每个传输符号随机变化。 这有效地将缓慢减退转化为快速减退。 我们展示了如何利用这个计划显著地改善特别是小型脱机概率的停机性能, 没有发射机和RIS的频道状态信息( CSI ) 。 此外, 即使只有两个可能的阶段值, 也能够取得同样的结果 。 由于我们不需要发射机或RIS 的完整 CSI, 拟议的计划没有额外的通信间接费用来调整这些阶段 。 这使得能够进行强大的超可靠通信, 减少频道估算的努力 。