Channel Hardening in RIS-Assisted Short-Packet Communication Systems

Finite block length information theory plays a pivotal role in the design and analysis of short packet communications systems, especially for applications requiring ultra reliability and low latency. Recently, leveraging reconfigurable intelligent surfaces (RISs) for such type of communications has proven to be very promising. However, investigating the channel hardening in such systems remains an open issue. In this context, this paper examines the channel hardening in RIS-assisted communication with finite block length. After investigating the properties of the achievable rate term, the paper analyzes the scaling law of the signal-to-noise power ratio with respect to the RIS size, and introduces a metric for quantifying the channel hardening. Results demonstrate the presence of hardening, and illustrate the effects of the main system parameters on the hardening property.