Extreme Level Crossing Rate: A New Performance Indicator for URLLC Systems

TL;DR

This paper introduces the Extreme Level Crossing Rate (ELCR), a novel statistical indicator for ultra-reliable low-latency communication systems that captures rare extreme events affecting performance metrics.

Contribution

The paper extends traditional LCR to include extreme events using extreme value theory, providing new analytical tools for assessing URLLC system reliability.

Findings

ELCR is analytically derived and validated through simulations.

New closed-form expressions for outage duration, error rate, and delay are provided.

ELCR offers deeper insights into rare event impacts on system performance.

Abstract

Level crossing rate (LCR) is a well-known statistical tool that is related to the duration of a random stationary fading process \emph{on average}. In doing so, LCR cannot capture the behavior of \emph{extremely rare} random events. Nonetheless, the latter events play a key role in the performance of ultra-reliable and low-latency communication systems rather than their average (expectation) counterparts. In this paper, for the first time, we extend the notion of LCR to address this issue and sufficiently characterize the statistical behavior of extreme maxima or minima. This new indicator, entitled as extreme LCR (ELCR), is analytically introduced and evaluated by resorting to the extreme value theory and risk assessment. Capitalizing on ELCR, some key performance metrics emerge, i.e., the maximum outage duration, minimum effective duration, maximum packet error rate, and maximum transmission delay. They are all derived in simple closed-form expressions. The theoretical results are cross-compared and verified via extensive simulations whereas some useful engineering insights are manifested.