Mission Reliability for URLLC in Wireless Networks

Achieving connectivity reliability for ultra-reliable low-latency communication (URLLC) is one major challenge for future wireless communications systems. The current understanding of reliability does not sufficiently cover time-related aspects, e.g., time-varying channels or the duration of a certain condition in a wireless system. Moreover, different applications require diverse execution periods during which no failure is allowed, which we denote as mission duration. In this letter, we focus on time-related aspects and introduce the performance metric mission reliability to wireless communications systems and employ its connection to the mean time to first failure, reflecting the expected time until the first failure occurs. As diversity is accepted to be essential for reliability, their evaluation is presented regarding a multi-connectivity system with Rayleigh fading, reflecting frequency diversity. We demonstrate the trade-off between mission duration, mission reliability, and the number of links used for multi-connectivity, which can stimulate the discussion on URLLC and advance the design of future wireless systems.