Mission Availability for Wireless URLLC

With the fifth generation (5G) of mobile networks the challenging field of ultra-reliable low latency communications (URLLC) is envisioned. In this area of research, reliability requirements are commonly formulated only in terms of packet loss rates. However, sparse packet loss can usually be tolerated by an application. Furthermore, the terms reliability and availability are usually loosely defined and not sufficiently separated in the wireless communications field. This paper applies fundamental metrics from dependability theory to wireless communications, providing more powerful key performance indicators (KPIs) for URLLC. In particular, we derive analytic expressions which reflect the up- and downtime distributions as well as the mission availability in a wireless multi-connectivity scenario with selection combining and Rayleigh fading. Further, we propose an appropriate approximation for the computationally complex expression of the mission availability.