Dependability Theory for Selection-Combined Channels with Rician Fading and Interference

The fifth generation (5G) of mobile networks aims to master the challenge of ultra-reliable low latency communications (URLLC). In this context, dependability requirements are usually formulated only in terms of very low packet loss rates. However, this key performance indicator (KPI) fails to reflect the performance with respect to time-related aspects. Hence, this paper studies the availability and metrics as a function of time by applying fundamental dependability theory to wireless communications. We show that it is possible and beneficial to leverage the existing toolset of dependability theory, e.g., Markov analysis, structure functions, and reliability block diagrams. We model the wireless communications system as a system comprising repairable components. Rician fading and interference are jointly considered as causes of failure. In particular, analytic expressions for the mean uptime (MUT), mean downtime (MDT), and availability are derived for single- and multi-connectivity with selection-combined channels. Numerical evaluations demonstrate the importance of analyzing not only availability alone but combinations of availability and time-based dependability statistics jointly.