  In this report, we introduce the concept of Rician $K$-factor-based radio
resource and mobility management for fifth generation (5G) ultra-dense networks
(UDN), where the information on the gradual visibility between the new radio
node B (gNB) and the user equipment (UE)---dubbed X-line-of-sight
(XLOS)---would be required. We therefore start by presenting the XLOS service
probability as a new performance indicator; taking into account both the UE
serving and neighbor cells. By relying on a lognormal $K$-factor model, a
closed-form expression of the XLOS service probability in a 5G outdoor UDN is
derived in terms of the multivariate Fox H-function; wherefore we develop a
GPU-enabled MATLAB routine and automate the definition of the underlying
Mellin-Barnes contour via linear optimization. Residue theory is then applied
to infer the relevant asymptotic behavior and show its practical implications.
Finally, numerical results are provided for various network configurations, and
underpinned by extensive Monte-Carlo simulations.
