  Network slicing has emerged as a key concept in 5G systems, allowing Mobile
Network Operators (MNOs) to build isolated logical networks (slices) on top of
shared infrastructure networks managed by Infrastructure Providers (InP).
Network slicing requires the assignment of infrastructure network resources to
virtual network components at slice activation time and the adjustment of
resources for slices under operation. Performing these operations just-in-time,
on a best-effort basis, comes with no guarantee on the availability of enough
infrastructure resources to meet slice requirements.
  This paper proposes a prioritized admission control mechanism for concurrent
slices based on an infrastructure resource reservation approach. The
reservation accounts for the dynamic nature of slice requests while being
robust to uncertainties in slice resource demands. Adopting the perspective of
an InP, reservation schemes are proposed that maximize the number of slices for
which infrastructure resources can be granted while minimizing the costs
charged to the MNOs. This requires the solution of a max-min optimization
problem with a non-linear cost function and non-linear constraints induced by
the robustness to uncertainties of demands and the limitation of the impact of
reservation on background services. The cost and the constraints are linearized
and several reduced-complexity strategies are proposed to solve the slice
admission control and resource reservation problem. Simulations show that the
proportion of admitted slices of different priority levels can be adjusted by a
differentiated selection of the delay between the reception and the processing
instants of a slice resource request.
