  The notions of softwarization and virtualization of the radio access network
(RAN) of next-generation (5G) wireless systems are ushering in a vision where
applications and services are physically decoupled from devices and network
infrastructure. This crucial aspect will ultimately enable the dynamic
deployment of heterogeneous services by different network operators over the
same physical infrastructure. RAN slicing is a form of 5G virtualization that
allows network infrastructure owners to dynamically "slice" and "serve" their
network resources (i.e., spectrum, power, antennas, among others) to different
mobile virtual network operators (MVNOs), according to their current needs.
Once the slicing policy (i.e., the percentage of resources assigned to each
MVNO) has been computed, a major challenge is how to allocate spectrum
resources to MVNOs in such a way that (i) the slicing policy defined by the
network owner is enforced; and (ii) the interference among different MVNOs is
minimized. In this article, we mathematically formalize the RAN slicing
enforcement problem (RSEP) and demonstrate its NP-hardness. For this reason, we
design three approximation algorithms that render the solution scalable as the
RSEP increases in size. We extensively evaluate their performance through
simulations and experiments on a testbed made up of 8 software-defined radio
peripherals. Experimental results reveal that not only do our algorithms
enforce the slicing policies, but can also double the total network throughput
when intra-MVNO power control policies are used in conjunction.
