Page 161 - ITU Journal, Future and evolving technologies - Volume 1 (2020), Issue 1, Inaugural issue

ITU Journal on Future and Evolving Technologies, Volume 1 (2020), Issue 1

ON THE EVOLUTION OF INFRASTRUCTURE SHARING IN MOBILE
NETWORKS: A SURVEY

Lorela Cano , Antonio Capone , Brunilde Sansò 3
1
2
1,2 Politecnico di Milano, Milan, Piazza Leonardo da Vinci, 32, 20133, Milano MI, Italy, Polytechnique Montréal,
3
2500 Chemin de Polytechnique, Montréal, QC H3T 1J4, Canada,
NOTE: Corresponding author: Lorela Cano (lorela.cano@polimi.it)

Abstract – Infrastructure sharing for mobile networks has been a prolific research topic for more than three decades
now. The key driver for Mobile Network Operators to share their network infrastructure is cost reduction. Spectrum
sharing is often studied alongside infrastructure sharing although on its own it is a vast research topic outside the scope
of this survey. Instead, in this survey we aim to provide a complete picture of infrastructure sharing both over time
and in terms of research branches that have stemmed from it such as performance evaluation, resource management
etc. We also put an emphasis on the relation between infrastructure sharing and the decoupling of infrastructure from
services, wireless network virtualization and multi-tenancy in 5G networks. Such a relation reflects the evolution of
infrastructure sharing over time and how it has become a commercial reality in the context of 5G.

Keywords – 5G, infrastructure sharing, mobile networks, multi-tenancy, spectrum sharing, wireless network virtu-
alization

1. INTRODUCTION among them and hence make their business more prof-

Infrastructure sharing in mobile networks is a multi- itable. In these lines, infrastructure sharing has accom-
panied the technology migrations from 2G to 3G and
faceted problem involving not only academic and indus- from 3G to 4G due to the high upfront cost met by
trial research entities but also national and international MNOs during these migrations. In turn, in 5G networks,
regulatory entities [51, 52, 65, 66], standardization bod- infrastructure sharing, besides from being a means for
ies [1–4] and vendors [45,107]. In essence, infrastructure cost-reduction, it is also an important pillar of the 5G
sharing in mobile networks is the shared use of existing architecture. Another paradigm strongly linked to in-
or jointly deployed network infrastructure among mul- frastructure sharing is spectrum sharing. The need for
tiple Mobile Network Operators (MNOs).
spectrum sharing comes from spectrum being an intrin-
Based on which network elements (nodes) MNOs agree sically scarce resource, even more so in the context of
to/can share, there are two main types of sharing: pas- 5G, given its target throughputs. However, spectrum
sive and active, the latter comprising the former. Pas- sharing alone is a really vast research topic and will be
sive sharing (also referred to as site sharing or co- outside the scope of this survey unless combined with
location [49]) implies the sharing of the site physical infrastructure sharing.
space and of the non-active elements on the site (such
as shelter, cabinet, mast, etc. [49,104]). Instead, active What’s more, in this paper we will also address some
sharing extends to active elements of the Radio Access literature on Wireless Network Virtualization (WNV)
Network (RAN) (such as antennas, Base Transceiver [91] and network slicing (enabling multi-tenancy) in the
Stations/Base Station Controller for 2G, Node B/Radio context of 5G [6], since both are based on infrastruc-
Network Controller for 3G, eNode B for 4G, and gN- ture and spectrum sharing. Conversely, WNV and net-
odeB for 5G) and part of the core nodes (in fact, core work slicing can be seen as enablers for infrastructure
node elements related to user billing and accounting are and spectrum sharing. Besides, another concept closely
not shared). related to infrastructure and spectrum sharing is that
of the decoupling of infrastructure from services, which
The phenomenon of infrastructure sharing has disrupted was envisioned by some of the early literature on in-
the business model of a conventional MNO, that is, an frastructure sharing (see Section 2). The concept has
MNO which is by itself responsible for (i) purchasing a been further carried out in the context of WNV and
spectrum license, (ii) deploying and managing the net- then in the context of network slicing. In fact, the dif-
work infrastructure, (iii) tailoring services for their sub- ferent research efforts on introducing Software-Defined
scribers (e.g., voice, data, etc.) and (iv) handling their Networking (SDN), virtualization in general and Net-
billing and accounting. The main reason for MNOs to work Functions Virtualization (NFV) in particular into
share infrastructure is to divide the infrastructure cost mobile networks seem to have converged into the 5G

© International Telecommunication Union, 2020 141