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5
MNO MNO
SP
(MVNO)
SP
(MVNO)
SP
(MVNO)
MVNO MVNO
SP SP SP
InP InP
MVNP MVNP MVNP
Fig. 2. Business models of wireless network virtualization. (a) A two-level
model; (b) A four-level model. SP - service providers; MNO - mobile network
operator; MVNO - mobile virtual network operator; MVNP - mobile virtual
network provider; InP - infrastructure provider.
MVNOs (including MVNPs and MVNOs) are the entities
responsible for providing virtual resources to SPs [10], [46].
In the XaaS concept, IaaS can be provided to MVNOs, and
MVNOs can provide NaaS to SPs. However, up to now,
most of the infrastructures and radio resources are owned by
the MNOs who do not want to share too much revenues to
potential MVNPs and MVNOs. Unlike this judgement, some
approaches (e.g., [49]) consider the MVNO as a special SP,
which provides enhanced services to focused customers. In this
situation, both MVNOs and MNOs are in a win-win situation,
since MVNOs help MNOs attract/retain greater number of
customers, and MVNOs may provide services including VoIP,
video telephony, live streaming, etc. [12].
The above business models can also be used for IEEE
802.11-based wireless networks. In commercial cellular net-
works, 802.11-based access technologies can be used as an
efficient supplement to cellular networks for the data traffic in
hot spots. In this case, as part of the whole wireless network,
802.11-based networks can follow the business models dis-
cussed above. In another model with 802.11-based networks,
called “Testbed as a Service” (TaaS) [50], [51], MNO and SPs
may be the equipment providers (administrators) and research
institutions (groups) separately instead of being commercial
entities.
C. Why Need Wireless Network Virtualization?
The motivations for wireless network virtualization range
from academic and industrial research to commercial markets.
In wireless networks, a significant connection between theoret-
ical research and practical implementation is the infrastructure-
based testbed used for identifying and evaluating new tech-
nologies and proposed ideas. Wireless network virtualiza-
tion can support powerful and efficient testbed systems that
can shorten the process of R&D of innovated technologies
in two folds. First, due to the flexibility, programmability
and customization of virtual networks, the proposed new
networking technologies and services can be implemented
in infrastructures for easier and faster evaluation without
considering the complicated interfaces and characteristics of
physical infrastructures. Second, due to the isolation between
virtual networks, multiple experiments can be run and operated
simultaneously, which means, even in the real infrastructure,
experimental functions can be tested and deployed without
disturbing the normal services [14].
In commercial markets, CapEx and OpEx can be lowered
significantly due to the sharing enabled by wireless network
virtualization. The authors of [49] estimate that up to 40%
of $60 billion used for OpEx and CapEx can be saved by
operators worldwide over a five-year period. A very detailed
analysis of OpEx and CapEx in sharing wireless network is
given in [52]. It is estimated that the sharing of sites and
antennas can reduce 20-30% of CapEx, 25-45% of CapEx can
be saved if the whole radio network is shared, and the sharing
of all the assets would decrease CapEx by an additional 10%.
Although OpEx varies largely in different countries, in general,
there is big space to reduce OpEx and CapEx by deploying
network sharing.
Over the past years, MVNOs and over-the-top (OTT) SPs
have become strong players in mobile network markets and
brought their featured services to impact the ecotope of the
traditional market dominated by MNOs. Fortunately, wireless
network virtualization brings a win-win situation for both
MVNOs and MNOs [12]. MVNOs or other types of SPs can
lease virtual networks from MNOs, and MNOs can attract
greater number of customers from MVNOs and SPs. For
MNOs themselves, since the network can be isolated into
several slices, any upgrading and maintenance in one slice
will not affect other running services. For SPs, leasing virtual
networks helps them “get rid of” the control of MNOs, so that
customized and more flexible services can be provided more
easily and the quality of service (QoS) can be enhanced as
well. This also brings impressive revenues to MNOs, because
SPs needs to pay more to the MNOs and reduces the undying
arguments between MNOs and SPs.
D. What are the Requirements of Wireless Network Virtual-
ization?
Wireless network virtualization can be developed based on
a specific business model. There are some requirements that
need to be met to implement wireless network virtualization.
Depending on the scope of virtualization, these requirements
can be classified as basic requirements and additional require-
ments.
1) Basic requirements:
a) Coexistence: In wireless network virtualization, phys-
ical infrastructures should allow that multiple independent
virtual resources coexist on substrate physical networks [46].
Actually, it is clear that the purpose of virtualizing network
is to make multiple systems to run on the same physical
resources.
Moreover, since virtual slices are created according to the
requirements of SPs, they are different among virtual slices.
Virtualization systems have to bear multiple virtual slices
who hold various QoS requirements, topology, services type,
security level, user behaviour, and etc.