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1553-877X (c) 2013 IEEE. Personal use is permitted, but republication/redistribution requires IEEE permission. See
http://www.ieee.org/publications_standards/publications/rights/index.html for more information.
This article has been accepted for publication in a future issue of this journal, but has not been fully edited. Content may change prior to final publication. Citation information: DOI
10.1109/COMST.2014.2352118, IEEE Communications Surveys & Tutorials
1
Wireless Network Virtualization: A Survey, Some
Research Issues and Challenges
Chengchao Liang and F. Richard Yu
∗
Depart. of Systems and Computer Eng., Carleton University, Ottawa, ON, Canada
Email: chengchaoliang@sce.carleton.ca; richard.yu@carleton.ca
Abstract—Since wireless network virtualization enables ab-
straction and sharing of infrastructure and radio spectrum
resources, the overall expenses of wireless network deployment
and operation can be reduced significantly. Moreover, wireless
network virtualization can provide easier migration to newer
products or technologies by isolating part of the network.
Despite the potential vision of wireless network virtualization,
several significant research challenges remain to be addressed
before widespread deployment of wireless network virtualiza-
tion, including isolation, control signaling, resource discovery
and allocation, mobility management, network management and
operation, and security as well as non-technical issues such as
governance regulations, etc. In this paper, we provide a brief
survey on some of the works that have already been done
to achieve wireless network virtualization, and discuss some
research issues and challenges. We identify several important
aspects of wireless network virtualization: overview, motivations,
framework, performance metrics, enabling technologies, and
challenges. Finally, we explore some broader perspectives in
realizing wireless network virtualization.
Index Terms—Wireless network virtualization, abstraction and
sharing, isolation, cognitive radio and networks, cloud computing.
I. INTRODUCTION
In the information and communications technology (ICT)
sector, virtualization has become a popular concept in dif-
ferent areas, e.g., virtual memory [1], virtual machines [2],
virtual storage access network [3] and virtual data centers [4].
Virtualization involves abstraction and sharing of resources
among different parties. With virtualization, the overall cost of
equipment and management can be significantly reduced due
to the increased hardware utilization, decoupled functionalities
from infrastructure, easier migration to newer services and
products, and flexible management [1]–[4].
In wired networks, virtualization has occurred for decades,
e.g., virtual private networks (VPNs) over wide area networks
(WANs) and virtual local area networks (VLANs) in enterprise
networks [5], [6]. Recently, network virtualization has been ac-
tively used in Internet research testbeds, such as G-Lab [7] and
4WARD [8], and applied in the cloud computing environment
[9]. It aims to overcome the resistance of the current Internet to
fundamental architecture changes. Network virtualization has
been considered as one of the most promising technologies
for the future Internet [10].
With the tremendous growth in wireless traffic and services,
it is natural to extend virtualization to wireless networks.
With wireless network virtualization, network infrastructure
can be decoupled from the services that it provides, where
differentiated services can coexist on the same infrastructure,
maximizing its utilization [11]. Consequently, multiple wire-
less virtual networks operated by different service providers
(SPs) can dynamically share the physical substrate wireless
networks operated by mobile network operators (MNOs).
Since wireless network virtualization enables the sharing of in-
frastructure and radio spectrum resources, the capital expenses
(CapEx) and operation expenses (OpEx) of wireless (radio)
access networks (RANs), as well as core networks (CNs),
can be reduced significantly. Moreover, mobile virtual network
operators (MVNOs) who may provide some specific telecom
services (e.g., VoIP, video call, over-the-top services) can help
MNOs attract more users, while MNOs can produce more
revenue by leasing the isolated virtualized networks to them
and evaluating some new services [12]. Meanwhile, wireless
network virtualization provides easier migration to newer
products or technologies while supporting legacy products
by isolating part of the network [12], [13]. In addition, the
emerging heterogeneous wireless networks need a convergent
and powerful network management mechanism, which can be
provided by wireless network virtualization [14].
Despite the potential vision of wireless network virtual-
ization, several significant research challenges remain to be
addressed before widespread deployment of wireless network
virtualization, including isolation, control signaling, resource
discovery and allocation, mobility management, network man-
agement and operation, and security as well as non-technical
issues such as governance regulations, etc. Particularly, unlike
wired networks, where bandwidth resource abstraction and
isolation can be done on a hardware (e.g., port and link)
basis, radio resource abstraction and isolation is not straight-
forward, due to the inherent broadcast nature of wireless
communications and stochastic fluctuation of wireless channel
quality. Another significant challenge of wireless network
virtualization is resource allocation, which decides how to
embed a virtual wireless network on physical networks. In
addition, a large number of intelligent devices/nodes with self
adaptation/context awareness capabilities induce non-trivial
security challenges to wireless network virtualization. These
challenges need to be tackled broadly by comprehensive
research effort.
In this paper, we provide a brief survey on some of
the works that have already been done to achieve wireless
network virtualization, and discuss some research issues and
challenges. A taxonomy graph of our approach towards the
1553-877X (c) 2013 IEEE. Personal use is permitted, but republication/redistribution requires IEEE permission. See
http://www.ieee.org/publications_standards/publications/rights/index.html for more information.
This article has been accepted for publication in a future issue of this journal, but has not been fully edited. Content may change prior to final publication. Citation information: DOI
10.1109/COMST.2014.2352118, IEEE Communications Surveys & Tutorials
2
Motivations
Wireless Network
Virtualization
Business Models
Requirements
Overview
Brief History
SDN and OpenFlow
Projects
Performance Metrics
Traditional Me trics
Virtualization-Specific Metrics
Framework
Radio Spectrum Resource
Wi rele ss Ne twork I n frastructure
Wireless Virtual Resource
Enabling Technologies
IEEE 802.11-based
Cellular-based
IEEE 802.16-based
Challenges
Isolation
Control Signaling
Resour c e Dis covery and
Allocation
Mo bi lity Manage me nt
Wireless Virtualization
Controller
Others
Network Management
Security
Broader Perspectives
Cognitive Radio and Networks
Multi-tier Wireless Networks
Cloud Computing
Fig. 1. Road map of wireless network virtualization.
design of wireless network virtualization is given in Fig. 1.
As shown in the figure, we identify seven important aspects
of wireless network virtualization where we would like to fo-
cus: overview, motivations, framework, performance metrics,
enabling technologies, challenges, and broader perspectives.
In the following sections, we elaborate on each such aspect
and discuss the related issues. Section II presents a brief
history of wired network virtualization. Then some projects
on network virtualization are introduced. Software defined
networking and OpenFlow are also presented. In Section
III, we will present the business models and the involved
parties. The motivations and requirements of wireless network
virtualization are also discussed. A framework is summarized
in Section IV with four main components: radio spectrum
resource, wireless network infrastructure, wireless virtual re-
source, and wireless virtualization control. Section V presents
some performance metrics that are necessary to evaluate the
performance and quality of a virtualized wireless networks.
Some enabling technologies for wireless network virtualization
are discussed in Section VI according to different radio access
technologies. Section VII presents research issues and chal-
lenges. Some broader perspectives are also presented. Finally,
we conclude this study in Section VIII.
II. O
VERVIEW OF NETWORK VIRTUALIZATION
In this section, we first present a brief history of wired
network virtualization. Then, some projects on network vir-
tualization are presented. Software defined networking (SDN)
and OpenFlow are also introduced in this section.
A. Brief History of Wired Network Virtualization
Virtualization has occurred in wired networks for decades.
Some examples of wired network virtualization include vir-
tual local area networks (VLANs), virtual private networks
(VPNs), active and programmable networks, and overlay net-
works, which are described in the following.
1) VLAN: A VLAN refers to a domain where a group
of hosts with a common interest are allowed to be logically
brought together under a single broadcast domain regardless
of their physical connectivity [15].
2) VPN: In a VPN, a private network, whose hosts are
distributed in multiple sites, connects through private and
secured tunnels (links) over public communication networks
(e.g., the Internet or PSDN) [16]–[18]. Depended on different
layers, VPNs can be classified into four classes: Layer 1
VPNs [19], Layer 2 VPNs [20], Layer 3 VPNs [21] and
higher layer VPNs [22]. It should be noted that Layer 1 VPNs
have no guarantee between data plane connectivity and control
1553-877X (c) 2013 IEEE. Personal use is permitted, but republication/redistribution requires IEEE permission. See
http://www.ieee.org/publications_standards/publications/rights/index.html for more information.
This article has been accepted for publication in a future issue of this journal, but has not been fully edited. Content may change prior to final publication. Citation information: DOI
10.1109/COMST.2014.2352118, IEEE Communications Surveys & Tutorials
3
plane connectivity, which means that each service network has
independent address space and L1 resource view, separating
policies and completing isolation from other VPNs. This is the
main difference between Layer 1 VPNs and Layer 2/3 VPNs.
3) Active and programmable networks: In response to
user demands, the need of creating, deploying, and manag-
ing novel services on the fly drives the research of active
and programmable networks. The fundamental discussion of
programmable networks is that separating communications
hardware from control software and allowing multiple parties
to run possibly totally different protocols on the same network
elements without any conflict. The open signaling approach
and the active networks approach are the two kinds of imple-
mentations of active and programmable networks [23].
4) Overlay network: A virtual network that creates a virtual
topology based on the physical topology of another network
can be considered as an overlay network where nodes are
connected through virtual links, which correspond to paths in
the underlying network. Overlays are typically implemented
in the application layer [6].
In the above four examples of wired network virtualization,
the scope of virtualization is limited to one or two layers.
However, to exploit the full benefits of virtualization, the
network needs to be fully virtualized, and services are clearly
separated from their underlying infrastructure.
B. Projects on Network Virtualization
Recently, several research projects have been started around
the world in the area of network virtualization, including X-
Bone [24] and Tempes [25] focusing on networking technol-
ogy; UCLP [26], VNET [27], AGAVE [28] and VIOLIN [29]
focusing on layers of virtualization; VNRMS [30], NetScript
[31], Genesis [32] and FEDERICA [33] focusing on archi-
tectural domain and management; and PlanetLab [34], GENI
[35], VINI [36], CABO [37], 4WARD [8] and NouVeau [38]
focusing on the granularity of virtualization; and VITRO [39]
focusing on virtualization of wireless sensor networks. Due
to the space limitation, we only give a brief introduction to
CABO, GENI, 4WARD and PlanetLab, which are important
projects on network virtualization.
1) CABO: In CABO, the concept of separation between
infrastructure providers (InPs) and SPs is promoted and im-
proved by an integrated project to support full virtualization
that allows SPs to provide end-to-end services over multiple
InPs’ infrastructure. CABO is also the first full virtualization
project in which virtual routers can move (are mapped) from
one physical node to another. It also provides guarantees
and customization to service providers to support end-to-end
services to the end users.
2) 4WARD: In 4WARD, more detailed business models
are introduced in addition to InPs and SPs, including vir-
tual network providers (VNPs) and virtual network operators
(VNOs). This business model gives more opportunities to
the market. The project also includes substantial work on
resource allocation and resource discovery of network virtu-
alization. Moreover, 4WARD also supports virtualization of
heterogeneous networking technologies. Another significant
contribution is that 4WARD implements network virtualization
not only in experimental networks and testbeds but also in
realistic networks.
3) PlanetLab: PlanetLab proposes a concept of slice-
ability, in which each application acquires and runs in a
slice of the overlay. Slice-ability is a crucial ability and
design principle in network virtualization, which dominates the
realization of both wired and wireless network virtualization.
4) GENI: GENI introduces network virtualization to the
wireless area. In GENI, virtualization techniques and slicing
techniques are proposed by utilizing TDMA, FDMA and
SDMA. Moreover, GENI gives researchers the opportunity to
create customized virtual networks unfettered by assumptions
or requirements of the existing Internet.
5) VITRO: VITRO proposes an integrated architecture of
enabling virtualization in wireless sensor networks while pro-
viding advanced services. The approach in VITRO realizes
the decoupling of the applications running on physical nodes
from the physical sensor deployment. This concept of virtual
sensor networking allows the dynamic cooperation among
sensor nodes, helping the proliferation of new services and
applications beyond the scope of the original deployment.
C. Software Defined Networking and OpenFlow
SDN is an emerging network architecture where network
control is decoupled from forwarding and is directly pro-
grammable [40]. It is considered as one of the most promising
technologies to realize virtual networks, especially in network
control. SDN focuses on four key features [41]:
• Separation of the control plane from the data plane.
• A centralized controller and view of the network.
• Open interfaces between the devices in the control plane
(controllers) and those in the data plane.
• Programmability of the network by external applications.
By separating a network’s control logic from the underlying
physical routers and switches that forward traffic, network
operators can write high-level control programs that specify
the behavior of an entire network. This is different from
conventional networks, where network operators must codify
functionalities in terms of low-level device configurations.
SDN allows network administrators to have programmable
central control of network traffic via a controller without
requiring physical access to the network’s switches. A configu-
ration of SDN can create a logical network control plane where
hardware is physically decoupled from the data forwarding
plane hardware, i.e., a network switch can forward packets
and a separate server can run the network control plane. The
decoupling allows for the control plane to be implemented
using a different distribution model than the data plane.
Control plane development and runtime environment tasks can
then be run on a different platform (other than the low-powered
management CPUs found on hardware switches and routers).
OpenFlow is a standard communications interface defined
between the control and forwarding layers of an SDN archi-
tecture [42]. The standard is managed by Open Networking
Foundation (ONF). OpenFlow allows direct access to and
manipulation of the forwarding plane of network devices, such
1553-877X (c) 2013 IEEE. Personal use is permitted, but republication/redistribution requires IEEE permission. See
http://www.ieee.org/publications_standards/publications/rights/index.html for more information.
This article has been accepted for publication in a future issue of this journal, but has not been fully edited. Content may change prior to final publication. Citation information: DOI
10.1109/COMST.2014.2352118, IEEE Communications Surveys & Tutorials
4
as switches and routers. With OpenFlow, the path of network
packets through the network of switches can be determined by
software running on multiple routers. A number of network
switch and router vendors have announced intent to support
OpenFlow standard.
III. M
OTIVATIONS,BUSINESS MODELS &REQUIREMENTS
OF
WIRELESS NETWORK VIRTUALIZATION
In this section, we will discuss the motivations of wireless
network virtualization. Business models with different roles in
the wireless network market and the functions of these roles
will be presented. Moreover, we will discuss the requirements
that need to be met to implement wireless network virtualiza-
tion.
A. What is Wireless Network Virtualization?
Wireless network virtualization can have a very broad scope
ranging from spectrum sharing, infrastructure virtualization, to
air interface virtualization. Similar to wired network virtual-
ization, in which physical infrastructure owned by one or more
providers can be shared among multiple service providers,
wireless network virtualization needs the physical wireless
infrastructure and radio resources to be abstracted and isolated
to a number of virtual resources, which then can be offered
to different service providers. In other words, virtualization,
regardless of wired or wireless networks, can be considered
as a process splitting the entire network system [13]. However,
the distinctive properties of the wireless environment, in terms
of time-various channels, attenuation, mobility, broadcast, etc.,
make the problem more complicated. Furthermore, wireless
network virtualization depends on specific access technologies,
and wireless network contains much more access technologies
compared to wired network virtualization and each access
technology has its particular characteristics, which makes
convergence, sharing and abstraction difficult to achieve.
Therefore, it may be inaccurate to consider wireless network
virtualization as a subset of network virtualization [11].
In this paper, we consider wireless network virtualization as
the technologies in which physical wireless network infrastruc-
ture resources and physical radio resources can be abstracted
and sliced into virtual wireless network resources holding
certain corresponding functionalities, and shared by multiple
parties through isolating each other. In other words, virtualiz-
ing wireless network is to realize the process of abstracting,
slicing, isolating and sharing the wireless networks. Since
wireless network resources are sliced into multiple slices, the
terms of virtual slice and virtual network have the similar
meanings of virtual wireless network resources. We may use
them alternatively in this paper
B. What are the Business Models of Wireless Network Virtu-
alization?
In wireless network virtualization, physical resources are
owned by some parties, and virtual resources are utilized by
some other parties. The question is who these parties are.
Business models can describe the constitution of the roles in
the wireless network market and the main functions of these
roles. As shown in Fig. 2(a), generally, after wireless network
virtualization, there are two logical roles, MNO and SP [12],
[37], [43]. All of the infrastructures and radio resources of
physical substrate wireless networks, including the licensed
spectrum, radio access networks (RANs), backhaul, transmis-
sion networks (TNs), and core networks (CNs), are owned and
operated by MNOs. MNOs execute the virtualization of the
physical substrate networks into some virtual wireless network
resources. For brevity, we use virtual resources to indicate
the virtual wireless network resources. SPs lease these virtual
resources, operate and program them so that to offer end-to-
end services to end users. In some papers (e.g., [5]), the MNO
becomes InP, which is only responsible for owing and leasing
wireless network resources to SPs. SPs will create and deploy
the virtual resource by themselves based on the leased and
allocated resource to satisfy the requirements of end-to-end
services.
The roles in in the above business models can be further
decoupled into more specialized roles, including InP, mobile
virtual network provider (MVNP), mobile virtual network
operator (MVNO) and SP [44]–[46], as shown in Fig. 2(b).
The functions of them are describing as follows.
a) InP: owns the infrastructure and wireless network
resources. In some cases, the spectrum resources may or may
not be owned by InP.
b) MVNP: leases the network resources and creates
virtual resources. Some MVNPs may have some licensed spec-
trum such that they do not need request spectrum resources
from InP. In some papers (e.g., [47]), MVNP is called mobile
virtual network enabler (MVNE).
c) MVNO: operates and assigns the virtual resources to
SPs. Meanwhile, in some approaches, MVNOs consists of
the roles of both MVNOs and MVNPs. Actually, this model
is fit for the emerging concept of so called XaaS [48] in
cloud computing. What provided in InPs is infrastructure-as-
a-service (IaaS) while what provided in MVNOs is network-
as-a-service (NaaS).
d) SP: concentrates on providing services to its sub-
scribers based on the virtual resources provided by MVNOs.
In other words, virtual resources are requested by SPs,
managed by MVNOs, created by MVNPs, and running at InPs
physically. Obviously, this four-level model can create more
opportunities in the market and simplify the functions of each
role intuitively. Nevertheless, more coordination mechanisms
and interfaces should be used, which may increase the com-
plexity and latency significantly.
Here, we give a short discussion on the role of MVNOs.
The definition of MVNOs is different in different countries
and communities [47]. The authors of [13] argue that MVNOs
do not own any spectrum and radio access networks for its
subscribers to access. However, in [47], MVNOs may or may
not own infrastructure, or may only own other parts of wireless
networks (e.g., CNs) except RANs and spectrum licenses. The
authors of [47] consider that MVNOs are the key players
who can break the value chain of telecommunications both
wired and wireless in the future mobile network markets. This
claim is based on the existence of pure InPs, which means
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