IEEE Communications Magazine - June 2017 - page 164

IEEE Communications Magazine • June 2017
162
0163-6804/17/$25.00 © 2017 IEEE
A
bstract
The provision of very high capacity is one of
the big challenges of the 5G cellular technology.
This challenge will not be met using traditional
approaches like increasing spectral efficiency and
bandwidth, as witnessed in previous technology
generations. Cell densification will play a major
role thanks to its ability to increase the spatial
reuse of the available resources. However, this
solution is accompanied by some additional man-
agement challenges. In this article, we analyze
and present the most promising solutions iden-
tified in the METIS project for the most relevant
network layer challenges of cell densification:
resource, interference and mobility management.
I
ntroduction
Network densification manifesting in deployments
of small cells (SCs) is an ongoing trend in con-
temporary cellular networks. Although SCs were
already commercially available for the 2G and 3G
technologies, the LTE and LTE-Advanced (LTE-A)
standards provide technical solutions that exploit
the local nature of such deployments. SCs are
well suited for handling large traffic demands in
hotspot areas with noticeable proliferation over
the last years of high-end devices capable of pro-
cessing data-heavy content (e.g., high definition
video). Moreover, people expect to have a broad-
band experience not only at home or office, but
also outdoors. These two trends combined create
a massive upsurge of cellular traffic, often referred
to as the 1000
traffic volume challenge [1]. The
next generation of cellular technology, fifth gener-
ation (5G), is expected to provide an economical-
ly justified system that will cater for this massive
demand and extravagant user requirements.
The performance of modern cellular networks,
mainly limited by the radio access network, is usu-
ally enhanced through solutions aimed at improv-
ing spectral efficiency, such as advanced antenna
techniques (including the use of massive numbers
of antennas) and endeavors of the cellular indus-
try to obtain more spectrum for wireless transmis-
sion in low and high frequency bands [1]. Despite
technical challenges, this way forward is definite-
ly a promising direction to improve capacity of
future 5G networks, but without a doubt, they will
not be sufficient to provide a ubiquitous high-end
user experience for the 2020-and-beyond mobile
society. As proven in contemporary cellular net-
works, in order to satisfy growing user demands,
improved spectral efficiency should be accom-
panied by further cell densification, especially in
dense urban areas and indoors. Massive rollout
of SCs immediately poses a question on its eco-
nomic feasibility. SC solutions available today rely
on methods such as distributed antenna systems,
unlicensed spectrum, and user-deployed SCs in
order to bring down the deployment costs. SCs
can also be extended to moving relays or nomad-
ic cells where antenna systems exploiting wireless
backhaul are mounted on cars, buses, and trains
in order to provide a broadband experience to
users inside or in proximity of vehicles.
The above-mentioned factors suggest that fur-
ther deployment densification, resulting in ultra-
dense networks (UDNs), is inevitable, which has
interesting consequences for future network
operations. Shrunken cell sizes lead to reduced
numbers of users served simultaneously by indi-
vidual SCs over a geographical area, and hence
to sharing the radio resources among fewer users.
Moreover, smaller user-to-access-node distances
decrease the probability of severe shadowing.
This factor plays a major role in wave propaga-
tion at higher frequencies, which are interesting
due to the availability of large bandwidths. Higher
frequencies are a perfect fit for UDNs since, par-
adoxically, their higher attenuation limits the inter-
ference to neighboring sites and users. On the
other hand, fewer users per cell leads to a more
bursty activity profile of SCs. In combination with
the time-division duplexing (TDD) mode, which is
expected to be extensively used in 5G due to its
capability to adapt to dynamic traffic demands,
this will pose a significant challenge to future 5G
resource allocation schemes. It is still an open
question to what extent advanced receivers and
transmission schemes will be able to cope with
the dynamic interference [2]. Another challenge
Resource and Mobility Management in the
Network Layer of 5G Cellular
Ultra-Dense Networks
Daniel Calabuig, Sokratis Barmpounakis, Sonia Giménez, Apostolos Kousaridas, Tilak R. Lakshmana, Javier Lorca, Petteri Lundén, Zhe Ren,
Pawel Sroka, Emmanuel Ternon, Venkatkumar Venkatasubramanian, and Michal Maternia
R
adio
C
ommunications
The provision of very
high capacity is one of
the big challenges of the
5G cellular technology.
This challenge will not
be met using traditional
approaches. Cell densi-
fication will play a major
role thanks to its ability to
increase the spatial reuse
of the available resources.
However, this solution is
accompanied by some
additional management
challenges. The authors
analyze and present
the most promising
solutions identified in
the METIS project for the
most relevant network
layer challenges of cell
densification: resource,
interference and mobility
management.
Daniel Calabuig and Sonia Giménez are with Universitat Politècnica de València; Sokratis Barmpounakis and Apostolos Kousaridas are with
National and Kapodistrian University of Athens; Tilak R. Lakshmana is with Chalmers University of Technology; Javier Lorca is with Telefónica I+D;
Petteri Lundén, Venkatkumar Venkatasubramanian, and Michał Maternia are with Nokia Networks;
Zhe Ren is with BMW Forschung und Technik; Paweł Sroka is with Poznan University of Technology;
Emmanuel Ternon is with DoCoMo Communications Laboratories Europe GmbH.
Digital Object Identifier:
10.1109/MCOM.2017.1600293
1...,154,155,156,157,158,159,160,161,162,163 165,166,167,168,169,170,171,172,173,174,...228
Powered by FlippingBook