IEEE COMMUNICATION SURVEYS & TUTORIALS, VOL. 17, NO. 4, FOURTH QUARTER 2015 1923
Device-to-Device Communication in LTE-Advanced
Networks: A Survey
Jiajia Liu, Member, IEEE,NeiKato,Fellow, IEEE, Jianfeng Ma, and Naoto Kadowaki, Member, IEEE
Abstract—Among the LTE-A communication techniques,
Device-to-Device (D2D) communication which is defined to
directly route data traffic between spatially closely located mobile
user equipments (UEs), holds great promise in improving energy
efficiency, throughput, delay, as well as spectrum efficiency. As a
combination of ad-hoc and centralized communication mecha-
nisms, D2D communication enables researchers to merge together
the long-term development achievements in previously disjoint
domains of ad-hoc networking and centralized networking. To
help researchers to have a systematic understanding of the
emerging D2D communication, we provide in this paper a
comprehensive survey of available D2D related research works
ranging from technical papers to experimental prototypes to
standard activities, and outline some open research problems
which deserve further studies.
Index Terms—Device-to-device communication, LTE-A, small
cells, heterogeneous networks.
I. INTRODUCTION
T
HE last decade has witnessed an unprecedented growth
in both the amount of mobile broadband traffic and the
user demand for faster data access. According to the latest
Cisco visual networking index [1], the traffic amount of global
mobile data grew 81 percent and the mobile network connection
speeds more than doubled in 2013. What’s more, smartphones
representing only 27 percent of total global handsets in use,
generated 95 percent of data traffic. Such massive consumer de-
mand for mobile data access has been pushing communication
engineers to seek for new cellular architectures and paradigms
to squeeze the last bit out of the limited f requency resources.
Considering the current 4 G technologies cannot fulfill the
huge gap between the actual communication performances and
the forthcoming user expectations, Third Generation Partner-
ship Project (3 GPP) has been developing an enhanced Long-
Term Evolution (LTE) radio interface called LTE-Advanced
(LTE-A). LTE-A radio interface is designed with a lot of ad-
vanced communication techniques such as carrier aggregation,
Manuscript received April 24, 2014; revised September 26, 2014; accepted
November 21, 2014. Date of publication December 2, 2014; date of current
version November 18, 2015. This work was partially supported by the National
Natural Science Foundation of China under grants 61372073, 61373043 and
61202394, and by the Key Program of NSFC-Guangdong Union Foundation
U1135002.
J. Liu and J. Ma are with the State Key Laboratory of Integrated Services
Networks, School of Computer Science and Technology, Xidian University,
Xi’an, 710071, China (e-mail: liujiajia@xidian.edu.cn).
N. Kato is with the Graduate School of Information Sciences, Tohoku
University, Sendai, 980-8579, Japan (e-mail: kato@it.ecei.tohoku.ac.jp).
N. Kadowaki is with the National Institute of Information and Communica-
tions Technology (NICT), Tokyo, 184-8795, Japan (e-mail: naoto@nict.go.jp).
Digital Object Identifier 10.1109/COMST.2014.2375934
massive multiple-input multiple-output (MIMO), millimeter
waves, low-power nodes (LPNs, e.g., pico eNBs, femto eNBs,
and relays), as well as D2D communication, which are believed
to be able to significantly enhance the current 4 G cellular
technologies in terms of system capacity, coverage, peak rates,
throughput, latency, user experience, etc. The requirement of
combining such a variety of technologies to operate together
in a seamless fashion, brings about the necessity of supporting
a LTE-A heterogeneous network (HetNet) deployment, which
typically consists of a variety of radio access technologies (e.g.,
LTE, HSPA, Wi-Fi, CDMA2000, etc.), multiple formats of cells
(i.e., mutli-tier cells) with different cell sizes and power levels,
various backhaul technologies, and many other aspects.
Among these LTE-A techniques, D2D communication is de-
fined to directly route data traffic between spatially closely lo-
cated mobile UEs. With D2D communication, the data between
a UE pair does not need to traverse through the eNB (abbrevi-
ation for evolved Node B or eNodeB, the evolution of the ele-
ment Node B in UTRA of UMTS) or the core network as long
as they are in proximity. Due to the short communication range
between a D2D pair, D2D communication holds great promise
in improving energy efficiency, throughput, delay, as well as
spectrum efficiency. The applications of D2D communication
include content sharing (e.g., videos and pictures), gaming,
connectivity extension, traffic offloading, disaster relief, etc.
Basically, D2D communication is a very flexible communi-
cation technique with unique advantages compared to available
communication techniques. In particular, a mobile UE may
have multiple radio access technologies simultaneously em-
bedded, given t he development trend of its processing power
and computation ability. For example, most of today’s mobile
phones support three radio access technologies, i.e., cellular (3 G
or 4 G), Wi-Fi, Bluetooth. The diversity of radio accessing in
mobile UEs provides for D2D communication lots of flexibility
in the aspects of link establishment, resource allocation, energy
efficiency, as well as applications and services. Fig. 1 illustrates
an example of D2D communications among multi-tier cells in
LTE-A HetNets, where the D2D pairs may exist in the same cell
or stretch over different cells, may communicate as an underlay
or overlay to the existing LTE-A network, or even operate in
industrial, scientific and medical (ISM) band or unused band.
As a combination (or mixture) of ad-hoc and centralized
communications, D2D communication enables communication
engineers and researchers to merge together the achievements
of long-term development in previously disjoint networking
techniques, i.e., ad-hoc networking and centralized networking.
D2D pairs may form clusters or multi-hop routes, and may
operate autonomously or under partial or full control of the
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