IEEE Wireless Communications • August 2016
68
1536-1284/16/$25.00 © 2016 IEEE
Guopeng Zhang is with
China University of Min-
ing and Technology.
Kun Yang is with the Uni-
versity of Essex.
Hsiao Hwa Chen is with
National Cheng Kung
University.
AbstrAct
Due to the popularity of mobile user devices,
D2D communications become a key technology
to improve local services in the next generation
cellular networks. However, the benefits count on
efficient radio resource allocation between cellular
links and D2D links, which poses critical challeng-
es. By exploiting the network knowledge extracted
from underlying mobile social networks (MSNs),
this article proposes a socially aware D2D com-
munication scheme to improve the spectrum and
energy efficiency in cellular networks. First, by
jointly considering the social and network knowl-
edge, we propose a cluster formation scheme to
categorize a group of UEs into multiple D2D clus-
ters. Within each cluster, highly spectrum-efficient
D2D multicasting (from the cluster head, i.e., a
D2D transmitter UE to multiple cluster member
UEs) is enabled. Next, a half-duplex scheme and
a full-duplex scheme are proposed to coordinate
the channel sharing between the cellular links and
the D2D links. Simulation results show that the
proposed schemes can form D2D clusters ratio-
nally among a group of UEs, and therefore largely
increase the spectrum and energy efficiency of the
network.
IntroductIon
The explosive popularity of smartphones, tablets,
and other mobile devices has led to a tremen-
dous growth of bandwidth-intensive multimedia
services, such as VoIP, video streaming, and real-
time surveillance. The Cisco Visual Index reports
that mobile video traffic is expected to grow over
26 times from 2010 to 2015 [1]. The continu-
ously increasing demand for wireless access has
strained the capacity of present-day wireless net-
works. In order to improve spectrum and energy
efficiency, thus alleviating the shortage of spec-
trum resources, major efforts have been made
on the development of next-generation wireless
networks, such as Third Generation Partnership
Project (3GPP) Long Term Evolution-Advanced
(LTE-A). One of the main concerns of the devel-
opments is to largely improve local services [2].
d2d use cAse And MAIn chAllenges
In conventional cellular networks, user traf-
fic should be routed via core networks even if
a transmitter and a receiver are geographical-
ly close to each other. A recently developed
technology component for LTE-A, referred to
as device-to-device (D2D) communication [3],
allows nearby user equipments (UEs) to commu-
nicate with each other directly under the control
of cellular network operators. The high channel
quality of short-range D2D links facilitates a high
data rate for local services, prolongs UEs’ battery
lives, and offloads heavy traffic of cellular base
stations (BSs).
D2D and cellular links can share the licensed
bands by using a non-orthogonal or an orthog-
onal method [4]. The non-orthogonal method
allows D2D links to underlay cellular links by
reusing the same frequency band. The spectrum
efficiency can be improved significantly, but the
transmit powers at the co-channel D2D and cel-
lular transmitters should be well coordinated to
avoid generating harmful interference. In con-
trast, the orthogonal method allocates dedicated
spectrum resources to D2D links, thus allowing
D2D links to overlay cellular links. It therefore
eases the task of interference management, but
the spectrum efficiency is always lower than that
of the non-orthogonal methods.
In D2D-enabled cellular networks, the choice of
cellular communication mode or D2D communica-
tion mode defines the mode selection problem for
UEs. Before mode selection, a UE needs to iden-
tify nearby UEs as D2D candidates, and recognize
their potential service. Both operations are accom-
plished through a peer discovery procedure. After
mode selection, the network operator needs to allo-
cate the radio resource such as frequency bands,
time slots, and transmit powers to the cellular and
D2D links accordingly. These problems of neighbor
UE discovery, communication mode selection, and
wireless resource allocation are intertwined with
each other, and are always coupled with user-level
behaviors and network-level loading and channel
conditions, hence bringing forth new challenges for
LTE-A cellular networks.
GuopenG ZhanG, Kun YanG, and hsiao-hwa Chen
Socially aware cluSter Formation and
r
adio reSource allocation in
d2d networkS
d e v i c e - t o - d e v i c e c o m m u n i c a t i o n S w i t h
S o c i a l a w a r e n e S S