IEEE INTERNET OF THINGS JOURNAL, VOL. 5, NO. 4, AUGUST 2018 2633
Energy-Latency Tradeoff for Energy-Aware
Offloading in Mobile Edge Computing Networks
Jiao Zhang, Xiping Hu, Zhaolong Ning , Member, IEEE, Edith C.-H. Ngai , Senior Member, IEEE,
Li Zhou
, Jibo Wei, Jun Cheng, and Bin Hu, Senior Member, IEEE
Abstract—Mobile edge computing (MEC) brings computation
capacity to the edge of mobile networks in close proximity to
smart mobile devices (SMDs) and contributes to energy sav-
ing compared with local computing, but resulting in increased
network load and transmission latency. To investigate the trade-
off between energy consumption and latency, we present an
energy-aware offloading scheme, which jointly optimizes commu-
nication and computation resource allocation under the limited
energy and sensitive latency. In this paper, single and multicell
MEC network scenarios are considered at the same time. The
residual energy of smart devices’ battery is introduced into the
definition of the weighting factor of energy consumption and
latency. In terms of the mixed integer nonlinear problem for
computation offloading and resource allocation, we propose an
iterative search algorithm combining interior penalty function
with D.C. (the difference of two convex functions/sets) program-
ming to find the optimal solution. Numerical results show that
the proposed algorithm can obtain lower total cost (i.e., the
weighted sum of energy consumption and execution latency)
comparing with the baseline algorithms, and the energy-aware
weighting factor is of great significance to maintain the lifetime
of SMDs.
Index Terms—Energy-aware offloading, mobile edge comput-
ing (MEC), resource allocation.
Manuscript received October 1, 2017; revised December 9, 2017;
accepted December 18, 2017. Date of publication December 22, 2017;
date of current version August 9, 2018. This work was supported
in part by the Shenzhen-Hongkong Innovative Project under Grant
SGLH20161212140718841, in part by the Shenzhen Engineering Laboratory
for 3-D Content Generating Technologies under Grant [2017]476, in part
by the Guangdong Technology Project under Grant 2016B010108010, Grant
2016B010125003, and Grant 2017B010110007, in part by the National Basic
Research Program of China (973 Program) under Grant 2014CB744600,
in part by the National Nature Science Foundation of China under
Grant 61403365, Grant 61402458, Grant 61502075, Grant 61632014, Grant
61601482, and Grant 61772508, and in part by the Program of International
S&T Cooperation of MOST under Grant 2013DFA11140. (Corresponding
authors: Xiping Hu; Zhaolong Ning; Li Zhou; Jun Cheng; Bin Hu.)
J. Zhang is with the College of Electronic Science, National University of
Defense Technology, Changsha 410073, China, and also with the Shenzhen
Institutes of Advanced Technology, Chinese Academy of Sciences, Shenzhen
518055, China (e-mail: zhangjiao16@nudt.edu.cn).
X. Hu and J. Cheng are with the Shenzhen Institutes of Advanced
Technology, Chinese Academy of Sciences, Shenzhen 518055, China
(e-mail: xp.hu@siat.ac.cn; jun.cheng@siat.ac.cn).
Z. Ning is with the School of Software, Dalian University of Technology,
Dalian 116620, China (e-mail: zhaolongning@dlut.edu.cn).
E. C.-H. Ngai is with the Department of Information Technology, Uppsala
University, 75105 Uppsala, Sweden (e-mail: edith.ngai@it.uu.se).
L. Zhou and J. Wei are with the College of Electronic Science,
National University of Defense Technology, Changsha 410073, China (e-
mail: zhouli2035@nudt.edu.cn; wjbhw@nudt.edu.cn).
B. Hu is with the School of Information Science and Engineering, Lanzhou
University, Lanzhou, China (e-mail: bh@lzu.edu.cn).
Digital Object Identifier 10.1109/JIOT.2017.2786343
I. INTRODUCTION
S
MART mobile devices (SMDs) are attracting enormous
popularity with the emerging of mobile technologies like
Internet of Things and wearable devices, which can provide
a powerful platform to support some novel mobile applica-
tions (e.g., interaction gaming, face recognition, and natural
language processing [1]–[3]). Such computing-intensive appli-
cations require higher computing capacity and more energy
than traditional applications on SMDs [4]. In general, SMDs
have limited computation resources [e.g., central process unit
(CPU) frequency and memory] and battery lifetime, bringing
in unprecedented challenge to effectively execute these mobile
applications [5]–[7]. Since the cloud sever has higher com-
putation capacity and storage than the SMD, mobile cloud
computing (MCC) is envisioned as a potential approach to
react the challenge via migrating computations from the SMD
to the cloud sever [8], which is referred to as computation
offloading. However, the cloud severs are spatially far from
SMDs, which causes high transmission latency and detains
the latency-sensitive applications.
Mobile edge computing (MEC) [9], [10], as a new archi-
tecture and key technology for 5G networks, relocates the
cloud computation resource close to SMDs. Compared with
MCC, MEC can provide lower latency and computing agility
in computation offloading. However, considering the eco-
nomic and scalable deployment, the computation capacity
of the MEC server is limited. In addition, the computa-
tion offloading especially in the ultra dense networks causes
more interference and results in unexpected transmission
delay [11]. Thus, it is impossible to offload all computa-
tion tasks to the MEC sever, and some of them should be
executed on SMDs (i.e., local computing). Although local
computing consumes more energy, it can significantly mini-
mize the execution latency without additional communication
or waiting delay. Thus, it is critical to make efficient offloading
decision and investigate the tradeoff between energy consump-
tion of SMDs and execution latency of the corresponding
tasks.
In this paper, we propose an energy-aware offloading
scheme to investigate the tradeoff between energy consump-
tion of SMDs and latency of their tasks. The motivations
behind this paper are attributed to the following observations.
1) With the finite computation resources in MEC server
and severe interference among networks, all tasks can-
not be offloaded to the MEC server. The computation
offloading decision should be rationally determined.
2327-4662
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