File downloading oriented Roadside Units deployment for vehicular
networks
q
Yazhi Liu
a,c
, Jianwei Niu
b,
⇑
, Jian Ma
c
, Wendong Wang
c
a
College of Information Engineering, Hebei United University, Tangshan 063000, China
b
State Key Laboratory of Software Development Environment, Beihang University, Beijing 100191, China
c
State Key Laboratory of Networking and Switching Technology, Beijing University of Posts and Telecommunications, Beijing 100876, China
article info
Article history:
Available online 7 May 2013
Keywords:
VANETs
File downloading
Roadside unit deployment
abstract
Vehicular Ad hoc Networks (VANETs) have been recently introduced to provide high-speed Internet
access to vehicles by deploying 802.11 enhanced Roadside Units (RSUs) along roads. However, few file
downloading oriented RSU deployment strategies have been proposed. In this paper, we propose a
new RSU deployment strategy for file downloading in VANETs. The encounters between vehicles and
RSUs are modeled as a time continuous homogeneous Markov chain. The optimal inter-meeting time
between vehicles and RSUs is analyzed based on the encounter model. Then, the road network is modeled
as a weighted undirected graph, and a RSU deployment algorithm is designed based on the depth-first
traversal algorithm for edges of a graph. Simulation results show that the proposed RSU deployment algo-
rithm can satisfy the file downloading service requirements with the lowest RSU deployment cost.
Ó 2013 Elsevier B.V. All rights reserved.
1. Introduction
Since the urban sprawls, cities around the world are expanding
on a massive scale. The resulting increased traffic congestion leads
people spend more time in vehicles [1]. A recent report shows that
drivers or passengers spend considerable time in vehicles. In Eur-
ope, the average time spent is 274 h per person per year, while it
is up to 541 h in America. On the other hand, with the emergence
of various mobile internet applications and social network services,
people want to access the rich-media contents on the Internet at
anytime from anywhere. Although people can use GPRS or 3G to
access the Internet in mobile vehicles, these internet access tech-
niques suffer from low bandwidth, high cost and long delay.
802.11 based Vehicular Networks (VANETs) can provide mobile
vehicles with high-speed and low-cost Internet access services [2–
5]. VANET is a kind of mobile ad hoc networks with infrastructures
called Roadside Units (RSUs) [6]. In VANETs, mobile vehicles and
static RSUs are connected by short range wireless communication
interfaces (e.g., 802.11 b, g, p). Messages in VANETs are forwarded
between vehicles hop by hop or delivered between vehicles and
RSUs. Ott et al. [2] proposed the drive through network infrastruc-
ture for VANETs based on 802.11b, by which vehicles can access
the Internet through RSUs deployed along roads, and this kind of
network infrastructure is also recognized as the Vehicle to Road-
side Unit (V2R) communication network infrastructure. With the
V2R infrastructure, a vehicle traveling at 80 km/h can communi-
cate with a RSU within 500 m and download 9 MB data. Thus,
V2R communication is a technique with a high potential to provide
low-cost and high-speed media file downloading services for
vehicles.
However, there are few VANET infrastructures deployed re-
cently which impedes the development of VANETs. How to deploy
VANET infrastructures with low cost to satisfy the application re-
quired network quality of service is an important issue to tackle
in the further development of VANETs. Since vehicles move fast,
the connection between vehicles and RSUs suffers from short peri-
ods and frequent disconnections. As a result, a mobile vehicle can
hardly download a whole media file from a single RSU. Therefore,
in VANETs files are always downloaded by means of file fragmen-
tation[7,8]. In other words, when a mobile vehicle encounters a
RSU, it downloads a piece of the required file, until all of the pieces
of the required file are downloaded [9–11].
V2R based file downloading will be affected by the deployment
of RSUs, the travel path of vehicles, and the road traffic conditions.
Recently, some RSU deployment strategies have been proposed for
different purposes. Abdrabou et al. [12] investigated the RSU
deployment strategy for the vehicle sensed data uploading in the
highway scenario. Zheng et al. [13] designed a RSU deployment
strategy to ensure that vehicles can encounter RSUs within
restricted distance. However, it is still to be studied that how to
1383-7621/$ - see front matter Ó 2013 Elsevier B.V. All rights reserved.
http://dx.doi.org/10.1016/j.sysarc.2013.04.007
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This work was supported by the Research Fund of the State Key Laboratory of
Software Development Environment under Grant No. BUAA SKLSDE-2012ZX-17, the
National Natural Science Foundation of China under Grant No. 61190125 &
61170296 & 61271041, the Program for New Century Excellent Talents in
University under Grant No. NECT-09-0028.
⇑
Corresponding author. Tel.: +86 13801164109.
E-mail address: niujianwei@buaa.edu.cn (J. Niu).
Journal of Systems Architecture 59 (2013) 938–946
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