Approaching Reliable Realtime Communications? A
Novel System Design and Implementation for
Roadway Safety Oriented Vehicular
Communications
Kai Xing
∗
, Tianbo Gu
∗
, Zhengang Zhao
∗
, Lei Shi
†
, Yunhao Liu
‡
,
Pengfei Hu
∗
, Yuepeng Wang
∗
, Yi Liang
∗
Shuo Zhang
∗
Yang Wang
∗
, Liusheng Huang
∗
,
∗
University of Science and Technology of China, Anhui, China 230027
Email: {kxing,gavin,angyan,lshuang}@ustc.edu.cn,
{tbgu,pfh, wangyuep,yiliang,zshuo}@mail.ustc.edu.cn
†
Hefei University of Technology, Anhui, China 230009
Email: thunder10@163.com
‡
Tsinghua University, Beijing, China 100084
Email: yunhao@greenorbs.com
Abstract—Though there exist ready-made DSRC/WiFi/3G/4G
cellular systems for roadway communications, there are common
defects in these systems for roadway safety oriented applications
and the corresponding challenges remain unsolved for years, i.e.,
WiFi cannot work well in vehicular networks due to the high
probability of packet loss caused by burst communications, which
is a common phenomenon in roadway networks; 3G/4G cannot
well support real-time communications due to the nature of their
designs; DSRC lacks the support to roadway safety oriented
applications with hard realtime and reliability requirements [1].
To solve the conflict between the capability limitations of
existing systems and the ever-growing demands of roadway
safety oriented communication applications, we propose a novel
system design and implementation for realtime reliable roadway
communications, aiming at providing safety messages to users in
a realtime and reliable manner. In our extensive experimental
study, the latency is well controlled within the hard realtime
requirement (100ms) for roadway safety applications given by
NHTSA [2], and the reliability is proved to be improved by two
orders of magnitude compared with existing experimental results
[1]. Our experiments show that the proposed system for roadway
safety communications can provide guaranteed highly reliable
packet delivery ratio (PDR) of 99% within the hard realtime
requirement 100ms under various scenarios, e.g., highways, city
areas, rural areas, tunnels, bridges. Our design can be widely
applied for roadway communications and facilitate the current
research in both hardware and software design and further
provide an opportunity to consolidate the existing work on a
practical and easy-configurable low-cost roadway communication
platform.
I. INTRODUCTION
In our daily lives, one most overriding concern on the road
is safety. Though great effort has been made on roadway safety
for years, the total number of fatalities and injuries involved
in motor vehicle traffic crash in the world remains high,
as reported by WHO [3], [4] (World Health Organization),
BTS [5] (Bureau of Transportation Statistics) and FARS [6]
(Fatality Analysis Reporting System). The high fatality/injury
and involved asset damage result in enormous economic
losses, which emphasize the necessity and importance of new
technologies to roadway safety.
To improve the roadway environment in the aspects of safety
enhancements, Inter-vehicle Communications (IVC) systems
are proposed as an enabling technology for roadway safety.
Wireless access in vehicular environments (WAVE), which is
based on the Dedicated Short Range Communications (DSRC)
standard (IEEE 802.11p Standard), is the latest IVC technol-
ogy that provides the physical platform for ITS (Intelligent
Transportation System) to achieve its claimed goals of safety,
management and data services.
In these communication protocols and technologies, from
the perspective of roadway safety communications the funda-
mental performance metrics are packet delivery ratio and la-
tency. Specifically, NHTSA (National Highway Traffic Safety
Administration) has identified a number of high priority safety
applications for DSRC-equipped vehicles, e.g., traffic signal
violation, emergency brake lights, pre-crash sensing, collision
warning, left turn assistance, lane change warning, stop sign
assistance, curve speed warning, most of which require single-
hop communications that the latency is required to be less than
100 ms and the packet delivery ratio is higher than 99%, where
the packet length is usually 64 bytes or less [2], [7].
However, most recent results in [1] show that DSRC lacks
the ability to fulfill the requirements of these roadway safety
applications, i.e., it is common in realistic roadway environ-
ments to observe poor (≤ 20%) or intermediate ([20%, 80%])
packet reception (or gray-zone phenomenon), which is far
from satisfying the 99% packet reception requirement. Further-
more, due to the burst communication nature of roadway safety
applications and the unreliable packet reception characteristics
of DSRC, realtime roadway communications (< 100 ms) is
still far away in realistic roadway safety environments at the
978-1-4673-5946-7/13/$31.00 ©2013 IEEE
2013 Proceedings IEEE INFOCOM
115