end platform (Wang Jianbiao, 2013). The advantages
of DSRC technology are high reliability and strong
real-time transmission, however, since the physical
layer technology of DSRC is the same as the WiFi
commonly used in people's lives, the communication
distance advantage is not obvious, the coverage
distance is short, and large-scale renovation and
investment in roadside facilities is required in
practical applications (Zhao Jing, 2018).
2.2 Internet of Vehicles Technology
Based on LTE
LTE-V2X is based on LTE technology, which is
divided into LTE-V-Cell and LTE-V-Direct. The
former uses existing spectrum and base station for
cellular communication, while the latter AS Ad hoc
network is used for V2X communication in small
scale. The LTE-V2X can reuse existing cellular
infrastructure and spectrum, and operators do not
need to deploy dedicated RSU and provide dedicated
spectrum (Xu Zijian, Yu Mei, 2016). LTE-V2X
mainly solves the problem of shared sensing among
traffic entities, it can expand the vehicle-mounted
detection system from tens of meters to hundreds of
meters or more, and improves effectiveness of AI,
and achieves assisted driving in relatively simple
traffic scenarios. In comparison, DSRC technology
has first-mover advantage, long verification time and
more mature technology, and keeps one step ahead in
network security. The advantage of LTE-V2X is that
it does not require new roadside facilities, its cost is
lower, and network covers longer distances, and can
smoothly evolve to 5G.
3 DEVELOPMENT HISTORY OF
V2X TECHNOLOGY
In 1986, experts from scientific research institutions,
transportation bureaus, etc. discussed the future
traffic regulations and believed that the future
transportation system must simultaneously ensure
safety, solve congestion and protect the environment.
In 1990, in Texas, the discussion on this issue reached
a climax, participants proposed the concept of IVHS,
namely intelligent vehicle and highway system, later,
and it evolved into the intelligent transportation
system ITS. In 1991, the ITS concept became part of
the Intermodal Surface Transportation Efficiency Act
(ISTEA). In addition, ISTEA has invested $6.6
billion in research and testing of ITS systems for the
next six years.
In 1992, the US Department of Transportation
(USDOT) launched the Automated Highway System
in the ITS research to liberate the driver's hands and
feet, the vehicle needs to travel on a road with
magnetic nails, this is the first time in history that the
interconnection of vehicles and highways has been
achieved. After the Automated Highway System test,
the USDOT launched the Intelligent Vehicle
Initiative in 1997 to accelerate the deployment of
anti-collision systems. Based on the smart vehicle
program, USDOT puts forward new demands on
improving traffic congestion and electronic
communication technology. At the 10th ITS World
Congress in Madrid in December 2003, USDOT
announced distribute 75MHz spectrum at 5.9GHz for
DSRC research, and proposed the VII project, the
goal of the project is to apply V2V and V2I
technologies in a small range. In December 2006,
USDOT and the five major automakers jointly tested
the role of V2V and V2I in anti-collision systems and
established new communication-based safety
facilities, including roadside networks and on-board
vehicle equipment. Only when there are enough
vehicles on the road to support V2V communication,
the role of V2V can be fully reflected. To this end, in
August 2014, NHTSA and USDOT proposed the
FMVSS No. 150 Act; this act mandated that new light
vehicles support V2V communication.
The generation of DSRC technology is based on
three standards: the first is IEEE 1609, which defines
the architecture and flow of the network, the second
is SAE J2735 and SAE J2945, which define the
information carried in the message packet, these data
include information from sensors on the car, such as
location, direction of travel, speed and brake
information, the third standard is IEEE 802.11p,
which defines the physical standards for DSRC. The
DSRC top-level protocol stack is developed based on
the IEEE 1609 standard, the V2V information
exchange uses the WAVE Short Message Protocol
instead of WIFI; and the TCP/IP protocol are used for
V2I and V2N information interaction. The DSRC
underlying layer, physical layer, and radio link
control are based on IEEE 802.11p. The IEEE 802.11
standards use the WIFI ecosystem, but WIFI was
originally designed for fixed communication
equipment, and later IEEE 802.11p supported mobile
communication devices.
With the development of cellular communication
technology, the role of cellular communication is
becoming more and more important; at present,
cellular communication technology has changed from
simply transmitting sound to transmitting audio and
data, changes from person-to-person to machine-to-