Chapter 1 Introduction: intelligent vehicular communications

1.2.2
VEHICULAR NETWORKS AND ITS
Research of vehicular networks toward the development of an ITS can be readily segmented into fol-
lowing application areas, such as advising or warning the driver (collision warning), moderately con-
trolling the vehicle either for steady-state driver assistance or as an emergency intervention to avoid 
a collision (collision avoidance), and fully controlling the vehicle (vehicle automation). From an ITS 
perspective, collision-warning systems include functions such as a forward-collision warning, blind-
spot warning, lane-departure warning, lane-change or -merge warning, intersection collision warn-
ing, pedestrian detection and warning, backup warning, rear-impact warning, and rollover warning for 
heavy vehicles. A special category of collision warning is driver monitoring, to detect and warn the 
driver of drowsiness or other impairments that prevent the driver from safely operating the vehicle. If 

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7
1.2 
EVOLUTION Of TRANSpORTATION MODELS
Table 1.1 Evolution of Transportation Networks
Attributes
First Generations
Second Generations
Third Generations
Fourth Generations
Period
1950s–1980s
1980s–2000s
2000s–near future 
decades
2000s–distant future 
decades
Technological 
background
Massive construction 
of transportation 
infrastructures
Early ITS technologies Wireless communication 
technologies
Cloud computing, 
Internet of Things, 
supercomputers
Objectives
Operate early 
transportation systems
• Create potential 
supply from existing 
infrastructure
• Balance supply and 
demand
Accommodate both 
human and automated 
driving
Active supply and 
demand management
• Real-time control 
and management 
of transportation 
systems
• Proactive control 
and management
Key charac-
teristics
• Empirical models
• Static models
• Descriptive models
• Dynamic model
• Statistical models
• Partial macroscopic 
control
• Independent models
• Behavioral models
• Actuated control
• Rich data environment
• Partial macroscopic/
microscopic control
• Interaction with 
vehicular network
• Transition between 
human and automated 
traveling
• Massive data 
environment
• Automated 
environment
• Fully integrated 
models
• Feedback-control 
models
• System optimal
Data and con-
trol environ-
ment
• Very limited data
• Static data
• Empirical data
• Basic control
• Sampled and 
archived data
• Automated traffic 
management
• Indirect and 
unidirectional 
communication
• Macroscopic 
dynamic control
• Localized perception
• Low market 
penetration
• Detailed real-time and 
archived data
• Direct and bidirec-
tional communication
• High market penetra-
tion
• High-resolution 
real time and 
archived data
• User-specific 
control
• Full or near-full 
market penetration
Issues
• Lack of dynamic 
data
• Lack of dynamic 
theories
• Suitable for design 
and planning, but 
not reliable for 
operations
• Planning models lack 
a clear relationship to 
traffic flow theory
• No representation 
of interaction at 
intersections
• Limited coverage 
(spatial/temporal or 
both)
• Limited accuracy
• Limited resolution
• Heavy data processing
• Complex data fusion 
and integration
• Strong interactions 
(V2V, V2I, and I2I)
• User interface
• Need to accommodate 
the transition from 
autonomous vehicle 
to fully controlled 
vehicles
• Privacy and system 
security
• Data mining on 
massive data
• Integration 
with existing 
information and 
control systems
• System reliability 
and robustness
• User-oriented 
services
• Stochastic demand 
management
• Privacy and system 
security

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8
CHAPTER 1 
INTRODUCTION: INTELLIGENT VEHICULAR COMMUNICATIONS
the driver does not adequately respond to warnings, collision-avoidance systems might take control of 
the steering, brakes, or throttle to maneuver the vehicle back to a safe state. Driver-assistance systems 
include functions such as adaptive cruise control, lane keeping, precision docking (which will be dis-
cussed later), and precise maneuvering. Vehicle-automation systems include low speed automation, au-
tonomous driving, and close-headway platooning (which provides increased roadway throughput), and 
electronic vehicle guidance in segregated areas such as busways and freight terminals. These systems 
can be autonomous, with all instrumentation and intelligence of the vehicle, or cooperative, where as-
sistance comes from the roadway, other vehicles, or both. Roadway assistance typically takes the form 
of passive reference markers in the infrastructure. Vehicle–vehicle cooperation lets vehicles operate in 
close proximity for increased efficiency, usually by transmitting key vehicle parameters and intentions 
to following vehicles. The general philosophy is that autonomous systems will work on all roadways in 
all situations at a useful performance level and take advantage of cooperative elements, as available, to 
augment and enhance system performance.
In ITS, each vehicle takes on the role of sender, receiver, and router to broadcast information to the 
vehicular network or transportation agency, which then uses the information to ensure safe and free 
flow of traffic. For communication to occur between vehicles and RSU, vehicles must be equipped with 
some sort of radio interface or OBU that enables short-range wireless ad hoc networks to be formed. 
Vehicles must also be fitted with hardware that permits detailed position information such as a GPS 
or a differential global positioning system (DGPS) receiver. Fixed RSUs, which are connected to the 
backbone network, must be in place to facilitate communication. The number and distribution of RSU 
are dependent on the communication protocol to be used. For example, some protocols require RSU 
to be distributed evenly throughout the whole road network, some require RSU only at intersections, 
while others require RSU only at region borders. Although it is safe to assume that the infrastructure ex-
ists to some extent and vehicles have access to it intermittently, it is unrealistic to require that vehicles 
always have wireless access to RSU. 
depicts the possible communication configurations in 
ITS. These include intervehicle, vehicle-to-roadside, and routing-based communications. Intervehicle, 
vehicle-to-roadside, and routing-based communications rely on very accurate and up-to-date informa-
tion about the surrounding environment, which in turn requires the use of accurate positioning systems 
and smart communication protocols for exchanging information. In a network environment in which 
the communication medium is shared, highly unreliable, and with limited bandwidth, smart commu-
nication protocols must guarantee fast and reliable delivery of information to all vehicles in the vicin-
ity. It is worth mentioning that intravehicle communication uses technologies such as IEEE 802.15.1 
(bluetooth), IEEE 802.15.3 (ultra-wide band), and IEEE 802.15.4 (Zigbee) that can be used to support 
wireless communication inside a vehicle, but this is outside the scope of this chapter and will not be 
discussed further.