KARAGIANNIS et al. : VEHICULAR NETWORKING: REQUIREMENTS, ARCHITECTURES, CHALLE NGES, STANDARDS AND SOLUTIONS 589
5,900
5,925
Frequency
(MHz)
5,925
5,800
700 MHz Band
5,875
1,000
5,905
5,725
5,815
5,795
5,855
5,875
5,850
500
902
5,850
928
5,770
10 MHz expected in this
an
Europe
North America
Japan
ITU-R
In use
Allocated
Potential
Fig. 1. DSRC frequency band specifications in Europe, North America and Japan, based on [33].
the dynamic nature of users and roadway environment. The
specification o f the protocols has not adequately considered
that the transmitter an d receiver are in motion relative to
each other. In particular, the DSRC/WAVE standards and
the resulting radio com munication implementations need to
be refined and should include measures such signal quality,
for UDP and IP-based two way transaction, an improved
services design logic, improved management of applications
and a rbitration of competing services from nearby providers.
Positioning: Positioning functionality is required, but the
specific provisioning means should not be prescribed since not
all terminals may be able to include GPS positioning system
for economic reasons. The position requirements must be
refined and extended to take into account the variations under
static and dynamic environments. Furthermore, significant
work has to be done to improve position accuracy and position
availability in all circumstances, mean ing that GPS based a nd
non-GPS based solutions should be investigated.
Security: The VII tests demonstrated that the b asic security
functions can be implemented and work in the context of the
system. However, more work has to be performed in analyzing
security threats and understand how to detect and solve such
threats and attacks. Furthermore, it is recommended that the
anonymous signing scheme be further analyzed, simulated and
implemented. The message signing and verification strategy
for the high rate messages, such as the Heartbeat messages
should be refined and analyzed to accomplish an optimal blend
for security and system throughput.
Advisory Message Delivery Services (AMDS): The AMDS
performed well during the VII POC tests, but it could be
improved to be more robust and more easy to use. It is
recommended that the system should be improved such that
it is clear how priority of messages should be interpreted in
the context of other user activities. In particular, the activation
criteria, e.g., which message is relevant, needs to be refined.
Furthermore, the overall management of system in terms of
prope rly setting configuration parameters and defining AMDV
parameters should be refined.
Probe Data Service (PDS): This service was shown to work,
but it was not clear if the huge amount of data from all vehicles
was necessary, since under most conditions, messages sent
from vehicles on the same roadway are strongly redundant.
Furtherm ore, the rules used to prevent th e availability to track
a vehicle and to maintain privacy are quite complex. It is
recommended that the probe data collected during the VII
proof of concept be analyzed and that representative models
of probe data user applications are developed to asses the
mathematically requirements on vehicle density and the scope
of the sampled vehicle p arameters. The privacy rules used for
PDS need also to be integrated in the d ata collection process,
such that it could be understood and controlled when PDS
should b e used and when not.
Vehicle Safety Communications (VSC):
The VSC
consortium specified several performance requirements
derived from the traffic safety applications, see [17]. From
these requirements, the most significant ones are: (1) safety
messages should have a maximum latency of 100 ms, (2) a
generation frequency of 10 messages per second and (3) they
should b e able to travel for a minimum range of 150 meters.
3) ITS architecture and protocol standards: This section
describes two ITS architectures.
The first ITS architecture introduced in this section is the
one that is defined by US DOT and is denoted as National