1.1.1 Relation of WAVE to the ITS station reference architecture

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23 Οκτ 2013 (πριν από 4 χρόνια και 17 μέρες)

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1.1.1

Relation of WAVE to the ITS station reference architecture

International developments for communications in the area of "Intelligent Transport Systems" (ITS) have
centered on the concept of abstracting applications from all of the lower OSI communication l
ayers
(
Communications Access for Land Mobiles,
CALM). The concept of CALM has been embodied an
architecture that allows ITS communication devices (ITS station reference architecture, ISO 21217) to
communicate on a peer to peer basis. One of the important d
evelopments was the creation of the concept of
an ITS station as a bounded secure managed domain. This has led to the development of a large number of
International Standards, most of which are given in Annex G.

The ITS station reference architecture is
sh
own in
Figure 1
.

An example of an application in this model would be Road Safety.
IPv6 and Geo
-
Routing, for example, reside in the Networking & Tansport layer.
IEEE 802.x, Bluetooth, and GPS are
examples of Access technologies
.

Recognizing the importance of road and transport safety of life and property, a significant effort has been
placed on applications inside of ITS stations that prevent collision avoidance and similar functionality.
These efforts have led to the creation o
f a new concept called Local Dynamic Map (LDM: ETSI
EN 302
895
,
ISO/NP 17424
). The LDM is
an example Facilities
-
layer function

and

is
proving a very useful facility
in the design and implementation of many ITS applications.

Complementary ITS applications,

relevant for authorities, road operators, and commercial purposes, are
being developed jointly by CEN TC278 WG16 and ISO TC204 WG18 under the title of "Co
-
operative
ITS". These types of applications also benefit from an LDM.

ISO 21217 /
ETSI EN 302 665

pr
esent the
ITS station reference architecture

that follows the principles of
the OSI model.
Figure 1

shows how the various IEEE WAVE standards map to the blocks of this reference
architecture.



Figure 1


Protocol models

One difference between the ISO ITS protocol and IEEE
WAVE protocols is that the ISO protocols
consistently use port numbers
at the Networking & Transport layer. WAVE uses standard

port numbers for
IPv6
-
based protocols (e.
g., TCP, UDP), but used PSID and an identifier in the context of WSMP as
described in
subclause

.

The SAPs employed by the two architectures are different;
h
owever a mapping can easily be achieved in
order to align better these two archi
tectural approaches.

WSA is very much aligned with the ISO "Fast Service Advertisement Protocol" (FSAP) specified in ISO
24102
-
4.

ISO 21218 provided a DSAP/SSAP value for WAVE, i.e. thus ena
bling WAVE as a separate protocol stack
in an ITS station. Note that

effort
s are underway

to further align WAVE and CALM.