 |
 |
 |
 |
|
 |
 |
SAE J2735-Draft-Rev26 [issued: 09-18-08]
-
22 -
This is an SAE Motor Vehicle Council draft document of the DSRC committee, subject to change.
4
The use of DSRC messages in Applications
This section contains introductory material about this edition of J2735, background information on the
rationale for the standard, and an introduction to the messages, which follow in Sections 5 to Section 9.
4.1
Introduction to DSRC Goals and Objectives
Public sector organizations throughout the world have identified the need to reduce fatalities and serious
injuries that result from vehicle crashes, as well as the need to reduce traffic congestion. The use of
wireless and computer technologies in vehicles, and on the roadway infrastructure, have been identified as
promising areas to provide solutions for these needs. Intelligent Transportation System (ITS) planning in
many regions of the world has therefore become focused on supporting applications that utilize a common
platform to address three priorities:
1)
Safety
2)
Mobility
3)
Commercial (or Private)
Safety applications, in particular, must be interoperable between vehicles from different manufacturers and
between vehicles and roadway infrastructure within all the areas where the vehicle is likely to travel. This
requirement for interoperability is also relevant to contemplated mobility applications. This SAE Standard
specifies initial representative standard message sets, data frames and data elements that allow
interoperability at the application layer without the need to standardize applications. This approach
supports innovation and product differentiation through the use of proprietary applications, while
maintaining interoperability by providing standard message sets that can be universally generated and
recognized by these proprietary applications.
The message sets specified in this SAE Standard depend upon the lower layers of the DSRC protocol stack
(or potentially other wireless communications systems) to deliver the messages from applications at one
end of the communication system (for example, in a vehicle) and the other end (for example, in another
vehicle). These lower layers of the DSRC protocol stack are defined and specified in standards developed
by other Standards Development Organizations (SDOs). In particular, the lower layers are addressed by
IEEE P802.11p, and the upper layer protocols are covered in the IEEE P1609 series of standards. The
DSRC family of standards developed by the various SDOs are meant to operate together in a harmonious
fashion. The message sets specified in this SAE standard therefore define the message content and
structure delivered by the communication system at the application layer. This specification consequently
defines the message payload at the physical layer. However, the operations at the physical layer, for
example, are specified by IEEE P802.11p, and the actual content of over-the-air packets will be determined
by layers below the applications layer, as specified in the IEEE standards.
The following subsection provides an overview of the DSRC architecture and protocol stack. Subsequent
annexes describe examples of how the message sets specified in this Standard might be used, which also
strongly influenced the philosophy of the message design. These message sets are presented in Section 5.
The particular message design techniques described in this Standard have allowed for the construction of a
dictionary of reusable, relevant data frames and data elements that support interoperability for currently
envisioned applications and are also intended to expedite the development of future message sets. The
standard data frames are presented in Section 6 of this Standard, and the data elements are specified in
Section 7. Data concepts reused from other areas of ITS work are presented in Section 8.
4.2
DSRC Overview
The WAVE communications system is designed to enable vehicle-to-vehicle and vehicle-to/from-
infrastructure communications in order to provide a common platform to achieve the safety, mobility and
 |