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SAE J2735-Draft-Rev18 [issued: 06-26-07]
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This is an SAE Motor Vehicle Council draft document of the DSRC committee, subject to change.
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
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 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. A subsequent
annex describes the concept of a Message Dispatcher function at the application layer, and the philosophy
of the message design used to develop the message sets specified in this Recommended Practice. These
message sets are presented in Section 5. The particular message design techniques described in this
Recommended Practice have allowed for the construction of a dictionary of reusable, relevant data frames
and data elements that are intended to expedite the development of future message sets. The standard data
frames are presented in Section 6 of this Recommended Practice, and the data elements are specified in
Section 7.
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
commercial priorities described in Section 4.1. Interoperability is a fundamental requirement of this
common platform, and WAVE is designed to provide the required interoperable wireless networking
services for transportation. As well, the WAVE system uniquely supports the high-availability, low-latency
communications requirements of vehicle safety applications, such as pre-crash collision mitigation,
intersection collision avoidance and cooperative collision avoidance.
The physical layer (PHY) of the WAVE system is defined in IEEE P802.11p. In general, the WAVE PHY
provides a control channel (CCH) and multiple service channels (SCH). The range of this system is
generally considered to be line-of-sight distances of less than 1000 meters. The PHY has been optimized to
support usage by vehicles traveling at highway speeds.