Communication advances Chapter | 2 23In the middle (network) layer, the IEEE 1609.3 standard defines the setup
and management process for the WAVE connection. In the lower layers, the
IEEE 1609.4 standard stands above IEEE 802.11p and allows the upper lay-
ers to communicate using multiple channels, without having knowledge of the
physical layer parameters. The standards extend the physical channel access
defined in WAVE and using IEEE 1609.1 define how applications will commu-
nicate using the WAVE interface. The relationship among IEEE 1609 and IEEE
802.11 standards is depicted in Fig. 2.4.
2.6 SAE J2735
The SAE J2735 is a standard that is frequently used in V2V communications.
It is essentially a Message Set Dictionary for DSRC and is maintained by the
Society of Automotive Engineers (http://www.sae.org). The standard defines
the set of messages that can be used in DSCR or WAVE communications, and
the data frames and elements that applications have to use in order to comply
with the standards of DSRC/WAVE communication.
SAE J2735 focuses on messages and the structure they must have and provides
all the information necessary to application developers that need to interpret the
exchanged messages that follow the DSRC standards. More specifically, the mes-
sage sets define the content of all messages delivered at the application layer and
at the same time allow us to calculate the payload for transmitting the message at
the physical layer. The message sets rely on the lower DSRC protocol layers of
the DSRC protocol for the appropriate message delivery from the application that
runs to the vehicle (e.g., in the vehicle’s OBU) to the application hosted on a road-
side unit. As it holds with WAVE and DSRC, the lower layers follow the IEEE
802.11p directions and the upper layers comply with the IEEE 1609.x family of
standards. This standardization of message sets, data frames and data elements
enhances the interoperability of DSRC applications at the data level.
FIGURE 2.4 IEEE 1609 family of standards.