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SAE J2735-Draft-Rev29 [issued: 12-11-08]
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237 -
This is an SAE Motor Vehicle Council draft document of the DSRC committee, subject to change.
Figure 1: Example Vehicle DSRC Safety System with Safety Message Handler
Figure 1 illustrates how a MH chooses outgoing message content based on the collective requirements of
the vehicle’s safety applications. An aspect of the MH functionality not shown is the determination of
message transmission time. The simplest case is a regular message schedule with uniform content in each
message. A more complex case arises if some information is sent more frequently than others. A MH may
opt to compose messages with different content to match the specific information rate requirements of the
applications. For example, if in Figure 1 the Lane Change Warning application only requires half the
information rate as the Forward Collision Warning and Intersection Warning applications, the message
shown on the right side of the figure might be sent every other message interval, interleaved with messages
that omit the Turn Signals and Headlights data elements.
Fwd Collision
Warning
Intersection
Warning
Lane Change
Warning
Safety
Message
Handler:
Sender Side
Position, Speed, Air
Bag, Brake Status
Position, Speed, Yaw
Rate, Vehicle Trail
Position, Speed,
Yaw Rate, Air Bag,
Brake Status,
Vehicle Trail, Turn
Signals, Headlights
Position, Turn
signals, Speed,
Headlights
Fwd Collision
Warning
Intersection
Warning
Safety
Message
Handler:
Receiver Side
Turn Signals,
Headlights
IGNORED
Implementation Specific
J2735 Standard
Position, Speed,
Yaw Rate, Air Bag,
Brake Status,
Vehicle Trail, Turn
Signals, Headlights
Position, Speed, Air
Bag, Brake Status
Position, Speed, Yaw
Rate, Vehicle Trail
Communication
system
Outgoing
Message
Incoming
Message