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SAE J2735-Draft-Rev15 [issued: 01-30-07]
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174 -
This is an SAE Motor Vehicle Council draft document of the DSRC committee, subject to change.
DE_VehicleWidth
Yes (3 Hz)
Yes (3 Hz)
DE_VerticalAccelerationThreshold
DE_VerticalAcceleration
DE_WiperRate
DE_WiperStatus
DE_YawRatePrecision
DE_YawRate
Ad Hoc Data
AHDE_CAWMap
Yes (10 Hz)
Yes (10 Hz)
Table: Data Frames, Data Elements with Identifier, and Tagged Data Elements as used by the two applications in this example.
3.2 Message Structure
The MD combines the different data frames and data elements required by the two applications into the
minimum size message. For this example, the MD uses the following logic to perform compose the message:
Duplicate data frames and data elements requested by both applications are not repeated.
If a data element requested by one application is also contained within a data frame requested by
another application, it is only included as part of the data frame.
Data frames and data elements are transmitted only at their maximum required frequencies. In fact, in
this example some data frames/elements are sent less frequently then others and they are not included
in each message.
Since the applications have registered data at three different frequencies, the MD will use the MSG_AlaCarte
message defined by this Standard to construct three different ad hoc messages called Msg10Hz, Msg5Hz and
Msg3Hz. Other message types may also e used. The contents are described below and are built using the
following pieces of information from the standard:
Standard data tags StdTagList are 1 byte long as defined by this Standard in the section defining the
data concept DE_StdTagList
Standard data frame and element lengths in bytes as defined in each data frame definition (clause 6).
Ad hoc data tags from the TwoByteTagList are 2 bytes long as defined by this Standard in section 4.3
Ad hoc data length and tag value may defined by the application and notified to the MD as described
in this annex.
Ad Hoc data tags defined by the CAW application that are outside this Standard. In particular, a the
CAW application defines one ad hoc data element called “AH_CAWMap” using the
TwoByteTagList as indicated this Standard: Upper byte of the tag is set to 127 (as required from this
Standard), lower byte of the tag is set to 123 (as defined by the CAW application). Refer to clause
4.3 for details.
Three different messages are structured as indicated below. (Note that data elements in the 10Hz message
also appear in the 5Hz message (for example). This is because every second send at 10Hz is essentially a 5Hz
message and rather than send two messages at that time a combined one is sent. This is process is further
illustrated in the next section.)
MSG10HZ ::= SEQUENCE {