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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.
-- type of vehicle and agency when known
vehicleType ITIS.VehicleGroupAffected, -- zero if NA
responseEquip ITIS.IncidentResponseEquipment, -- zero if NA
responderType ITIS.ResponderGroupAffected, -- zero if NA
... -- # LOCAL_CONTENT
XML Representation:
<xs:element name="emergencyVehicleAlert" type="EmergencyVehicleAlert"/>
<xs:complexType name="EmergencyVehicleAlert" >
<xs:sequence>
<xs:element name="msgID" type="DSRCmsgID" />
<!-- App ID value, 1 byte -->
<xs:element name="atisMsg" type="atis:RoadSideAlert" />
<xs:element name="responseType" type="ResponseType" />
<!-- zero if NA -->
<xs:element name="sirenUse" type="SirenInUse" />
<xs:element name="lightsUse" type="LightbarInUse" />
<xs:element name="multi" type="MultiVehicleReponse" />
<!-- combine above three into one byte! -->
<xs:element name="mass" type="VehicleMass" />
<!-- gross size and axle cnt
type of vehicle and agency when known -->
<xs:element name="vehicleType" type="itis:VehicleGroupAffected" />
<!-- zero if NA -->
<xs:element name="responseEquip" type="itis:IncidentResponseEquipment" />
<!-- zero if NA -->
<xs:element name="responderType" type="itis:ResponderGroupAffected" />
<!-- zero if NA -->
<xs:element name="localEmergencyVehicleAlert" type="local:EmergencyVehicleAlert"
minOccurs="0"/>
</xs:sequence>
</xs:complexType>
5.5 Message: MSG_GenericTransferMsg
Use: The GenericTransferMsg provides a basic means to exchange one or more blocks of data across the
interface. Each application using this message frame SHALL have a unique value assigned to the
applicationID value and is allowed to have up to 255 simultaneous transfer sessions in operation at one
time. If an application requires only a single session, it SHALL set the sessionID to be the value of zero.
Within each unique applicationID / sessionID value pair there MAY be up to 65535 unique blocks of data
sent, each with its own word count up to 65535 bytes in length. This is followed by the payLoad value, a
sequence of octets up to 65535 bytes in length. Proper interpretation and any re-assembly of these blocks
of data (if needed) SHALL be the responsibility of the application layer and is outside the scope of this
message definition. In general, this message depends on the lower layers of the DSRC protocol for
successful message delivery, but not to ensure message delivery order. A CRC value is provided (which is
generated over the entire msg content including the payload) to detect data corruption.
In order to transfer data payloads larger than 65535 bytes in length, the sending application SHALL break
them down into sequential blocks, and then send each with a common sessionID and its own blockID
value. The total expected number of blocks can be determined from the blockCount value. The total size
of the complete data payload MAY be determined by multiplying the blockCount value by the wordCount,
although individual applications MAY establish their own rules for this (i.e word counts that vary across
blocks are expressly allowed).
Therefore, the typical use of this message by an application is to establish a sessionID which will be static
for the life of the transfer, devise a reasonable wordCount for each payload, divide the overall payload by
the wordCount into N such payloads, and thereby creating the value for the blockCount. If the blockCount
is more than one, then the message is sent with the blockID set to 0,1,2, etc. and the payload Octets and
CRC set as needed until all the data is sent and the blockID is N-1 the value of the blockCount (indicating
the last block is being sent). Upon receipt of this last message by the receiver, the sessionID may be used