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SAE J2735-Draft-Rev29 [issued: 12-11-08]
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This is an SAE Motor Vehicle Council draft document of the DSRC committee, subject to change.
1609.3 and 1609.4 copy the J2735 defined application layer message priority to the MAC
transmission priority, should not concern the application designer and/or developer.
Provider Service Identifier (PSID): As described within IEEE WG 1609.3, the PSID is a
number that identifies a service provided by an application. A PSID has no relevance [FP1]for the
J2735 defined message priority. It is related to service priority and is considered out of scope
here.
Resource Manager Message Priority: As described in IEEE WG 1609.1, a Resource Manager
Message format consists of a header and message contents. Each Resource Manager message
priority is in the range of 0 to 3 where messages of priority 0 are of highest priority, or most urgent
(if the Resource Manager Message Priority is specified as being from 4 to 255, it is treated as
being Resource Manager Message Priority 3).
Display Priority: A receiver may define a priority associated with displaying messages. This
would likely be proprietary to the OEM deploying the receiver and is out of scope for this
discussion.
Message Priority Enforcement
This annex is intended only to provide guidance for recommended priority assignments to messages and
message sets. It is informative only.
Neither the Technical Committee nor its associated subcommittees are chartered to police or enforce the
J2735 defined application layer priorities detailed here; such enforcement will be, in all likelihood, the
responsibility of an empowered governmental agency. This annex and its associated table are simply a tool
to promote harmony and communication within a DSRC community.
Message Priority Table
J2735 Message Priority is based upon a balance between the importance and urgency of a message to be
transmitted; the interpretation of the terms being as follows:
IMPORTANCE: The first level of priority is associated with societal and/or safety impact, and
prioritizes safety above all other applications and/or communications. The greater the potential for
saving life or preventing injury, the higher the importance the message and message sets receive.
Though this is as per the USA Federal Communications Commission, there is no intent to limit
this guideline to any single country.
URGENCY: Many applications are predicated upon allowable communications latency. The
range of that latency defines the urgency of the message; if the message requires quick transfer
from sender to listener, it has a higher associated urgency.
Each row in the Message Priorities table includes an example application and suggested message priority.
In addition, an estimate of the allowable latency is provided as an indication of urgency.