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SAE J2735-Draft-Rev15 [issued: 01-30-07]
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171 -
This is an SAE Motor Vehicle Council draft document of the DSRC committee, subject to change.
Figure D1 Message Dispatcher (MD) sender (upper figure) and receiver (lower figure) components. In this example
the Data Probe application is missing on the receiver side and its data is simply discarded.
To help prevent the possibility of vehicle broadcast messages overloading the channel bandwidth in dense traffic
environments, particularly with regard to transmissions on the control channel, a mechanism should be added to
the dispatcher to evaluate immediate parameters (for example, current channel loading, number of vehicles
transmitting in immediate vicinity, speed of vehicle, priority of messages) and then adjust various aspects of the
vehicle broadcast transmissions (for example, transmission power, frequency of repetition, timing of transmissions
relative to proposed assignment of synchronized “listen” interval).
Changes in Temporary IDs: To avoid the possibility of Temporary IDs changing during a critical time, a
mechanism should be added to the dispatcher to send a ‘no ID change for the next 500ms’ request to the lower
DSRC stack layers. The ‘no ID change’ state is managed by the dispatcher via applications and is renewable.
Server Brake
Warning
Collision
Avoidance
Warning
Data Probe
Message
Dispatcher
Sender
Position, Speed, Air
Bag, Brake Status
Position, Speed, Yaw
Rate, Ad Hoc Map
Position, Speed,
Yaw Rate, Air Bag,
Brake Status, Ad
Hoc Map, Car Model,
Car Model, Car Type,
Headlights
Server Brake
Warning
Collision
Avoidance
Warning
Message
Dispatcher
Receiver
Position, Speed, Air
Bag, Brake Status
Position, Speed, Yaw
Rate, Ad Hoc Map
Position, Speed,
Yaw Rate, Air Bag,
Brake Status, Ad
Hoc Map, Car Model,
Car Model, Car Type,
Headlights
DISCARDED
OEM Specific
This Standard