National Connected Vehicle Field Infrastructure Footprint Analysis Deployment Concepts
A.7
APPLICATION BACKHAUL REQUIREMENTS SUMMARY While most field terminals (conventionally referred to as RSEs) support a variety of applications, there is no basic requirement that RSEs be connected to center equipment at all. As a result, the requirements on the backhaul, if any, depend on the applications the RSE is expected to support and the broadcast message management approach used. This section provides a summary of example backhaul requirements based on the different applications and message management approaches. In general the message sizes are based on the J2735 standard. These “requirements� are not intended to be normative but are instead provided to illustrate relative data loads for different backhaul approaches. There are two basic approaches for managing broadcast messages. These have a significant impact on the need for and the data loads on the backhaul network. These are described below: x
Store and Transmit: This architecture includes provision in the RSE to store messages and to transmit them repeatedly according to a message transmission schedule (typically provided with the message). In this model the messages transmitted by the RSE reside in the RSE. The RSE may acquire these messages via several mechanisms. For example, they could be pre-programmed into the RSE during configuration, they could be provided by field equipment over a local network connection, they could be provided to the RSE from a mobile programmer (for example a service vehicle that establishes a wireless connection to the RSE and delivers messages for later transmission), or they could be provided by center facilities over a backhaul link. A store and transmit RSE can operate independently.
x
Pass-through: In the pass-through architecture, the RSE has no ability to store any messages and no ability to transmit them according to a schedule. Instead every message to be transmitted is provided from a center facility over the backhaul link or by local field equipment over a local network and it is then immediately transmitted.
The applications supported by an RSE will determine the size of the messages that may need to be carried over the backhaul. This applies to messages to be broadcast by the RSE, and to messages sent by mobile terminals and collected by the RSE on behalf of the center facility. It should be noted that message collection at the RSE could also involve storing messages received over some time interval and periodically transmitting them as a bundle to the center, but this approach would mean that the collected data was not timely, and over 128