WG9 was originally convened to develop standardized rail TCIP profiles and data dictionaries (standard IEEE 1544), a mammoth task. This original mission remains the long-term goal of the working group; however, the work has been broken down into manageable “packages” which will be addressed in sequence.
After a number of meetings, the working group realized (based on industry input) that the original goal of a comprehensive rail TCIP standard was less important in the short term than standardization of inter-vehicle interfaces and train-level interoperability. The WG9 PAR (project authorization request) was revised to reflect this, and the working group’s focus shifted to developing standard data elements and data structures for train-level interoperability, with elements required for train control having first priority.
Given the shift in focus, the working group decided to concentrate first on developing standard control data elements and data structures for use with the IEEE 1473-T train bus (WTB per IEC 61375-1). This decision was supported by the fact that the LonMark Transportation Group was in the process of developing similar standards for the IEEE 1473-L train bus. WG9 agreed to provide LonMark with the data dictionary from which the standard LonMark profiles would be developed, along with recommended grouping of data elements for SNVT (standard network variable type) definitions.
Early on, WG9 started working with LonWorks profiles developed for NYCT R142 and R142A, together with IEEE 1475, in a first attempt to develop a standard LonMark profile for the master controller and cab control. However, the working group also recognized that the European standard UIC 556 was more applicable to the IEEE 1473-T train bus since it was developed specifically for use with that bus. The decision was ultimately made to use UIC 556, 2nd edition, as the baseline for standard IEEE 1544.
UIC 556 defines application layer messaging for the IEC standard train bus (WTB). Messaging is divided into two classes, as follows:
R-Telegrams: These contain time-critical process control data (and related status) and are transmitted deterministically every 100 ms.
E-Telegrams: These are event-driven messages that are transmitted as network traffic permits. Although these can be (and are) used for control signals, the non-deterministic transmission makes this form of messaging unsuitable for time-critical control.
The standard defines three R-telegram types: R1, R2 and R3. These are used as follows:
R1: Transmits control commands from the leading (controlling) vehicle to trailing vehicles.
R2: Transmits control responses from trailing powered vehicles.
R3: Transmits passenger coach control information between vehicles.
UIC 556 also provides for application-level train inauguration and transmission of self-describing properties between vehicles.
The working group is in the process of preparing an updated release of IEEE P1544, scheduled for completion by February 5, 2002.