OCIT Outstations


OCIT Outstations interfaces use the Internet technology


OCIT Outstations interfaces use the Internet technology. They connect traffic controllers with central devices. Their task is the safe supply, the operation and monitoring of the device. This requires an immediate acknowledgement or error handling. Special meaning has therefore the transmission protocol BTPPL developed for OCIT Outstations

Communication model

With OCIT Outstations a universally applicable interface was created, which is not fixed on a certain communication medium. The communication media comprises older range limited 2-wire lines, radio communications, Ethernet and Internet. The data communication based on standards of the telecommunications technology and can use all usual media and telecommunication services, which are tied up by the layers 2 and 1. In OCIT-O for it so-called Profiles are defined. Transitions between different transmitting media, telecommunication services and topologies are possible.
Traffic controllers with OCIT-O interfaces must control complex traffic dependence locally and seize and process traffic measured values.

Time performance

OCIT systems with OCIT Outstations interfaces transfer instructions and data only with the arrival of certain events. The synchronization of all devices in the system is made by exact clocks (radio clock or time service of the central device).

Protocols

The data communication uses the ISO standard OSI Layers.


OSI layers of the transmission profile for point-to-point connections

The OCIT Outstations protocol is the transmission protocols of the user level. It covers the integration of the OCIT Outstations functions into the equipment software and the optimized protocol BTPPL. With exception of the OCIT Outstations protocol BTPPL only standard protocols are used. TCP/UDP/IP are transportation protocols of the middle levels. (* The use of the UDP protocol is no longer recommended.)

Characteristics of BTPPL

Substantially smaller data overhead and shorter transmission times. Therefore still existing old 2-wire lines with bad transmission quality can be used. A firm component is the SHA-1-Algorithmus, which ensures by password protection a high transmission reliability by 24-bit-Codierung, so that hackers cannot manipulate the field devices.

Functions and objects

All executable functions must be implemented by conformal devices in same way, in order to ensure a uniform system function. The exact specification of the objects takes place in the OCIT documents. The pertinent data definitions use the data description language XML (Extensible Markup Language). They are the basis for the implementation in the field devices. OCIT Outstations objects are fixed in the documents OCIT-O Basis and OCIT-O Lstg. They represent the standard.

Member Numbers

With the help of the Member Nummbers a distinction between standard OCIT objects and the definitions of the manufacturers (manufacturer objects) is possible in the OCIT system.

OCIT-O for Traffic Controllers Version 3.0

With OCIT-O V3.0, the OCIT system provides integration with the cooperative radio-based infrastructure in the automotive sector. This makes it possible in the OCIT system.

  • Decentralized Environmental Notification Message (DENM)
  • Quality Assurance, Statistics and Measurements of Floating Car Data (Cooperative Awareness Message, CAM)
  • Prioritization of public transport and special vehicles
  • Forecast data (Signal Phase and Timing, SPaT)
  • Supply of topology information (MAP)

to integrate into traffic management.

New functions in OCIT-O V3.0

Status information (CAM)

  • Acquisition of vehicle data such as date, time, position, speed, direction and vehicle type
  • Aggregation of traffic data such as average speed, queue time, number of stops

Environmental notifications (DENM)

  • Acquisition of all environmental notifications
  • Distribution of environmental notifications such as road works, accidents, critical sections from the traffic control center to the vehicles
  • Retrieval of current environmental notifications

Priorization of public transport (CAM)

  • Transmission of prioritization requests from the central system to the traffic controller.

Intersection topology (MAP)

  • Configuration of topology information with the standardized remote configuration mechanism.

Signal prognosis (SPaT)

  • Acquisition of forecasted signal state

 

On one hand it is possible to transfer environmental notifications (DENM) from the central system into the vehicles. On the other hand it is possible to acquire, filter environmental notifications from the vehicles and transfer them to the central system. Thus the operator has an overview of the current traffic situation.
The moving traffic is acquired with CAMs. This data is transferred to a central system after aggregation and processing. For the prioritization of public transport, the messages CAM (registration) and SPaT (acknowledgment) are used.

OCIT-O for Traffic Controllers Version 2.0

OCIT-O for traffic controllers version 2.0 is the upgrade of the existing OCIT-O definitions with version 1.1. The characteristic system functions of Version 2.0 are

  • the standardised supply channel and
  • the standardised process data communication between traffic engineering work place, central devices and the controllers.

Practical experiences led to a set of improvements and new definitions. OCIT-O for version 2.0 is backwards compatibly to OCIT-O V1.x. Central devices with version 2.0 covers therefore also all functions of the version 1.x.