CBTC Connectivity Solutions White paper Edition 2011

Reliable RF and FO connectivity solutions Simplified 3D overview of a radio-based CBTC system architecture

3 Train control enhanced by modern communications technology 4 Radio-based CBTC 5 Connectivity components for backbone networks 5 Connectivity components for radio networks 6 Trackside equipment 9 Trainborne equipment 10 Conclusion Train control enhanced by modern communications technology The overall performance of a rail rapid transit system depends largely on the performance of the automatic train control (ATC) system employed. A communication-based train control (CBTC) system is devised by adding modern communication technologies to the ATC concept. CBTC signalling is currently standardised...

Radio-based CBTC Conventional ATC systems divide the railway track into fixed sections which are separated by signals and signalling is automated by means of fixed balises, which act in a similar way to induction loops or RFID transponders. Due to the static nature of this system, the sections are called fixed bocks. ATC fixed block architecture Radio-based CBTC enables continuous two-way digital communication between each train and control centre. The control system benefits from enhanced information such as train performance data and continuous train position and speed. Systems of this type...

CBTC connectivity solutions Connectivity components for backbone networks The physical layer of backbone networks consists of single mode fiber optic cables having a relatively high capacity (e.g. 96 fibers) and specific characteristics due to the operating environment (tunnels and/or outdoor installation). In particular, these cables must be made of selected sheath materials in order to • Comply with stringent fire and smoke performance requirements • Resist fluids such as acid, alkali and tunnel-cleaning products • Be protected against rodents (armoured cables) Example of an armoured fiber...

Trackside equipment Trackside equipment is built from radio access points distributed along the tracks at intervals ranging from several tens of meters to several hundreds of meters, depending on the track topology, e.g. curves, straight sections, obstacles, etc. Subject to installation constraints, The radio access points and its complementary equipment can be mounted, e.g. on a mast. Example of trackside mast architecture

CBTC connectivity solutions Fiber optic connectivity The radio access points are linked by dedicated, redundant fiber optic distribution loops, thus ensuring high communication safety and availability level in a given zone area. The zone areas are linked by the backbone network and each zone is under the control of a zone controller. While the fiber capacity of the backbone network is relatively high, that of the distribution loops is generally lower (e.g. 12 or 24 fibers), as the zone areas are limited in size. Alternatively, Cat5 or Cat6 copper cables can be used for the distribution loops...

For the connection of the fiber optic distribution loops to the backbone network optical distribution frames are used. These are installed in technical rooms, e.g. located in railway stations. Example of a LiSA optical distribution frame Radio frequency connectivity The trackside radio access point is equipped with robust radio frequency (RF) coaxial connectors to enable connection to the trackside antennas via RF feeder and jumper cable assemblies. RF power splitters are required in order to implement the safety redundancy architecture. RF power splitter Trackside antenna All RF components and...

CBTC connectivity solutions Trainborne equipment Due to the two-way operation of the trains and redundancy requirements, both driver’s cabs are equipped with the same setup, i.e. on-board ATC equipment and radio modems. Vehicular directional antennas are installed in the near area of each driver’s cab and are connected to the radio modems via RF low-loss cable assemblies. The radio modems provide the communication signal to the on-board ATC equipment. RF connectivity to vehicular antenna Both antennas and RF cable assemblies must comply with the requirements of the rolling stock industry for...

Conclusion Continuous two-way train-to-track communication is essential for ensuring the reliability of a CBTC system. Failures in communication have an immediate impact on train operation. One of the key performance indicators for CBTC system suppliers is system and train availability. For these reasons, radio frequency and fiber optic connectivity components implemented in such systems must be selected with great care. They must be capable of withstanding severe environmental conditions and meeting demanding functional requirements. HUBER+SUHNER delivers excellent radio frequency, fiber optic...

Find more information in our catalogues Fiber Optic Cabling Systems Edition 2010/2011 Railway products Train-to-shore communication Item no. 84110507 Item no. 84112422 Fiber Optic Cabling Systems Item no. 84104358 11

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