Deterministic, train-wide communication over the train power distribution cable already required for train-wide energy supply.
Logical Architecture
The train power distribution cable simultaneously supplies energy and serves as the communication medium.
This architecture separates:
•Application layer (Ethernet / CAN systems)
•Logical train backbone
•Physical transmission layer (one cable for power and data)
Physical Layer: Broadband PLC over Train Power Distribution Cable
PTB uses broadband Power Line Communication (PLC) based on ple-tec’s Power Line data bUS (PLUS) platform which specifically targets high-reliability and real-time (Mission-and-Time Critical) communication over power distribution networks in aircraft, trains, etc. PLUS uses the physical layer of the IEEE 1901 standard.
PLUS is optimized for challenging communication channel conditions which are common for the freight train power distribution cable
•Signal damping and reflections
•Impedance variations (e.g., in e-couplers in the DAC)
•Electrical noise and electromagnetic interference (EMI)
PTB maintains stable communication without any shielding, shelter or corrugated pipes for the train power distribution cable.
Any AC or DC voltage for the train power distribution cable can be used.
Each wagon is equipped with a compact PTB Node that couples non-intrusively to the train power distribution cable.
Automatic Train Topology Detection (PLUS-TTD)
After every coupling or uncoupling event, PTB automatically detects and reconstructs the train topology, based on the integrated PLUS-TTD protocol.
Capabilities of PLUS-TTD include
•Wagon order determination
•Direction detection
•Identification of last wagon
•Dynamically allocates PTBN addresses
•Based on high-precision time-of-flight measurement
The topology is detected without any manual configuration.
This enables the Automated Train Functions:
•Train Composition Detection
•Automated Brake Testing
•Train Integrity Monitoring
Deterministic Communication – PLUS-TOKEN Protocol
Beyond the physical layer, PTB implements rail-specific higher-layer protocols such as PLUS-TOKEN.
This protocol
•Coordinates message exchange across the shared medium
•Allocates guaranteed transmission slots
•Prevents collisions
•Provides known worst-case latency
Deterministic behaviour is essential for time-critical functions in the Full Digital Freight Train.
Key characteristics
•Predictable latency
•Controlled access to medium
•Scalable across long train consists
Designed for Real Coupling Processes
Freight train coupling is mechanically harsh. The DAC, including the e-coupler and its electrical contacts, are exposed to harsh operational and environmental impacts both during the coupling process and while driving.
PTB avoids sensitive data contacts in the coupler by transmitting communication signals over the power contacts, which are designed for high mechanical robustness.
Advantages
•Minimum number of electrical contacts in the e-coupler interface
•Maximum size of electrical contacts for increasing robustness
•Maximum creepage distances between electrical contacts and to the e-coupler housing
•Compatibility with multiple contact types
•Spring loaded contacts more tolerant to ice, dirt and wear as well as misalignment
Communication reliability is preserved without introducing fragile interfaces.
System Integration
PTB provides Ethernet- or CAN-transparent data transport, allowing higher-layer applications to operate independently of the physical medium.
This ensures:
•Compatibility with TCN-based systems
•Integration with existing wagon electronics
•Long-term scalability