Minimized Headways with Safe Operations for CBTC

  • CBTC uses constant bi-directional radio communications between train and trackside equipment to increase line capacity by reducing headways. To do this, the moving block train control system needs real-time train operating data to enforce safe spacing. Any communications loss may disrupt the CBTC and bring trains to a stop. Consequently, CBTC networks have strict standards for availability and latency. In metro lines, frequent train roaming may cause long latency in RF-based CBTC networks. A roaming handoff time of less than 50 ms is vital for uninterrupted trainto-trackside connectivity. Momentary breaks may occur on radio networks; but a CBTC can only tolerate a packet loss rate of under 0.1%.

    Layer 2 CBTC
  • Network Requirements

    • Fast secure roaming:
      ▫ Handoff of less than 50 ms for continuous CBTC operations
    • Sufficient throughput:
      ▫ 4 Mbps throughput to support all CBTC functions
    • Error tolerance:
      ▫ Packet loss rate of less than 0.1%
    • Network latency:
      ▫ Maximum latency of 5 ms to achieve overall CBTC
      performance
  • Moxa Solutions

    • Layer 2 Turbo Roaming (handoff <50 ms):
      ▫ WAC-1001 wireless access controller enables rapid roaming
         with centralized security
      ▫ 3 non-overlapping channels of roaming for less interference
      ▫ Packet loss rate of under 0.1%
    • Network latency under 1 ms
    • Stable throughput: 4 Mbps of throughput
    • Roaming diagnosis service

EN 50155 Products:

    WAC-1001 Layer 2 Wireless Access Controller
    WAC-1001
    Layer 2 Wireless Access Controller
  • Enables layer 2 roaming with centralized security
  • Supports inter-controller roaming
  • IEEE 802.11i-compliant wireless security
  • Redundancy via hot standby controller
    AWK-3121-RTG Series Industrial IEEE 802.11a/b/g wireless AP/Client
    AWK-3121-RTG Series
    Industrial IEEE 802.11a/b/g wireless AP/Client
  • QoS (WMM) and VLAN for efficient network traffic
  • Supports controller-based Turbo Roaming
  • Compliant with essential sections of EN 50155
  • M12 anti-vibration connectors (AWK-3121-M12-RTG)
  • -40 to 75°C operating temperature range (T models)
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