Introduction
A DCS architecture provides the data connectivity between onboard applications and ground infrastructure, regardless of the position of the train along the line. The architecture is protected by a high-level security system to prevent unauthorized access. A moving train is only connected to a specific wayside AP for a few seconds, and handover times that exceed 100 ms may cause critical data loss. The rail industry therefore faces a stark challenge in order to achieve uninterrupted, reliable communications: reduce roaming time to below 50 ms in a redundant DCS system.
Application Requirements High-speed roaming with network security
| Minimal adjacent channel interference
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Moxa's Solution
| Pre-authentication by the wireless controller | To allow seamless roaming for high-speed trains, Moxa’s rail-specific Turbo Roaming technology is enabled by a Wireless Access Controller (WAC) that offers centralized security management. When roaming to another AP, the client can be pre-authenticated by the WAC to bypass the re-authentication process, which reduces the switch-over time to 50 ms. High-standard security with WPA, WPA2, and 802.11i is provided to ensure secure network access. | |
| Inter-controller roaming for large-scale WLANs | Deployed at the OCC, each WAC-1001 can manage up to 200 APs on the same LAN. For larger-scale WLANs, inter-controller roaming can be used to support hundreds of APs. When a client roams from one WAC’s zone to another, the two controllers exchange security keys and the new controller copies the security key to the new AP. The client can thus continue to roam between APs at under 50 ms, while still maintaining network security. | |
| Three-channel roaming | On a WLAN, adjacent APs should work through different channels to avoid radio interference. Moxa provides three non-overlapping channels for roaming to avoid adjacent channel and co-channel interference. | |
| Various wayside antenna scenarios | To ensure effective handoff for vital and non-vital applications, Moxa’s universal roaming method is suitable for many wayside antenna combinations and scenarios, including directional, omni-directional, leaky cable, and waveguide antennas. | |
| Rugged Anti-vibration M12 connection | Moxa provides entire M12 connection products that can tolerate constant vibration and heavy shockin the harshest railway environments | |
| Completely redundant links | A CBTC relies heavily on the WLAN to support continuous train-to-ground communications, and the safe way to avoid link failure on a WLAN is through redundancy. Moxa offers multi-redundancy technology that includes wireless redundancy using dual-RF design, Ethernet redundancy using RSTP, and power redundancy using dual DC inputs and PoE, which sufficiently guarantees secure transmissions for video, voice, and other demanding applications such as real-time PIS systems. |
Application Architecture
Seamless Roaming Across Redundant Train-Ground Networks
Redundant Wireless Wayside NetworkDual APs for redundancyWayside APs are interconnected to Ethernet switches?
Redundant Wired Backbone Network
| Redundant Wireless Wayside Network
| Redundant Onboard Network
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| Product Offerings | AWK-RTG Series Train-to-ground AP/Bridge/Client | |
| • Supports all AWK-RTG series products • Roaming delay < 50 ms • Security with WPA/WPA2 and 802.11i • Supports up to 200 APs • One 10/100 Ethernet port • Railway hardened - IP30, DIN-Rail, -40 to 75°C | Single-RF Solutions AWK-3121 AWK-4121 Dual-RF Solutions AWK-5222 AWK-6222 | • Sub-50 ms Roaming • Security: WPA/WPA2/802.11i • Multi-redundancy (dual-RF solutions) • Wireless, Ethernet, power redundancy • Supports three-channel roaming • Train speed at 120+ km/h • Railway Hardened: • Ruggedness - M12, IP68, and -40 to 75°C - One SSC fiber optic port • Certifications - Onboard: EN 50155/50121-3-2 and IEC 61373 - Trackside: EN 50121-1/50121-4 |
