Automatic Train Operations (ATO) and Automatic Train Protection (ATP) greatly improve the efficiency and safety of train operations. In order to enable communications between train and trackside, CBTC (Communications-based Train Control) now uses WLAN as its basis. WLAN solutions have become a vital tool for inter-carriage and train-to-ground ommunications networks because they provide freedom from cabling requirements. With increased reliability and bandwidth, WLAN is also tapped to support on-board video surveillance, passenger infotainment systems, and train control, which are important components of ATO and ATS. Rolling stock is an operating environment with unique challenges; all equipment used onboard must meet EN50155 standards, including specifications for EMC, shock, vibration, extreme temperature, and humidity resistance.

• Seamless connections between ground and moving train
• Provide coverage within train carriages
• Flexible carriage changes and low maintenance
• Reliable real-time Passenger Infotainment Systems
• High throughput for real-time public address and video surveillance systems
• Compliant with critical onboard standards

 

Passenger safety and highly available connectivity are top priorities for onboard train networks. These networks allow rail operators to share real-time information between trains, OCC, and stations to provide immediate status updates and emergency controls.

In this application, the train has six carriages. The AWK series is used to provide Wi-Fi within the train. Each carriage is equipped with a VPort 15 IP surveillance camera, which is connected to the wireless network via an integrated Ethernet port. The AWK-3121, a single RF device, is used as a client to access the camera in the front and rear carriages. The AWK-5222, a dual RF device, is deployed in the four central carriages, and can be configured in AP-client connection mode. In this mode, the first RF provides an inter-carriage link or an AP mode, while the second RF provides a client mode to access the camera. One path uses 802.11b 2.4 GHz, and the other path uses 802.11a 5 GHz, to overcome RF interferences in challenging RF environments.

To maintain constant communications while in transit, the fourth carriage includes an extra 802.11n AWK-3132 that acts as a client and is linked via the AWK-5222's Ethernet port. The outdoor 802.11n AWK-4132 is set up as an AP outside the station. This IEEE802.11n architecture provides high bandwidths to ensure that the on-train PA (public address) system and video surveillance are real-time. Faster roaming ensures seamless train-to-ground connectivity while the AWK-3132 on the train is in motion. An onboard server that is linked via an EN50155 managed switch is located in the front carriage to handle all onboard traffic and data transfer between the train and ground.