The Argenia Wayside Interface Unit (WIU) is the link between the back office and the mobile trains in CBT, or train monitoring and advanced warning systems implementation It communicates with the back office over a fiber optic link and communicates with the trains over a wireless frequency hopper radio. The trains may also use a cellular interface which would be used only if a connection to the WIU was not found.
The Argenia wayside Interface Unit (WIU) is comprised of three sections:
- A Fiber Optic Transceivers to send and receive data simultaneously from a Back Office and other downstream WIUs.
- A Wireless network employing a single or dual Frequency hopper radio with diverse antennae and communication software to communicate with trains in its zone
- Optional Axle Counters for primary fixed block train detection. or other RFID train identification devices. Other track coding systems can also be interfaced, as well as Crossing Controllers.
The WIU maintains constant communications with the back office, which reads the WIU replies to regularly spaced polling commands.
The dual Frequency Hopper radio must use separate antennae with diverse positions so as to create significantly different LOS path. For example, one antenna on each side of the tracks.
The train radios are capable of searching for WIU transceivers and will connect to the first link it finds, which is usually the next station WIU. The WIU may use two radios to increase the chance of a good connection. As the train progresses, it find the next 'cell' automatically and never loses contact.
All the WIUs in a zone reside on the same fiber. A unique address is given in each data packet so only one WIU will respond in a particular time slot. The overall network can be broken into zones where each zone may be comprised of 30 or more WIUs. Wius should be placed no more than 4 km apart.
The fiber used is a bidirectional single mode fiber that can send and receive at two different frequencies simultaneously.
The WIU can be solar powered and contains a backup battery for 8 hours of backup operation. When equipped with a cellular modem, the WIU becomes an Internet IoT device as well.
At the control room, standard industrial hardened PCs can be used which connect to a Argenia High Speed Fiber Optic Poller module which drives the fiber segments using Argenias Secure Protocol. A second strand can be used for each segment to allow for a backup link. A fiber Ring topology is also used so every fiber is in a ring where a break anywhere on the ring can be tolerated and does not bring the link down.