3 vital needs
- Keeping in touch. Drivers are on the move and change cells frequently. They may work on a different train every day and even switch trains during a shift.
- Excellent coverage. For metros, radio coverage is needed in tunnels, which limit the propagation of radio waves.
- Reliable contact. Whether trains run on the ground or under it (or both), public safety demands instant, reliable, two-way communication between drivers and dispatchers, stations and security personnel.
How to meet these needs?
This is how TETRA radio communication systems from Airbus can meet these three vital needs:
1. Keeping in touch
- Seamless call handovers are a must. This requires that both the system and the radio terminal use Type 1 Handover. This is the call handover type that ensures that the connection is not cut when users move from one base station cell to another. Radios with Type 1 Handover synchronise themselves with a new base station as soon as it is detected.
- Call the train, not a driver. Secondly, when the driver of a particular train needs to be reached, it is important that either the train number or the train line number can be used. It is also essential to reach the driver of the train even if the person changes as people change shifts.
- … Even when the driver carries a handheld radio. Role-based numbering is also desirable, ensuring the correct driver can be reached using the train/line number even when the driver does not use a radio unit that is permanently installed in the train car.
2. Excellent coverage
- Choose the base stations right. When building radio coverage, the trick is to balance the uplink - traffic from a radio terminal to the base station - and downlink - from a base station to the radio terminal. The uplink is far more critical, so a base station should have significantly better than average uplink connection. This allows better coverage with fewer base stations, cutting costs.
- Think small and handy. Setting up a network in difficult locations such as tunnels with very limited accessibility and little space can be challenging. Sensitive, powerful base stations with low power consumption and small physical size are important, as is an ability to be able to operate and maintain them remotely.
- Consider mini base stations instead of RF repeaters. Thirdly, while regular RF repeaters are an option for tunnels, a miniature base station that requires less power, does not need line of sight to the serving base station, has no RF-isolation requirements and needs no RF expertise for setting up, all mean easier and faster installation.
3. Reliable contact
Instant connections are essential in the fast-moving rail environment. Users do not want to wait for call setup. Group calls in TETRA systems by Airbus save time, with a connection delay that is always less than half a second.
Users are on the move all the time in this business. They need to be able to roam anywhere in the network, yet use the same services in the same way.
Priority scanning is another must. Normal scanning allows the radio users to monitor their own talk groups. Priority scanning means that talk groups each have a priority that is specific to an organisation. A radio can scan two or more talk groups while it is engaged in a call. When a higher priority call starts, the radio may leave a current call to join this new call.
+ 3 bonus benefits
These are three additional features that every train operator should have:
- Special applications are effective at streamlining dispatching. With a TETRA system from Airbus, it is possible to make semi-conference group calls, where group members can hear the dispatcher, but only the dispatcher can hear group members. It is also possible to integrate the radio network with the trains' onboard computer systems, allowing downloading of route plans and other data.
- Use in a variety of ways. It is also a benefit to be able to use the same, reliable TETRA network for different purposes, from scheduling a train’s arrival at a station, to security notifications and passenger information, all of which can be accomplished with one system.
- Reach people nearby. It is very useful to be able to define communication groups by location, so that users can call everyone in their vicinity. With Airbus TETRA, when users push the PTT button, the system automatically checks their location. Then it sets up any group calls to other members in the same place. The user always “sees” and uses the same group, but the system gathers together the correct users each time they make a group call.