Imagine yourself inside a tube train, commuting to work like on any other day. But today something is wrong: you start to feel dizzy and you know you need urgent medical assistance.
At this point, you use the intercom (on-board telephony) in the carriage to communicate with the control centre, which activates the protocols to send an emergency team that will meet you at the next stop, thereby coordinating a quick and necessary response to improve your health.
But have you ever wondered how that intercom works? The carriage is in motion, often without a driver because it is an automatic line. Nonetheless, communication with the control centre is quick and safe.
These critical communications, which must always be available, are supported by TETRA (Trans European Trunked Radio) networks. This is an international standard, created more than 20 years ago, able to establish communications even without the need for an operational antenna nearby.
Most countries have a radio frequency reserved for critical communications (380-400 MHz), and this low frequency allows greater coverage for each of the antennas installed.
Cellnex has implemented this type of network and maintains the connectivity project on line 9 of the Barcelona metro, a complex project designed for a large line: more than 47 km of tunnels, 50 stations, 2 train sheds, a workshop area …
Cellnex is an expert in connectivity solutions for suburban transport networks and environments. The company currently manages the connectivity services of the Underground system of Madrid, Milan and Brescia among others; and the communications networks for security and emergencies on the aforementioned Line 9 of the Barcelona and Valencia Metro systems.
The evolution towards LTE
TETRA networks, used for critical communications, are used primarily to transmit voice. They can also transmit data, but at lower speeds. That is why we are working at a technological level on hybrid TETRA-LTE projects.
LTE (Long Term Evolution) is another mobile communications standard characterised by the possibility for high data download and upload rates (bandwidth) with low latency (from 10 ms). The benefits of adopting this hybrid approach to critical communications include lower costs with the sustainability of previous investments, while increasing flexibility with a smooth introduction of new service possibilities such as querying and submitting images in streaming or consulting databases, among others.