All change? Metros’
evolving requirements
TETRA and Wi-Fi are the dominant radio standards for metro and light rail
communications and signalling systems, but LTE is starting to make inroads
in the market, as James Atkinson nds out
The number of metro and light rail systems is
Marta Fontecha, product marketing director at Hytera
subsidiary Teltronic, notes that TETRA was also attractive
to metro operators because it is relatively easy to update
and expand as the metro system grows. “TETRA’s greatest
value though is that a single network supports voice and
datacommunications.”
Voice systems
TETRA enables instant push-to-talk (PTT) individual
and group communications with priority and pre-emption
services between the driver, control centre/dispatchers,
depots, station operations and platform sta, security,
maintenance and engineering crews. Direct mode operation
allows crews on the same train to talk to each other and
to platform sta. e metro TETRA system can also be
integrated with external TETRA networks used by the
emergency services.
TETRA can be integrated with the metro intercom
system and public address solutions, so the driver or the
control room can communicate with passengers on the
trains. It can also connect with other train subsystems both
locally and in the control centre including PABX and PSTN
telephony networks, computer aided dispatch (CAD),
the passenger information system and, very importantly
growing at a phenomenal rate as populations
ock to the cities, placing increasing demands
on urban transport systems. As a result, urban
authorities are building new metro lines,
particularly in the Asia Pacic region (see box on page 27).
Modern metros rely heavily on wireless radio systems for
voice, data, signalling and safety systems, and this reliance
is increasing as levels of automation rise and more driverless
metros come on-stream. Metros require mission-critical
communication standards with high levels of resilience,
availability and security. e TETRA two-way radio
standard is unsurprisingly, therefore, a popular choice.
“TETRA systems dominate the radio communications
market for metro networks today,” says Eric Davalo, head
of strategic development, Secure Land Communications at
Airbus. “ere is some LTE use starting to come in, largely
driven by the Chinese market.”
How did this dominance come to pass? “TETRA was
attractive to metro operators looking to move to digital,”
recalls Mark Skinner, solutions architect at Motorola
Solutions. “TETRA is an open European standard, there
are lots of suppliers and the equipment is all interoperable
between vendors.”
24 www.criticalcomms.com June 2019
/www.criticalcomms.com