Communications & IT
authorities that have migrated to the
IP-based systems.”
While the migration to IPS is
currently being thought of in terms of its
impact on data link communications,
Pendergast believes that the real
advantages of the change are much
broader in scope.
“From an operational standpoint it
will open up all of the possibilities of
IP-based applications used for airline
operations that we currently enjoy for
our personal and business use,” he says.
“Airlines will be able to develop
applications that can optimize how
the aircraft is flying, fuel efficiency
and maintenance.”
Meanwhile, on the ground IP-based
systems will allow for greater situational
awareness, Pendergast believes: “The
latest radar systems have a much higher
ability to send weather data. With IP
capability in aircraft, they can become
flying nodes, capable of receiving weather
data down from other aircraft and
sharing it so that Air Navigation Service
Providers have a much better awareness
of developing weather and turbulence.”
Pendergast envisages applications that
use real time weather data to provide
much quicker re-routing of flight paths
between air traffic controllers and flight
dispatchers in the event of extreme
weather events.
IMPLEMENTATION CHALLENGES
According to Pouzet there are two key
challenges to implementing IPS: mobility
and security. “For the OSI protocol the
mobility is inherent to the application. In
the context of aviation this means that an
aircraft anywhere on the Earth can
connect to the network,” he says.
IPv4, the most widely used version of
IP, cannot facilitate this level of mobility.
But IPv4’s successor, IPv6 can. For this
reason, ICAO has chosen to base its IPS
systems on IPv6, which now accounts for
about a quarter of all internet traffic.
Perhaps a bigger challenge is
overcoming the security risks in
migrating to a system which is based on a
technology much more widely known,
AIR TRAFFIC COMMUNICATION
FUNDAMENTALS
The arrival of Voice over Internet Protocol
(VOIP) to , an internet-based voice
communication, seems at first glance to
be disruptive to existing legacy systems.
However, VOIP only impacts ground-ground
communication. “Controller to controller
communication and controller to the
ground radio station will be affected by
this technological change. VOIP ground
radio stations will continue to use legacy
technology to communicate to the pilots via
the mobile link,” says Eurocontrol’s
Liviu Popescu.
When a controller talks into a voice switch
the communication is sent via fiber optics to
a remote site, where it is converted to radio
waves and transmitted up to the plane via
the existing analogue system.
Dieter Thigpen, air-ground voice
communications manager at the FAA says,
“The ED-137 standard is dealing with the
on-the-ground protocol for a voice switch
to talk to a voice switch, a voice switch to
talk to a recorder, a voice switch to talk to a
radio or to a remote radio node. It’s all on the
ground.”
Thigpen believes the biggest advantage
with VOIP for ATC is the extra bandwidth
and the ability to more easily reconfigure
the system in the event of an outage. “If you
have an ATC tower and a remote site goes
down you can reconfigure and talk to a
different remote site, so you can remain in
communication with the aircraft, because
with an IP-based system each location has
its own address,” he says.
Some ANSPs are already using VOIP,
notably Romania. “They were actually
the first country to put fibre optics in the
ground,” says Thigpen. “They jumped a
generation of technology.”
Popescu says that it is now the right time
beginning to think about the next stage in
the evolution of voice communications –
making air-ground communications fully
digital. “It’s a phase that will come but we
need to see what new IP technologies come
about with the development of ATN IPS data
link,” he says.
AEROSPACETESTINGINTERNATIONAL.COM // DECEMBER 2019 55
which is being developed by SESAR and is based on
4G and 5G and is the most advanced of the three
new technologies.
The three technologies will combine to provide
what’s known as the Future Communications
Infrastructure (FCI), complementing each other to ensure
smooth and efficient communications in aviation.
“We’re foreseeing that in the future there will be a
mix of communications,” says Pouzet. “On board aircraft
there will be VHF/analogue for voice communications.
There will also be VDL mode 2 because it’s already
mandated. We also expect to have SATCOM and LDACS.
“So there will be at least three different
communication links operating in different frequency
bands potentially with different protocols to make sure
we are providing the appropriate level of availability and
redundancy that is required by aviation.”
CREATING CONSISTENCY
This mix of communication systems also reflects the fact
that adoption of IPS around the world is very likely to be
inconsistent, says Pendergast.
“Change in aviation typically moves slowly,” he says.
“Airlines are going to have a mix of aircraft, some new
and some old. Aircraft still operating with legacy
systems have to be able to communicate with aviation
1 // Communications in ATM is
shifting away from the Open
Systems Interconnection and
VDL Mode 2 standards to use
three technologies, Satcom,
LDAC and AeroMACS
1
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