Invention: Radio signals for better satellite navigation
Space-based radio navigation positioning has made significant strides in recent decades. It is now poised to make a greater leap thanks to Galileo, Europe's global navigation satellite system (GNSS). Signalling technology developed by a team of European engineers not only helps Galileo deliver better accuracy and clear up signal clutter; it also pushes satellite navigation and its features to the next level.
A European team, led by French engineer Laurent Lestarquit and his Spanish colleague José Ángel Ávila Rodríguez and including German Günter Hein and Belgian Lionel Ries, has a unique specialism: sending clear signals from space. A virtual cacophony of radio frequencies is sent down to earth from the more than 50 navigation positioning satellites currently in orbit - including those of the US-led Global Positioning System (GPS), Russia's Global Navigation Satellite System (GLONASS) and more recently Europe's Galileo system. This team has helped ensure that signals do not interfere with each other, and that users and developers alike will be able to profit from the next-generation positioning technology that Galileo offers.
The team's contribution of modulation and spread-spectrum signal technologies forms one of the joint European
satellite positioning system's core
components, delivering signals that enhance accuracy, save on satellite power
and ensure interoperability with GLONASS and the current GPS and its possible upgrades.
When fully operational in 2020, Galileo will be the most advanced and
accurate GNSS in the world, with horizontal and vertical positioning accuracy to
within a metre for standard signals - and within a few centimetres when using
high-end signals and precise positioning techniques. It will also provide better
positioning services at high latitudes, advanced global search-and-rescue functions
and a host of other capabilities.
Societal
benefit
Apart from initial gains in
navigational and positioning accuracy, Galileo will benefit its users thanks to
a forward-looking concept designed to work with emerging technologies ranging
from autonomous driving and travel optimisation to machine-to-machine
communication and the Internet of Things.
In the not-so-distant future, GNSS is
likely to have a direct influence on transport, increasing time and fuel
savings as well as improving safety. Galileo might be incorporated into
national road toll systems, support smart agriculture to make better use of
available land and aid in more accurate surveying.
Further afield, modern European 'smart cities' are
likely to use information from Galileo for more efficient urban management and
planning. Shipping companies already turn to GNSS-based solutions for
multimodal logistics to better track and time shipments. Even pressing
international issues such as climate change, environmental concerns or natural
disasters could see innovative solutions thanks to the satellite positioning system.
Galileo stands to enrich such an
array of public, private and research applications, because it is specifically
designed for civilian use - unlike GLONASS and GPS, which have their roots in
military applications. The system reserves one secured signal for strategic and
security applications, but leaves the rest open to the public, ensuring
Europeans and all other users access to an independent satellite navigation
system.
Economic benefit
Galileo aims to raise Europe's share in the global GNSS market, which will
generate an estimated EUR 350 billion in annual revenues by 2020. A 2015 European
GNSS Agency report predicts that the global GNSS downstream market (the full
retail price of devices with GNSS chipsets) will see a 7% compound annual
growth rate during this period, outpacing global GDP.
GNSS technologies are spurring on companies ranging
from massive mobile phone and device manufacturers to tiny global positioning
speciality firms. According to AZO, a start-up
facilitating agency, in the German state of Bavaria alone there are 119
start-ups implementing or exploiting Galileo signals, which employ about 1 600
people in high-tech jobs and produce an estimated EUR 130 million in combined
annual turnover.
When
Galileo is fully operational in 2020, with the planned total of 30 satellites -
counting six spares - it is expected to lead to significant economic benefits,
including R&D investment by the aerospace sector generating a social return
of around 70%. In other words, for every EUR 100 million invested in R&D,
GDP should grow by EUR 70 million in other sectors over the longer term.
Once
fully operational, Galileo is expected to have an economic impact of EUR 90
billion over the next 20 years.
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Lionel Ries, Günter Hein and Jean-Luc Issler (from left to right)
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José Ángel Ávila Rodríguez and Laurent Lestarquit holding a satellite model (from left to right)
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Günter Hein and Lionel Ries (from left to right)
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Laurent Lestarquit, Lionel Ries, José Ángel Ávila Rodríguez, Jean-Luc Issler and Günter Hein (from left to right)
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Jean-Luc Issler, Lionel Ries and José Ángel Ávila Rodríguez (from left to right)
How it works
Lestarquit
developed a patented modulation technique called Alternative Binary Offset Carrier modulation
(AltBOC), which effectively
packs four signals into one large one: two highly accurate signals from Galileo's
open service - the free-of-charge channel for consumer applications - and two
signals from its Safety-of-Life service - a paid service designed for
applications such as aviation, where lives might depend on signal integrity.
AltBOC not only offers extremely high accuracy for specialised receivers, it
also helps save satellite power.
The
team has also developed an innovative spread-spectrum technique that creates a
new single waveform via what is called Composite Binary Offset Carrier (CBOC) modulation.
This signal will allow high-end receivers to accurately calculate positions,
but is also compatible with older, lower-end devices and other GNSS signals.
The CBOC patent includes a novel concept allowing the combination of open CBOC
and secured Public Regulated
Service (PRS) signals in a
single frequency. PRS signals are designed to be used by civil authorities,
such as police, coastguards and customs agencies. PRS is encrypted and includes anti-jamming mechanisms.
The inventors
The inventor of AltBOC modulation and
co-inventor of the CBOC waveform, Laurent Lestarquit became interested in GNSS
technology while it was an emerging field not yet taught at university. He
graduated from the French Space and Aeronautics Institute in 1996, one year
after GPS went live. Aside from his work on AltBOC and CBOC, he has contributed
to the development of the PRS signal and was part of the French delegation at
the GPS and Galileo negotiations, which determined the parameters for
compatibility of the two systems. Lestarquit's
navigational pursuits extend beyond
his career: he has competed in high-level orienteering contests using
traditional, non-GNSS skills to navigate. He has also been a navigator in the
international, off-road "Camel Trophy" race.
Ávila Rodríguez received
his PhD in Aerospace Engineering from the German Federal Armed Forces
University in Munich and over the past 15 years has held GNSS engineering
positions, worked as a senior consultant and served as a manager or member of
numerous GNSS-related programmes. Ávila Rodríguez, who has authored or
co-authored over 60 scientific articles in the field of satellite navigation,
has held the position of GNSS Evolutions Signal and Security Principal Engineer
at the European Space Agency since 2015. He is the recipient of numerous awards
for his work in the field of GNSS.
Supporting Ávila Rodríguez
and Lestarquit were principal members of the Galileo Signal Task Force
and co-inventors of the CBOC patent: Frenchman Jean-Luc Issler, who not only helped assemble the team, but also develop
one of the other frequency bands used by Galileo; German academic Günter Hein,
who developed and taught navigational technology and design in a career
spanning over 40 years; and French-Belgian national Lionel Ries, who has
authored or co-authored 25 patents and about 100 research papers, mostly relating
to satellite navigation.
Did you know?
Global positioning with satellites has a myriad of
applications and one of the most distinct is to give further evidence to support
Albert Einstein's theories of special
and general relativity. Special relativity postulates that, the faster an
object travels, the slower the time on the object elapses relative to a slower
moving body. General relativity sees gravity as a curvature in "spacetime", where more massive bodies
bend time and space around them.
Both theories are measurable through
GNSS technology. Fast-moving global positioning satellites equipped with atomic
clocks show a relative time shift of about 7 additional microseconds
(millionths of a second) per day due to their roughly 14
000-km/h orbit speeds. However -
pushing time in the other direction -
the effects of a lessened gravitation pull (less spacetime curvature) actually
cause their clocks to run 40 or so microseconds faster than they would on
Earth.
Galileo's atomic clocks accommodate these principles, and other "time-changing" phenomena like the Sagnac effect
caused by the Earth's rotation,
by slightly slowing their clock speeds and synchronising every 100 minutes or
so. It's interesting to know
that the technology being employed in your GNSS device is helping to prove
Einstein right, then. Take a look at other ways in which space and
satellite technology supports scientific discoveries and industry.
