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Interference into GLONASS is a more difficult problem due to the closer frequency separation.
No diplexers are available that are able to remove the out-of-band interference from SATCOM
transmissions into GLONASS, but as the system has not yet been installed in western
commercial aircraft, the problem does not exist.
Without international co-ordination, the radio spectrum would rapidly become unusable due to
incompatible signal formats, strengths and frequencies. Use of the radio spectrum is coordinated
by the International Telecommunications Union (ITU) through international conferences
with the agreements published in the Radio Regulations; however, states are at liberty to make
exceptions to the regulations for internal radio services and to transmit on any frequency within
Document prepared by EVP Europe, August 1999 Page 9 of 14
their national boundaries. Exceptions are usually registered as footnotes to the regulations;
however internal military transmissions are generally unregistered.
Allocations for GNSS and mobile Satellite Communications before 1992
VHF datalink appear “better than” satellite communications9
Switching between ground-based VHF and satellite-derived datalink for CNS/ATM operations can
be a seamless procedure, according to tests carried out by the Dutch National Laboratory NLR
and ARINC. In general, the ground-based system proved faster and broader than the satellite
link. An NLR Cessna Citation III equipped with a EuroTelematik advanced flight management
system connect to ARINC’s VHF digital Mode 2 (VDLM2) and satellite communication
(SATCOM) networks, made a number of low-altitude flights over the North Sea to test automatic
switching of networks needed due to the line-of-sight limitations of VHF.
9 From Jane’s Airport Review, July /August Vol11, Issue 6.
Document prepared by EVP Europe, August 1999 Page 10 of 14
Under test was the end-to-end delivery of Automatic-Dependent-Surveillance (ADS), Controller-
Pilot Datalink Communications (CPDLC) and Aeronautical Operational Control (AOC)
messages. The trials were attended by the European Commission and Eurocontrol. “Although
performance analysis of the different sub-networks was not an objective of the project, it was
found the quality of service of VDLM2 was significantly better than SATCOM” according to Eric-
Jan Hartlieb, NLR’s Program Manager. “The transfer delay of messages was less than a second
for VDLM2, while SATCOM introduced delays of at least 10 seconds. Also the throughput of
VDLM2 was significantly better that that of SATCOM. Although no extrapolations for operational
use can be made based upon these results, the performance difference was too significant to
ignore”.
7. Economic study
The initial costs up to 2001 are estimated at Euro 58.4 million. The overall costs for GNSS I and II
will be discussed below in Parts 2 and 3.
B. GNSS-2
1. Technical aspects
Civilian navigation overlay systems are the first step. Not only Europe proposes to advance the
civilian use of satellite navigation, moving from the current GPS and GLONASS systems to a
next-generation system that meets the needs of the most demanding civil users. Development
work on a non-military GNSS has started in Europe, with operational hardware already in orbit.
The service entry of EGNOS and equivalent systems in the US and Japan will certainly not mark
the end of the development of satellite navigation systems. Research has already started in
Europe on developing technologies for a second generation of satellite navigation systems –
which includes satellites, user and ground equipment – the performance of which would meet
civilian user requirements.
This new technology would ,for example, lead to a sufficiently accurate, redundant and
independent system for use as the sole means of positioning, timing and navigation, including
the most demanding applications. Such a future system is known as GNSS-2 or the Second
Generation Global Navigation Satellite System. Initial European studies show that there are no
unsolvable technical problems that would prevent development of a GNSS-2. GNSS-2 may also
integrate other services, potentially even communications links.
The EC and the ESA have both recently launched contracts to study an action plan and to define
a possible system architecture for GNSS-2. The studies will examine a variety of operational
scenarios that could meet, at the very least, existing civilian operational requirements. Aviation
users, for example, are looking for GNSS-2 to be accurate and reliable enough to allow its use
as a sole means of navigation for the Category 3B precision approach – which allows landings in
　
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