Technology Breakthrough Boosts Performance Of UK System
A recent breakthrough in ADS-B
technology by Raytheon Systems Limited (RSL) is now being run
through its paces by various air traffic authorities around the
world. ADS-B (Automatic Dependent Surveillance - Broadcast) is the
next generation of secondary surveillance techniques and
complements Secondary Surveillance Radar (SSR).
RSL's solution for ADS-B uses 1090 MHz Mode S Extended Squitter
(ES)for its data link and since carriage of TCAS, which also uses
Mode S, is already mandated in Europe, all new and many existing
commercial aircraft already have ADS-B capability.
This 1090 MHz frequency band is already extensively used and to
overcome congestion, (also known as 'FRUIT' - False Replies
Unsynchronized In Time) and RSL has conducted extensive development
work to improve decoding capability. Trials have shown the system
works very effectively in congested air traffic environments
extracting and successfully decoding ADS-B messages even when
overlapped or garbled by other signals.
Mike Speed, RSL's director of Air
Traffic Management Systems, said: "RSL has established an enviable
reputation for secondary surveillance radar and now we have
invested in taking the next step in this area of technology.
Following our visits to various air traffic authorities,
demonstrating the considerable advantages of our ADS-B solution, we
will then be concentrating on providing an ADS-B ATMS solution for
our customers.
"Initial feedback is very positive," he added.
Demonstrator systems have been shipped from the UK to locations
as diverse as Singapore, Mongolia, Canada, the USA, Ireland and
Germany. These trials have been of varying duration and dependent
on the requirements of the individual authority.
Raytheon says the introduction of ADS-B would enable the safe
reduction in aircraft separation where there is currently no radar
coverage. ADS-B also offers considerable cost and space benefits
over existing SSR system. Unlike SSR, ADS-B does not use a rotating
antenna and the system itself is highly compact compared with SSR
electronics cabinets. Cost benefits could be substantial compared
to those of a Secondary Radar in a 'green field' situation.
ADS-B is likely to enter operational service in the near future,
initially to supplement and, potentially in the longer term, to
replace SSR.
It is generally accepted that the 1090 MHz frequency band,
already congested with SSR/IFF replies, TCAS communications and out
of band interference from PSR, DME etc, will become even more
congested with the future addition of ADS Extended Squitter (ES)
messages. Hence to perform effectively in such a demanding RF
environment, a high performance decoder will be a critical enabler
for ADS-B on 1090 MHz ES. Hitherto no decoder has demonstrated the
level of the performance required to support ADS-B in the highest
traffic densities predicted for 2015 and beyond. RSL effort has
been to develop a decoder that can meet the projected high FRUIT
environment of the future.
The trials have been conducted in a very varied environment with
contrasting operational needs with great success and support the
extensive modelling results conducted during the development phase.
The trials have been conducted under varying conditions:
The trial in Canada, which was set up at the new Nav Canada
radar site at Almonte, near Ottawa, recorded data over a four week
period. This enabled Nav Canada to evaluate the system's
performance and, in particular, given Canada's unique geographical
situation, the range over which the system is capable of accurately
monitoring air traffic.
Frankfurt is recognized as one of Europe's most dense traffic
environments. The emphasis of the trial here was the performance of
the system in a high FRUIT environment. The system performed
excellently providing high probability of detection, accuracy, as
well as coverage out to 250 nm. In addition additional FRUIT was
injected into the system to simulate future predictions.
The Irish trials focused on long range oceanic coverage. The
Irish Aviation Authority has responsibility for oceanic traffic
entering into U.K. airspace. Their interest was extending the
surveillance range of the existing radar. The ADS-B ground station
range was only limited by the earth's curvature with range in
excess of 250 nm achieved.
The FAA are conducting extensive laboratory testing against the
Minimum Operations Standards (MOPS) and previous system results.
Whilst in the early stages results are very promising with the RSL
solution outperforming previous systems in all aspects. The system
will continue laboratory evaluation prior to being deployed for
field trials including multi-sector antenna evaluation.