ACP WG-F/28 WP19
International Civil Aviation Organization
WORKING PAPER
AERONAUTICAL COMMUNICATIONS PANEL (ACP)
28th MEETING OF WORKING GROUP F (WG-F)
Lima, Peru 11 – 23 March 2013
Working Paper on AMS(R)S in the MSS L Bands
(Presented by John Taylor)
SUMMARY
This paper discusses some of the history of AMS(R)S in the MSS 1.5-1.6 GHz
bands, and the proposed Inmarsat introduction of an enhanced AMS(R)S
safety service program that is planned to meet ICAO RCP requirements to
support reduced aircraft separation in oceanic airspace, and clarification by the
ITU on the allocation of AMS(R)S in the MSS bands.
1.
INTRODUCTION
1.1
The use of satellite for communications in civil aviation has a long history, initially
recommended by the 10th Air Navigation Conference in 1991 as part of the future CNS/ATM systems
concept. The ICAO Council later endorsed the recommendations of the 10th ANC that future satellite
communications concepts support voice and data. AMS(R)S systems are an essential element of the
ICAO standardized communication infrastructure for the provision of safety and regularity of flight.
1.2
Under an AMS(R)S allocation, the provision of voice and data for aeronautical safety is
by commercial satellite providers for both the space and ground segments. SARPs were adopted by ICAO
in 1995 for the provision of AMS(R)S, which ensures that system operators provide a service meeting the
required integrity and reliability.
1.3
Prior to 1997, in the ITU frequency allocation table, the frequency bands 1 530-1 544
MHz (space-to-Earth) and 1 626.5-1 645.5 MHz (Earth-to-space) were allocated to the maritime mobilesatellite service and the frequency bands 1 545-1 555 MHz (space-to-Earth) and 1 646.5-1 656.5 MHz
(Earth-to-space) were allocated on an exclusive basis to AMS(R)S. However, as time went by, due to low
usage of AMS(R)S communications in the exclusive allocation together with the intense demand for other
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commercial services in the L-Band spectrum, WRC-97 made a generic allocation to the MSS in the bands
1 525-1 559 MHz and 1 626.5-1 660.5 MHz. In doing so, WRC-97 adopted 5.353A related to the Global
Maritime Distress and Safety System (GMDSS), and 5.357A giving priority to accommodating spectrum
requirements for AMS(R)S communications as defined within priority categories 1 to 6 in Article 44 in
the frequency bands 1 545-1 555 MHz and 1 646.5-1 656.5 MHz.
1.4
Whilst trying to find efficiencies in the use of MSS spectrum, and at the same time
respecting the priority and pre-emption requirements of 5.357A for AMS(R)S traffic over non-safety
communications, studies were performed in the ITU-R on the technical and operational feasibility of
priority and pre-emption amongst different satellite service provider networks. In the end, it was
concluded in Report ITU-R M-2073 that inter-system prioritisation and pre-emption was not technically
feasible or operationally possible.
1.5
Meanwhile the coordination of frequency assignments between MSS operators is done on
a multi-lateral basis using a capacity planning approach at frequency coordination meetings. This is
overseen by the notifying State Administrations who meet and intervene in the process when required.
Currently there are some MSS systems that provide safety communications in the generic MSS frequency
bands 1 525-1 559 MHz and 1 626.5-1 660.5 MHz. WRC-12 debated the frequency assignment and
coordination matters and agreed on a procedure contained in an Annex attached to Resolution 222 as
modified by WRC-12.
1.6
WRC-12 addressed concerns that demand for spectrum in the frequency bands 1 525-1
559 MHz and 1 626.5-1 1660.5 MHz by several mobile satellite systems is increasing, and that the
application of Resolution 222 may impact the provision of both safety and non safety services in the
MSS. Stemming from this point, WRC-12 also endorsed the call for efficient use of spectrum expressed
in resolves 2 of Resolution 222: “that notifying administrations of mobile-satellite networks shall ensure
the use of the latest technical advances in their mobile-satellite systems, in order to achieve the most
flexible, efficient and practical use of the generic allocations” (1 525-1 559 MHz and 1 626.5-1 1660.5
MHz).
1.7
The need for efficient use of spectrum in all frequency bands has clearly been articulated
by the ITU and was the basis for adopting the generic MSS allocations at WRC-97. To ensure efficient
use of the generic MSS bands 1 525-1 559 MHz and 1 626.5-1 1660.5 MHz by several mobile-satellite
service providers for the provision of safety and non-safety communications in the aeronautical, maritime
and commercial domains, it is very important that the frequency assignment and coordination process
allow operators to take advantage of the flexibility offered by the generic allocations. This will enhance
the efficient and practical use of the spectrum and is a benefit to the users of the service, in particular to
the aviation community through having access to AMS(R)S communications across the generic MSS
bands.
2.
RECENT ACTIVITIES
2.1
The recent proposal by Inmarsat to offer an enhanced AMS(R)S safety service program
in the oceanic regions is based on the availability and development of newer satellite technologies. The
enhanced safety service program has been designed to meet ICAO RCP requirements on link availability
and reliability, with additional services and higher data rates that are not available with the current Classic
Aero service.
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2.2
Presently the Classic Aero avionics support ATC and AOC voice and data services. The
ATC and AOC data services are provided using the ACARS character based data protocol. The Inmarsat
Classic Aero service operates in the 1 545-1 555 MHz and 1 646.5-1 656.5 MHz bands. The enhanced
safety service oceanic program is designed to operate in 1 525-1 559 MHz and 1 626.5-1 1660.5 MHz
bands, as well as the extended MSS 1 518-1 525 MHz and 1 668-1 675 MHz bands, while still meeting
ICAO and ITU requirements.
2.3
Further, there are future plans by ANSPs towards implementation of reduced aircraft
separation in oceanic airspace regions. Implementation of reduced aircraft separation in designated
airspace regions will require the satellite communication links to meet RCP requirements on availability
and reliability. Enhanced aircraft position reporting through ACARS, Prioritised IP, etc, will be required
to meet the higher service availability and lower message latency. Availability of this service to aviation
will provide efficiencies that support the benefits of reduced separation in oceanic airspace, also the
ability for pilots to request optimum altitudes and flight routing based on dynamic weather updates
received enroute, thereby maximizing efficiencies in aircraft fuel burn, while at the same time minimizing
carbon emissions.
2.4
By comparison, the current Classic Aero system was not designed to meet any
developing RCP requirements for link availability and reliability, however the service has been a
significant cornerstone for many years in supporting the satellite communications concepts envisioned by
the 10th ANC in 1991. Moreover, with the recent advancements in satellite technologies there are
technical and operational efficiencies to be gained through the use of Inmarsat’s enhanced oceanic safety
program that will provide AMS(R)S capability to aviation throughout the MSS bands, and not limited to
the 1 545-1 555 MHz and 1 646.5-1 656.5 MHz bands, thus easing the frequency coordination process
and maximizing the efficient use of spectrum.
2.5
Considering the regulatory changes prior to 1997 when AMS(R)S had an exclusive
allocation, and post 1997 when the WRC made generic allocations to the MSS, it has been widely
assumed that AMS(R)S was only permitted in the 1 545-1 555 MHz and 1 646.5-1 656.5 MHz bands.
However, development of more advanced satellite technologies, coupled with the vision of ICAO to
promote reduced oceanic airspace separation, and the ITU requirement to achieve spectrum efficiency,
has in some ways led to the need to seek clarification from a regulatory perspective as to how the
allocation to AMS(R)S is authorised within the MSS bands.
2.6
Clarification was sought from the ITU Bureau on the provision of AMS(R)S in the MSS
bands, and to know if the allocation was restricted or limited in accordance with the Radio Regulations.
The reply from the ITU Bureau clearly stated that the allocation to AMS(R)S is throughout the MSS
bands, 1 525-1 559 MHz and 1 626.5-1 1660.5 MHz bands, as well as the extended MSS bands 1 518-1
525 MHz and 1 668-1 675 MHz.
2.7
It is noted that ICAO Annex 10 SARPs and also ICAO Doc 9925 do not specify any
frequency band in which AMS(R)S must operate. The Annex 10 SARP’s requirement states, that when
providing AMS(R)S communications, an AMS(R)S system shall operate only in frequency bands which
are appropriately allocated to AMS(R)S and protected by the ITU Radio Regulations.
2.8
Considering the potential for limitations on the efficient coordination of available
AMS(R)S frequency assignments in the 1 545-1 555 MHz and 1 646.5-1 656.5 MHz bands for oceanic
use and to support the ICAO RCP satellite link requirements for reduced separation in oceanic airspace,
there is a need to apply the allocation to AMS(R)S in accordance with the ITU Radio Regulations.
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3.
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CONCLUSION
3.1
WG-F is invited to consider the information in this paper, and to endorse the frequency
spectrum needs stemming from:
 The concept and implementation of reduced aircraft separation in oceanic airspace
envisioned by ICAO.
 That, in order to support reduced aircraft separation in oceanic airspace, the ICAO RCP
requirements for satellite link availability and reliability need to be met.
 The efficiency benefits available to aviation through the use of reduced separation in
oceanic airspace (as noted in 2.3).
 That in a competitive MSS market, the number of service providers offering AMS(R)S is
extremely limited.
 That any constraint on the coordination of limited MSS frequency assignments to provide
AMS(R)S could have an impact on the implementation of reduced separation airspace in
oceanic regions, and the vision of ICAO may not be fulfilled.
 That some of the above points could place a burden on the continued availability of
AMS(R)S service provision and the efficient utilisation of spectrum resources if the
bands available for assignment are restricted to 1 545-1 555 MHz and 1 646.5-1 656.5
MHz.
 That the MSS operators and notifying administrations when coordinating frequency
assignments for AMS(R)S, have the capability to efficiently coordinate spectrum
assignments throughout the MSS bands as allocated by the ITU Radio Regulations for
AMS(R)S use.