IP13 - ICAO International Civil Aviation Organization

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International Civil Aviation Organization ACP-WGF23/
IP-13
INFORMATION PAPER

AERONAUTICAL COMMUNICATIONS PANEL (ACP)

23rd MEETING OF WORKING GROUP F

Cairo, Egypt 21 – 27 September 2010

Agenda Item 3: Development of material for ITU-R meetings

Operation of Unmanned Aircraft Systems Under The Fixed Satellite Service
Allocation

(Presented by Michael Biggs)

SUMMARY
This paper describes a method by which non-payload control links of
Unmanned Aircraft Systems might be operated in non-segregated airspace
under a Fixed Satellite Service Allocation
ACTION

It is proposed that the meeting recognize the benefits offered by allowing UAS
(non-payload) control links to operate under a fixed satellite service allocation
and to support the development of the necessary technical and regulatory
provisions required for such operation.

1. INTRODUCTION

1.1 Under Agenda Item 1.3 for the 2012 World Radio Conference (“WRC-12”), the ITU
Radiocommunications (“ITU-R”) sector has undertaken the following tasks:

a) Determining the amount of spectrum required for the transmission of control signals that
would permit the safe operation of Unmanned Aircraft Systems (“UAS”) in non-
segregated airspace. The spectrum must be large enough to accommodate the following
radio links:
i. Unmanned Aircraft Telecommand
ii. Unmanned Aircraft Telemetry
iii. Relay of voice communications between the air traffic control (“ATC”) and
the pilot of the unmanned aircraft (“UA”)
ACP WG-F23/IP-xx -2-

iv. Relay of sense and avoid data from the UA to the remote pilot.
b) Identifying frequency bands that would satisfy the UAS spectrum requirements.
c) Determining if new service allocations need to be added to the ITU Table of Frequency
allocations.

1.2 The ITU-R has determined that 34 MHz and 56 MHz of spectrum would be required for
the terrestrial and satellite components of the UAS, respectively. The remainder of this document briefly
discusses how satellites in the fixed satellite service might be used to provide for the operation of UAS in
non-segregated airspace.

2. DISCUSSION

2.1 Aeronautical Mobile Satellite (Route) Service (“AMS(R)S”) Spectrum

2.1.1 The current International Civil Aviation Organization (ICAO) WRC-12 position calls for
UAS beyond line-of-sight control links (via satellite) to operate under an AMS(R)S allocation. It should
be noted, however, that even though there have been existing AMS(R)S allocations, to date no dedicated
AMS(R)S satellite has been launched.

2.1.2 Additionally, it is difficult to achieve new AMS(R)S allocations, as due to its safety-of-
life connotation it arguably has “super-priority” over all other services, and in any frequency coordination
discussion, an AMS(R)S/FSS operator would have an unfair leverage/advantage over other co-primary
services in the band, particularly the fixed satellite service (“FSS”). This could force commercial satellite
operators to abandon frequency bands that have an AMS(R)S allocation, so such new allocations are
heavily resisted.

2.2 FSS Approach

2.2.1 Although operation under an AMS(R)S allocation would provide assurance that UAS
control links would have priority over other co-primary services, an AMS(R)S allocation does not
guarantee immunity from interference. From a technical standpoint, UAS radio links could be relayed via
commercial satellites using an FSS service allocation. Specifically, UAS satellite links could be designed
to operate within the established satellite interference environment and meet the technical Standards and
Recommended Practices (“SARPs”) that have been developed by ICAO. In that approach, UAS would
be operating as an FSS application, with all responsibilities and liabilities of the FSS and UAS operator
specified in a commercial contract.

2.2.2 Such operation of UAS links would require modification of the ITU Radio Regulations to
permit the mobile UAS to communicate with a FSS satellite. Additionally, it would require a World
Radio Conference (“WRC”) Resolution that contains the technical and regulatory requirements for such
operation.

2.2.3 An important point to be emphasized is that UAS satellite links would operate within the
established satellite interference environment. This interference environment is established by FSS
satellite operators through coordination agreements. Coordination agreements typically specify 1) the
maximum power density and Equivalent Isotropically Radiated Power (EIRP) density of carriers, 2) the
off-axis gain characteristics of transmitting and receiving antennas, and 3) the placement of carriers with
high power density.
-3- ACP-WGF23/IP -xx

2.2.4 The service contract between the satellite and UAS operators takes the coordination
results into account as well as the performance requirement and other conditions of operation such as pre-
emption needs.

2.2.5 Internationally, such agreements are contained in a formal document that is approved by
the involved satellite operators and their respective administrations. Domestically, a formal agreement
may or may not be required, depending on the regulations of each administration.

2.2.6 Existing commercial FSS systems at Ku and Ka-band offer immediate access to spectrum
for UAS. Specifically, various segments of the Ku-band (10.95 – 14.5 GHz) and Ka-band (17.30 – 31.0
GHz) are suitable for UAS control links. Additionally, there is existing satellite earth station equipment
that has been developed and successfully operating onboard aircraft.

2.2.7 Studies by the ITU-R have shown that commercial Ku/Ka band satellites can support
UAS control links and meet the desired link availability. Moreover, commercial satellites have the
following attributes:

a) Long lifetime, typically greater than 15 years.
b) Low satellite and transponder failure rates.
c) Back-up capacity available on the same satellite or a different satellite
d) High Equivalent Isotropically Radiated Power (EIRP) and antenna gain to thermal
noise ratios (“G/T”).
e) High radio link availability, typically ranging from 99.5% to 99.96%
f) Provide connectivity over large geographic and oceanic areas, which terrestrial links
cannot provide.
g) Multiple transponders available on each satellite, e.g. 24 Ku-band transponders
h) Bandwidths of satellite transponders range from 24 to 120 MHz, with the most
common bandwidth being 36 MHz.

2.2.8 A customer can lease a transponder on a non-preemptible basis, whereby its
transmissions cannot be moved to another frequency in order to restore another customer’s transmissions.

2.2.9 Given the benefits that commercial satellites provide, it would be advantageous to
introduce the appropriate ITU-R regulatory regime to permit UAS control links to operate under an FSS
allocation for beyond line-of-site communication. The use of FSS spectrum would provide flexibility to
UAS operators with regard to the frequency bands that are available to them. Without this possibility,
provision of such satellite based services would not be available for many years and would severely
impact the growth of the UAS industry.

3. ACTION BY THE MEETING

3.1 It is proposed that the meeting recognize the benefits offered by allowing UAS (non-
payload) control links to operate under a fixed satellite service allocation and to support the development
of the necessary technical and regulatory provisions required for such operation.