1
ACP-WGF21/WP-221.0INTRODUCTION
At the 21st meeting of Working Group F, the Panel reviewed multiple documents considering the spectrum for satellite control links for Unmanned Aircraft Systems (UAS) under 2012 World Radiocommunication Conference agenda item 1.3. At the 2007 World Radiocommunications Conference, the aviation communitysuccessfully proposed the inclusion of agenda item 1.3 for WRC-12to address the spectrum requirements of UAS. The intention behind the agenda item was to identify suitable spectrum that could be used by UAS for command and control and sense and avoid in order that unmanned aircraft can operate in airspace in an equivalent manner to manned aircraft. The work to date on this agenda item has identified the need for 34 MHz of terrestrial and 56 MHz of Satellite spectrum.
2.0DISCUSSION
The initialICAO Position to WRC-12 on this specific agenda itemstates :
“Spectrum for UAS for safety and regularity of flight, and in particular when the UAS operates in civil airspace, needs to be accommodated under an allocation to the aeronautical mobile (R) service(AM(R)S), aeronautical mobile satellite (R) service(AMS(R)S), or the Aeronautical Radionavigation service(ARNS), in order to receive the sufficient status and protection from harmful interference”
The intention is to support unmanned aircraft operations in airspace in an equivalent manner to manned aircraft. In order to allow this the link between the unmanned aircraft and the pilot will have to allow that pilot to navigate the aircraft and interact with ATC as if he were on-board that aircraft. This therefore requires a link to be provided between the unmanned aircraft and the ground pilot. This link can either be provided via a terrestrial line of sight link or an over the horizon satellite link. In accordance with ICAO standards and recommended practises (SARPS), the aircraft airworthiness and certification process regarding flight safety communications requires the use of protected frequency bands as recognized by ITU and also, of globally harmonized spectrum to ensure world-wide inter-operability.
Since the use of terrestrial and satellite links is intended to address different aircraft pilot link configurations it cannot be assumed that there is link diversity. Therefore, it should be assumed that each link will have to be certified as a sole means of communication. Since for manned aircraft any radio system provided for either communications or navigation purposes that are certified for sole means operation is currently allocated in spectrum identified for safety services it would appear logical that the unmanned aircraft - pilot link should also be provided in safety spectrum.
Irrespective of the ICAO Position, Among among the UAS community some stake-holders advocate the alternative use of unprotected spectrum, arguing that interference mitigation measures such as radio equipment redundancy and interference protection techniques, initially developed for otherpurposes, can be implemented in practice to ensure the high level of communication performance and integrity suitable to meet the safety objectives of WRC-12 agenda item 1.3. For example, certain portions of FSS or MSS bands have characteristics that make them attractive for consideration for protected UAS operations. While these satellite bands do not carry an aeronautical mobile satellite (R) service (AMS(R)S) allocation or indeed any aeronautical spectrum designation, the questions occur are the level of potential interferences providedby neighboring satellite systems and how to avoid or limit them?.
Commercial satellite operators are greatly concerned that if any portion of an existing FSSor MSS band is allocated to AMS(R)S, they would be unable to offer that segment to other customers due to the safety service attribute of an AMS(R)S allocation. Additionally, there is a concern that AMS(R)S traffic on one satellite network could place additional protection requirements on neighboring satellite networks not carrying AMS(R)S traffic, due to the safety service aspect of AMS(R)S, thereby creating difficulties in the current Article 9 coordination regime. These concerns have made it difficult to consider bands with existing commercial satellite operations. Further, some allocations have sharing issues because they are heavily utilized or because they are allocated to both Earth-to-space and space-to-Earth transmissions allowing little opportunity to provide the low levels of interference necessary for safe operation of UAS.
Furthermore by not adhering to the ICAO standards and regulatory framework - whose purpose is to allow ICAO contracting States to mutually recognize aircraft certification and operation approval granted nationally in each one of them - UAS access to non segregated airspace internationally could only be granted on an ad-hoc national basis. As such this access would then be limited to those countries’ airspace for which an UAS operator would have first obtained authorizations to fly through, following individual requests filed for each one of those. In the long run, such an approach could be detrimental to UAS industries and operators’ interests.
One way round this problem would be to draft a Resolution to allow, under specific circumstances, an application such as UAS to operate under a different service definition (e.g. a feeder links in the FSS being operated under an aeronautical mobile satellite (R) service). An example of such an approach is Earth Stations on Vessels (ESVs) where ITU-R Resolution 902 (WRC-03) allows the operation in the Fixed Satellite Service even though the stations are mobileving. In this example underthe specific constraints in resolution 902 wouldthat might be unacceptable for safety reasons so that a different Resolution would be required.
For terrestrial services the only spectrum currently regarded as pertaining to aeronautical safety falls under the service definitions of aeronautical mobile (R) and aeronautical radionavigation. Since the unmanned aircraft – pilot link is considered a communications link, the only appropriate service would be aeronautical mobile (R).
2.1State UAS
The ICAO convention does not apply to State aircraft. State aircraft are subject to national regulation with the contracting State being responsible for ensuring that such aircraft operate in a manned that ensures the safety of civil aircraft. State aircraft that fly over another State must obtain permission form the relevant contracting State. Therefore, the spectrum requirements for State UAS should be a matter resolved at the national level. Some discussion within ICAO WG F may help experts contribute to this process for each member’s State.
2.2Link aspects
Figure
Links involved in BLOS (beyond line-of-sight) communications via satellite
The links 5 and 6 referred in the figure above have to use an AM(R)S allocation
The links 2 and 3 referred in the figure above have to use an AMS(R)S allocation
The links 1 and 4 referred in the figure above are those identified in the section 2.0 above,possibly under a suitably developed the proposedresolution Resolution and have to respect the principle detailed in the section 2.3 below.
2.3Principles to apply for the satellite component (link 1 and 43 in the figure above)
The following principles apply to service allocations and the use of frequencies for the satellite component of UAS radiocommunications within the scope of WRC-12 Agenda item 1.3:
1)Under No. 191 of the ITU Constitution, international telecommunications must give absolute priority to all telecommunications concerning safety of life.
2)All UAS radiocommunications within the scope of WRC-12 Agenda Item 1.3 are radiocommunications concerning safety of life.
3)No. 1.59 of the RR states that any radiocommunication service used permanently or temporarily for the safeguarding of human life and property is a safety service.
4)No. 4.10 of the RR states that Member States recognize that the safety aspects of radionavigation and other safety services require special measures to ensure their freedom from harmful interference and that it is necessary therefore to take this factor into account in the assignment and use of frequencies.
5)It is recognized that the aeronautical safety of life aspects need to be treated within ICAO through the development of new standards and recommended practices (SARPs)
6)Any special measures as referred to above must be clear, implementable in practice and designed to avoid creating difficult regulatory situations.
7)Taking No. 1.59 of RR into account, provided existing allocations to services described hereafter and in frequency bands listed in section 5 can support safety of life UAS radiocommunications, existing allocations should be considered before considering the need for new allocations.
3.0CONCLUSION
TBD