Need for Spectrum for Future Air/Ground Communication Systems

Need for Spectrum for Future Air/Ground Communication Systems

International Civil AviationOrganization



Cairo, Egypt 7-13 June 2006

Agenda Item 5: / AM(S)R Spectrum requirements


(Presented by the Secretary)

This paper presents background information on the future use of additional spectrum that needs to be made available for the aeronautical mobile (R) service at WRC-2007
The meeting is invited to note this information

1 Introduction

1.1Adequate radio frequency spectrum is an essential element for almost all aviation activities. The growth in the aviation industry, as well as the increased requirements satisfying the needs of the aviation industry as a whole, has increased the demand for radio facilities. In the past, for communication as well as navigation systems, this increased demand could be addressed by introduction by the aviation community of techniques resulting in a more efficient use of the radio frequency spectrum. This was achieved through a reduction in channel spacing (ILS, VOR, AM-voice systems) or by other techniques (use of single side-band technology in the HF bands and multiplexing techniques in DME systems). In addition, in some frequency bands, sharing of aviation services with other (non-aeronautical) services was introduced or certain band-edge compatibility problems surfaced, reducing the effective use of the available spectrum for aviation.

1.2Although the aviation community is facing shortage of radio frequency spectrum for both air-ground communication systems and for navigation systems in various bands and in particular in Europe, the shortage and expected saturation of the frequency band for communications for line of sight systems (the only band that has been made available for this purpose is the band 117.975 – 137 MHz), is most acute. Saturation of this frequency band in Europe is expected by 2015, at which time new systems, providing enough capacity for future growth, needs to be in place. These new systems cannot be accommodated in the current band 117.975 – 137 MHz and additional spectrum to be made available for aviation is one of the keystones for enabling aviation to accommodate these new systems. To meet an already aggressive schedule for implementing such new systems, ICAO Standards and Recommended Practices need to be in place around 2010. The progress of this work makes it imperative to for aviation to have such additional allocations secured at WRC-07. The new system, which concentrates on the introduction of air/ground data links, is intended to be implemented globally. This would delay congestion/saturation of the VHF band in other parts of the world as well.

1.3.Appendix A provides an overview of aviation radio frequency spectrum issues, showing that there are currently in Europe seven frequency bands allocated for aviation use with critical capacity shortfalls and six frequency bands that require urgent attention. It is worth noting that the availability of sufficient spectrum in the ILS frequency band is critical because of the fact that interference from FM broadcasting station has been planned and coordinated in this band, with the view to assist FM broadcasting in the band below 108 MHz to operate (i.e. only ILS assignments in operation at the time of implementing FM broadcasting stations were considered, reducing significantly the ability to make new ILS assignments. No such a situation exist in the corresponding ILS glide path band.

2Choice of frequency bands

2.1In accordance with Resolution 414 (WRC-03) on the “Consideration of the frequency range between 108 MHz and 6 GHz for new aeronautical applications” , ICAO has investigated as a first step the bands currently available for aeronautical systems in this frequency range for additional allocations to the aeronautical mobile (R) service. From this work, the following bands were identified as being candidates for the introduction of these new systems and would require an allocation to the AM(R)S:

112 – 117.975 MHz

960 – 1215 MHz

5000-5030 MHz

5091-5150 MHz.

2.2Other aeronautical frequency bands used by aviation were considered not to be capable to provide the necessary access to radio frequency spectrum. Frequency bands currently being used by international civil aviation have been consideredso far.

2.3.It was observed that introduction of AM(R)S in the 960-1215 MHz band and the 5 GHz bands would require compatibility to be addressed with systems not in use for international civil aviation.

3Communications operating concept and requirements (COCR) for the future radio system (FRS)

3.1Since a number of years ICAO is involved in developing the communications operating concept and requirements (COCR) for future radio systems (FRS) that would assist in the selection of technologies and systems to satisfy future communications requirements.

3.2The Future Communications Study (FCS) has two main activities

1) to identify the future requirements based on emerging global future Air Traffic Management (ATM) concepts taking into account the needs of civil aviation; and

2) to identify the most appropriate technologies to meet these communication requirements.

3.2.1The operational requirements are drawn from the ATM and aeronautical operational control (AOC) operating concepts expected to be implemented in the highest density airspace regions of the world to achieve the required capacity, safety and security. In particular, the ICAO Global ATM Operating Concept and the IATA ATM Roadmap were considered. Lower density regions of the world have also been considered, but the communicationrequirements for those regions may be less demanding and therefore these regions cancontinue to utilise current systems for a longer period of time.

3.2.2.The two primary drivers for the FRS are:

1) to provide an appropriate communicationinfrastructure to support future air traffic growth; and

2) the need for a consistent globalsolution to support the goal of a seamless air traffic management system. and air/air data communications for ATS are a relatively recent developmentand necessitate a complex end-to-end system involving interaction amongst humans,automation and Communications, Navigation, and Surveillance (CNS) systems.

3.2.3.Analogue voice communications capabilities remain initially central to the provision of ATM. Even after the implementation of data link, voice will continue to be used for exceptional circumstances or in areas that donot require extensive data link implementation. The FRS should be capable ofsupporting, at least, the data communications required through air/ground and air/airusing broadcast, multicast and/or addressable modes such as point-to-point. Voicecommunication may be supported by the FRS provided it meets the requirementsdefined in this document.

3.2.4.States and Regions will have differing needs and timeframes for the introduction of datalink services to meet their requirements. In some regions of the world, data link services are alreadybeing introduced through trials or implementation programmes. Other regions may start implementation at any time, or not at all, based on their ATM needs.

3.3The scope of this activity is to identify concepts, requirements and trends thatwill be the basis for selecting the FRS. Air Navigation Service Providers (ANSPs) andindustry are in the formative stages of determining many of the underlying futureconcepts considered in this activity.

3.4Civil-military interoperability has also been addressed in the development of the COCRthrough co-ordination with the relevant military representatives (e.g. theEUROCONTROL Military Unit). This helped refine requirements in the areas ofintegrity, reliability and security, which have been taken into account.

3.5The aviation community is currently considering the requirements for operatingunmanned aerial vehicles (UAVs) or remotely operated vehicles (ROVs) within the air traffic management (ATM) infrastructure. Studies considering the implications of operating UAVs inun-segregated airspace are underway in several regions of the world and, when complete,could serve as a basis for further work in this area.Theair/ground radio links required for UAV/ROV may generate a significant volume ofcommunication traffic. All communications for the command and control links associated with UAVs orROVs are considered to be thesame as those with manned aircraft i.e. UAV operation is transparent for the air traffic control (ATC)system and require explicit allocations to the aeronautical mobile (R) service (AM(R)S. Additional requirements, for the purpose of UAV telemetry, are not considered as necessary for the safety and regulatory of flight. In some parts of the world the number of these vehicles may represent a largeportion of the traffic load of air traffic services units (ATSUs)in the future. Any function that would relay aninstruction sent from an ATSU to the UAV or ROVmust be communicatedto the UAV or ROV through to a “remote pilot”. The command that is sent to the UAV to executethe instruction, has to meet ATC operational performance requirements just like any otheraircraft in the system.

3.6A number of new services in support of monitoring and controlling of thephysical security of aircraft and the air traffic system are currently under consideration.

These include services to provide real-time video transmission from the cockpit, and toprovide direct communications between aircraft and security organisations. Theseservices are still being defined and it is not clear whether the FRS, a passengercommunications system, or a new dedicated communications system would be used toprovide them. .

3.7The ATM environment in the timeframe of the future communication study will continue to consist of ground human-machine interfaces (HMIs), voice switches, automatic Flight Data Processing Systems (FDPS), ground communications systems, routers, networks, radio ground stations, airborne radios, and communication end systems (e.g., airborne Communications Management Units (CMUs) and ground Data Link Application Processors). These components, combined in an end-to-end chain must meet the required performance and safety for voice and data applications. The term FRSis used to refer to the physical implementation of the radio components of a communication system that meets these requirements. The scope of the FRS is illustrated in Figure 1 below. The FRS is part of the overall Future Communications Infrastructure (FCI), which includes all the components (e.g., processors, applications, and networks) needed for Air Traffic Service Providers, Aeronautical Operational Control, and individual aircraft to communicate with each other.

Figure 1- Scope of the Future Radio System (FRS)

as part of the future communications infrastructure

3.8A summary of the CORC for the future FRS is at Appendix B .

Note: a full description of the current status of the COCR activities is available at the

ICAO website at /WG/C/wgc10/ (WP04).

4Need for additional allocations.

4.1Frequency band 112-117.975 MHz.

4.1.1This band is heavily used for VOR systems in Europe. Although it is currently expected that in Europe the number of VOR stations may be reduced in the longer term, the availability for the use of this band by VOR needs to be continued to be secured. Introduction of certain communication systems in this band needs to protect its prime use for aeronautical radionavigation. Because of this requirement, the use of this band by air-ground communication systems is limited. However, the need for the use of this band in providing a relative short term relieve to the congestion/saturation of the band 117.975-137 MHz has been recognized. Through a process whereby sub-bands for use by air-ground communication systems may be established, introduction of new technologies (e.g. broadband CDMA) that can “overlay” over the VOR assignments etc. some capacity for air-ground communication systems can be made available. However, considering the need to protect VOR in all cases, the expected additional capacity is limited in particular in the shorter term.

4.1.2In order to provide for the necessary flexibility to ICAO in its work on standardizing on a new air-ground communication system in this band, an allocation from 112-117.975 MHz has been requested.This band provides excellent line-of-sight propagation conditions. Current plans in ICAO focus on keeping the VHF band available for voice communications, because of global implications. However, using other frequency bands also for voice communications is not excluded from ICAO’s considerations, in particular to satisfy demands for such services in areas where voice requirements cannot be satisfied in this part of the radio frequency spectrum.

4.2Frequency band 960-1215 MHz (DME/SSR/RNSS)

4.2.1For new communication systems, ICAO’s considerations concentrated on using the band 960-1024 MHz for long-range data communication systems. This was driven in part by the technical assessment concluding that developing line-of-sight air-ground capabilities in the 5 GHz range may likely not be affordable because many more ground stations may be required in order to overcome the effects of the propagation conditions in this band while maintaining compatibility with other users of frequency bands in this range. However, using the 5 GHz band for long-range communications has not been excluded, in particular when the available capacity in the band 960-1215 MHz is not sufficient to meet aviation’s requirements.

4.2.2.Systems that could be considered using this band would, taking into account the perceived operational requirements, need a minimum total aggregate data rate of approximately 15 megabits/second. Difficulties experienced in the past with aircraft co-site compatibility issues (other radio equipment being used in close proximity or on the same aircraft) as well as difficulties expected to achieve compatibility with other (national) systems, including the need for certain features to be implemented in AM(R)S equipment would translate the above requirement into approximately 60 MHz of new AM(R)S spectrum. This can be accommodated in the band 960-1024 MHz. This amount of spectrum may need to be adjusted to take into account the ability of the new AM(R)S system(s) to fit in its intended environment. Therefore, and with the view to provide spectrum managers and frequency planners the necessary flexibility, and allocation of the frequency range 960-1215 MHz to AM(R)S is requested.

4.3Bands 5000-5030 MHz and 5091-5150 MHz

4.3.1Issues related to the allocation of new services, including the aeronautical mobile (R) service and the need to protect the ICAO microwave landing system (MLS) are addressed in the ICAO submission to PT3 on the “future use of the frequency band 5000-5150 MHz”. This paper was also reviewed at a recent meeting of ITU Working Party 8B.

4.3.2A review of initial estimates for communication throughput for projected airport local area network(s) Depending on the overhead to be used in specific systems that are being considered, approximately 60-100 MHz of radio frequency spectrum would be required for these systems. In this regard it is worth noting that certain applications in these airport local area networks also include communications with aircraft in flight near airports (depending on the technology to be used, up to about 40-100 NM and a flight level of approximately 20.000-30.000 ft.


5.1Compatibility of the new system with existing on-board equipment, the operating conditions of the airborne transmitter/receiver (operating at high altidues resulting in potentially large (line-of-sight) interference contours, the need for protection of other systems (not intended to be used by civil aviation in shared frequency bands and band-edge compatibility reduce significantly the effective use aviation can make of allocated spectrum. These effects need to be considered when making allocations for aviation use, and for communication systems (two-way transmissions in the a-g and g-a direction) in particular. Although ICAO considers addressing compatibility issues between ICAO standardized activities as a normal part of its standardization activities, potential compatibility issues with other systems needs to be addressed in ITU. ICAO is committed to support such activities.

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