International Civil Aviation Organization

World-wide CNS/ATM Systems

Implementation Conference

Rio de Janeiro, 11 – 15 May 1998

WW/IMP-WP/42

11/5/98

Item 1

Agenda Item 1:	Overview of CNS/ATM systems implementation

CNS-SYSTEMS IMPLEMENTATION AND THE NEED TO SECURE RADIO-FREQUENCY SPECTRUM REQUIREMENTS

(Presented by the Secretariat)

Information Paper

Summary

The increased pressure from non-aeronautical sources for new or shared frequency bands to satisfy their requirements has in the past targeted spectrum allocated to aeronautical radio services. This trend endangers the availability of adequate protected spectrum, necessary for the implementation of the CNS/ATM system. This paper presents some of the related difficulties encountered at recent and expected at future International Telecommunications Union (ITU ) meetings. It reviews measures deemed necessary to enhance support to the aviation spectrum requirements at ITU meetings.

1.	Introduction.

1.1	At recent ITU meetings, several portions of the RF frequency spectrum were considered for review for allocation to non-aeronautical services, either on a shared or an exclusive basis. The general trend at these meetings is to provide a level of protection or access to the RF spectrum which is not in conformity with the ICAO requirements as contained in the relevant ICAO positions which are approved by the Council.

1.2	At the ITU World Radiocommunication Conferences in 1995 (WRC-95) and 1997 (WRC-97) changes affecting the aeronautical use of several bands were approved:

a)	in the bands 1545 – 1555 and	1646.5 – 1656.5 MHz	, the exclusive allocation to the Aeronautical Mobile Satellite (Route) Service (AMS(R)S) was replaced with a generic allocation to the Mobile Satellite Service (MSS). As a consequence, aviation will have to share the band with maritime and land-mobile users. In the long term, aviation access to the full spectrum required for AMS(R)S could no longer be safeguarded;

b)	in the band 5090 – 5150 MHz	allocated to the microwave landing systems (MLS), the introduction of allocations to the fixed-satellite service has led to restrictions to access by MLS; and

c)	in the band 15.4 – 15.7 GHz allocated to airborne and ground based radar systems, because of the introduction of allocations to the fixed-satellite service, protection of airborne radars against interference is no longer guaranteed on a global basis.

1.3	At WRC-97, a proposal to introduce the Mobile Satellite Service (space-to-earth) in the band 1559 –1567 MHz, i.e. within the band 1559 – 1610 MHz which is currently used by the Radionavigation Satellite Service for GNSS (GPS and GLONASS), was only rejected after a long and intense debate. At the ITU Radiocommunication Assembly, which preceded WRC-97, it was only after a long technical debate that the necessary protection was afforded to MLS and GNSS against interference from non-aeronautical sources operating outside the aviation frequency bands.

2.	Need for protection of spectrum.

2.1	Most elements of today's and future aeronautical communications and navigation systems make use of radio-frequency spectrum that has been allocated to these services, corresponding to the established requirements. It is the ICAO position that in general, this spectrum shall be available for aeronautical usage. Increased requirements are generally accommodated through the implementation of new technology and through techniques such as channel splitting.

2.2	Some of the frequency bands are considered as providing essential specific radio-frequency characteristics for the introduction of key elements of the CNS/ATM system, such as the bands for satellite communications and satellite navigation (GNSS). In case these bands are made no longer available under the conditions established for the CNS/ATM system concept, full implementation or full benefits of these systems may not be achievable.

2.3	ICAO has consistently emphasized the need for increased and active support from ICAO Contracting States to the ICAO position, to be provided through the national delegations attending the ITU meetings and conferences.

2.4	At the second meeting of the ALLPIRG Advisory Group, which was held from 16 - 18 February in Montreal, it was recognized that the issue of radio-frequency protection should be brought to the attention of ICAO Contracting States attending the World-wide CNS/ATM Systems Implementation Conference. The ALLPIRG meeting also recognized that the common proposals which are being developed by regional telecommunication organizations (such as CEPT, CITEL, APT) have come to dominate the discussions at the ITU conferences. Therefore, the need to increase ICAO's efforts at the regional level of preparatory activities for ITU conferences has been fully supported.

2.5	The Air Navigation Commission (13th meeting of the 147th session) agreed to accord a higher status to activities related to radio-frequency spectrum protection by assigning the responsibility for those activities to its Aeronautical Mobile Communication panel (AMCP). The Commission also supported the development of a draft resolution to be presented to the ICAO Assembly, urging ICAO Contracting States to support the ICAO positions at WRCs and in regional and international activities conducted in preparation to WRCs.

3.	Future ITU Conferences.

3.1	On the basis of the agendas drafted for the future ITU conferences (1999 and 2001), a summary of frequency bands and related aeronautical systems that may be affected by the decision of these conferences is provided as follows:

a)	review of the use of the HF bands between 2.8 – 22 MHz allocated to the Aeronautical Mobile (R) Service. This agenda item may affect the available HF spectrum for aviation. A statement of aviation requirements, including the need for spectrum for the introduction of HF-data link, is necessary;

b)	review of the feasibility of the introduction of an allocation to the Mobile Satellite Service (space-to-earth) (MSS) in the band 1559 – 1567 MHz. The ICAO GNSS panel is currently developing material addressing the technical and operational aspects for the protection of GNSS, which is also using this band. In ICAO's view, sharing is not feasible in practice, as a viable implementation of MSS in this band would be prevented by the stringent restrictions required in order to protect GNSS. For civil aviation, this issue is seen as one of the most important subjects on the agenda of the next WRC;

c)	the status of the fixed service operating in the band 1559 – 1610 MHz. The current operation of fixed service in more than eighty countries may interfere with the reception of GNSS (GLONASS and GPS) signals. This matter is also under consideration in the GNSS Panel. In case harmful interference from the fixed service is proven likely, removal of the fixed service from the frequency band 1559 –1610 MHz will be necessary in order to allow the use of GNSS in those countries;

d)	the availability of new allocation in the 1215 – 1300 MHz range to provide for frequency diversity in GPS and GLONASS. Frequency diversity will improve the performance of satellite positioning systems;

e)	the use of the band 15.4 –15.7 MHz for ground based and airborne radar systems. Continued availability of the band needs to be ensured against attempts by MSS operators to reduce the constraints imposed on their systems by the need to protect the band for aeronautical use;

f)	the use of the band 415 – 426.5 kHz by the aeronautical radionavigation service and the maritime mobile service. Aviation uses this band for NDB;

g)	proposals are be expected to introduce non-aeronautical service in the 2700 – 3100 MHz band (e.g. mobile or fixed). These bands are heavily used for ground based radar systems for aeronautical and maritime usage; and

h)	the use of the bands for MLS (5000 – 5150 MHz). Aviation needs to have stated its requirements for this spectrum at that time.

4.	Conclusions

4.1	There is an urgent need for civil aviation to secure its requirements for RF spectrum for communication, navigation and surveillance. Both on a national level as on an international level, ICAO Contracting States need to ensure that the necessary support to the coordinated ICAO requirements is provided in ITU fora.

4.2	General guidance is given in the ICAO Handbook on Radio Frequency Spectrum Requirements for Civil Aviation, including statement of approved ICAO policies. This handbook is available and will be published by ICAO in August 1998.

4.3	The detailed ICAO position for the ITU WRC-99 is currently being developed and a first draft is expected to be sent to States for comments later this year. Specific attention should be given, both by States and ICAO to the preparation of common proposals to ITU WRC's developed by regional telecommunication organizations.

4.4	In particular, the active support from ICAO Contracting States at ITU meetings, both through the participation of aeronautical experts in the national delegations to these conferences as well as in presenting proposals to the conferences that include major elements of the ICAO position, is indispensable and the only way to secure that the necessary spectrum for the implementation of CNS/ATM systems will remain available and adequately protected.

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