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ACP-WGW02/WP-04
/
International Civil Aviation Organization
WORKING PAPER / ACP-WGW02/WP-04
2008-04-14

DRAFT

AERONAUTICAL COMMUNICATIONS PANEL (ACP)

FIRST MEETING OF THE WORKING GROUP OF THE WHOLE

Montreal, Canada 21 – 25 April 2008

Agenda Item 1c: / Spectrum requirements for future terrestrial and satellite communication systems.

FREQUENCY BAND SELECTION FOR THE FUTURE COMMUNICATIONS SYSTEM

(Presented by Mr A Knill)

SUMMARY
This paper highlights the timeframe for the next World Radiocommunications Conference and the work that needs to be completed before that meeting in order to ensure that the requisite radio regulatory provisions are in place to support the implementation of the future communications infrastructure.
ACTION
1) To incorporate within the working structure of the ACP a task to investigate the feasibility and develop the technical standards for an L-band datalink component of FCI.
2)To incorporate within the working structure of the ACP a task to develop the basic technical parameters of a VHF solution such that ITU can complete their studies for WRC-11

1.INTRODUCTION

1.1Following the development of the Communications Operating Concept and Requirements document Working Group T have been evaluating the suitability of various candidate technologies to provide the Future Communications Infrastructure (FCI)[1]. In their report to this meeting WG T recognises that no single technology meets all the requirements and that both the VHF and L bands have their advantages and disadvantages but that on balance L-band offer the greater potential benefit for the initial datalink implementation. The report therefore recommends that an L-band solution for the datalink elements of the FCI be developed, however recognising that the VHF band is likely to be required for the digital voice elements of the FCI and may be required to support the datalink elements if a solution cannot be found in L-band.

1.2World Radiocommunications Conference (WRC) 2007, Agenda item 1.5 sought to address aviations needs for additional aeronautical mobile (R) allocations to meet the perceived needs of the terrestrial radiocommunications elements of FCI. In response to this agenda item, noting the lack of information with respect to the characteristics of some elements of the FCI, allocations were made in the VHF (112-117.975 MHz), L (960-1164 MHz) & C (5091-5150 MHz) bands subject to conditions outlined in resolutions 413 & 417 that need to be fulfilled prior to operational use. Additionally an agenda item was agreed for The 2011 WRC to review the work undertaken in respect of resolutions 413 & 417 and to consider any further regulatory requirements that may be necessary.

2.discussion

2.1As stated previously WRC-07s ability to conclude on sharing studies to prove that the new allocations to the aeronautical mobile (R) service would be compatible with existing non-ICAO systems were limited due to a lack of technical information on the FCI. One option considered was to make no allocations at the conference and carry the agenda item forward to WRC-11. Therefore the decision to allocate spectrum in the VHF and L bands subject to the conditions stipulated in resolutions 413 & 417 with an agenda item for WRC-11 to allow the studies to be completed, reviewed and any further regulatory provisions needed to be put in place was about the best aviation could have expected

2.2In order to meet the WRC timescales aviation will have to be a position to provide the ITU with sufficient technical information on the system(s) likely to be deployed in the band or bands of choice in time for the studies called for in Resolutions 413 & 417 to be completed prior to the WRC. On this basis and the timescales shown below, the technical information will have to be provided to the regional groups and ITU Working Party 5B by either November 2009 or February 2010 dependant on whether it is a spring or autumn 2011 conference.

World Radiocommunications Conference / Spring 2011 / Autumn 2011
Conference Preparatory Meeting / Autumn 2010 / Spring 2011
Last Meeting of ITU WP5B
(Finalise Studies and Prepare CPM Text) / May 2010 / September 2010
Meetings of Other Concerned Working Parties
(Review studies relevant to their services / December 2009-May 2010 / March 2010-September 2010
ITU WP5B Meeting
(Complete studies for review by other relevant working parties) / November 2009 / February 2010

2.3If the timescales are not met then there is a chance that the WRC will not make a decision and hence aviation will have to await a future conference with no guarantee that the issue will be placed on the agenda of the next or subsequent Conference.

2.4In it’s proposal to the meeting Working Group T proposes that the next step in the development of the FCI is to assess whether a practical solution can be found for the datalink elements of the FCI that operates in L-band and is compatible with existing systems operating in that band. This step would presumably be followed by work on a VHF solution for either digital voice or digital voice and data. For this strategy to deliver the necessary information to the ITU for them to complete their studies in both bands or only the VHF band, a decision would have to be taken by January 2009 on the practicality of an L-band solution. Failure to deliver the requisite information on time with respect to the VHF band would potentially jeopardise any potential exploitation of the VHF band for the FCI.

2.5This strategy, given some of the issues to be resolved (see appendix 1) would appear to be tight as well as risky since any delay could jeopardise progress within the ITU on the VHF band. ACP is therefore faced with the following options:-

2.5.1a)Develop an L-band solution and then tailor a VHF solution to meet the requirements not solved within the L-band. For this option to be practical, the future work programme will have to be aggressive and any slippage risks the possibility of ICAO not being able to deliver the information on both bands within the timeframe necessary.

2.5.2b)Develop an L-band solution and sufficient detail of a VHF solution in parallel to meet ITU needs for compatibility studies. This option requires members of the ACP to commit sufficient resources to allow the development of both an L-band solution and an outline VHF solution in parallel.

2.5.3c)Develop an L band solution only. This option discards a solution in the VHF band and runs the risk that if an L-band solution is not practical then it will be to late to develop a VHF solution whose operation encompasses the frequency band 112-117.975 MHz

2.6All three alternatives have risks however in my opinion option b) minimises those risks. It is therefore recommended that ACP should establish a work programme that concentrates it’s effort on investigating the feasibility of an L-band solution, providing technical details of this solution to the ITU whilst also developing the basic technical parameters of a VHF solution to meet ITU requirements studies in parallel.

3.ACTION BY THE MEETING

3.1The ACP WGW is invited to:

1) To incorporate within the working structure of the ACP a task to investigate the feasibility and develop the technical standards for an L-band datalink component of FCI.

3)To incorporate within the working structure of the ACP a task to develop the basic technical parameters of a VHF solution such that ITU can complete their studies for WRC-11

Appendix 1

Issues to be resolved

Compatibility with DME: Aircraft use DME to determine their distance from a land-based transponder by sending and receiving pulse pairs - two pulses of fixed duration and separation. In order to optimise reply efficiency DME’s are fitted with short distance echo suppression where blanking is applied to the ground receiver for a period prior to the expected receipt of the second pulse. The period of this blanking varies dependant on the manufacturer and the requirement of the ATC provider. Within the UK this blanking is virtually the whole time between pulses. A new digital communications system may trigger the DME ground receiver causing it to blank and the impact of this blanking has to be assessed especially in light of the blanking already caused by JTIDS.

Compatibility with JTIDS: NATO operates a military frequency agile communications system that hopes over 52 frequencies in the frequency band 960-1164 MHz. The operation of this system is agreed on a bilateral basis between the military and civil aviation authorities within each country and is normally subjected to some form of frequency clearance agreement. Within the UK this agreement is designed such that the maximum JTIDS pulse density allowable is approximately 9dB below the point where DME will fail to meet it’s operation requirement. As it is unlikely that a new frequency clearance agreement, restricting the pulse density even further, could be agreed with the military the future communications system will only have approximately 9dB of margin to use.

Compatibility with SSR: Secondary Surveillance Radar operates on two frequencies, 1030 & 1090 MHz globally. This system operates by the ground radar interrogating an airborne transceiver which then responds. A new digital communications system will have to be compatible with this system, probably by avoiding the use of this band.

Compatibilty with Other Non-ICAO Radionavigation Systems: During the last study cycle within the ITU Working Party 8B’s attention was drawn to use in a number of countries of a radionavigation system that has not been standardised by ICAO. Consideration will have to be given to as to whether the FCI is compatible with this system and if it is not whether this presents an issue or not.

Compatibility with Adjacent Bands: The band below 960 MHz is used for mobile phone applications and that above 1164 MHz is current used by DME and JTIDS but will in the future also be used by Global Navigation Satellite Services. The design of any new digital communications system will have to ensure it meets the out of band emission limits by the band edge.

On-Board Integration: It is currently envisaged that the future communications system will be implemented in a phase approach with the first phase being the introduction of additional datalink capabilities to support traffic in the known environment. Any new communications system operating in the frequency band 960-1164 MHz will have to integrate with other systems on-board the aircraft. For civil airliners and large freight aircraft that might be possible given the size of the aircraft and hence the separation that might be achieved. However it will not just be large aircraft that fly in known airspace, it will also be military aircraft such as fast jets, corporate business jets and also small general aviation aircraft. Will it be possible to achieve the isolation required on these aircraft.

Weight and Drag: Airlines are currently under pressure to reduce fuel burn and green house gas emission. In order to aid this any new system introduced onto an aircraft should be capable over a finite period of time of allowing another system or systems to be removed from the aircraft. If this is not achieved then we are introducing additional weight on to the aircraft and possibly an additional antenna that will increase drag thus increasing fuel burn.

[1] In the context of this document FCI refers to the line of sight air ground element of the future communications infrastructure.