STATUS OF INMARSAT/MTSAT-IRIDIUM RF COMPATIBILITY …



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International Civil Aviation Organization

WORKING PAPER |ACP-WGW2/WP-12

21/04/08

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AERONAUTICAL COMMUNICATIONS PANEL (ACP)

FIRST MEETING OF THE WORKING GROUP OF THE WHOLE

Montreal, Canada 21 – 25 April 2008

|Agenda Item 2: |Complete Part III (Classic Aero) of the AMS(R)S Manual |

Status of Inmarsat/MTSAT-Iridium RF Compatibility Studies

(Presented by the Secretary ACP on behalf of J Nemes)

|SUMMARY |

|This paper provides an update to the ACP on the on-going volumetric analysis by Honeywell and Inmarsat towards ensuring the RF |

|compatibility of Inmarsat/MTSAT and Iridium services. This analysis is still being checked for accuracy but the indications at |

|this time are that the probability of any interference from satcom fitted aircraft operating in either AMSS, i.e., |

|SwiftBroadband or Swift 64 (i.e. services offered by Inmarsat), or AMS(R)S (i.e. services offered by Inmarsat and MTSAT) and |

|different aircraft using Iridium communication systems in the oceanic airspace with 30/30 separation, 1000 ft RVSM, and aircraft|

|complying with RNP4, is small, of the order of 10-3 per flight hour. The probability of harmful interference that endangers the|

|functioning of an Iridium AMS(R)S, or seriously degrades, obstructs, or repeatedly interrupts an Iridium AMSS or AMS(R)S appears|

|to be between one and three orders of magnitude lower. Inmarsat and Honeywell propose that these probabilities are acceptable |

|for oceanic operations. |

|ACTION |

|The ACP WGW is requested to note the current status and findings of the analysis and extend an invitation to Honeywell to make a|

|briefing on the outcome of the analysis at the June ACP WG-M meeting, thus enabling finalization of Part III of the AMS(R)S |

|Manual. |

1. INTRODUCTION

Completion of Part III (Classic Aero) of the AMS(R)S Manual has been delayed due to the need to confirm through analysis the RF compatibility of Inmarsat/MTSAT and Iridium services operated simultaneously on different aircraft in the same oceanic airspace.

Honeywell and Inmarsat have been conducting volumetric analysis (based on a previous analysis originally started in the 1999-2001 in RTCA SC-165) towards ensuring the RF compatibility of Inmarsat/MTSAT and Iridium services. (Appendix A, provided by Honeywell, gives a more detailed explanation of the history of this analysis.) This work is nearing completion and hence timely for update to the ACP.

2. discussion

The analysis is still being checked for accuracy but the indications at this time are that the probability of any interference from satcom fitted aircraft operating in either AMSS, i.e., SwiftBroadband or Swift 64 (i.e. services offered by Inmarsat), or AMS(R)S (i.e. services offered by Inmarsat and MTSAT) and different aircraft using Iridium communication systems in the oceanic airspace with 30/30 separation, 1000 ft RVSM, and aircraft complying with RNP4, is small, of the order of 10-3 per flight hour. The probability of harmful interference that endangers the functioning of an Iridium AMS(R)S, or seriously degrades, obstructs, or repeatedly interrupts an Iridium AMSS or AMS(R)S appears to be between one and three orders of magnitude lower.

Inmarsat and Honeywell propose that;

a) These probabilities are acceptable and,

b) Hence, subject to confirmation of the analysis, Inmarsat and Iridium services operated simultaneously on different aircraft in the same oceanic airspace are compatible.

Honeywell are intending to make briefing at the RTCA SC-215 and/or AEEC AGCS meeting in May. It is suggested that, following these industry meetings, Honeywell are invited by the ACP to present a briefing on the outcome of the analysis at the June ACP WG-M meeting.

Appendix A also provides an overview of how the analysis has been updated to align with the recent RTCA DO-306 Oceanic airspace description.

3. ACTION BY THE MEETING

The ACP WGW is invited to:

a) Note the current status and findings of the analysis,

b) Endorse an invitation to Honeywell to make a briefing on the outcome of the analysis at the June ACP WG-M meeting, and

c) Endorse the plan to finalize Part III of the AMS(R)S Manual at the June ACP WG-M.

APPENDIX A

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Aerospace Research and Technology Center

7000 Columbia Gateway Drive

Columbia, MD 21046

MEMO Number CNSRTC-EFCL-0295

DATE: April 13, 2008

TO: Alan Schuster-Bruce

FROM: EFC LaBerge

SUBJECT: Status of Inmarsat-Iridium Compatibility Studies

BACKGROUND

This information paper provides a summary of the status of on-going analytical studies regarding the compatibility of Inmarsat AMSS and AMS(R)S services and Iridium AMSS and AMS(R)S services operated simultaneously on different aircraft in the same oceanic airspace. This work is a continuation of an extensive analysis effort related to this issue that was undertaken by RTCA SC-165 in the 1999-2001 timeframe. This earlier effort focused on a "volumetric" model of aircraft operations. Results of this earlier volumetric analysis showed that the probability of Inmarsat-induced interference to Iridium services was small, but SC-165 reached no final consensus on the matter before being disbanded by the Program Management Committee of RTCA in late 2001.

Current efforts

In response to an open action from ACP, Inmarsat and Honeywell revived the dormant volumetric analysis. A summary of an updated analysis, based largely on Iridium information as of the 2001 time-frame, was presented as a strawman approach for consideration by RTCA SC-215 at the second plenary meeting of SC-215 in July, 2007. SC-215 had no specific comments at that time. At a later meeting of SC-215, Mr. Thomas Kraft, Chief Scientific & Technical Advisor for Aeronautical Communications Aviation Safety (AVS) for FAA, suggested that the airspace description provided by RTCA DO-306, Safety and Performance Standard for Air Traffic Data Link Services in Oceanic and remote Airspace (Oceanic SPR Standard), would be an appropriate operational concept to use in such an analysis.

Consequently, the volumetric analysis briefed to SC-215 in July 2007 has been completely updated based on the Oceanic airspace described in DO-306 and using the relevant Iridium operational parameters for voice, short-burst-data, and circuit-switched data services as described in the draft material for DO-262 and DO-270. The DO-262 material regarding equipment standards is fairly mature, and is expected to be approved for Final Review and Comment at the next meeting of SC-215, April 30 and May 1, 2008. The DO-270 material regarding overall system standards is somewhat less mature, but is expected to be approved by the end of 2008. The updated interference analysis is based on the stated ΔT/T required by ICAO and the in-band susceptibility declared in the Iridium-specific material for DO-262, as modified by inputs from several engineers in the spectrum and aircraft certification offices of the FAA. As with the earlier analysis, the updated analysis deals solely with oceanic airspace, but the methodology can be extended to other airspace for which separation criteria and RNP requirements are defined.

Although the analysis is still being checked for accuracy before public release, the indications at this time are that the probability of any interference from Inmarsat equipped aircraft operating in either AMSS, i.e., Swift Broadband or Swift 64, or AMS(R)S, i.e., Classic Aero, modes and aircraft using Iridium communication systems in the oceanic airspace with 30/30 separation, 1000 ft. RVSM, and aircraft complying with RNP4, is small, on the order of [pic]per flight hour. The probability of harmful interference that endangers the functioning of an Iridium AMS(R)S, or seriously degrades, obstructs, or repeatedly interrupts an Iridium AMSS or AMS(R)S appears to be between one and three orders of magnitude lower.

The updated DO-306-based analysis has been undertaken by the same Honeywell (formerly Allied-Signal) engineers who initially developed the volumetric model under Iridium's auspice in the 2000-2001 time frame. Honeywell plans to provide a briefing on the status and results of the current analysis either at the upcoming SC-215 meeting or at the upcoming AEEC Air-Ground Communications Subcommittee meeting in Annapolis in mid-May.

END

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