E.F.C.LaBerge Senior Fellow, Honeywell CNS RTC June 18, 2008 [email protected] Updated Analysis of Inmarsat and Iridium Aeronautical Services in the Same Oceanic Airspace. 1 IEEE/AIAA 26th DASC, October 2007, Paper 213 EFC LaBerge & D. Zeng Purpose and Scope of the Analysis • Investigate Iridium AMSS/AMS(R)S and Inmarsat AMSS/AMS(R)S on separate aircraft in the same oceanic airspace • Analysis is limited to Oceanic Airspace structured following DO-306 guidelines, since FANS-1/A datalink Air Traffic Service (ATS) has widespread approval for operations in oceanic airspace • Conclusions are not applicable to other operational scenarios or airspace, including: - Polar, continental enroute, terminal, approach, and airport surface airspace as defined in Eurocontrol/FAA COCR document; - Simultaneous independent operation of Iridium and Inmarsat AESes on the same aircraft; and - All non-aeronautical terminals and non-aeronautical services 2 Released to ICAO ACP WGM June 18, 2008 Conclusions • The probability of Inmarsat AMSS/AMS(R)S causing a service interruption that would affect the availability of Iridium AMSS/AMS(R)S operating on separate aircraft in oceanic airspace is very small • In oceanic airspace, Inmarsat AMSS/AMS(R)S out of band emissions from one aircraft do not cause harmful interference to Iridium AMSS/AMS(R)S on another aircraft: - The functioning of Iridium AMSS/AMS(R)S is not endangered; - No serious degradation, obstruction or repeated interruption of the operation of Iridium AMSS/AMS(R)S 3 Released to ICAO ACP WGM June 18, 2008 Full disclosure, etc. • This work was based on the volumetric interference approach briefed to AMCP WGA in 1998-2000… • …and supported by Iridium, LLC (the old Iridium). • The current effort has been updated to include DO- 306 and new Inmarsat services and specs… • …and has been jointly supported by Inmarsat and Honeywell Research & Technology Center funding. • Representatives of Iridium Satellite, LLC (the new Iridium) have been briefed on the contents, conclusions and methodology of this study. 4 Released to ICAO ACP WGM June 18, 2008 Interference Cases • Inmarsat uplink on Iridium downlink - Subject of this analysis, oceanic airspace • Inmarsat uplink on Iridium uplink - Subject of Inmarsat-Iridium discussions, not considered here • Inmarsat downlink on Iridium uplink - No issue due to frequency separation • Inmarsat downlink on Iridium downlink - No issue due to frequency separation • Iridium uplink on Inmarsat uplink - No issue due to lower EIRP of Iridium • Iridium uplink on Inmarsat downlink - No issue due to frequency separation • Iridium downlink on Inmarsat uplink - No issue, Inmarsat satellite in back lobe of Iridium transmitters - No interference path to Inmarsat satellites via edge of earth • Iridium downlink on Inmarsat downlink - No issue due to frequency separation 5 Released to ICAO ACP WGM June 18, 2008 Overview of the downlink analysis methodology • First, define the systems and their performance • Second, define the airspace • Third, build the models • Fourth, assess the results,… InteractionInteraction • …iteratively with interactions w/w/ stakeholdersstakeholders DefineDefine DefineDefine BuildBuild AssessAssess SystemsSystems AirspaceAirspace ModelsModels ResultsResults Classic Aero (AMS(R)S) Service t (Iridium) = 60 H 0 10 SBB Service t (Iridium) = 60 H -1 0 10 10 DO-210D -2 -1 S64 Service t (Iridium) = 60 H 10 10 0 DO-210D 10 -3 -2 10 10 -1 ARINC 781 10 ARINC 781 -4 -3 10 10 -2 10 -5 -4 10 10 -3 DO-262A Honeywell 10 10-3 DO-262A Honeywell event Printerference -6 1998-2001 10 -5 10 -4 1998-2001 10 Printerference event Printerference (draft) Public Internal -7 -6 10 10 -5 (draft) DO-306 Public ICAO & RTCA Internal 10 -8 -7 event Printerference DO-306 ICAO & RTCA 10 -6 10 DO-270 Documents Technical 0 100 200 300 400 10500 600 Time in Seconds DO-270 Documents Technical -8 10 -7 Working Papers 0 100 200 10 300 400 500 600 Working Papers Time in Seconds (working) Documents -8 10 (working) Documents 0 100 200 300 400 500 600 Time in Seconds IridiumIridium ICAO ICAO p = ppp××for p ==0.1ρ TechTech Manual Manual SF S F SST SST HSN / IM11+ IM3 / IM5 IM7 / IM9 Iridium OOB Classic 5.3961e-004 0 0 2.2008e-003 SBB 3.1890e-004 1.0261e-005 2.9951e-006 9.7069e-004 S64 (old) 2.5331e-004 1.0885e-005 3.2837e-007 8.3957e-004 6 Released to ICAO ACP WGM June 18, 2008 Assumptions about Iridium • TDM format defined to ICAO • AES meets 25% ΔT/T aggregate from all sources without degradation, as required by ICAO SARPS • AES meets link budget (SC215) including aeronautical margin and 25% ΔT/T aggregate from all sources. • AES noise level of 630K (SC215) • AES antenna below horizon -10 dBi (per GPS interference assumption) • AES meets -72 dBm out-of-band susceptibility (SC215) constant throughout Inmarsat band • Iridium AES operation over the entire 1616-1626.5 MHz band • Iridium AES receive frequencies are assumed uniformly distributed over band • Beam handoff approximately every 60 seconds with independent frequency selection • Intra-beam handoff not considered 7 Released to ICAO ACP WGM June 18, 2008 Assumptions about Inmarsat • All current services – Classic, Swift 64(S64), and Swift Broadband (SBB) • Intentional EIRP: 17 dBW Classic, 20 dBW SBB, 19 dBW S64 • DO-210D HSN emissions -70 dBc/4 kHz constant throughout Iridium band • DO-210D or A781 IM performance • AES: Minimally compliant with DO-210D, A781 • Idealized 12 dBi gain antenna pattern with circular cross section (larger than rectangular cross section) • Assume -15 dB sidelobes (-3 dBic) • Ignore victim aircraft below source flight level • System • Frequencies are assigned at random from total available pool 8 for service beingReleased considered to ICAO ACP WGM June 18, 2008 Assumptions about airspace • Assume high-latitude (North Atlantic) oceanic airspace based on DO-306 - High latitude means low elevation angle to Inmarsat satellite - Inmarsat AES antenna pattern has a large component toward parallel tracks to the south. • 30 nmi / 30 nmi separation (along track / cross track) • Uniformly-distributed RNP4 navigation performance • Independent along track alignment of tracks and altitudes • Single North Atlantic “box” - ~500 nmi along track (~1 hour flight time) - 120 nmi across track (5 North Atlantic tracks) - 13 flight levels (FL290 to FL410) • Source (Inmarsat) aircraft uniformly distributed in altitude 9 Released to ICAO ACP WGM June 18, 2008 Probability of Long-term interruption 30/30 • Independent frequency selections for each beam handoff ⎢⎡tt/ H ⎥⎤ ppppLTC=× S SST × F Classic Aero (AMS(R)S) Service t (Iridium) = 60 H 0 10 -1 SBB Service t (Iridium) = 60 10 H 0 10 -2 10 S64 Service t (Iridium) = 60 -1 H 0 10 10 -3 10 10-3 -2 -1 10 10 -4 10 -3 -2 10 10 10-3 -5 10 -4 -3 10 10 -3 Printerference event Printerference 10 -6 10 -5 -4 10 10 -7 10 event Printerference -6 -5 10 10 -8 10 event Printerference -7 -6 0 100 20010 300 400 10500 600 Time in Seconds -8 -7 10 10 0 100 200 300 400 500 600 Time-8 in Seconds 10 0 100 200 300 400 500 600 Time in Seconds 10 Released to ICAO ACP WGM June 18, 2008 Why is this analysis conservative? • The assumption that Inmarsat and Iridium terminals both only marginally meet the ICAO/RTCA requirements. • The assumption that none of the Iridium margin can or will be used to increase the downlink Eb/(N0+I0) • The RNP4 uniformly distributed assumption • The idealized Inmarsat beam with constant gain • The additional -15 dB sidelobe assumptions about the Inmarsat AES antenna. • The uniform -10 dBi pattern assumption on the Iridium receive beam. • The constant Inmarsat emissions level across Iridium operating band assumption. • The constant Iridium out-of-band susceptibility level across the Inmarsat band • No account taken of Iridium channelization • The 100% Iridium equipage and usage in the airspace assumption. 11 Released to ICAO ACP WGM June 18, 2008 Conclusions • The probability of Inmarsat AMSS/AMS(R)S causing a service interruption that would affect the availability of Iridium AMSS/AMS(R)S operating on separate aircraft in oceanic airspace is very small • In oceanic airspace, Inmarsat AMSS/AMS(R)S out of band emissions from one aircraft do not cause harmful interference to Iridium AMSS/AMS(R)S on another aircraft: - The functioning of Iridium AMSS/AMS(R)S is not endangered; - No serious degradation, obstruction or repeated interruption of the operation of Iridium AMSS/AMS(R)S 12 Released to ICAO ACP WGM June 18, 2008 The bottom line There should be no obstacle to operation of Inmarsat AMSS/AMS(R)S services and Iridium AMSS/ AMS(R)S services in the same 30/30 RNP4 oceanic airspace. 13 Released to ICAO ACP WGM June 18, 2008.