Attachment redacted

This document pretains to SAT-MOD-20031118-00333 for Modification on a Satellite Space Stations filing.

IBFS_SATMOD2003111800333_415533

Repuitoy Cooml Mobile Satelite Ventures to mok msier m mx SWls tevngnanscon Jonuary 14, 2005 Via Hand Delivery Ms. Marlene H. Dortch, Secretary Federal Communications Commission 445 12th Street, S.W. Washington, D.C. 20554 Res Ex Parte Presentation of Mobile Satellite Ventures Subsidiary LLC 1B Docket No. 01—185 File No. SAT—MOD—20031118—00333 (ATC application) File No. SAT—AMD—20031118—00332 (ATC application) File No. SES—MOD—20031118—01879 (ATC application) Dear Ms. Dortch Mobile Satellite Ventures Subsidiary LLC ("MSV") hereby submits the attached analysis further demonstrating how its L—band AncillaryTerrestrial Component ("ATC") base stations will not cause harmfulinterference to Inmarsat aeronautical terminals. Please direct any questions regarding this matter to the undersigned. Very truly yours, Ton C.Levin ces Donald Abelson Jim Ball Williom Bell Richard Engelman Chip Fleming Howard Gribof® Karl Kensinger Paul Locke Kathym Medey Robert Nelson Sean O‘More Roderick Porter Steve Spacth David Strickland Cassandra Thomas Thomas Tyez John Janka, Counsel forInmarsat

Technical Response to Inmarsat‘s January 5, 2005 Filing Downlink Interference Potential. Inmarsat‘s recent filing (January 5, 2005) continues to show significant errors in the interference analysis ofthe acronautical case, specificallyin failing to account for shielding by the body ofthe aireraft. When shielding is accounted for, i is apparent that Inmarsatreceivers will be protected from MSV base stations operating at the permitted power levels even at very low altitudes. MSV has asserted that an AMS(RYSreceiver that is only 35 meters above an ATC base station (65 meters above ground) can maintain positive margin against overload. MSV states: "With one ATC base station emitting 32 dBWEIRPper sector and using the relazed base station antena characteristic, an airborne AMS(RYS receiver can be as low as 65 meters above ground (only 35 meters above the base station) and still maintain positive margin against overload. As the horizontal distance between the AMS(RYS receiver and the base station tower increases, the available margin increases rapidly as shown in the Table below."". The Table referred to in the above excerpt, illustrates the aireraft trajectory over the base station and specifiesthe available margin against overload at different points along the trajectory at horizontaldistance increments of 600 meters. The referenced Table is reproduced below." AMS(R)S Receiver Trajectory over one ATC Base Station Emitting 32 dBW EIRP per Sector and using the Relaxed Overhead Gain Suppression Pattern (AMS(R)S Receiver at 65 Meters Altitude; Base Station Located at X, = 0, 0 km) x a ar o| as o[ as as a o is i i [an] m v 2|3 aa c as as on on [ as [ 3 t e mes e s se an n se an o w a n c n w o Tez tes 5e um| es mz as7 w | m| us se | s|5 m ms o w | as se an im o| in m| wan in| «n n in| w mas| in | mas n Inmarsat‘s January 5 filing repeats the assumptions that MSV associates with the above Table and uses them to extrapolate the overload margin at the zenith ofthe base station, at which point Inmarsatderives a negative margin.. Then, Inmarsat concludes: "This shows there is a problem."" However, there‘s no problem. The assumptions stated by MSV (and used by Inmarsat)are valid only for the points ofthe aireraf‘s trajectory ‘ Mobile Satellite Ventures Subsidiary LLC, Opposition, File No. SAT—MOD— 2003111—00333, File No. SAT—AMD—20031118—00332, File No. SES—MOD—20031118— 01879 (December 23, 2004) (*MSF Opposition), Technical Appendix at 2. "MSV also stated that t should be emphasized that critical air—to—ground communications during take—offs and landings rarely, ifever, are based on the use of Inmarsat‘s system."" See MSV Opposition, Technical Appendix at 3. To which Inmarsat remains silent. > See Inmarsat Ventures Ltd., Reply, File No. SAT—MOD—20031118—00333, File No. SAT—AMD—20031118—00332, File No. SES—MOD—20031118—01879 (January 5, 2005) ("hmarsat Reply"), Appendix A at 3 & 4.

that MSV addressed in the above Table. Notall of the stated assumptions remain valid, however, when the elevation angle from the AMS(R}Santenna to the base station antenna becomes negative and is in the region between —30° and —90°. For that range of negative elevation angles, the body ofthe aircraft significantly limits the AMS(RJS anterna gain. The effect ofshielding of aitbome antennas by the aircraft is well recognized by the RTCA specifications and was first described by MSV in its ATC Application, Appendix L, at 4 & 5.. The rationale is as follows. RTCA Document DO—235A (dssessment ofRadio Frequency Interference Relevant to the GNSS) provides GNSS antenna pattems at angles below the aireraft (negative elevation angles). The RTCA assessment is based on results from simulations, patterm measurements made with GPS antennas mounted on a full—scale fuselage section, and patten measurements made on a scale—model aircraft. Based on these studies, the RTCA has concluded that an average back lobe antenna gain below the aircraft of10 dBic is representative ofthe elevation angle range from 30 to —90 degrees below the horizon. This gain value applies to en—route, non—precision approach, and Category I precision approach aireraft types. See RTCA/DO—235A, Appendix G. With regard to acronautical antennas used for AMS(R)S service, RTCA document DO—210C (Minimum Operational Performance Standards for Aeronautical Mobile Sarellite Services (AMSS), defines two types of antennas; a high gain antenna and a low» gain omni—directional antenna. Performance and coverage specifications for the low—gain version are similar to those defined by the RTCA for GNSS antennas. The high gain AMSS antenna is specified to be significantly more directive than the low gain version in terms of discrimination against adjacent satellite, Tt is reasonable, therefore, to expect that its average back lobe (below the aircraft) is at least as good as that of the broader— beam low—gain antenna. Both AMS(R)S and GNSS antennas are installed on top of the aircraft and use right—hand circular polarization. While RTCA/DO—210C does not provide specifications for AMS(R)S antenna gain below the aircraft, it is reasonable to believe that this gain may be modeled using the value given by RTCA/DO—235 for GNSS antennas; thatis, 10 dBic for elevation angles from —30° to —90°. NTIA, in its Ex Parte interference analysis dated November 12, 2002, used a similar rationale to conclude that an AMS(RJSreceive antenna gain of—10 dBic below the aircraft may be used to derive a conservative estimate of the received interference power level. Figure 1 below illustrates the geometry between an aireraft and a base station. As the approaching aireraft reaches point A, representing —30° look—angle toward the base station, the base station enters the shielded region, below the aireraft, where the * See Application of Mobile Satellte Ventures Subsidiary LLC, File No. SAT— MOD—20031118—00333, File No. SAT—AMD—20031 118—00332, File No. SES—MOD— 20031118—01879 (iled November 18, 2003) (collectively, "MSYATC Application), Appendix L at 4—5.

additional 10 dB of isolation is present. ‘The base station remains in the shielded region until the aireraft reaches point B. Figure 1: Aircraft Shiclded Region 30° c90° P 30° Shielded Shielded region o region a downtilt Based on the above, the Table below presents the overload profile associated with the aircraft‘s rajectory, in increments ofapproximately 45 meters ofhorizontaldistance, as the aircraft ravels from (X, Y) = (—0.3, —0.3) km to (%, Y) = (0.3, 0.3) km (the base station is at (X, ¥) = (0,0) km). It is seen that over a horizontal distance of approximately 200 meters centered aboutthe base station zenith the overload margin is approximately zero dB; not —6 dB as Inmarsatasserts." For a horizontal distance that is greater than approximately 100 meters from the base station zenith, the overload margin increases to over 4 dB.° * See Inmarsat Reply, Appendix A at4. * When the elevation angle from the AMS(R}S antenna to the base station antenna is in the region between —30° and —90°, the antenna gain ofthe AMS(R} receiver is assumed to be —10 dBic. Over this (near—zenith) region all three sectors ofthe ATC base station are assumed to impact the AMS(R)R receiver equally. Outside of the stated near— zenith region the antenna gain ofthe AMS(R)S receiver is assumed to be 0 dBic and only one sector of the ATC base station (the one radiating in the direction of the AMS(R)$ receiver) is assumed to impact the AMS(RJSreceiver.

AMS(R)S Receiver Trajectory over one ATC Base Station Emitting 32 dBW EIRP per Sector and using the Relaxed Overhead Gain Suppression Pattern (AMS(R)S Receiver at 65 Meters Altitude; Base Station Located at X, Y = 0, 0 km) x as as as as ar a1 on a or on ar TT To v as o s aa an w on e ai"| [ a| as on on dremm| 4o on on n on w n w w n e s se [ Te nee 5e ame)] se ns snn 17 ses |s ce n |s is e | s| wne se wegs n en vaa is ras c ons ae ar ons css 100| ie se on Finally, as the aireraft travels from (X, Y) = (0.3, 0.3) km to (X, Y) = (1, 1) km significant positive margin is maintained, contrary to Inmarsat‘s assertion, as seen from the Table below. Over this region, thaireraf‘s body shielding is 0 dB, and only one sector of the base station (the one facing towards the aireraf) is assumed to influence the AMS(R)S receiver. AMS(R)S Receiver Trajectory over one ATC Base Station Emitting 32 dBW EIRP per Sector and using the Relaxed Overhead Gain Suppression Pattern (AMS(R)S Receiver at 65 Meters Altitude; Base Station Located at X, Y = 0, 0 km) x a a a o a o s a o o & w as y 7| ar oi o as"| o o as"| o7 o o as" on in Gre max ie| @ on o ce an c c o o ce on n e e s hes 5e ue s| sea s | es se| s | ma one o | uo cma on|s sns wegan en es an ass on an rir m| on i im i| is n

Jan 14 2008 2iiirh morite snTELLITE VENTURES 7092902770 p.e CERTIFICATION 1, Dr, Peter D. Kurabinis, Vice President & Chief Technical Officer of Mobile Satellite Ventures Subsidiary LLC (‘MSV")cextify under penlty of perjury that: 1 am the technically qualified person with overall responsibility for preperation ofthe information contained in the foregoing. T am familiar with the requirements ofthe Commission‘s rules, and the information contained in the foregoing is rue end correct. on January 14, 2005 Dr. Peicr D. Kerabinfs Vice President & ChiefTechnical Officer


Document Created: 2005-01-27 16:18:45
Document Modified: 2005-01-27 16:18:45
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