Inmarsat Reply Comme

REPLY submitted by Inmarsat Inc.

Inmarsat Reply Comments

2018-07-19

This document pretains to SAT-AMD-20180531-00045 for Amended Filing on a Satellite Space Stations filing.

IBFS_SATAMD2018053100045_1467375

3C SYSTEMS COMPANY Design, Development, Analysis, & Regulation of Communications Systems Mark A. Sturza 16161 Ventura Blvd., C-815 +1 818 907 1302 Encino, CA 91436, USA +1 818 907 1357 (fax) mark@3CSysCo.com 6 July 2018 Ms. Marlene H. Dortch Secretary Federal Communications Commission 445 12th Street, S.W. Washington, D.C. 20554 RE: Amendment to License Modification Applications IBFS File Nos. SES-MOD-20151231- 00981, SAT-MOD-20151231-00090, and SAT-MOD-20151231-00091, IB Docket No. 11-109 Dear Ms. Dortch: I have reviewed the DoT GPS ABC Assessment in light of Ligado’s May 2018 Modification Applications Amendment. Based on my over 40 years’ experience with GPS, review of the Modification Applications Amendment, review of the DoT GPS ABC Assessment, familiarity with the NASCTN report 1, participation in the Roberson and Associates study, and participation in the IWG, my opinion is that operation of the Ligado system in compliance with the Modification Application Amendment will not result in harmful interference to space-based receivers or certified aviation receivers. Background I have over 40 years’ experience in the design, development, analysis, and application of GPS systems. I graduated from Caltech with a BS in Applied Mathematics in 1977 and hold a graduate degree from USC, I spent the first part of my career at Teledyne and Magnavox. In the early to mid-80’s, as Director GPS Development, I led Litton Aero Products GPS efforts leading to development of the LTN-700, LTN-710, and µNAV GPS Navigation Systems, and the codeless L2 signal-processing technique incorporated in Western Atlas Aero Service's GPS survey set (MINI- MAC). In the late 80’s, I joined Litton Guidance and Control Systems. I founded my consulting company, 3C Systems Company, in 1989, with which I have worked on a range of complex GPS matters, and since 2009 I have advised Ligado, and its predecessor companies, on GPS issues. In addition, I hold thirty US patents in GPS and related fields, nine of which specifically cover GPS technology. I have several additional patents pending. I have presented over 30 technical papers, 21 of which focused on GPS technology. I am a Senior Member of the IEEE, a Senior Member of the American Institute of Aeronautics and Astronautics, and am a member of the Institute of 1 NASCTN, NIST Technical Note 1952, LTE Impacts on GPS Final Report, February 2017.

Navigation, the Pacific Telecommunications Council, and the Society of Satellite Professionals International. I hold a General Radiotelephone Operator License from the FCC. Review of DoT GPS ABC Assessment Having reviewed the DoT GPS ABC Assessment, I am of the opinion that operating the Ligado system in conformance with the Modification Application Amendment will not result in harmful interference to space-based receivers or certified aviation receivers. To form this conclusion, I reviewed the following documents: • Amendment to License Modification Applications IBFS File Nos. SES-MOD-20151231- 00981, SAT-MOD-20151231-00090, and SAT-MOD-20151231-00091, IB Docket No. 11- 109, 31 May 2018. • United States Department of Transportation Global Positioning System (GPS) Adjacent Band Compatibility Assessment, Final Report, December 2017, including all appendices. I also developed a simulation program to verify the NASA simulation results reported in Section 4.2 and Appendix K of the assessment. In the Modification Application Amendment, Ligado proposes to: 1. Limit ATC base stations operating in the Lower Downlink Band to a maximum 9.8 dBW EIRP with a +/- 45-degree cross-polarized base station antenna 2. Prohibit any ATC base station antenna in the Lower Downlink Band from operating at a location less than 250 feet laterally or less than 30 feet below an obstacle clearance surface established by the FAA 3. Comply with the reporting, notification and monitoring obligations set forth in Exhibit 1 to the amendment The DoT GPS ABC assessment took the approach of determining interference tolerance masks (ITMs) or tolerable interference levels. “The ITM defines, for a given frequency, the maximum power allowed to ensure the tested GPS/GNSS receiver did not experience more than a 1 dB reduction in carrier-to-noise density ratio (CNR) for various categories of GPS/GNSS receivers.” 2 In my opinion this analysis does not address the question the FCC must answer: whether GPS devices will experience harmful interference. Instead, it uses an overly restrictive criteria for determining adjacent band operating levels. 3 As a general matter, it is worth noting that statements like “[when the] receiver exceeds a 1 dB signal-to-noise density (C/N0) interference protection criteria … the behavior of the GPS/GNSS receiver can become unpredictable in its ability to meet the accuracy, availability, and integrity requirements of its intended application and a receiver in a mobile application may not be able to reacquire GPS positioning …” 4 and “… the total unwanted N0 + I0 level is now 25% higher which is highly significant to system designers” 5 are misleading at best. If GPS/GNSS receivers became unpredictable when experiencing a 1 dB drop in C/N0 (or equivalently 25% higher N0 + I0 level), 2 Page 18. 3 See Mark A. Sturza, White Paper, “Changes in C/N0 Are Not a Reliable Indicator of KPI Impact” at 3, attached as Attachment B, attached to Reply Comments of Ligado Networks, IB Docket No. 11-109 (June 6, 2016), https://ecfsapi.fcc.gov/file/60002097963.pdf. 4 Page IV. 5 Page 45.


Document Created: 2018-07-19 22:06:08
Document Modified: 2018-07-19 22:06:08
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