Attachment comment

This document pretains to SAT-AMD-20031118-00332 for Amended Filing on a Satellite Space Stations filing.

IBFS_SATAMD2003111800332_399896

«RK.RABTE QRLATE FILED Hnangenoo. msoersoe To: annssrze rec sn evrazor botones LATHAMe«WATKIN S« es.Aom Toome Hime Jw Stanies ORIGINAL hn Sowps Kergiong e~ (tes Sandige September 16, 2004 t infi F Govome Sn tan Int‘l Duroaik sowe — Marlene H. Dortch, Secretary & Hese Tobs Federal Communications Commission SEP 2 9 2004 Houteg.oc. 445 12th Street, SW Washington, DC 20554 Re: Mobile Satellte Ventures Subsidiary LLC RECEIVED TB Docket No. 01—185 File No. SAT—MOD—20031118—00333 SeP 1 6 zo0 File No. SAT—AMD—20031118—00332 File No. SES—MOD—20031118—01879 reomecommonas commens Expartepresentation gas Dear Ms. Dortch: On August 31, 2004, Mobile Satellite Ventures Subsidiary LLC (MSV") made an exparte submission in the above—cited proceedings, a paper entitled "Technical Considerations for Measuring the Receiver Overload Threshold of an Inmarsat Mobile Earth Terminal (MET)."Enclosed of behalf of Inmarsat Ventures Limited are its comments on that paper. Respectfully submitted, John AleCBrHochn cc: ChipFleming Howard Gribof Kathryn Medey Sean O‘More Lon Levin Bruce Jacobs

P)) inmarsat InmaristLintad, 90 ty Ras, Londo ECY 12%, Untad egion T oae chaorranto0ei +t (020 77201044 ininnanatcom Comments On MSV Proposals For Procedures To Test Receiver Overload Performance Of Inmarsat Terminals i/ ue an nmarst ventures conpary innass.acinie gota paver oh Wt aty Canclontis

y inmarsat Inmarsat provides the following comments on the test procedures proposed by MSV in its August 31, 2004 submission. At the outset, it is important to understand that the MSV submission both raises and ignores certain citcal ssues that are currently at issue in the ATC proceeding, such asthe need to consider the impact of ATC interference on the entire RF chain ofan Inmarsatreceiver, and the impact of intermodulation effects from ATC base station transmissions. Inmarsat has briefed those issues fully before. For purposes ofprompily responding to the recent MSV proposal,Inmarsat provides the following briefcomments, and will be glad to elaborate as needed. Section ILA 1) Figures 1 and 2 in Section II ofthe MSV document show a spectrum analyzer being connected to the output of the RF unit of the Inmarsat terminal, which supgests a measurement ofterminal nonlinearity based on the RF unit alone. As Inmarsat has explained in is previous pleadings, the whole ofthe RF chain plays a role within the performance specifiation and isolating justhe RF unit or the modem will not give a true measure of the MES non—linearity performance. Furthermore, the input t the modem is not readily availsble and disassembly of the MES may be required to achieve this. This in itself may cause additional problems and inaccuracies. Section ILB 2) There is no need to ty the (Fig 2) solution as additionalantennas have been supplied thatfiilitate the connection ofthe MES o the test equipment atthe L—band diplexer point. Section IILA 3) The performance ofthe InmarsatSystem is based upon achieving a minimum acceptable BERat the minimum received operational RF level. A "typical" received level, as supgested by MSV, does not exit, as Inmarsat uses power control to reduce the downlink EIRP where excess downlink margin exiss, such as would occur away from the beam edgelocations. This power control system, which provides just he necessary power for every link, is erucialto maintaining effcient use of satelite power and hence the economic viability of the system. Therefore the FCC tests should measure the minimum BER atthe minimum RF level since this corresponds to the situation that the users of the system are currently operating with, and is the situation specified forthe system. This is eritcal, particularly in the operation of safety services. 4) MSV‘s supgestion to icrease the satelite transmited power to combat interference is not a standard practice and raises two issues: it could affect the reuse arrangements in place with other operators and it would increase the power consumption of the satelites, The lattepoint is particularly important, as the Inmarsat—3 satellites already operate close to saturation. / ueC an marsat ventresconpary hnnasit acine doatparoeo t Mor y Canginstio

iinmarsat L P 5) Inmarsat‘s currently operational MES cannot automatically change their link data rate to cope with interference. Iterference over and above that catered for would mean cither poor BER or ultimately loss of communications. Section IILB 6) Comment 3 applies Section IILC 7) There is no such thing as a "Standard Subjective Test". Tests have to be specific to the codec used.In designing the Inmarsat codec, Inmarsat performed substantial Mean Opinion Score (MOS) testing and adapted the codec design to optimise performance, This included adaptations to account for Chinesand Arabic sounds. Inmarsat has also developed, in collaboration with the original designers of the Inmarsat codec, an electronic testtool fotesting implementations ofthe codec. This tool[called a "gold brick"}is only available at the manufacturers premises and provides a detailed analysis of the variations from the optimum for a large number of detailed characteristes ofthe codec implementation. Inmarsat does not believe that MOS testing based upon a limited number of listeners" of imited languages should be used; this would not be representativof the full range ofInmarsatusers and would add no eredibility to theinterference evaluation. ) Inmarsat needs to provide the customer with the expected communications quality and not only ‘inteligible transmissions. Section IHI (additional commen) 9) A further concem with SectionIHI is that it only talks about the interfering carier separation from the wanted signal as fthe test involves only a single interfering signal. "The FCC should do intermodulation measurements where the 3rd order IM product fall in the Inmarsatreceive channel. Tt is essentiato do these testsas well as the pure overload ones. Section IV 10) Section 1L.A comments & SectionIHI.A comments apply. 11) Seetion IV ofthe MSV document (and ts Appendix 1) places too much emphasis on the 1 dB compression point. This does notdirecly relat to the expected ATC interference levels. Inmarsat encourages the Commission to measure the interference resulting from 3rd order (and maybe higher odd order) intermodulation products falling in the Inmarsat receive band. a0 nmarsat venturs conpany We Innacsiuindoalsasef h Wl Rty Chanion


Document Created: 2004-10-06 18:08:59
Document Modified: 2004-10-06 18:08:59
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