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SLS-RFM WG deadlock over 2.4.18

SLS-RFM WG deadlock over 2.4.18. NASA’s position Rec. 2.4.18 has a number of critical flaws including a logical dependence upon an SFCG recommendation (on maximum occupied bandwidth) which does not and may never exist

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SLS-RFM WG deadlock over 2.4.18

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  1. SLS-RFM WG deadlock over 2.4.18 • NASA’s position • Rec. 2.4.18 has a number of critical flaws including a logical dependence upon an SFCG recommendation (on maximum occupied bandwidth) which does not and may never exist • NASA agreed to adopt 2.4.18 with the proviso that Rec. 2.4.1 would be adopted pursuant to footnote 4; Rec. 2.4.1 would have included conventional modulations, and therefore in the absence of Rec. 2.4.1 current rec. 2.4.18 is null, void, and without force or effect • The changes proposed for 2.4.18 by CNES to correct these flaws are not editorial in nature and should not be approved without agency review • Agreement reached at 2001 meeting at Pasadena called for introducing filtered OQPSK as a recommended modulation for the general case for the 8025-8400 MHz band in Rec. 2.4.1 • Subsequent discussions at Paris and College Park meetings modified this proposal to include also GMSK and 4D-8PSK TCM for the general case • NASA’s interpretation of Rec. 2.4.18 as currently phrased is that it has no applicability because it is conditioned upon a non-existing SFCG recommendation

  2. SLS-RFM WG deadlock over 2.4.18 • CNES’s position (1) • ð Referring to CCSDS procedure manual §3.2.3 concerning CCSDS Recommended Standards (Blue Book), "A CCSDS Recommended Standard must be reconfirmed or updated every five years, or it shall be retired to "CCSDS Historic" status". The Rec 2.4.18 has been published in June 2001 and by this fact should not be deeply modified till June 2006. So only editorial changes have to be discussed in May 2004 meeting. • ð     CNES considers that the modifications proposed by other agencies to correct "critical flaws" are not editorial in nature. • ð    CNES position on Rec. 2.4.1 has then changed as far as there is still the ambiguity of when applying Rec. 2.4.1 or Rec. 2.4.18 for 8025-8400 MHz band use. • ð     The work of SFCG concerning the use of 8025-8400 MHz band is still in process. The strict channelization noted in CCSDS rec 2.4.18 may not be recommended. But the provisional SFCG Rec14-3R5 recommends in point 6 "that bandwidth efficient modulation and coding techniques be used in accordance with CCSDS Rec (401)2.4.18, taking also into account SFCG Rec21-2 regarding adjacent channel interference". So we can then note that SFCG encourages the use of 4D-8PSK-TCM.

  3. SLS-RFM WG deadlock over 2.4.18 • CNES’s position (2) • ð     Adding filtered OQPSK and GMSK as proposed by the other agencies will correspond to a backward or at the best a static process in the sense of the use of more bandwidth efficient modulations as far as those scheme are far less efficient than the actual recommended one and no real power gain (more than 2 dB) can be offered by this techniques even when associated with sophisticated coding schemes. • ð     The new ESA proposition to add SCCC-8PSK to Rec 2.4.18 has to be done according the CCSDS new procedure : measurements on equipments (or mockup) have to be presented to agencies before entering in a White new recommendation as far as there are still important open questions on this scheme. In parallel, the study of applicability to CCSDS of the ETSI DVB-S2 standard has to be conducted and measurements have also to be presented as this is also a candidate solution. • ð     CCSDS MC and the IOAG have asked to limit the number of recommended modulations and coding in order to ensure systems interoperability, but all the new added propositions in Rec 2.4.18 are going in the wrong way.

  4. SLS-RFM WG deadlock over 2.4.18 • CNES’s position (3) • ð     CNES is worrying about the fact that numerous missions of the others agencies plan to transmit few to ten Mb/s in X band (8025/8400 MHz) instead of using S band (2200/2290 MHz) due to the fact that the S band is already very used (agencies are forced to coordinate themselves). X band is already populated by most of Earth Exploration Satellite Services (40 missions operational and 40 missions planned to be launched before 2015). This migration to X band has to be monitored in order to avoid soon the same coordination problem. Frequency is not unlimited resource so the best effort has to be done by each agency to optimize the most efficiently the use of the band. • ð     CNES recalls that X band is issued in the Global Monitoring Environment Satellites (GMES) agreement between agencies and is so used for Civil Security services (such as forest fire, floods, …). Interference cases are not acceptable as far as a loss of data may lead to loss of life.

  5. SLS-RFM WG deadlock over 2.4.18 • CNES’s position (4) • ð     CNES proposes to set up an Action Item to: • 1.     Define with accuracy how to compute without any doubt spectral efficiency • 2.     Define then what is a bandwidth efficient modulation shaping and coding techniques • 3.     Generate a measurement based snapshot of the different standardized techniques in terms of spectral efficiency and power margin. Then this will be used to recommend without ambiguity adequate separation criteria for applicability of Rec 2.4.17A and Rec 2.4.18.

  6. SLS-RFM WG deadlock over 2.4.18 • Aerospace’s position • Rec. 2.4.18 needs some changes to align it with SFCG Rec. 14-3R5 • Since 4D-8PSK TCM is a combined modulation and coding scheme, any other type of coding are not recommended. Therefore for those missions which are more concerned about power efficiency than bandwidth efficiency (such as small aperture ground terminals), more power-efficient codes and/or modulations cannot be accommodated. • Furthermore, those missions which need to be more bandwidth efficient than 4D-8PSK TCM may need to use higher order alphabets such as 16QAM.

  7. SLS-RFM WG deadlock over 2.4.18 • ESA’s position • ECSS RF & Modulation Standard allows both SRRC-OQPSK and 4D-8PSK TCM for symbol rates higher than 2 Ms/s in the 8025-8400 MHz band • ESA is in favour of approving Rec. 2.4.1with conventional modulations thereby aligning CCSDS with ECSS • Furthermore, ESA is proposing to add SCCC-8PSK to 2.4.18 for missions requiring higher power efficiency than 4D-8PSK TCM for the same spectral efficiency • ESA has participated to the work of DVB-S2 (subject to patents) and does not see any advantage over SCCC-8PSK as shown in the presented ESA paper but does not object to other Agencies’ evaluations

  8. SLS-RFM WG deadlock over 2.4.18 • Conclusions • WG decided to ask SLS Area Director for guidance on this issue with the aim of progressing the work of the WG • WG suggests that the AD consult with the CESG and/or the CCSDS management council • If in the future WG unanimity as per CCSDS Procedures Manual cannot be reached, how can consensus be interpreted?

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