CCSDS 2011 SPRING MEETING

Transcription

1 CCSDS 2011 SPRING MEETING Berlin (Germany) May 2011 SLS RF&Modulation Working Group - Minutes of the Meeting 1. Action items review AI_09-16 (Provide simulations of UQPSK and GMSK with PN ranging) is closed by input paper SLS-RFM_ AI_10-03 (Verify the GMSK ranging acquisition results with realistic synchronization) is closed by input paper SLS-RFM_ AI_10-09 (Generate the first draft version of the CDMA Green Book) is closed by input paper SLS-RFM_ AI_10-10 (Resolve the differences between NASA SLS-RFM_10-20 paper and its presentation, add the OBO to the total degradation) is closed by input paper SLS-RFM_ AI_10-11 (Modify recommendation (8PSK vs. 4D-8PSK-TCM) for consistency with DVB-S2 and SCCC books when they become blue) is open pending books approval. AI_10-12 (Consider the two missing spectral efficiency cases and finalize the analysis for Recommendation on 4D-8PSK-TCM impairments) is open and expected to be closed at the next meeting. AI_10-13 (Editorially modify charter and projects along the agreement reached at the meeting, and distribute charter to the WG and the SLS AD) was closed in November The revised charter was meanwhile approved. 2. New recommendations (22, 26, 32 GHz plus Lunar and Earth Relay 2 GHz links, HR TLM and PN ranging) 2.1 High rate telemetry and PN ranging Document SLS-RFM_11-04 was presented by NASA. Such document is the response to AI-09_16) and reported on the independent NASA simulations of GMSK/PN and UQSPK/PN with the goal of verifying the ESA results presented to date. All the proposed PN shaping (square, sine and SRRC with roll-off 0.5) were simulated along with both GMSK (BTs=0.25 and 0.5) and UQPSK modulations and both ranging (T4B and T2B) codes. For GMSK/PN, the ranging modulation index was normalized as in ESA documents with a 2 factor in front of the sine wave shaping impulse response. The only difference in the assumptions was that for UQSPK NASA used the 10-W ESA s SSPA model while ESA simulations assumed a TWTA. Additionally, the NASA simulations assumed ideal synchronization while ESA s paper SLS-RFM_11-01 assumed realistic synchronizers. GMSK/PN spectra are identical to ESA s results. Conclusions are that both GMSK schemes have the same performance with PN ranging. The combined telemetry and ranging signal 1/10

2 (with sine wave shaping) almost meets the SFCG mask for telemetry only while even better results are obtained with SRRC filtering. UQPSK/PN spectra exceed the above mentioned SFCG mask due to the SSPA. ESA s results (worse than NASA s due to the use of a TWTA) show discrete spurious lines at the clock frequency (and its harmonics) that are not visible in NASA simulations. D. Lee took the action (AI_11-01) to verify if the missing discrete lines are due to the resolution bandwidth used. Additionally, for the case of rectangular shaping, the spurs by NASA are lower than the ones by ESA but this could be due to the use of SSPA vs. TWTA. Discussion continued with the performance results. The GMSK modulator in the receiver was implemented by NASA as an ideal GMSK modulator. The transfer function of the LPF filter in the receiver was not available and D. Lee took the action (AI_11-02) to provide this function. The BER degradation for the GMSK/PN case is of the order of db as per ESA simulations. The ranging chip error rate is also identical to ESA results. No significant variations were found among the various shaping and modulation combinations. The BER losses for the UQPSK/PN case are around 1.1 db while ESA results were around 1.3 db. This could be explained by the SSPA vs. TWTA used in the simulations and by the real synchronizers used in ESA simulations. The ranging chip error rate is also smaller than the one computed by ESA. In conclusions, GMSK/PN is more spectrally efficient than UQPSK/PN, the SFCG mask can be met by SRRC shaping and almost met by sine wave shaping, T4B is slightly more efficient than T2B. No difference in BER losses or ranging chip error rate degradation was noticed between T2B and T4B. For UQPSK/PN, SRRC is the only way to meet the SFCG mask. Document SLS-RFM_11-01 was presented by ESA. Such document is the response to AI ) and reported on the GMSK/PN performance for the case of real synchronizers. The document shows that the simulated receiver scheme correctly works for the considered cases in which the ranging chip rate is exactly or almost equal to the telemetry bit rate or twice this value. The losses due to synchronization are in the range db. No significant differences were found among the various ranging pulses and codes: it is therefore convenient to use the more bandwidth efficient solutions (SRRC or sinusoidal pulses) to transmit the PN ranging signal. As for telemetry, again there are no significant differences in the performance of GMSK with BTs = 0.5 or Acceptable values of h are from 0.05 to 0.2, where h = 0.05 favors telemetry and h = 0.2 favors ranging. The intermediate value h = 0.1 is a good compromise, and is the suggested value in practical applications. If h is smaller than 0.05, then the ranging acquisition time increases dramatically. Different chip rate/telemetry symbol rate ratios were also simulated by ESA and found not to differ too much for the presented cases. They are included in an ESA internal document that upon internal approval will be made available to CCSDS. Considering both papers SLS-RFM_11-01 and SLS-RFM_11-04, the group concluded that the necessary work was completed and that standardization of GMSK/PN could proceed with two small exceptions resulting in two action items. The first action item (AI_11-03) calls for G. Sessler to carry out a link budget for missions at Mars and Lagrange (L2) so as to determine the expected typical end-to-end performance for this new modulation. 2/10

3 It is recalled that due to the normalization used for the sine wave shaping, the ranging modulation loss is given by: L mod J h 2 whereas for the square wave shaping this is given by: L mod h sin 2 2 The second action has to do with the effect of phase array jumps and NCO offset on the GMSK/PN modulation scheme in light of the small modulation index associated with ranging. An action item (AI_11-04) was taken by G. Sessler to check the effect of phase array jumps and NCO offset on ranging. It was agreed to draft a stand-alone recommendation to be inserted in 401. The following points were noted: Consider if appropriate to have one recommendation for deep space missions and one for missions to Lagrange points. Consider if both BTs value for GMSK should be used. If two recommendations were to be proposed (see previous bullet), it would make sense to adopt 0.25 for Lagrange missions and 0.5 for deep space missions consistent with recommendation A and B. Consider the PN ranging shaping: sine wave only? Consider the range of ranging mod index h. Select h=0.1 or specify range with preferred value 0.1? Consider if both T2B and T4B should be included or only one code selected. Propose a range of chip rate/telemetry symbol rate ratios. Consider if constraints from the result of the action item on phase array jumps/nco offset need to be included. It was also agreed to prepare a summary of results to justify the selections for the above bulleted options GHz modulation Document SLS-RFM_11-02 was presented by NASA. The document was in response to AI_ Initial results presented by NASA in previous paper did not include any phase imbalance compensation. This is significant for 32 and 64 APSK. The overall results compare favorably with ESA and POLITO results. There still is less than 0.25 db difference in some cases and NASA results give better performance than ESA. This is expected to be due to the quantization used by ESA whereas NASA used floating point arithmetic. No error floor has been detected by NASA down to a BER of NASA considers therefore that the verification work is completed and recommends adding decoder specs in the SCCC book. 3/10

4 2.3 Modulation for Earth Relay 2-GHz links CCSDS SLS-RFM WG MEETING The working group reviewed and disposed all the RIDs (by DLR, ESA and NASA) received during agency review of the CCSDS red book R-1. Disposition of the individual RIDs can be found in each RID as submitted to CCSDS Secretariat. A revised document was generated and agreed at the meeting. However, some editorials mainly involving pictures in the document could not be fixed at the meeting due to the limited time availability. This editorial task was therefore assigned to the chairman with help from V. Sank. As soon as this is done, the document will be sent to CESG/CMC for adoption as Blue Book. Concerning the Green Book, the first draft provided per action AI_10-09 was briefly discussed at the meeting. It was noted that the title had to be the same as in the Blue Book. Figure 8A was found to have the same mistake (in code generators) as in the BB and should be changed. Also the figures containing NASA codes examples should be replaced with CCSDS codes examples. Performances should be added as well as an expanded section on time correlation. An action item was given to everybody to review the current draft GB as far as the material that is covered (AI_11-05) and provide comments within 2 months from this meeting. V. Sank took the action (AI_11-06) to provide a revised draft version 2 months prior to the Fall 2011 meeting. 2.4 Other work items (Miscellanea) GHz modulation Paper SLS-RFM_11-05 by NASA was presented. This input deals with recommendation B that recommends GMSK for symbol rates higher than 20 Msps. Since no modulation scheme is specified for lower rates, a non efficient scheme below this rate could use up all spectrum. Additionally, residual carrier modulation is needed for specific radio science experiments and for autotracking of certain antennas. NASA advocates both NRZ-L and bi-phase modulation directly on the carrier with a mod. index around 72 deg (1.25 rad). ESA stated that NRZ-L directly on the carrier would not be a good choice (was discarded for the 2 and 8 GHz bands) and would defeat the requirement for a clean carrier. It was noted that a companion paper on adopting 60-MHz channels was being sent to the upcoming SFCG. If such channelization was adopted by SFCG, CCSDS could start working on the needed modulation. The issue was tabled for the next CCSDS meeting Agency revision of pink recommendation (CCSDS P-20.1) Four RIDs were received from INPE and one from ECSS. The INPE RIDs were rejected since the changes requested by INPE were as a matter of fact the ones included in the pink version. The RID by ECSS was partly accepted and partly rejected. The accepted part relates to replacing may with could in the considering, and adding should in the recommend. The other requested changes (basically, a completely new structure for any recommendation) was rejected on the ground that the necessary resources to change this as well as all other individual recommendations in 401 are not available. 4/10

5 Disposition of the individual RIDs can be found in each RID as submitted to CCSDS Secretariat. The WG agreed to request CESG/CMC to proceed with adoption of the revised recommendation Proximity-1 Physical Layer Blue Book Paper SLS-RFM_11-03 by CNES was presented. This input deals with the frequency bands of the BB. Currently only the bands MHz (FW) and MHz (RT) are specified along with placeholders for unspecified S, X and Ka bands. The proposal by CNES is to add also the bands currently being proposed by CNES at SFCG for the lunar proximity. It was remarked that the current BB is restricted to Martian missions and therefore does not encompass lunar missions. Decision was taken to only leave the and MHz bands in the BB, delete all references to S, X and Ka bands, and add a generic placeholder section called Other frequency bands. Such decision resulted in changes to SLS-RFM_11-06 that would be presented at the joint meeting with C&S, NGU, RNG, SLP. 3. Joint meeting with C&S, NGU, RNG, SLP 3.1 NGU joint issues A short discussion took place on time tagging of telemetry with regenerative PN Ranging. Regenerative ranging requires inclusion of sophisticated correlating hardware in the flight transponder for the time-tagging of the spacecraft clock. 3.2 C&S joint issues Document SLS-RFM_11-02 by NASA was briefly presented also to this larger audience. Conclusions are as per section 2.2. No further work is needed since NASA and ESA results for SCCC are aligned. 3.3 Prox-1 physical layer BB issues Before presenting SLS-RFM_11-06 with the additional changes agreed by the RFM WG meeting on the frequency bands, discussion started on the common definitions to be used in all three Proximity-1 books. After several attempts, a symbol rate definition was agreed to be applied across these 3 books with the specific interface for the PL BB in the figure below: 5/10

6 This figure will be inserted in the PL BB along with the necessary text. Additionally, there is a need to cross check all instances of data/bit/symbol rates in the book so that they are aligned with the above definition (including checks of the bi-phase rate peculiarity). The frequency band changes agreed in the RFM WG meeting were presented to the joint meeting and accepted. E. Vassallo took the action (AI_11-07) to insert the frequency band changes, the symbol rate definition figure, cross check/change all data rates occurrences in the book and generate a clean document for further distribution to all interested WGs. G. Kazz and E. Vassallo took the action (AI_11-08) to submit the clean document generated by AI_11-07 to the NASA and ESA EXOMARS teams for an independent review. The goal is to finalize all discussions at the Fall 2011 meeting. It was agreed in principle to include the PICs pro-forma as an exception also in the PL BB for consistency with the other Prox-1 books. 5. Charter discussion The following was noted: Some activities (review of CDMA book and revised rec , high rate TLM and PN RNG, 26 GHz modulations) are approximately on schedule; Some activities (CDMA green book, 4D-8PSK TCM impairments) are behind schedule since required effort could not be made available. It was decided to revisit the charter at the Fall 2011 meeting. 6. Resolutions The meeting resolved to request publication of the revised recommendation 401 (2.2.8), on high rate telecommand. The meeting resolved to request publication of the blue book B-1, on CDMA for 2 GHz DRS links. 6/10

7 Annex 1 - Action Item List AI # AI description Actionee Due date AI_10-11 Modify recommendation (8PSK vs. 4D- 8PSK-TCM) for consistency with DVB-S2 and SCCC books when they become blue E. Vassallo (2) AI_10-12 Consider the two missing spectral efficiency G. Lesthievent (1) cases and finalize the analysis for Recommendation on 4D-8PSK-TCM impairments AI_11-01 Verify if the missing discrete lines in UQPSK/PN D. Lee (3) spectra is due to the resolution bandwidth used and check the levels of the existing lines AI_11-02 Provide the transfer function of the LPF filter in D. Lee (3) the receiver for the GMSK/PN case AI_11-03 Carry out a link budget for missions at Mars and G. Sessler (1) Lagrange (L2) so as to determine the expected typical end-to-end performance of GMSK/PN AI_11-04 Check the effect of phase array jumps and NCO G. Sessler (1) offset on ranging for GMSK/PN AI_11-05 Review the current draft CDMA GB as far as the ALL (4) material that is covered (contents) and provide comments AI_11-06 Provide revised draft CDMA GB V. Sank (5) AI_11-07 Insert the frequency band changes, the symbol E.Vassallo (6) rate definition figure, cross check/change all data rates occurrences in the Prox-1 PL BB and generate a clean document AI_11-08 Report on an independent review of the clean G. Kazz, (7) document generated by AI_11-07 via the NASA E.Vassallo and ESA EXOMARS teams (1) 2 weeks prior to Fall 2011 meeting. (2) Date dependent on approval of the two mentioned Blue Books. (3) 2 weeks after the Spring 2011 meeting. (4) 2 months after the Spring 2011 meeting. (5) 2 months prior to the Fall 2011 meeting. (6) By 1 September (7) By 1 October Note: deadlines shown in yellow highlight are those for which an early action is needed. 7/10

8 Annex 2 - List of Participants RF and Modulation Meeting CCSDS SLS-RFM WG MEETING (Please see other WG minutes for joint meetings participants) Name Affiliation E Vassallo (chairman) ESA enrico.vassallo@esa.int M. Bertinelli ESA massimo.bertinelli@esa.int G. Sessler ESA gunther.sessler@esa.int M. Baldi ESA/UNIVPM m.baldi@univpm.it L. Wu BITT wlmsh2000@sohu.com L. Li CAST lili.xian2012@gmail.com Y. Xu CAST yangxu561@hotmail.com X. Liang CSSAR/CAS liangxf@cssar.ac.cn J.L. Gerner CNES jeanluc.gerner@yahoo.com J.L. Issler CNES jean-luc.issler@cnes.fr G. Lesthievent CNES guy.lesthievent@cnes.fr D. Dikanskis DLR daniils.dikanskis@dlr.de W. Fong NASA/GSFC wai.h.fong@nasa.gov V. Sank NASA/GSFC/MEI victor.j.sank@nasa.gov H. Garon NASA/GSFC/MEI howard.garon@nasa.gov D. Lee NASA/JPL dennis.k.lee@jpl.nasa.gov F. Pollara NASA/JPL fabrizio.pollara@jpl.nasa.gov A. Schlesinger NASA/JSC adam.m.schlesinger@nasa.gov E. Chistov RFSA chistov@laspace.ru 8/10

9 Annex 3 - List of Input Papers Radio Frequency and Modulation: Paper Title Available/ Distributed Author SLS-RFM_11-XX 01 Synchronization analysis for GMSK/PN Modulation y/y M. Visintin, E. Vassallo 02 GFSC Evaluation of SCCC-based ESA Schemes - Findings and y/y H. Garon et. al. Recommendations 03 New frequencies proposed to be added to the PL-1 frequency set y/y J.L. Issler 04 Simulations of GMSK/PN and UQPSK y/y D. Lee 05 Proposed Changes to 32 GHz Modulation Recommendation y/y D. Lee 06 Proximity-1 Physical Layer Consolidated ESA and NASA changes y/y ESA and NASA 07 CCSDS 415 (CDMA) Agency Review - ESA RIDs y/y ESA 08 CCSDS 415 (CDMA) Agency Review - NASA RIDs y/y NASA 09 CCSDS 415 (CDMA) Agency Review - DLR RID y/y DLR 10 CCSDS 401 (Rec ) Agency Review ECSS RID y/y ECSS 11 CCSDS 401 (Rec ) Agency Review INPE RIDs y/y INPE 12 CDMA Green Book first draft version y/y V. Sank 9/10

10 Annex 4 - Agenda Date Item AI/REC Actionee / Author May 17 - a.m 1 Action items review Comments / Input Papers 2 New recommendations (22 and 26 GHz, Lunar and Earth Relay 2 GHz links, HR TLM and PN ranging) AI_09-16 AI_10-03 D. Lee E. Vassallo SLS-RFM_11-04 SLS-RFM_11-01 May 17 - p.m 3 New recommendations (22 and 26 GHz, Lunar and Earth Relay 2 GHz links, HR TLM and PN ranging) AI_10-10 H. Garon SLS-RFM_ Miscellanea Prox-1 frequencies J.L. Issler SLS-RFM_11-03 Prox-1 Physical Layer ESA and NASA SLS-RFM_ GHz modulation D. Lee SLS-RFM_11-05 Rec RID disposition May 18 - a.m. 5 New recommendations (22 and 26 GHz, Lunar and Earth Relay 2 GHz links, HR TLM and PN ranging) AI_10-09 ECSS INPE ESA NASA DLR V. Sank SLS-RFM_11-10 SLS-RFM_11-11 SLS-RFM_11-07 SLS-RFM_11-08 SLS-RFM_11-09 SLS-RFM_ Joint meeting with C&S, NGU, SLP May 19 - p.m. NGU joint issues C&S joint issues H. Garon SLS-RFM_11-02 Prox-1 Physical Layer ESA and NASA SLS-RFM_ /10