1. Navigation solutions powered by Europe SUPPORT TO IWG25 12 th June 2013

2. Navigation solutions powered by Europe 2 Contents  Reminder IWG#24 2 families of candidate ICD’s  UDRE ICD (ICD1 - limitation 51SV  no further studied) and its alternative (up to 90 active SV)  DFRE ICD (ICD2) and its alternative (use of spare CI bits to refresh DFRE when less than 4 const.)  At IWG#25 Analysis of clock prediction models (incl. OBAD) ICD1 alternative / ICD2 Performance comparison Conclusion - Comparison with IWG partners results (Stanford) and Recommended way forward 15 April, 2015 PROSBAS

3. Navigation solutions powered by Europe  To characterise the accurracy of clock prediction models  Two different clock correction propagation models UDRE_ICD (ICD_1): RRC method (inherited from L1 MOPS) DFRE_ICD (ICD_2): Linear clock model  Two different clock estimates used as inputs for the analysis Equivalent to current EGNOS design (EGNOS V2) Potential evolution of EGNOS design: Precise Orbit and Clock estimation algorithms (State of the art ODTS foreseen for EGNOS V3)  Same set of SV’s (from different blocks) and days used for the comparison 15 April, 2015 3 PROSBAS Analysis of clock prediction models

4. Navigation solutions powered by Europe  Definition of Study Cases. ICDs 15 April, 2015 4 UDRE ICD DFRE ICD RCC method: Linear extrapolation of two previous clock estimations to current epoch Linear Clock model: offset and drift clock computation from previous clock estimation data and propagation to current epoch PROSBAS Analysis of clock prediction models

5. Navigation solutions powered by Europe 15 April, 2015 5  Conclusion : two ways of improvement of clock corrections propagation (valid for any ICD) Use Precise Orbit and Clock estimation algorithms in SBAS Use a more accurate clock correction propagation method: Linear clock model better than RRC PROSBAS  Results comparison Analysis of clock prediction models

6. Navigation solutions powered by Europe 15 April, 2015 6  Analysis to define a degradation model (OBAD or MT7/10 data) Acceleration model (ai parameter): from SBAS L1 MOPS Polynomial model (Ccorr, Rcorr, Acorr): from DFRE proposal PROSBAS Acceleration model (current L1 MOPS): to be discarded. Polynomial model OK Recommendation: to tune scale factors for Polynomial model  OBAD analysis Analysis of clock prediction models

7. Navigation solutions powered by Europe 15 April, 2015 7  Two ways of improving the extrapolation of clock corrections Precise orbit and clock estimation algorithms in SBAS Using a more accurate method for propagating the clock corrections to the current epoch (linear clock model instead of RRC)  OBAD analysis Feasibility confirmed through experimentation that OBAD model included in “L1/L5 SBAS MOPS to Support Multiple Constellations” paper is feasible Linear or polynomial degradation (no more quadratic as in L1 MOPS) Include this model in UDRE ICD MT7/10 Highly recommended: a tuning of scale factors and effective ranges of the OBAD to allow a better fit to the degradation factors PROSBAS  Conclusions Analysis of clock prediction models

8. Navigation solutions powered by Europe 15 April, 2015 PROSBAS 8 SBAS L1/L5 ICD models: Refinement of Definition & performances  Strategy followed in this analysis  Update the bandwidth considerations to refine key parameters values (DeltaT_FC, DeltaT_IP) for each of the candidate ICD’s  Re-evaluate preliminary performances achieved with the SBAS L1/L5 ICDs under analysis (ICD1, ICD2 and alternatives)

9. Navigation solutions powered by Europe 15 April, 2015 9 Bandwidth tuned for 75% margins  FCs update intervals (DeltaT_FC values) used to estimate the Delta_FC parameters (key parameter to estimate performance) updated SBAS L1/L5 ICD models: Refinement of Definition & performances  MT2 update intervals are much smaller than those considered in DFRE ICDs 15 April, 2015 PROSBAS DFRE & DFRE Alternative ICD (ICD2 & ICD2 alternative) UDRE Alternative ICD (ICD1 alternative)

10. Navigation solutions powered by Europe 15 April, 2015 10 SBAS L1/L5 ICD models: Preliminary Performances Summary  ICD1 alternative and ICD2 (with or w/o alternative) provide quasi optimal performance NB: -Pessimistic case slightly better for ICD1 alternative than ICD2, yet felt due to (conservative) margins on UDRE border effect in the model (effective difference expected lower(tbc)). -ICD1 performance suffers from DOP limitation when more than 2 constellations 15 April, 2015 PROSBAS Full System Protection Results (considering Integrity Message time-out for ICD2)

11. Navigation solutions powered by Europe 15 April, 2015 11 SBAS L1/L5 ICD models: Preliminary Performances Summary 15 April, 2015 PROSBAS Full System Protection Results (considering Integrity Message time-out for ICD2) LPV-200: All cases below 35m Cat I autoland (VAL 10m to 15m): 2 constellations cases always below 15m..3 & 4 constellations and nom. & opt. cases seem very promising especially with ICD1 alternative (and possibly also with ICD2, since border effect is conservative in the model), even for 10 m-threshold. 35 m 15 m 10 m 35 m 15 m 10 m 15 m 10 m

12. Navigation solutions powered by Europe 15 April, 2015 12 ICD comparison 15 April, 2015 PROSBAS  ICD comparison Status at IWG#25 Availability: both ICD1 alternative and ICD2 (or its alternative) achieve close to optimal performances: up to 4 constellation / 91SV’s, low DFREi/Delta FCi values (provided by optimised ODTS and clock extrapolation), low VPL ICD1 alternative (with up to 90 active SV)  Flexible as per current L1 MOPS :  Provides comfortable margins with respect to border effect  Offers capability to rapidly react (updating all DFREi’s) upon event  increasing (continuity) robustness  not constraining system design  Offers room for enhancement : removal of FC’s, replacement of user RRC by system extrapolation parameter, optimised degradation model and tuning of OBAD parameters  Bandwidth limitation to be further analysed (LTC/MT28 rate)

13. Navigation solutions powered by Europe 15 April, 2015 13 ICD comparison 15 April, 2015 ICD2  Basically tailored for simple scheduler  Yet ICD2 rigidity (e.g. wrt. events impacting many SV, UDRE border effect) compared to current L1 MOPS. This is due to limitation in DFREi update mechanism  ICD2 would deserve being enhanced with flexible/dynamic but simple to implement mechanism (for instance by adding an on event pair of MT6 like messages allowing to recover DFREi within 2s after a general integrity alert message, or by another mechanism to be investigated) In the end, the enhanced ICD1 and enhanced ICD2 could become very close to each other. Unification into a single/common (selected) DFMC ICD seems now achievable target. PROSBAS

14. Navigation solutions powered by Europe 15 April, 2015 14 Recommended way forward until end 2013 and for 2014 15 April, 2015 PROSBAS  Analyse the enhanced ICD1 and enhanced ICD2 (as defined in previous slide) so that ICD1 is better optimised (incl. for BW) see slide #12 ICD2 is made capable of handling dynamic events without constraining the system design  (Tentatively) Unify the above enhanced ICD’s in a unique and common (pre-)selected ICD < end of 2013  Refine the mechanism to maintain integrity upon message loss (handling of repetitions upon DFREi change, OBAD, DFREi resolution table, etc.)  2014 would then be devoted to validate/refine the very details of the selected ICD (e.g. using EC/ESA pro-SBAS simulator)   Objective : interim (validated) MOPS ICD < end 2014