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

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

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, PROSBAS Analysis of clock prediction models

Navigation solutions powered by Europe  Definition of Study Cases. ICDs 15 April, 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

Navigation solutions powered by Europe 15 April,  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

Navigation solutions powered by Europe 15 April,  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

Navigation solutions powered by Europe 15 April,  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

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)

Navigation solutions powered by Europe 15 April, 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)

Navigation solutions powered by Europe 15 April, 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)

Navigation solutions powered by Europe 15 April, 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

Navigation solutions powered by Europe 15 April, 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)

Navigation solutions powered by Europe 15 April, 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

Navigation solutions powered by Europe 15 April, Recommended way forward until end 2013 and for 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