navigation solutions powered by europe support to iwg25 12 th june 2013

Navigation solutions powered by Europe

SUPPORT TO IWG25

12th June 2013


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

21 April 2023 PROSBAS


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

21 April 2023 3PROSBAS

Analysis of clock prediction models


Definition of Study Cases. ICDs

21 April 2023 4

Clock estimation

(I nput)

UDRE I CD DFRE I CD

magicSBAS ODTS Fast Corrections

magicSBAS_ODTS_UDRE_ ICD magicSBAS_ODTS_DFRE_ ICD

magicSBAS Fast Corrections

magicSBAS_UDRE_ ICD magicSBAS_DFRE_ ICD

UDRE ICD DFRE ICDRCC 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



21 April 2023 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



21 April 2023 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



21 April 2023 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



21 April 2023 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)


21 April 2023 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

SATS in MASK

SATS monit MT1

MT2 Update Int MT2 # Mss

MT2_New

MT6-1 # Mss MT6-1

MT6-2 # Mss MT6-2

MT7+10 MT9 MT12 MT17

MT25 # Mss MT25

MT28 # Mss MT28 MT18 MT 26

MT30 # Mss MT 30

Num Messages per MT 1 1 1 1 3 0 0MT Update interval 120 6 6 120 60 300 300 240 240 300 300 300

TOTAL BW

4C 91 91 0,0083 54 4 0,0741 1 0,1667 1 0,1667 0,0083 0,0167 0,0033 0,0100 23 0,09583 46 0,1917 0,0000 0,0000 0 0,000 74,15743C 82 68 0,0083 24 3 0,1250 1 0,1667 1 0,1667 0,0083 0,0167 0,0033 0,0100 17 0,07083 34 0,1417 0,0000 0,0000 0 0,000 71,75002C 58 45 0,0083 11 4 0,3636 0 0,0000 1 0,1667 0,0083 0,0167 0,0033 0,0100 12 0,05 23 0,0958 0,0000 0,0000 0 0,000 72,28031C 31 24 0,0083 5 2 0,4000 0 0,0000 1 0,1667 0,0083 0,0167 0,0033 0,0100 6 0,025 12 0,05 0,0000 0,0000 0 0,000 68,8333

MT2 update intervals are much smaller than those considered in DFRE ICDs


SATS in MASK

SATS monit MT_B

MT_D Update Int

MT_D No Mss MT_D MT_C MT_F MT_E MT12 MT_G MT18 MT 26

MT30 No Mss MT 30

Num Messages per MT 1 1 1 1 1 3 0 0MT Update interval 120 6 120 60 300 120 300 300 300

TOTAL BW

4C 91 91 0,0083 175 91 0,5200 0,1667 0,0083 0,0167 0,0033 0,0250 0,000 0,000 0 0,000 74,8333

3C 68 68 0,0083 131 68 0,5191 0,1667 0,0083 0,0167 0,0033 0,0250 0,000 0,000 0 0,000 74,7417

2C 45 45 0,0083 87 45 0,5172 0,1667 0,0083 0,0167 0,0033 0,0250 0,000 0,000 0 0,000 74,55751C 24 24 0,0083 47 24 0,5106 0,1667 0,0083 0,0167 0,0033 0,0250 0,000 0,000 0 0,000 73,8972

DFRE & DFRE Alternative ICD (ICD2 & ICD2 alternative)

UDRE Alternative ICD (ICD1 alternative)


21 April 2023 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


Full System Protection Results (considering Integrity Message time-out for ICD2)

0

2

4

6

8

10

12

14

VPL 95% Nominal Case. ECAC + AFI

ICD_1

ICD_1 Alt magicSBAS

ICD_1 Alt magicSBAS ODTS

ICD_2

ICD_2 Alt magicSBAS


0

2

4

6

8

10

12

VPL 95% Optimistic Case. ECAC + AFI

ICD_1

ICD_1 Alt magicSBAS


ICD_2

ICD_2 Alt magicSBAS


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4

6

8

10

12

14

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VPL 95% Pessimistic Case. ECAC + AFI

ICD_1

ICD_1 Alt magicSBAS


ICD_2

ICD_2 Alt magicSBAS



21 April 2023 11

SBAS L1/L5 ICD models:Preliminary Performances Summary


Full System Protection Results (considering Integrity Message time-out for ICD2)

0

5

10

15

20

25

30

35

Max VPL Nominal Case. ECAC + AFI

ICD_1

ICD_1 Alt magicSBAS


ICD_2

ICD_2 Alt magicSBAS


0

5

10

15

20

25

30

Max VPL Optimistic Case. ECAC + AFI

ICD_1

ICD_1 Alt magicSBAS


ICD_2

ICD_2 Alt magicSBAS


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5

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15

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35

40

Max VPL Pessimistic Case. ECAC + AFI

ICD_1

ICD_1 Alt magicSBAS


ICD_2

ICD_2 Alt magicSBAS


• 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 m10 m

15 m

10 m


21 April 2023 12

ICD comparison


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)


21 April 2023 13

ICD comparison

21 April 2023

• 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


21 April 2023 14

Recommended way forward until end 2013 and for 2014


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

navigation solutions powered by europe support to iwg25 12 th june 2013

Documents

different clock estimates

previous clock estimations

drift clock computation

previous clock estimation

obad model

degradation model obad

udre icd mt710highly

l1l5 sbas mops