Horizontal Advanced RAIM: Operational Benefits and Future Challenges …signav.recherche.enac.fr/files/9014/5198/4446/Mikael... · 2016. 1. 5. · International Technical Symposium

1 International Technical Symposium on Navigation and Timing - 2015 17 / 11 / 2015

Horizontal Advanced RAIM:

Operational Benefits and

Future Challenges

International Technical Symposium on Navigation and Timing 2015

Session Air Navigation

November 2015 – Toulouse/France


ICAO ABAS augmentation

► ICAO has defined three types of augmentation systems: > ABAS > SBAS > GBAS

► ABAS systems were the first one implemented on-board aircraft based on

> Airborne Autonomous Integrity Monitoring implementation > Receiver Autonomous Integrity Monitoring implementation

► RAIM technics > Provides an autonomous integrity monitoring capability based on

satellite failure assumption for safety critical applications down to Non-Precision Approach or Lateral NAVigation

> Uses the redundancy of satellites measurement to detect, exclude and overbound the navigation position.


RAIM assumptions and operational limitation

► Traditional RAIM algorithms were design to detect single failure > Not accounting for potential multiple failure cases

► Traditional RAIM algorithms allocate the same probability fault for each satellite

► The fault free state in RAIM algorithm is based on zero mean Gaussian distribution with know variance

► Some operational limitations have been observed for Non-Precision Approach service[1]

> All GPS+RAIM implementation don’t lead to 100% of NPA or LNAV operation over the globe


GNSS evolution

► GNSS elements are under development/modernization > GPS is broadcasting on L1 and (some SV) L5 frequencies

> Galileo is being deployed and is broadcasting on E1 and E5a

> GLONASS and Beidou are also looking at evolution plan to

broadcast on L1/L5 equivalent band.

► GNSS will be dual-frequency and multi-constellation

(DFMC) > ICAO supports the development of next-generation GNSS to

further improve current services and benefit from increased

performance

> ABAS based on RAIM will be dramatically improved through

the availability of new dual-frequency measurements


ARAIM Concept

► New integrity monitoring technique has been proposed by US GEAS program [2]: Advanced RAIM (ARAIM)

> Taking credits for DFMC evolution context > Designing a measurement error model based on Gaussian distributions

and nominal bias supported by a new kind of airborne integrity monitoring algorithm [3]

> Targeting precision approach including global vertical guidance APV I / LPV 200 capability

> Introducing a light ground infrastructure referred as Integrity Support Message (ISM)

> Correcting current RAIM assumptions that no longer hold true

► The ARAIM concept has been further developed by EU-US WG-C ARAIM Technical Sub-Group which has detailed in its report ARAIM system architecture [4]:

> ARAIM off line architecture sustaining horizontal then vertical guidance > ARAIM on line architecture providing additional information such as

ephemeris overlay


Offline ARAIM Architecture


Aviation Standardisation Context

► RTCA SC 159 plans to develop new dual-frequency/multi-

constellation equipment in 2020+ > Based on SBAS L1/L5 augmentation system

> Based on DFMC RAIM in non SBAS area as current SBAS standard

► There is an interest to evaluate ARAIM performance for

horizontal operation (H-ARAIM) because > Horizontal guidance requirements are less demanding than vertical

guidance

> Horizontal operations are less safety critical which can simplify the

implementation of ARAIM feature in certified avionics

> Horizontal operations needs may be less stringent on the ISM

dissemination scheme to sustain acceptable operation performance - With less complexity on the GNSS core constellation or receiver design


▏ H-ARAIM benefits analysis

▏ Future challenges

▏ Conclusion

A

B

C




▏ Conclusion

A

B

C


Benefits Assessment Methodology

► Definition of the targeted operation > Identification of the associated requirements

► Definition of the tools and means to assess the benefits

► Definition of operational scenarios > Characterisation of H-ARAIM robustness based on nominal of

degraded mode of operation

> Characterisation of sensitive parameters to H-ARAIM

performance

► Results analysis


H-ARAIM operation targets in Navigation

► Most stringent horizontal NAV application defined by ICAO PBN [5] :

> RNP 0.1 NM - Required Total System Error at 0.1 NM for accuracy and 0.2 NM for integrity - Allocation between Navigation System Error (NSE), Path Definition Error

(PDE) and Flight Technical Error (FTE) is manufacturer/avionics-specific - 0.1 NM has been retained as integrity alerting requirement for the NSE - Definition of the HPL to achieve 99.9% Availability metric to characterize the

H-ARAIM NSE performance.

► Current operation realized with ABAS RAIM equipment > Lateral Navigation (LNAV)

Accuracy (m) Alert Limit (m) Integrity Risk

LNAV 220 556 10-7/hour

RNP 0,1 92 184 10-7/hour


H-ARAIM operation targets in Surveillance

► Automatic Dependent Surveillance – Broadcast (ADS-B) applications uses GNSS positioning in ADS-B report

► Two types of ADS-B mandates have been issued currently > ADS-B mandate targeting non-radar airspace with the objective to

provide radar-like separation services (e.g. Australia, Canada, Singapore, Fiji, Vietnam, etc.).

> ADS-B mandate targeting ADS-B use in addition to radar based on RTCA DO-260[6] - ADS-B mandate considered in Europe and in the United States - EU and US mandates are more stringent in terms of positioning information to

be reported by the aircraft

Accuracy (m) Alert Limit (m) Integrity Risk

Europe Mandate 185 1111 10-7/hour

US Mandate 92 370 10-7/hour


ARAIM simulation platform

► A simulation platform has been built with respect to the ARAIM concept architecture

Space Segment

• Number of constellation

• Number of satellite

• Frequency broadcasted

ISM

configuration

• URA

• Psat

• Pconst

• Bnom

User segment

• User Grid

• Time setting

• User error models

• User ARAIM algorithm


Operational scenarios: Objectives

► Provide simulation framework to assess the performance

of the ARAIM algorithm for horizontal based operations

► Characterize the robustness of H-ARAIM operations

► Identify the most sensitive parameters on H-ARAIM

performance

► Provide initial recommendation on realistic service

commitment targets


Operational scenarios: Overview

► Operational scenarios take into account: > Potential nominal and fall back mode of the future DFMC

receiver - Recent information on the Galileo IOC and FOC configuration [7] - The 2014 Federal Radio Navigation Plan [8] indicating that the GPS L5 FOC

will be postponed to 2024 > Main inputs related to the ARAIM algorithm processing or the

information provided by the ISM

► Scenarios introduced in this presentation:

> Constellation/Satellite failure impact scenario > Satellite clock and ephemeris sensitivity scenario > Constellation/Satellite geometry impact scenario including

- Downgraded or partial Galileo constellation design scenarios - Downgraded or partial GPS constellation design scenarios - Non-nominal GPS constellation design scenarios


Operational scenarios: Assumptions and Model

► Assumption > 5° mask angle and all in view

- No implementation of minimum standard requirement in terms of tracking channel

> 10 days of simulation sampled at 5 min > 5°*5° user grid over latitudes [-90°;90°]

► Model > Measurement error model as described in RTCA DO 229D [9]

- σUERE2 = σURA

2 + σRX2 + σMP

2 + σtropo2 plus nominal bias considered

> Troposphere model of RTCA DO 229D [9] > Multipath and receiver noise based on SESAR 9.27 recommendations

► Constellation > GPS + Galileo scenarios case > GPS constellation simulated as provided in GPS SPS [10]

- 24 satellites in a nominal configuration

> Galileo constellation simulated as provided in latest public document [7] - 24 satellites in a nominal configuration

► Algorithm: ARAIM user algorithm [3]


Operational scenarios: Assumptions and Model

► Simulation reference setting > The following table provides the reference settings of the H-

ARAIM algorithm used in simulation.

> Each scenario introduce the specific parameters that is

modified having in mind that the other or set according the

reference table

Parameters Settings

Constellations 24 + 24

Signals L1/E1 + L5/E5a

URA / URE 1 / 0.5

SISA / SISE 1,5 / 0,75

Bnom 0,75

PsatGAL / PsatGPS 10-5 / 10-5

PconstGAL / PconstGPS 10-5 / 10-5


Results: Constellation/Satellite Failure Scenario

► NSE requirement below 30m is sufficient to provide generous FTE budget margin for RNP 0.1 applications in a 24+24 constellation case

► 100 % Availability reached in each scenario. > Limited impact observed on the 99.9% HPL > Not a key parameter in H-ARAIM compared to

LPV 200 ARAIM analysis

► Demonstration of Pconst at 10-3 and Psat at 10-4

level from core constellation service provider (CSP) may be sufficient to sustain civil aviation needs for horizontal applications

Parameters Settings

Constellation 24 + 24

Signals L1/L5 and E1/E5a

URA / URE 1 / 0.5

SISA / SISE 1,5 / 0,75

Bnom 0,75

Scenarios

description

Reference case

• PsatGAL / PsatGPS : 10-5

• PconstGAL / PconstGPS : 10-5

Degraded Pconst effect


• PconstGAL / PconstGPS : 10-4

Degraded Galileo case

• PconstGPS / PsatGPS : 10-5

• PconstGAL / PsatGAL : 10-4

Realistic case


• PconstGAL : 10-3

• PconstGPS : 10-8

Operational

Scenario

99.9 % HPL

(meters)

RNP 0.1

Availability

LNAV

Availability

US ADS-B

Availability

EU ADS-B

Availability

Reference

case

20.26 100% 100% 100% 100%

Degraded

Pconst effect

22.15 100% 100% 100% 100%

Degraded

Galileo case

22.33 100% 100% 100% 100%

Realistic case 23.08 100% 100% 100% 100%


Results: Reference Case Details


Results: Satellite Clock & Ephemeris Scenario

► Increased values for URA and SISA have a more significant impact on the results than low Psat/Pconst on the 99.9% HPL figure

> but not on the availability results

► The worst case has been built upon the current GPS

broadcasted URA value and the worst case SISA that could be encoded by Galileo

> Leads to increase of 13 meters on the 99.9 % HPL which still provides a lot of margin compared to the requirements for all horizontal applications

Parameters Settings

Constellation 24 + 24


Bnom 0,75


PconstGAL /

PconstGPS

10-5 / 10-5

Scenarios

description

Optimistic case

• URA = 1 m /

URE = 0,5 m

• SISA = 1,5 m /

SISE = 0,75 m

Realistic case

• URA = 2,4 m /

URE = 2 m

• SISA = 3 m /

SISE = 1,5 m

Worst Galileo

case

• URA = 2,4 m /

URE = 2 m

• SISA = 6 m /

SISE = 3 m

Operational

Scenario

99.9 % HPL

(meters)

RNP 0.1

Availability

LNAV

Availability

US ADS-B

Availability

EU ADS-B

Availability

Optimistic

GPS and

Galileo

20.26 100% 100% 100% 100%

Realistic GPS

and Galileo

32.71 100% 100% 100% 100%

Worst case

Galileo

33.41 100% 100% 100% 100%


Results: Constellation/Satellite Design Scenario

Operational

Scenario

99.9 % HPL

(meters)

RNP 0.1

Availability

LNAV

Availability

US ADS-B

Availability

EU ADS-B

Availability

24 GPS + 24

GAL

20.26 100% 100% 100% 100%

24 GPS + 18

GAL

1830 48.72% 57.50% 53.76% 60.76%

27 GPS + 24

GAL

669.3 98.97% 98.96% 98.63% 100%

27 GPS + 18

GAL

1830 48.72% 57.50% 53.76% 60.76%

23 GPS + 23

GAL with the

DOP method

1033 99.81% 99.85% 99.85% 99.96%

23 GPS + 23

GAL removing

PRNs 2

770.2 99.85% 99.89% 99.85% 100%

Parameters Settings


URA / URE 1 / 0.5

SISA / SISE 1,5 / 0,75

Bnom 0,75


PconstGAL /

PconstGPS

10-5 / 10-5

► H-ARAIM availability is above 99.8% in GPS/GAL 23 satellites downgraded constellation situation

► Sensitivity of ARAIM to the constellation design and number of satellites > An increased number of satellites don’t necessarily bring additional performance

benefits > Algorithm is very sensitive to “partial / IOC” constellations with the failure

probability model used


Results: Constellation/Satellite Design Scenario

Operational

Scenario

99.9 % HPL

(meters)

RNP 0.1

Availability

LNAV

Availability

US ADS-B

Availability

EU ADS-B

Availability

24 GPS + 24

GAL

20.26 100% 100% 100% 100%

24 GPS + 18

GAL

1830 48.72% 57.50% 53.76% 60.76%

27 GPS + 24

GAL

669.3 98.97% 98.96% 98.63% 100%

27 GPS + 18

GAL

1830 48.72% 57.50% 53.76% 60.76%

23 GPS + 23

GAL with the

DOP method

1033 99.81% 99.85% 99.85% 99.96%

23 GPS + 23

GAL removing

PRNs 2

770.2 99.85% 99.89% 99.85% 100%

Parameters Settings


URA / URE 1 / 0.5

SISA / SISE 1,5 / 0,75

Bnom 0,75


PconstGAL /

PconstGPS

10-5 / 10-5

► H-ARAIM availability is above 99.8% in GPS/GAL 23 satellites downgraded constellation situation

► Sensitivity of ARAIM to the constellation design and number of satellites > An increased number of satellites don’t necessarily bring additional performance

benefits > Algorithm is very sensitive to “partial / IOC” constellations with the failure

probability model used


Results: Partial Galileo Constellation Details

► Additional analysis is conducted to further characterise

this limitiation in terms of performance using > Recent information on 10-8 Pconst for GPS [11]

> Downgrading satellite scenario for GPS


Results: Partial Galileo Constellation Scenario

► The targeted applications are available at 100%

► A nominal high performing constellation mixed with a

constellation with a limited service record could bring

operational benefits > Overcoming current ABAS/RAIM limitations of operations

based GPS L1 signals only.

Operational

Scenario

99.9 % HPL

(meters)

RNP 0.1

Availability

LNAV

Availability

US ADS-B

Availability

EU ADS-B

Availability

Optimistic

PsatGAL = 10-5 26.87 100% 100% 100% 100%

Medium

PsatGAL = 10-4 27.44 100% 100% 100% 100%

Worst

PsatGAL = 10-3 27.48 100% 100% 100% 100%

Parameters Settings

Constellations 24 GPS + 18 GAL


URA / URE 1 / 0.5

SISA / SISE 1,5 / 0,75

Bnom 0,75

PsatGPS 10-5

PconstGAL /

PconstGPS

10-3 / 10-8


Results: Partial GPS Constellation Scenario

► A very low level of availability is obtained > Due to the fact that not enough satellites where available in some

areas when the Galileo constellation and one GPS satellite are out. > Same number of satellites is simulated compared to the previous

results

► The constellation with the better failure probability needs to be

well populated to sustain a user availability of anything near 99%.

> Additional simulations have indicated that a 99% availability target can be achieved with 21 GPS satellites.

Parameters Settings



URA / URE 1 / 0.5

SISA / SISE 1,5 / 0,75

Bnom 0,75

PsatGPS 10-5

PconstGAL /

PconstGPS

10-3 / 10-8

Operational

Scenario

99.9 % HPL

(meters)

RNP 0.1

Availability

LNAV

Availability

US ADS-B

Availability

EU ADS-B

Availability

Optimistic

PsatGAL = 10-5 Infinite 47.39% 56.65% 53.35% 63.42%

Medium

PsatGAL = 10-4 Infinite 47.35% 56.57% 52.83% 63%

Worst

PsatGAL = 10-3 Infinite 47.27% 56.49% 52.79% 62.86%


Non-nominal GPS constellation

Operational

Scenario

99.9 % HPL

(meters)

RNP 0.1

Availability

LNAV

Availability

US ADS-B

Availability

EU ADS-B

Availability

Reference case 20.26 100% 100% 100% 100%

Modified 24 GPS

constellation 78.07 100% 100% 100% 100%

Parameters Settings



URA / URE 1 / 0.5

SISA / SISE 1,5 / 0,75

Bnom 0,75


PconstGAL /

PconstGPS

10-5 / 10-5

► The availability of the targeted operations has not been

harmed because of the high level of horizontal alert limit

► Increase of 280% of the 99.9 % HPL




▏ Conclusion

A

B

C


Main challenges for H-ARAIM

► Core constellations commitments

► ISM dissemination and implementation in the receiver

► ARAIM algorithm complexity

► ARAIM concept of operation and standardisation


Core constellation commitments

► The Integrity Support Message (ISM) information will not change the performance of H-ARAIM except if the Pconst goes below 10-7.

> Such performance will provide a 100% availability even with a low number of satellites from the second constellation.

> Drop of performance observed with an incomplete Galileo constellation is fully mitigated by a strong commitment on failure probabilities for GPS.

> Some values of Psat and Pconst have a significant impact on the final user performance but not all combinations.

► There is a reduced need to qualify a new CSP with a very low Pconst for H-ARAIM as long as a robust constellation with low Pconst is used in addition

► The number of satellites and their slot alignment within the orbit shall be carefully monitored

> Especially for the “established” constellation GPS


ISM issues

► The ISM and the means to disseminate the information is a key driver in performance/cost/complexity/readiness analysis

> Different ISM architectures based on an “on-line” scheme or an “off-line” scheme have been introduced [4]

> An ICD has been recently proposed describing the ISM message content [12]

► Results indicate that a dynamic ISM may not be required

> H-ARAIM can operate under severe failure conditions > H-ARAIM can operate with degraded performance with respect to clocks and

ephemeris error and downgraded satellites conditions

► An ARAIM receiver with fixed and conservative assumption with regards to ISM parameter may be capable to sustain operational needs

> Accommodate receiver manufacturer concerns on complexity, cost and certification burdens expressed in EUROCAE and RTCA

► An updatable on-board ISM provides benefits in the long term as it can take credit of core constellations service changes without impacting airborne equipment certification

► A trade off has to be found on H-ARAIM to set a receiver architecture that can: > Accommodate change in the CSP performance > Minimize standardization/certification cost


ARAIM algorithm complexity

► Iteration loops are implemented for the computation of

the HPL and VPL in the ARAIM algorithm

► The flexibility of ISM parameters may lead to different

number of subsets to be evaluated > Non fix architecture

> The computation power require may change pending on the

Psat/Pconst information used

► These are limitations for the standardisation of the

current ARAIM algorithm into certified avionics receiver


H-ARAIM ConOps and Standardisation

► There is an opportunity to embed H-ARAIM in the next generation of avionics receiver as a fall back integrity monitoring scheme to SBAS and GBAS.

► Standardisation bodies will require that a concept of operation is further developed to consider standardisation related activity.

> For the definition of system SARPS > For the definition of user equipment MOPS

► It should include at least :

> Complete description of the H-ARAIM architecture > Definition of message and retained solution for the provision of the ISM

content > Description of the interaction between ARAIM actors, operation and

system components > Allocation of responsibility over the different actors

- CSP role and responsibility - ANSP role and responsibility - ISM provider role and responsibility - Receiver and aircraft role and responsibility




▏ Conclusion

A

B

C


A promising concept …

► H-ARAIM is an interesting concept > Overcoming current operation limitation with GPS L1 + RAIM

> Providing robustness navigation and surveillance service

performance

> Aligning its design with constellation failure and multiple

satellite failures conditions

> Taking credits of multiple constellations and dual frequency

measurement

► There is a need to further develop an ABAS DFMC

concept to back up ground based augmentation system

solution in future DFMC receiver > H-ARAIM could be this new concept


… with still challenges to be tackled

► Lot of uncertainties in the concept and architecture make

the H-ARAIM concept not as mature as current SBAS

DFMC concept. > ISM definition

> User algorithm structure

> Role and responsibility of ARAIM actors

► Commitments will be needed on core constellation failure

probabilities to further developed > ICAO standard

> User receiver standard

36 European Navigation Conference 2015 09 / 04 / 2015

Thank you for the attention

Thanks to Egis

Partners on ARAIM: Questions ?


Acronyms Acronym Description Acronym Description

AAIM Airborne Autonomous Integrity Monitoring ISM Integrity Support Message

ABAS Airborne Based Augmentation System LNAV Lateral Navigation

APV Approach with Vertical Guidance LPV Localizer Performance with Vertical Guidance

ARAIM Advanced RAIM NPA Non Precision Approach

CSP Constellation Service Provider PBN Performance Based Navigation

DFMC Dual Frequency Multi Constellation RAIM Receiver Autonomous Integrity Monitoring

FOC Final Operational Capability RNP Required Navigation Performance

GBAS Ground Based Augmentation System SARPS Standard and Recommendation Practices

GNSS Global Navigation Satellite System SBAS Satellite Based Augmentation System

HPL Horizontal Protection Level SISA Signal In Space Accuracy

ICAO International Civil Aviation Organisation SV Satellite Vehicle

ICD Interface Control Document URA User Range Accuracy

IOC Initial Operational Capability VPL Vertical Protection Level


Reference

1. B. Roturier, M. Mabilleau, “Analysis of SBAS and RAIM performance versus ADS-B mandates”, ICAO NSP WG1 &WG2 5th meeting, Sept/Oct 2014.

2. J. Blanch, T. Walter, P. Enge, Y. Lee, B. Pervan, M. Rippl, A. Spletter, “Advanced RAIM User Algorithm Description: Integrity Support Message Processing, Fault Detection, Exclusion, and Protection Level Calculation”, Proceedings of the 25th International Technical Meeting of The Satellite Division of the Institute of Navigation (ION GNSS 2012), September 2012.

3. GNSS Evolution Architecture Study group, “GNSS Evolution Architecture Study Phase II report”, February 2010.

4. EU-U.S. Cooperation on Satellite Navigation Working Group C-ARAIM Technical Subgroup “Milestone II report”, February 2015.

5. ICAO, “Performance Based Navigation Manual”, doc 9613 Vol II

6. RTCA/EUROCAE, “Minimum Operational Performance Standards for 1090 MHz Extended Squitter Automatic Dependent Surveillance – Broadcast (ADSB) and Traffic Information Services – Broadcast (TIS-B)”, DO 260 B / ED 102 A, 2011

7. European Commission, “Galileo Program Status Update”, EUROCAE WG62 39th meeting, June 2015

8. US Department of Defense, US Department of Homeland Security, US Department of Transportation, “2014 Federal Radionavigation Plan”, May 2015

9. RTCA, “Minimum Operational Performance Standards for Satellite Based Augmentation System Receiver”, DO 229 D, December 2006

10. GPS NAVSTAR, Department of Defense, “Global Positioning System Standard Positioning Service Performance Standard”, 4th edition, September 2008.

11. T. Walter, J. Blanch, “Airborne Mitigation Of Constellation Wide Faults”, Institute Of Navigation International Technical Meeting (ION ITM), January 2015.

12. J. Blanch, T. Walter, P. Enge, JP Boyero, B. Pervan, M. Joerger, S. Khanafseh, J. Burns, K. Alexander, Y. Lee, V. Kropp, C. Milner, C. Macabiau, N. Suard, G. Berz, M. Rippl, “Progress on Working Group-C Activities on Advanced RAIM”, Institute Of Navigation GNSS (ION GNSS), September 2015.

Documents

Horizontal Advanced RAIM: Operational Benefits and Future Challenges …signav.recherche.enac.fr/files/9014/5198/4446/Mikael... · 2016. 1. 5. · International Technical Symposium