navisp-el1-027 alternative space-based pnt data layer

Presentation Template wide screenFinal Presentation
Agenda
4 November 2020, Skype
Aim of this meeting:
Project Overview
Project Objectives
• The main objective of this project was to:
- “Study new, innovative concepts and trade-off the main design drivers for a PNT
data layer system, based on on-board processing, alternative to conventional on-
ground computation based systems”
• AltPNT was an ambitious 12-month project addressing a number of challenging objectives:
- Improve Safety-of-Life (SoL) service performance
- Improve security
5All rights reserved © 2019, Telespazio
Project Team
• Telespazio VEGA UK (TPZV-UK) is the Prime contractor
- Responsible for the overall project and technical delivery
• Supported by Thales Alenia Space UK Ltd (TAS-UK) and Nottingham Scientific Ltd (NSL)
- Bringing essential technical and scientific expertise required by the project:
Project Tasks
- Architecture Definition
• Definition of high-level architectural concepts with particular focus on the payload features and main
constituents, identifying main functions and data flows for each component and performing main system trade-
offs.
alternative architectures are expected, for instance on data latency, and providing insight into the main design
drivers.
• Assessment of the status of existing technology vis-à-vis functional and architectural needs, identifying areas
for technology evolutions such as radiation-hardened space computer or on-board processing capabilities.
- SWOT Analysis
• Analysis of strengths, weaknesses, opportunities and threats of the studied architecture, taking into account
security aspects, operations approach and service provision models. The study concluded on the interest of the
alternative architecture and proposed further steps
Schedule and Milestones
Kick-off
12 October 2020
M1 M2 M3 M4 M5 M6 M7 M8 M9 M10 M11 M12
Delivery Milestones KOM PM1 MTR PM2 DR FR FP
WP ID Task
0 Project Management
1 Architecture Definition
2 Performance Analysis
3 Technology Survey
4 SWOT Analysis
Primary Deliverables
- D1 – High-level Architecture Definition
• Detailed analysis of the system elements of the proposed concept
- D2 – Preliminary Performance Analysis
- D3 – Technology Survey Report
• Survey of existing technology that could fulfil the defined architecture
- D4 – SWOT Analysis Report
• Strengths, weaknesses, Opportunities and Threats analysis of the proposed solution
• The study provides a usable assessment of the interest in alternative architectures
• based on on-board processing
• and identification of areas where technology evolution is a prerequisite
9All rights reserved © 2019, TelespazioAll rights reserved © 2019, Telespazio
Main Project Results
Rajesh Tiwari (TPZV-UK)
Elisa Benedetti (NSL)
Simon Chalkley (TAS)
Case Study Selection
Rajesh Tiwari (TPZV-UK)
Case Study Selection
• Identified cases where an alternative PNT architecture may apply, included:
- Differential GNSS (DGNSS)
- Wide-Area RTK (WARTK)
Case Study 1: Differential GNSS Overview
• A typical implementation of a DGNSS system
could include the following components:
- Multi-frequency GNSS receivers covering the
service area and control station (CS)
• for performance monitoring and integrity
check
• for distribution of correction and/or reference
data to the users
- UE (user equipment) receiver
base on the corresponding specification
Case Study 1: Differential GNSS Assessment
• Technical Assessment
- Ground Infrastructure Requirements
- Augmentation data requirements
Case Study 2: Wide-Area Real-Time Kinematics (WARTK) Overview
• The WARTK concept provides accurate
ionospheric corrections. It needs reference
stations separated by 500-900kms
could include the following components:
- Reference Stations Network (RSN)
- Central Processing Facility (CPF)
- Internal Communication Subsystem (ICS)
- Broadcast Communication Subsystem (BCS)
Case Study 2: Wide-Area Real-Time Kinematics (WARTK)
• Technical Assessment
data via satellite downline, instead of terrestrial-based
communication in a fully ground-based architecture;
• After applying ionospheric correction to triple frequency,
ambiguities fixing using three-carrier ambiguity
resolution (TCAR) approach, called WARTK-3 algorithm
otherwise WARTK-2 for dual frequencies.
• Programmatic Assessment
Case Study 3: Precise Point Positioning (PPP)
Technology Background
• A typical implementation of a PPP system could include
- A communication link, disturbing the precise satellite products to the users.
Technology Assessment
- Infrastructures provider: IGS, CNES/CLS, JPL, ESA/ESOC. NRCAN, GFZ and CODE/Bern University
• RTCM SSR standard
Programmatic Assessment
• System benefits and impacts;
• User benefits and impacts;
• Development and exploitation cost
- Most commercial PPP services have a space segment, which works as a data dissemination channel
only from the control centre to the user.
- Combining an alternative space-based architecture and PPP, the following characteristics would cause
the main impacts on development and exploitation costs:
• Shifting on-ground centralised data processing to on-board the satellite (extra payload needed);
• Removing the need for ground communication network, with data communication mainly between the
satellite and monitoring stations;
• The regional PPP services (at the continent level) eliminates the need to have a global network of
reference stations.
Real-time PPP
Real-time PPP in a Satellite-based architecture
Case Study 4: Space-Based Augmentation System Overview
Mission Control Centres with CPF
Ranging & Integrity Monitoring Stations
Navigation Land Earth Station
Case Study 4: Space-Based Augmentation System
Technology Assessment
• Satellite position error; Satellite clock errors; Ionospheric delay;
- The corrections apply to pseudorange measurement from the user receiver;
- Integrity data on residual errors and Time-to-Alert provided with the SoL services.
• Satellite position error
- Ground Infrastructure
• MSN, CPF (a large number of monitoring stations), GEO satellite control centre, GEO Communication layer
Programmatic Assessment
• The main impact on development and exploitation costs
- Shifting the on-ground data processing load to on-board the satellite (extra payload)
- Removing the need for a ground communication network (data communication mainly between the satellite and MSs)
Case Study 5: Space-Based Augmentation System – DFMC
• DFMC SBAS
- is independent of L1 SBAS and has two main functions
• Ionospheric-free differential correction function;
• Optional ranging function similar to the L1 SBAS ranging function
- is self-contained with all ephemeris parameters, correction and integrity information provided within L5
(1176 MHz) frequency
- provides: improved availability by enabling of SBAS services in regions with active ionosphere and
robustness against single GNSS constellation degradation by augmenting multiple constellations
• Programmatic Assessment included:
- Shifting the on-ground data processing load to on-board;
- Removing the need for a ground communication network
- Shifting ionospheric delay mitigation from augmentation to user processing (a benefit due to DFMC
SBAS), hence the requirement for fewer monitor stations.
Accuracy Performance for GNSS and GNSS Augmentation
Preliminary Architecture
Preliminary Architecture – Overview
CC MS
GPS & Galileo
GEO Augmentation
Preliminary Architecture – Space Segment
NAVISP-El1-027 Alternative Space-Based PNT Data Layer – Final Presentation
• Space Segment Components of the Alternative Space-based PNT Data layer system
- GEO satellite - minimum 3 with:
• Augmentation payload including on-board processing units
• Navigation payload generating and transmitting GPS-like signals modulated with correction data and
integration information
• Communication payload
– with direct links to the ground-based monitoring station and control centre
• The proposed GEO satellites themselves have integrity, secure systems which are protected against
– Unauthorised commanding
Preliminary Architecture – Payload Features / Main Components
M & C
Integrity Monitoring
architecture was considered
Preliminary Architecture – Augmentation Payload
• Refinement of the augmentation
potential implementation of the
Preliminary Architecture – Ground Segment
• Ground Segment Components of the Alternative Space-based PNT Data layer system
- Monitoring Stations Network (MSN)
• consisting of a number of monitoring stations (MS) equipped with multi-frequency GNSS receivers
and antenna
- Control Centre (CC)
• providing control data to the MSN and the GEO including its on-board payload, and other elements
(release validation facility and certification facility)
Preliminary Architecture – User Segment
• User Segment Components of the Alternative Space-based PNT Data layer system
- Correction information
- Integrity data stream
- Integrity information, which is the output from the Processing Set of on-board CPF
- Integrity information, which is the output from the Check Set of on-board CPF
Preliminary Architecture - Main Data Flows
Ground Segment Space Segment
Augmentation Payload (Sat 1)
Integrity raw data stream
Correction raw data stream
Performance Analysis
Performance Analysis – Simulation
• Simulation goals
- availability, accuracy, integrity and continuity
- Highlight the major benefits of the AltPNT architecture with respect to the classical SBAS
- ground segment simplification and TTA reduction
• Requirements [MOPS and SARPs]
Parameter Threshold Value
Horizontal Accuracy 16m
Vertical Accuracy 4m
Minimum Number of MS – First iteration
Performance Analysis – Simulation Scenarios and Results
Results El Mask (deg) N of sat Area MS Availability N of MS Comments
1.a, 1.c 5 24 GPS + 24 Gal [1.a]
27 GPS + 27 Gal [1.c]
20 N – 70 N (Lat) [1.a] 20 N – 72 N (Lat) [1.c]
40 E – 40 W (Long)
100% 16 The MS considered in the simulation are: ACR, MAD, LPI, CNR, LSB, SDC, GLG, PAR, ROM, BRN, GVL, SOF, KIE, GOL, ALY, H
1.d 5 27 GPS + 27 Gal 20 N – 72 N (Lat) 40 E – 40 W (Long)
100% 14 From a starting scenario using 16 MS it is possible to remove only the stations in the SE corner such as ALY and H (requirements not met if any other station is excluded)
1.f 5 27 GPS + 27 Gal 20 N – 72 N (Lat) 40 E – 40 W (Long)
99% 17 Starting from a scenario with 14 MS, 3 stations must be added in SE and W areas (H+ALY+AGA)
2.b 10 27 GPS + 27 Gal 20 N – 72 N (Lat) 40 E – 40 W (Long)
100% 20 10 deg elevation mask influences the number of satellites available. Starting from a scenario with 14 MS, the S and N peripheral areas require 6 additional stations (H + ALY+ ATH+ AGA + KIR + TRO)
2.d 10 27 GPS + 27 Gal 20 N – 72 N (Lat) 40 E – 40 W (Long)
99% 22 Starting from a scenario of 20 MS, 2 MS (RKK+EGI) are added in Iceland
Performance Analysis – Continuity
1.a – 16 MS, 20N–70N(Lat), 24Gal+24GPS, 5 deg,100% MS av. 1.c – 16 MS, 20N–72N(Lat), 27Gal+27GPS, 5 deg,100% MS av. 1.d – 14 MS, 20N–72N(Lat), 27Gal+27GPS, 5 deg,100% MS av.
1.f – 17 MS, 20N–72N(Lat), 27Gal+27GPS, 5 deg, 99% MS av. 2.b – 20 MS, 20N–72N(Lat), 27Gal+27GPS, 10 deg, 100% MS av. 2.d – 22 MS, 20N–72N(Lat), 27Gal+27GPS, 10 deg, 99% MS av.
Performance Analysis – Accuracy, Integrity and Availability
Parameter Min, Max, Avg
Vertical Accuracy [m]
1.0, 3.9, 1.7 1.1, 3.9, 1.9 1.1, 5.6, 2.3 1.0, 4.4, 1.8 0.9, 4.3, 1.7
Horizontal Accuracy [m]
0.8, 3.2, 1.4 0.9, 3.4, 1.6 0.9, 4.8, 1.6 0.8, 3.5, 1.3 0.8, 3.4, 1.2
Vertical Protection Level [m]
2.7, 10.7, 4.7 2.9, 10.6, 5.2 3.0, 15.3, 6.1 2.6, 11.8, 4.8 2.5, 11.6. 4.7
Horizontal Protection Level [m]
1.6, 6.5, 2.7 1.7, 6.6, 3.0 1.7, 10.0, 3.2 1.5, 7.3, 2.6 1.5, 6.9, 2.5
Vertical Availability 90.7, 100, 99.86 90.6, 100, 99.8 80.4, 100, 99.5 86.8, 100, 99.7 95.2, 100, 99.9
Horizontal Availability
100 100 100 100 100
Parameter Min Max Avg Req Vertical accuracy [m] 1.0 4.4 1.9 4
Horizontal accuracy [m] 0.8 3.7 1.4 16 VPL [m] 2.7 12.0 5.1 10 HPL [m] 1.6 7.5 2.8 40
Performance Analysis – TTA Baseline (Legacy SBAS)
3.8 s 1.4 s 0.8 s
Performance Analysis – AltPNT TTA
• Optimised AltPNT TTA • AltPNT TTA with high rate MS output
Technology Survey
Onboard Computing Technology Survey
• 3 main processors / FPGAs were identified as most the advanced European technologies,
with the potential to meet the requirements of the AltPNT architecture:
- LEON4 by Cobham Gaisler
- LEON5 by Cobham Gaisler
Onboard Computing Technology Survey – LEON4
• LEON4 GR-740
- Implementable on FPGA and ASIC technologies
- Highly configurable, well suited to SoC designs
- SPARC V8(E) based
- Available under a low-cost commercial license
- 64-bit or 128-bit AMBA 2.0 AHB bus interface
- Supports IP core plug & play method
- Separate I/D multi-set L1 caches, optional L2 cache for increased performance
- Supports MUL, MAC and DIV instructions
- IEEE-754 floating-point unit (FPU) and Memory Management Unit (MMU) optional
Onboard Computing Technology Survey – LEON5
• LEON5
- Incremental versions of LEON5 expected to be released from Nov 2020 and throughout 2021. Starting
with FT basic LEON5 subsystem for rad-hard FPGA, finishing with advanced LEON5 subsystem for
ASIC without RH stdcells (advanced hardening by design)
- Provides backward compatibility for implementations of LEON3 and LEON4
• AMBA 2.0 AHB bus interface
• Supports IP core plug&play method
• Supports MUL and DIV instructions, an IEEE-754 floating-point unit (FPU) and Memory Management Unit (MMU)
• Separate I/D multi-set L1 caches, optional L2 cache
- Suited to high-end FPGAs and deep-submicron ASIC technologies
- Processor pipeline design superior to LEON4 - up to 85% faster execution for single threaded integer
benchmarks
- ~3000 DMIPs estimated
Onboard Computing Technology Survey – DAHLIA
• DAHLIA Cortex R-52
- Part of Horizon 2020 programme
- Uses Very High Performance SoC
• STMicroelectronics European 28nm FDSOI technology with multi-core ARM processors
- Highly reliable
- FPGA fabric allows hardware to accelerate parts of the algorithms
- 1344 DSP blocks capable of 18-bit MACs at 100 MHz+
- ~4000 DMIPs
Onboard Computing Technology Survey – Requirements
• Preliminary assessment of processing power required for AltPNT architecture
- Indicates multiple of these state of the art devices are required
• Also required
- Software development
- Further study
Software Technology Survey – Overview
• RTOS proposed for AltPNT due to high speed and safety criticality
- RTEMS SMP usable on LEON and ARM
• Large parallel operations managed by hypervisors
- to maintain and validate code
• Mixed criticality code
- DAL B and DAL C should be kept independent from one another
Software Technology Survey – Tools
• Development Tools
- Emulators e.g. ARM Fast Models or Cobham Gaisler TSIM (ERC32 or LEON processors), GRSIM
(LEON2, 3, 4) and TSIM3 (GR740)
- ARM C/C++ compiler toolchain
- Cobham Gaisler offer complete framework for SoC design development including simulators and
compilers running VxWorks operating system and RTEMS
- Development approach using formal methods more important than the tool. Systematic errors result
from software or design errors – guarded against through adherence to prescribed
processes/standards and applying maximum rigour.
• Test tools e.g. ADA Test 95 and Cantata (C)
• Possible reuse of existing critical software design for:
- Collection of GNSS/SBAS measurements and data
- Transfer of measurements and data for processing
- EGNOS message transmitted to users
Ground Segment Technology Survey – Receiver hardware
• GNSS Receiver Hardware – Multiple feasible COTS available e.g.
- Leica Geosystem GR50
- Novatel WAAS G-III
Ground Segment Technology Survey – Antenna and Front-end
• GNSS Antenna and Front-End – Multiple feasible COTS available e.g.
- Leica AR25
- Tallysman VC6050 Verachoke
Ground Segment Technology Survey – Receiver Software
• GNSS Monitoring Receiver Software
- Collection of GNSS and SBAS raw data same as classical DFMC SBAS
- Novatel’s RAIM
SWOT Analysis
SWOT Analysis – Achievable Performance – Strengths and Weaknesses
Strengths (S) Weaknesses (W) High performances in terms of Availability, Accuracy, Integrity and
Continuity (stringent requirements i.e. Cat I and maritime are fully
met)
High level of performance is ensured with a lower number of MSs
(i.e. half) used in current and imminent SBAS realisations (e.g.
EGNOS V2 and V3)
Lower density of MS is required at high latitudes with respect to
current and imminent SBAS realisations (e.g. EGNOS V2 and V3)
Full coverage is ensured on the area more extended with respect
to Legacy SBAS, even with a lower number of MS
Simplification of the ground communications (i.e. elimination of
ground CPF) implies the reduction of TTA (of max 2 seconds)
Some areas are very sensitive to MS number change
(e.g. Southeast and Southwest part of ECAC region)
Southwest area requires densification of MSs to ensure
full coverage
side, for both SoL and non-SoL services that normally
use single frequency devices (i.e. automotive, drones,
maritime), which are more expensive
SWOT Analysis – Achievable Performance – Opportunities and Threats
Opportunities (O) Threats (T)
existing applications that commonly don’t rely on SBAS (for
example automotive, drones, precision agriculture etc.)
High integrity performance in terms of VPL and TTA can enable
greater support of SA CAT I operations and beyond (SA CAT II) in
conjunction with GBAS technology
service for safety-critical railway applications [RD 1] e.g. in ERTMS
Full coverage on a more extended area including high latitude
makes the service more compliant with applications such as
maritime
Simplification of the ground segment implies that the waiting time
delays are deterministic, hence further optimisation and refinements
of processing tasks are possible, with a potential further reduction
of TTA
In the case of MS failure, discontinuity of the service
could occur in peripheral areas (Southeast, Southwest)
which are more sensitive to the change of MS number
SWOT Analysis – Implementation Challenges – Strengths and Weaknesses
Strengths (S) Weaknesses (W)
there is access for the COMMS and NAV payload antenna.
LEON 4 and DAHLIA technology is likely to be widely adopted
across the European industry so the number of potential HW
suppliers should be sufficient.
replace any failed/failing equipment.
processing technology, which would be much more suitable
in terms of performance, is not viable and lower performance
technology must be deployed.
SWOT Analysis – Implementation Challenges – Opportunities and Threats
Opportunities (O) Threats (T) As other (faster, cheaper) processing technologies become
available it should be possible to replace these systems with
smaller and more compact versions to serve the future need
for such a system.
has not been qualified and the development and
qualification process may be complex and time-consuming.
In particular, the SW qualification for the highest
dependability could be very time-consuming.
Alternative improvements in ground processing may make
the space-based system less attractive.
SWOT Analysis – Security and Other Aspects – Strengths and Weaknesses
Strengths (S) Weaknesses (W)
cyber-attacks and external interferences with fewer assets on the ground, include
proprietary MS-GEO links, end-to-end Security management.
Another safety-related aspect is the system robustness against physical and cyber-
attacks like jamming or spoofing of the satellite uplink and MSs.
Ground segment development cost is expected to be decreased overall, due to
simplified ground infrastructure. The Control Center (CC) functions will be simplified
with an associated cost reduction expected.
Ground segment operation and maintenance costs are expected to be reduced also,
due to simplified ground segment functions and comms.
The space segment development
payload needed on-board the
communications from the MSN
(more channels and higher
centralised onboard data processing
(compared to the classical
SWOT Analysis – Security and Other Aspects – Opportunities and Threats
Opportunities (O) Threats (T)
organised bringing some interesting new aspects mainly due to
its innovative architecture, and more scope of inter-satellite
link features.
remains a threat at MS level
Study Conclusions
Conclusions – Technology
• 5 cases of GNSS augmentation systems were reviewed and analysed in terms of technology
background, technical assessment and programmatic assessment:
- DGNSS
- WARTK
- PPP
- SBAS L1-legacy
- SBAS DFMC
• Candidates for AltPNT were assessed to determine benefits to user/system in terms of:
- Complexity
- Feasibility
- SBAS L1-legacy
- SBAS DFMC
Conclusions – Architecture
- The augmentation payload (on-board CPF)
• Preliminary assessment of the end-to-end performances of the AltPNT architecture took place,
considering
- Data volume system budget
Conclusions – Simulation outcomes
• AltPNT performance in terms of accuracy, integrity, availability and continuity was analysed
within a simulation environment
• ~1200 km spacing on average
- CAT I and maritime requirements as a test scenarios selected
- MS were added or removed based on different inputs
• number of satellites, elevation mask, MS availability, and the above requirements
- Based on the above tests, between half and one third of the total number of MS planned for
EGNOS V3 ground segment are proposed for the AltPNT system
• A key advantage of the AltPNT, is the potential reduction of TTA
- Correction parameters are up to 2 seconds younger, resulting in benefits such as
Conclusions – Key advantages
• Advantages of an AltPNT SBAS architecture, as opposed to the classical SBAS architecture,
include:
- Lower exploitation cost over 15 years
Conclusions - Challenges
• The technology survey and suitability assessment of architectural elements from both space and ground
segment indicates a number of challenges can be expected:
- Space segment is more challenging with respect to technology readiness
- Singular-qualified device would not meet the required performance for the CPF
• OXCO Clock function
- It is anticipated that COMM payload will have an OXCO clock function to provide a GNSS-disciplined
reference to all satellite sub-systems
• Hardware
- For the Ground Segment, there are many HW options to investigate that could meet requirements
- Due to IPR of COTS products, in-depth analysis was not possible, but certainly the satellite link is
anticipated to operate on Ku band.
Future Work
Potential for Future Work
• Definition of a comprehensive system model of the AltPNT architecture
- Digital engineering model of processing set
- To allow simulation of main tasks and operations
• On-board processor viability studies
- Analysis of tool requirements for development/testing
Questions from the audience…..

navisp-el1-027 alternative space-based pnt data layer

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