
111 - Managing GNSS Local Effects in the Railway Environment for Advanced Safe Train Positioning
DESCRIPTION
The European Rail Traffic Management System (ERTMS) is a single European signalling and speed control system that ensures interoperability of the national railway systems throughout the single European railway area. ERTMS is comprised of the European Train Control System (ETCS, an in-cab signalling system that includes Automatic Train Protection – ATP) and a track to train radio communication system (GSM-R and the Future Railway Mobile Communication System – FRMCS).
Advanced Safe Train Positioning (ASTP)
The European railway and CCS (Control-Command and Signalling) supply industry are working on the evolution of ERTMS, which includes a new ASTP element that is expected to use GNSS and EGNOS to provide safety-related train position, speed and acceleration to ETCS using multiple sensors in a multi-sensor architecture. GNSS is considered one of several sensors in an ASTP architecture, where other sensors potentially include inertial, rotational, radar-based, and optical sensors. The ASTP is being specified by industry as a black box, allowing manufacturers the flexibility to integrate GNSS/EGNOS in their solutions without a high level of prescription on the ASTP design. It is on this basis that manufacturers compete in their ERTMS product offerings as they have some margin to innovate. Interoperability is a key requirement for the ASTP, where stringent safety and performance requirements need to be met, with a modular approach for the ASTP element in terms of the on-board CCS architecture.
EGNOS for Rail
The EGNOS for Rail workplan was established as a collaboration between the rail sector and the space sector. Participants in the rail sector include: the Europe’s Rail Joint Undertaking (ERJU); CCS suppliers, railway infrastructure managers, and railway undertakings involved in Flagship Area 2 of the ERJU; the European Railway Agency (ERA); and the ERTMS Users Group (EUG). Participants from the space sector include ESA and EUSPA.
The objective of the EGNOS for Rail workplan is the development of an EGNOS railway Safety of Life (SoL) service based on pseudorange domain integrity commitments excluding impact from the local environment. ESA activities aligned with this workplan include Horizon Europe HE-024 (EGNOS System Studies on Railway).
Rationale for the Activity
As mentioned above, the ASTP is considered a black box where the management of local effects, including multipath and NLOS, and ensuring resilience against interference and spoofing, is responsibility of the manufacturer and it is a gap that needs to be addressed to meet the stringent application-level performance targets.
This activity aims to support the successful bidder in the development of concepts and techniques suitable for managing local effects of the railway environment in the ASTP with the required performances. This includes assessing novel approaches such as the use of estimators based on robust statistics and associated integrity concepts for harsh environments. The activity intends to develop the fundamental enabling technologies needed for managing local effects, where the TRL would then be increased through a possible follow-up activity in NAVISP Element 2.
This activity is also expected to contribute to the understanding of achievable performances of user barriers (via reporting made publicly available), potentially providing:
- Input to assumptions on user barriers enabling an assessment of end-to-end performances of ASTP and GNSS/EGNOS contribution (relevance to HE-024 EGNOS System Studies for Railway; EGNOS4Rail workplan WP3.4 for assessing performances of EGNOS for Rail SoL Service)
- Input / contribution to future railway user standards for GNSS/SBAS (e.g., Minimum Operational Performance Standard (MOPS) for Railway SoL Service, contributing to future CCS Technical Specification for Interoperability (TSI) for ASTP)
This activity has been coordinated with key stakeholders in the EGNOS for Rail workplan and with EUSPA.
The key objective of the activity is to study, design, implement, and demonstrate solutions for managing GNSS local effects in the railway environment for the ASTP with a level of confidence compatible with target Tolerable Hazard Rates (THRs).
The activity foresees the following tasks:
- Study and identification of candidate PNT integrity algorithms / approaches suitable for managing GNSS local effects in railway (e.g., severe multipath and NLOS, spoofing, interference) as part of an integrity concept using EGNOS (Railway SoL pseudorange domain integrity service) considering assumptions on receiver, target THR, scenarios (e.g., dynamics), etc. The use of estimators based on robust statistics to improve performances in harsh railway environment shall be considered in the possible approaches.
- Definition of candidate multi-sensor architectures to support allocation of requirements including integrity requirements to elements of the architecture (e.g., considering the possible use of multiple GNSS receiver chains and application of concepts of diversity / dissimilarity to relax requirements on a single receiver chain).
- Considering candidate multi-sensor architectures, a trade-off assessment of candidate algorithms / approaches and allocations between selected user barriers and over-bounding models (faulty / nominal) in proposed concepts.
- Design, implementation and demonstration of proposed concepts including methods and user barriers for management of local feared events. This includes design of user barriers / approaches for providing resiliency against spoofing and interference.
- Validation and assessment of performances of proposed concepts (size of ATPL, ATP accuracy, etc.) using real data from test campaigns.
ESA will potentially provide, as an item made available, synthetic fault-injection data and spoofing scenarios from the railway simulation testbed in the TEC navigation laboratory. The activity is also expected to utilise field data from representative railway environments (RF samples, ground truth, etc.) provided from previous industry test campaigns.
The main output of the activity will consist of:
- Documents (review, trade-off analysis, technical specification, test and validation reports)
- Implementation and demonstration of proposed concepts