GAlileo user Receiver Development Activity
Background & Objectives
The user segment, and in particular the user receiver, is at the heart of business opportunities. Tools and systems adapted to user requirements need to be developed in order to enable the optimal integration of Galileo services (timing, positioning and navigation) into everyoneâ€™s life. Receivers and user terminals must be commercially available in time for the Galileo exploitation phase to ease and catalyse the market penetration of Galileo services. Therefore, the user segment of Galileo must be developed in parallel with the core system. Furthermore, fostering the European industry in the area of GNSS receivers and terminals is another important motivation, recognising that Galileo is a unique opportunity to encourage the development of GNSS receivers in Europe.
GARDA has developed a prototype receiver capable of processing L1, E5a/E5b and E6 Galileo signals in addition to GPSL1. The aim of the GARDA project was also to develop a modular architecture that could be the basis for future TAS-I GPS/Galileo receiver products and prepare the way for user receivers to be already on the market when the Galileo system becomes operational.
Much time was given to user-receiver development plan definition, with an increased analysis depth and involvement of system and service providers (through surveys and interviews). Three main classes of receivers have been defined: consumer, professional and safety critical.
GARDA identified the core technological areas as being essential for future Galileo receivers and selected a set of specific topics that have been subsequently studied in detail. GRANADA covers a dual role: it is a test bench for integration and evaluation of receiver technologies and a software receiver as an asset for GNSS application developers. It is conceived as a modular and configurable tool, in which the user can embed and test his/her own algorithms with a user-friendly interface.
The GARDA receiver architecture is composed of three main modules (see Figure 1):
- antenna and RF front-end section
- RF/IF section
- digital section.
The receiver model has been tailored towards high performance, professional and safety-of-life applications. The receiver is capable of processing the Galileo signals on the L1, E5a, E5b and E6 bands and the GPS (EGNOS/WAAS) signals on the L1 band. Laboratory equipment designed to produce signals that faithfully represent the GNSS SIS are an indispensable tool for the development and verification of GNSS user receivers.
This is particularly true for the case of Galileo, whose space and ground-segment are being concurrently developed. A Galileo Mono Channel Simulator (GMCS) has been therefore designed as a tool to support the development and performance assessment of Galileo receivers. The GMCS is able to generate the three carriers defined in the Galileo SIS ICD produced by a single satellite of the constellation.
These features made the GMCS a complete and self-standing test set for validating the GARDA receiver prototype. GARDA receiver prototype test Receiver functional and performance testing has been carried out using Galileo single/multi channel RF signal simulators. Live testing activities have been performed using the SATIMO antenna and it has been possible to acquire and track GPS satellites on L1CA.
The following were primary objectives of the GARDA project, which have been organised into three main tasks:
- define a road map to the Galileo receiver pre-development (Task 1)
- identify and study the receiver core technologies (Task 2)
- develop a software receiver, an open tool conceived for receiver developers and receiver users supporting investigation on the core technologies (Task 2)
- develop a receiver prototype (Task 3)
- develop a Galileo mono-channel simulator to support prototype receiver test and validation (Task 3)
Coming up with a time frame in which the Galileo signal-in-space (SIS) specification is not definitively frozen, one of the main issues has been the design for flexibility, in order to be able to react promptly to the evolution and changes in the Galileo signal specification. The GARDA project has also provided the opportunity to analyse the future market of Galileo applications, to study some core receiver processing techniques and to develop two important components such as the Galileo multi-frequency RF signal simulator, as well as a complete Galileo receiver and environment software simulation tool.
Work performed & results
The GARDA receiver is one of the first Galileo receivers and this is the basis of several ongoing projects and future receiver product lines: - the GIRASOLE safety-of-life receiver will be the pre-cursor of a combined GPS/Galileo receiver product to be used in rail, aviation and maritime applications; - building blocks from the GARDA design are being re-engineered for use within the Galileo reception chain receiver (GRC), which is a key element of the Galileo mission segment ground infrastructure; - building blocks from the GARDA design are also being re-engineered for the test user-receiver that will be used to test the performance of Galileo in the in-orbit validation phase; - The GRANADA software simulator tool as well as the Galileo RF signal simulator (see Figure 2) are available to Galileo receiver and user applications and will be further improved to include additional features. The receiver has been tested with the multi-frequency RF signal simulator and it is also worth mentioning the successful attempt to track the live in-space signal provided by the test satellite GIOVE A.