A typical GPS receiver, from the handheld version to the more sophisticated one, uses dedicated hardware circuits in order to implement most of the signal processing algorithms.
The aim of the Softrec project was to change this approach, transferring all the ad-hoc hardware processing into a set of software algorithms running on a general purpose hardware platform.
The only hardware required was a RF front-end is in charge of signal reception, down conversion and digitization.
As a result, Softrec is a real time GPS-EGNOS L1 software receiver completely written in the "C" language and runs on a standard PC with the Linux operating system.
The Softrec project was funded by ESA and undertaken by Intecs S.p.A. which operated in collaboration with UNIPI (Università di Pisa) for the development of the processing algorithms.
The software has been successfully delivered to ESA in 2005.
There are several SW receivers already developed but only a few are operating in real time and embed EGNOS data processing as Softrec does.
The great flexibility and reconfigurability of the Softrec product makes it ideal for adoption in future advanced projects where the GALILEO system is to be supported and where its integration in a complex system is crucial for the definition of new Location Based Services (LBS).
Main Technical specifications:
- More than 12 GPS channels in Real-Time (only limited by CPU resources)
- Up to 3 EGNOS channels
- Replay Mode
- Real Time Power Level Computation
- User Position Initialization to perform satellite visibility prediction
- Fast Acquisition (FFT)
- Output Data Rate: 0.02Hz min, 1Hz typical
- TTFF (Cold Start) < 120sec
- TTFF (Warm Start) < 36sec
- Re-Acquisition Time < 1sec
- Accuracy: better than 15m (GPS only, CEP50)
better than 3m (GPS+EGNOS, CEP50)
The natural development of the real-time software receiver has been the SoftrecG extension to a fully software Galileo E1BC receiver. SoftrecG has been tested with the first experimental GALILEO satellite (GIOVE-A) and delivered in 2006. It is currently used in the “Galileo Test Range” (GALILEO signal permanent laboratory), and in the “GALILEO Ground System Integration & Validation” facility.
On-going Developments in Softrec
Softrec is a strategic product under continuous development and benefits from of the broad experience of INTECS in European Space field and in satellite navigation.
The integration of a more compact front-end based on the Maxim MAX2741 and the simultaneous processing of all GPS, EGNOS and GALILEO on a 4MHz band centered on L1 is ongoing.
Furthermore, INTECS is pursuing the integration of Softrec as onboard navigation software payload in future LEO satellite missions.
The last word on Galileo standardization is not said: many aspects regarding especially signal modulation (MBOC, TBOC, etc) are still open. The study and the analysis of the performances obtained with different signals are necessary to reach a final choice. This situation of innovation is not only present in Galileo contest; modernized GPS, Chinese Compass, a revamped Russian Glonass are in a standardization phase. A tool with high level of flexibility is useful and necessary to face this situation.
SoftrecG3 has then been developed to explore the features of all GALILEO signals. Most of them require significant computational power (e.g. E1A, E5AltBOC, E6A), thus the real-time requirement has been relaxed to enable a powerful digital signal analysis capability.