I/NAV improvements now available to Galileo Open Service users

August 29, 2023  - By
Image: ESA

Image: ESA

The Galileo Open Service has been upgraded with three features added to its I/NAV message, one of the four message types broadcast by Galileo satellites. These features are now available to all Galileo Open Service users. 

The process of upgrading the Galileo Full Operational Capability constellation satellites has been finalized and the I/NAV improvements are openly accessible through the I/NAV message carried by the E1-B signal. If users have experienced delays when turning on a GNSS device, the recent I/NAV improvements may reduce them significantly, reported the European Union Agency for the Space Programme (EUSPA).   

The I/NAV message is now faster and offers more robust positioning. The Reed Solomon Outer Forward Error Correction (RS FEC2) increases demodulation robustness, which enhances the sensitivity. It also improves the overall time to retrieve clock and ephemeris data (time to CED) with the broadcasting of additional, redundant CED information while allowing for the device to restore potentially corrupted data autonomously. 

The Reduced CED (RedCED) enables fast initial positioning, with lower than nominal accuracy, by decoding a single I/NAV word, while waiting to receive the four I/NAV words carrying the full-precision CED.  

The combination of RS FEC2 and RedCED enables I/NAV to obtain a first course position solution faster and to reduce the time required to obtain a first full accuracy solution (RS FEC2). This translates into a reduced time to first fix (TTFF) for the Open Service users, particularly when operating in harsh environments. 

Additionally, the improvements benefit applications working in assisted GNSS (A-GNSS) mode, through the Secondary Synchronisation Pattern (SSP). In A-GNSS mode, when navigation data is received from non-GNSS channels and the receiver’s knowledge of the Galileo System Time is affected by a relatively large error, typically in the order of a few seconds, the clock uncertainty must be resolved quickly and stably.  

With the I/NAV improvements, receivers will be able to do this via the new SSP feature, thus reducing the TTFF, also in A-GNSS mode. 

For more information, please see the I/NAV Navigation Message Improvements Info Note. 

While the I/NAV improvements are fully operational, EUSPA will launch a testing campaign open to receiver manufacturers, that will consist of several testing windows. The tests will allow the participants to have a confirmation of the correct implementation of the OS SIS ICD 2.0 — i.e., the right processing of the three I/NAV improvements in their products. 

The tests will be conducted at the laboratories of the European Commission’s Joint Research Centre in Ispra, Italy, and of the European Space Agency ESA/ESTEC in Noordwijk, The Netherlands.  

EUSPA will assign each applicant to one of the two laboratories depending on the specific conditions and availability. 

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About the Author: Maddie Saines

Maddie was a managing editor at GPS World.