On potential CBOC/TMBOC common receiver architectures
International audience ; Under the 2004 Agreement on the Promotion, Provision, and Use of Galileo and GPS Satellite-Based Navigation Systems and Related Applications, the member states of the European Union and the United States agreed on working together, intensifying thus the cooperation on interoperability and compatibility issues between Galileo and GPS. Among other topics, one important focus was the E1/L1 frequency band, centred at 1575.42 MHz, where the Galileo E1 Open Service (OS) signal and the modernized GPS L1 civil (L1C) signal are going to be transmitted along with many other RNSS signals. Recent efforts made by US and European experts identified a common optimized Power Spectral Density (PSD) frame, known as Multiplexed BOC (MBOC), in which both the Galileo E1 OS and the GPS L1C signals would fit. This normalized MBOC PSD is actually formed by the sum of 10/11 of the normalized BOC(1,1) PSD and 1/11 of the normalized BOC(6,1) PSD. Because the MBOC is defined in the frequency domain, the time representation cannot be uniquely defined, and at least two different implementations that would still comply with the MBOC spectrum exist: CBOC and TMBOC. Indeed, the latest developments indicate that the main Galileo E1 OS and GPS L1C candidates will exhibit different features [3],[4]: - The current GPS L1C main candidate will have a pure BOC(1,1) data channel gathering 25% of the total signal power while the pilot channel will use a Time- Multiplexed BOC (TMBOC) modulation with 75% of the total civil signal power. - The current Galileo E1 OS main candidate will equally share its power between its data and pilot channels, with the important difference with respect to TMBOC that in both channels a Composite BOC (CBOC) modulation with BOC(6,1) will be used. It is well-understood that the definition of a common PSD for the GPS and Galileo civil signals on E1/L1 calls for an increased interoperability and compatibility of these signals at the user level. However, to really promote the use of GPS/Galileo E1/L1 ...