Precise Positioning Galileo E5 AltBOC: Results with Live Signals

Harvesting the benefits of Galileo E5 for high precision applications involves several challenges, ranging from receiver signal processing and radio frequency to positioning algorithms. In Ref. [1] we presented the first prototype of an AltBOC receiver with first positioning results based, at the time, without live Galileo satellites. In this paper we present the continuation with the new G3 dual frequency E1-E5 AltBOC DEIMOS receiver and also using Galileo live signals, confirming performances and the potential of Galileo for new applications. Galileo E5 AltBOC, according to [2], is by far the most sophisticated signal among all the signals used for Global Navigation Satellite Systems. With four codes modulated onto the two phases of orthogonal sub-carriers, the signal occupies a wide bandwidth of around 51 MHz (first two main lobes). In open sky scenarios, the precision of the E5 AltBOC code measurements is around few cm, which is an unprecedented performance in satellite ranging for navigation. The potential of the E5 AltBOC (code precision and multipath robustness) is enormous [3] as it can open new avenues for the use of GNSS like GNSS-based surveying in urban areas and the use of the code measurements as a replacement for phase measurements in myriad applications where horizontal and vertical accuracy requirements are below 5 cm and 10 cm (1-sigma level) respectively. COREGAL project [4], funded under the European H2020 program, allowed to develop the G3 receiver and positioning algorithms for high precision applications, specially tailored to operate in contexts such as those in Brazil where the availability of ground reference stations is sparse, especially in remote locations. The use of the E1 CBOC and E5 AltBOC code measurements in differential mode does not pose any new challenge to existing technology and algorithms. Similar arguments can be used for differential carrier phase positioning with the exception that double differenced integer ambiguities can obviously be fixed in a faster and more reliable way if code measurements are more precise and accurate. From an applications and algorithmic point of view the interesting but challenging steps are those related to long-range nondifferential positioning in its various forms which, essentially, boils down to ionospheric delay determination. Since the E5 AltBOC is a unique signal, any combination with other signals must be done carefully as the higher noise of the other signals makes any combination useless for high accuracy applications. Receiver processing of AltBOC also involves processing of a very high bandwidth signal which can be achieved with different strategies, from combining individual components E5a and E5b to simultaneous full AltBOC components that within this paper we name Full AltBOC Processing (FAP).