The reception of a Global Navigation Satellite System (GNSS)‘ signals in indoor and urban canyon environments is complicated due to the frequent blocking or important fading of the line-of-sight (LOS) components as well as due to the reception of multipath components received with a much higher intensity than the direct components. In the past, many multipath mitigation and high sensitivity architectures/algorithms have been proposed in an attempt to cope with these challenging environments. However, many of these architectures/algorithms are either not suitable or do not take full advantage of the new signal and modulation properties that are available from the new and improved GNSS satellites. In this context, the focus of our research will be on the investigation and development of advanced algorithms and architectures especially designed to exploit the new GNSS signal properties and capabilities in order to improve the availability, reliability, and accuracy of GNSS in difficult indoor and urban canyon environments.

In a first step, we will concentrate on the Galileo E5 signal centered at 1191.795 MHz. This signal is an Alternate Binary Offset Carrier (AltBOC(15,10)) signal that can be seen as composed of two Binary Phase Shift Keying (BPSK) signals (E5a and E5b) having a chip rate of 10.23 Mcps and transmitted at 15.345 MHz below and above the central frequency of 1191.795 MHz. However, as the E5 signal is coherently generated in the satellite, we will consider its processing in the GNSS receiver as a single coherent signal transmitted on a 90MHz bandwidth. Such a wide bandwidth translates into a very narrow autocorrelation peak that is particularly interesting for the difficult indoor and urban canyon environments as it allows an improved multipath mitigation. The data free component available on E5a and E5b can also be used to track the strongly attenuated signals and thus obtain a very high sensitivity. In a further step, we also plan to consider and investigate the use of GNSS frequency diversity information obtained by receiving more than one signal transmitted on different frequencies from the same GNSS satellite in order to gain some extra knowledge about the statistical properties of the indoor propagation channel. We expect this knowledge could be very useful to design advanced algorithms able to classify a direct propagation path from a non line-of-sight (NLOS) one and thus mitigate the positioning error due to NLOS propagation.

In both cases, we plan to validate the theory with simulations and real experiments, making use of a multi-frequency GNSS acquisition platform conceived in our laboratory to receive and process simultaneously the different open service Galileo signals transmitted by the two Galileo experimental satellites GIOVE-A and GIOVE-B and later by the first operational satellites.