João S. Silva

Design of a very high sensitivity acquisition system for a space GNSS receiver

Increasing the GNSS receiver sensitivity and robustness in very harsh environments has become a central topic for the GNSS community. This paper addresses the design of a very High Sensitivity (HS) acquisition scheme for weak GNSS signal detection down to 5/10 dB-Hz in the particular space environment of the Lunar Low Orbit. A theoretical analysis for the determination of optimal extended coherent integration time and non-coherent accumulations allowing the achievement of pre-defined acquisition metrics will be presented and then validated by means of simulations. Complete data navigation bits and secondary code synchronization achieved thanks to the use of external aiding sources or self-assistance techniques is considered along the analysis which will provide results for weak GNSS signal acquisition in the GPS L1/L5 and Galileo E1/E5 frequency bands. Presence of a Doppler aiding source is considered and a detailed study on the required Doppler aiding accuracy is also presented.

GRANADA Factored Correlator Model blockset verification using an FPGA-Based GNSS receiver

The Factored Correlator Model (FCM) is an analytical model for the outputs of a GNSS receivers correlators. The FCM precludes the need for simulation of the lower-level signal processing stages, significantly increasing simulation speed and considerably decreasing processing and memory requirements, while still keeping a high level of realism. Results for the FCM validation using statistical models (available from previous Galileo studies) and the GRANADA Bit-True Simulator have been presented in the past. However, FCM results have never been compared to those of a real hardware receiver, whose performance is influenced by effects that have not been taken into account in the FCM (as quantization and fixed-point arithmetic, just to name a few). This paper shall present the verification and validation results of the FCM using a real hardware signal processing chain, up to the correlator outputs, implemented on an FPGA, in the scope of ongoing projects. It shall also highlight the new features of the latest GRANADA FCM Blockset release and demonstrate its applicability and value for receiver algorithms design.

GNSS hybridization for indoor positioning

We describe a hybridized receiver architecture tightly coupled with different sensors, namely MEMS accelerometers and gyroscopes, Wi-Fi engine and a barometer, allowing significant increase of positioning performance for indoor GNSS signal reception. This is possible due to the increase of integration times, use of higher sensitivity GNSS receivers and by resorting to external aiding sensors tightly coupled with the receiver. Expected overall navigation performance increase is described and the benefits of using such external sensors are quantified. Indeed, hybridization of GNSS receivers with other sensors is expected to be a key technology that will enable new services and applications for the use of GNSS for navigation in indoor and densely urbanized environments.

ENCORE: Enhanced code Galileo receiver for land management applications in Brazil

Taking benefit of the new Galileo ranging signals, the ENCORE (Enhanced Code Galileo Receiver) project aims to develop a low-cost Land Management Application to cover needs of the Brazilian market in terms of geo-referencing and rural/urban cadastre, using a low-cost Enhanced Galileo Code Receiver as baseline. Land management applications require precision and accuracy levels from a few to several decimetres that are under-met with current pseudorange-based receiver and over-met with phase observations. This situation leads either to a waste of resources, or to lack of accuracy. In this project, it is proposed to fill this gap using the new possibilities of the Galileo ranging signals, in particular E5 AltBOC and E1 CBOC. This approach reduces the cost of the end-user solution, helping the rapid penetration of Galileo technology outside Europe