Preliminary performance analysis with a GPS+Galileo enabled chipset embedded in a smartphone

The main objective of this work is to investigate on precise positioning with a GPS and Galileo enabled chipset embedded in a smartphone. The analysis is carried out with code and carrier-based algorithms in different scenarios: simulated, stationary, pedestrian and vehicular. The areas investigated are precise positioning with single frequency, the benefits of multi-constellation GNSS and raw data quality provided by a smartphone. Currently the smartphones use only one frequency (L1): this is an important constraint in the design of the precise positioning algorithm mainly due to ionospheric effect. Hence, the work is based in two main algorithms: the first uses the carrier phase differential approach (Static or Kinematic) in conjunction of a reference GNSS networks; the second is based on the variometric approach using the VADASE algorithm, as the previous it uses the carrier phase but without external data. Modern GNSS chipsets are multi-constellations (GPS, GLONASS, Galileo, Beidou) and the increased number of satellites that can be tracked allows to increase the convergence time and to estimate the user's position very precisely. In the proposed work, at least the GPS+Galileo combination is considered. The purpose is to evaluate the benefit of tracking different GNSS constellations in terms of accuracy and convergence time. To develop software capable of this type of positioning, or perform these computations with existing software, pseudoranges and carrier-phase measurements are required. In principle, after the release of the N version of the Android operating system, the raw data are obtainable from a phone or tablet. However, from a technical point of view, the raw data, especially the carrier-phase, are not directly available in standard format and must be properly parsed. The paper analyses the main errors sources’ of the GNSS chipset embedded in smartphone. The primary error source on smartphones lies not in the GNSS chipset, which actually offers great performance in terms of tracking availability and codebased accuracy, but in the antenna, whose chief failing is its poor multipath suppression. High accuracy positioning requires a stable antenna position for referring the position. However, moving smartphones are constantly changing attitude (which affects the antenna gain also), altitude (e.g. when the smartphone is kept in hand along the body or in front of the face for reading) and obstruction conditions. In order to quantify the impact of these scenarios, tests with internal and external antenna have been conducted.