## 5 Conclusions  
This paper reports the design, proof-of-concept implementation, and preliminary performance assessment of a HS-GNSS receiver, providing practical details of a working prototype. The proposed design is based on a SoC-FPGA GNSS receiver architecture, combining the massive parallelism and energy efficiency of FPGAs with the flexibility of embedded processors. The proof-of-concept demonstrator is implemented using COTS products. This receiver can be used to test novel high-sensitivity algorithms, including those addressing typical effects of indoor GNSS scenarios. The device is fully configurable, delivering GNSS products in standard open formats, including GPX, KML, GeoJSON, RINEX files (for navigation and observables), RTCM v3.2, and NMEA-0183 for sensor integration. After presenting the system architecture, the receiver was tested. It demonstrated the capability to acquire and track weak Galileo E1b/c signals in real-time. The receiver processes Galileo E1b/c signals with a carrier-to-noise ratio (\(C/N_{0}\)) as low as 20 dB-Hz, successfully obtaining navigation solutions. Moreover, it simultaneously handles Galileo E5a, GPS L1 C/A, and GPS L5 signals at their nominal power levels. This capability enhances the availability of satellite signals wherever possible. The estimated power consumption of the SoC-FPGA implementing the proposed receiver is 12 W, enabling its operation in battery-powered devices. The physical dimensions of the receiver prototype are relatively large, measuring 23.749 cm \(\times\) 24.384 cm, with the analog front-end measuring 14 cm \(\times\) 9 cm. However, the receiver remains portable. It can be placed in backpacks, for instance, to facilitate testing in soft indoor environments. In the context of future work, we envision several enhancements for the proposed receiver. At present, incorporating a TCXO into the receiver requires a manual estimation and correction process to address the CFO resulting from clock instability. However, it is desirable to increase the robustness of the receiver algorithms in this regard. Future developments include enhancing the acquisition algorithm's resilience to CFO and integrating it with the proposed receiver utilizing a TCXO. Furthermore, the acquisition and tracking of weak GNSS signals are currently limited to Galileo E1b/c. Receiver availability in moderate indoor scenarios (the proportion of time the software receiver is in a functioning condition) may be significantly improved by acquiring and tracking weak GPS and Galileo E5a signals as well. This would improve the success rate of positioning and the quality of the navigation solutions by receiving more satellite signals in harsh environments. Finally, the proposed receiver is primarily designed to acquire and track weak GNSS signals. The quality of navigation solutions, however, can significantly deteriorate when tracking these signals due to variations in received signal strength, satellite geometry, and potential signal reflections. Currently, the receiver does not incorporate multipathmitigation algorithms, which are relevant for addressing these challenges. Therefore, implementing such algorithms and improving the accuracy of navigation solutions through improved methods is a key area for future work. Conceptualization, M.M., J.A., and C.F.-P.; methodology, M.M., J.A., and C.F.-P.; software, M.M., J.A., and C.F.-P.; validation, M.M. ; formal analysis, M.M. ; investigation, M.M. ; resources, M.M. ; data curation, M.M. ; writing--original draft preparation, M.M. ; writing--review and editing, M.M., J.A., and C.F.-P.; visualization, M.M., J.A., and C.F.-P.; supervision, M.M., J.A., and C.F.-P.; project administration, M.M., J.A., and C.F.-P.; funding acquisition, J.A. and C.F.-P. All authors have read and agreed to the published version of the manuscript.