With the development of advanced driver assistance systems (ADAS) and autonomous vehicles (AV), recent years have seen an increasing evolution of onboard sensors and communication interfaces capable of interacting with available infrastructures, including satellite constellations, road structures, modern and heterogeneous network systems (e.g., 5G and beyond) and even adjacent vehicles. Consequently, it is essential to develop architectures that cover data fusion (multi–sensor approach), communication, power management, and system monitoring to ensure accurate and reliable perception in several navigation scenarios. Motivated by the EMERGE project, this paper describes the definition and implementation of an On Board Unit (OBU) dedicated to the navigation process. The OBU is equipped with the Xsens MTi–630 AHRS inertial sensor, a multi–constellation/multi–frequency Global Navigation Satellite System (GNSS) receiver with the u–blox ZED–F9P module and communication interfaces that afford access to the PointPerfect augmentation service. Experimental results show that GNSS, with corrections provided by augmentation, affords centimetre accuracy, with a Time To First Fix (TTFF) of about 30 s. During the on–road tests, we also collect: the output of fusion with inertial sensor data, monitoring information that assess correct operation of the module, and the OBU power consumption, that remains under 5 W even in high–power operating mode.

Nowadays, Global Navigation Satellite Systems (GNSS) and complementary positioning technologies are expanding, offering new resources to the localization process. Software Defined Radio (SDR) is emerging as an alternative to developing flexible and multi-technology solutions in a dynamic environment. This work describes the main operational signals in GNSS systems that can be used in a multi-constellation, multi-frequency receiver. Also, it proposes the reception of GNSS signals using a modular architecture based on SDR. The SDR GNSS receiver is confronted with two platforms operating as Front-Ends: ADALM-PLUTO and Ettus USRP X310 - UBX160. The results, corresponding to the capture of GPS signals in the L1 band, show the impact of the platforms performances in the satellite acquisition signal process.