Antenna Array Based GNSS Signal Acquisition: Real-time Implementation and Results

The use of Global Navigation Satellite System (GNSS) technology in safety- and mission-critical services has raised the concern in recent times about possible GNSS Denial of Service (DoS) situations. In that sense, the GNSS vulnerability to interferences could become a real threat to the entire service integrity. In this work the interference mitigation capability of antenna arrays in GNSS signal acquisition process is addressed from a realistic implementation perspective. A two-fold objective is pursued: on one hand, we introduce the design and the implementation of a flexible FPGA-based GNSS antenna-array receiver platform, intended to be used as a reliable research tool tightly coupled with software defined GNSS receivers. In that sense, all the platform components, from the multichannel coherent front-end to the FPGA hardware accelerators and the embedded software defined processor, are presented in detail and validated using RF signal generators with realistic GPS-like waveforms. On the other hand, a novel array-based acquisition algorithm that uses the Generalized Likelihood Ratio Test is implemented using the platform. Statistics extraction modules such as the estimation of the array autocovariance matrix are included. Realistic interference scenarios were tested, including CW jamming and Long Term Evolution (LTE)-like in-band interferences. The results show that the algorithm offers excellent protection against uncorrelated directional interferences, even if the array is moderately uncalibrated.