Use of diversity techniques for weak GNSS signal tracking in fading environments

Abstract

This research focuses on improving the GNSS signal measurement performance in harsh multipath environments. The nature of GNSS signal propagation in typical signal impeding wireless channels such as indoors and urban environments is studied. The signal power distribution, delay spread, and Doppler spread characteristics of real GNSS signals in such environments are investigated. Based on the observations obtained from this characterization, a closed-loop tracking architecture based on spatial diversity reception is proposed. The proposed algorithm is tested on real data collected using two antennas in indoor static and urban kinematic scenarios. The carrier loop tracking, code loop tracking, and pseudorange errors are compared between single antenna reception and dual antenna spatial diversity reception for different scenarios. Results show that the proposed tracking method improves the Doppler measurement by more than 50% and pseudorange measurements by 2–5 m compared to a single antenna receiver.