Non-coherent Processing of E6b Signals

The processing of Global Navigation Satellite System (GNSS) signals carrying a navigation message can be significantly improved by adopting non-coherent integrations implemented through the squaring of the correlator outputs. Squaring removes the data symbols that modulates the signal and allows extended integrations. This paper investigates the usage of non-coherent integrations for the processing of Galileo E6b data signals that will deliver Precise Point Positioning (PPP) corrections. The analysis is conducted using a custom Software Defined Radio (SDR) receiver able to process Galileo E6b signals under different configurations. Different processing schemes are compared including standard data processing, non-coherent integrations through squaring and signal tracking with a Decision Directed (DD) Phase Lock Loop (PLL). These techniques are compared with pure pilot processing performed using the Galileo E6c pilot channel. A hardware simulator is used to generate scenarios where the Carrier-to-Noise Power Density Ratio (C/N-0) of the different signals is progressively decreased. Data are collected using two SDR front-ends with different local clock stabilities. Moreover, inter-channel frequency aiding is implemented by considering the joint processing of Galileo E1c and E6b signals. Galileo satellites broadcast signals on several signals that share the same communication channel. Thus, the pilot signal from one frequency channel can be used to aid the processing of data signals on a different frequency. The analysis shows that the sensitivity gap between data and pilot processing can be successfully bridged by implementing non-coherent integrations and inter-channel aiding. The first technique is used to increase the processing gain while the second approach is effective for reducing the impact of clock and user dynamics.