Demodulation Performance of Galileo E1 OS and GPS L1C Messages in a Mobile Environment

The demodulation performance of the different GNSS signals, GPS L1C and GALILEO E1 OS, has already been analyzed in open environments. This type of environment is characterized by a permanent availability of a direct line of sight (LOS) satellite signal and weak multipath power relative to the LOS signal power. However, nowadays, there is an increasing demand for positioning services in urban environments, where the satellite signal propagation channel is significantly different from the Gaussian channel and thus the received signal may be notably affected. The main differences between these 2 environments are the diminution of the direct signal power due to shadowing and/or obstacles blockage effect, and the strong presence of multipath in relation to the LOS signal power. Consequently, the received signal is the sum of the direct LOS signal and the multipath component, and this results into an equivalent received signal with a power and a phase changing constantly. The aim of this paper is thus to analyze the demodulation performance of the GPS L1C and GALILEO E1 OS signals when they are transmitted through a mobile channel. More exactly, this paper studies the level of Bit Error Rate (BER), of Word Error Rate (WER) and of Ephemeris Error rate (EER) with respect to the C/N0 for each of the previously defined GNSS signals. The mobile channel is modeled as a channel providing a received signal following a Loo distribution [12]. Three different phase tracking methods are analyzed: a PLL, an ideal phase estimation from an ideal channel estimation and a phase estimation obtained from a real channel estimation.