Evaluation of Galileo BOC Modulation versus GPS BPSK Modulation in Multipath Propagation Scenarios

摘要

Reflection, diffraction, scattering, shadowing, and attenuation are common propagation effects for wireless signals. This gives rise to multipath signal propagation with different versions of the signal arriving at the receiver with various delays, phase offsets, and magnitudes. Depending on the delays and phase offsets, the combined signal undergoes constructive and destructive interference. This paper analyzes multipath propagation effects on BOC modulated signals, as planned for Galileo and compares them with multipath propagation effects on BPSK modulated signals, as currently used for GPS. Circular crosscorrelation functions of BOC versus BPSK modulated Gold codes for various multipath propagation scenarios are determined based on the equivalent lowpass representation of the multipath channel model. The illustrations show how BOC modulation has the potential to better resolve the different multipath components. Simulations for different phase offsets furthermore show the distinctly different fading behavior of BOC versus BPSK modulation. The phase offsets that produce constructive and destructive interference are different for BOC and BPSK modulation, since the BOC subcarrier introduces a second fading component.