Comparison of the Sensitivity Limits for GPS and Galileo Receivers
in Multipath Scenarios
Proc. of the IEEE Position Location and Navigation Symposium (PLANS), (2004)Zusammenfassung
The global navigation satellite systems (GNSS) market is anticipated
by most market researchers to experience exponential growth in the
consumer segment, to the largest extend through the introduction
of location based services (LBS). LBS - inlcuding the US. E-911 mandate
- require position fixes at demanding rural sites, such as urban
canyon, moderate indoor, and in vehicles without external antennae.
The satellite signals are not only attenuated, but also subjected
to strong multipath fading. Developing GPSGalileo receivers for high-volume
markets requires support for LBS, which in turn necessitates enhanced
receiver sensitivity and multipath robustness. Which business cases
are feasible is therefore partially determined by the maximally achievable
sensitivity under various multipath scenarios. These sensitivity
limits form a baseline for the receiver design . This paper algebraically
derives the sensitivity limits for acquisition (i.e. synchronization)
of direct sequence spread spectrum positioning signals under multipath
propagation conditions. The derived formulas are then evaluated exemplarily
for the parameters of the openly accessible L1-band GPS and Galileo
signals, while they are also valid for other positioning signals.
As commonly applied in wireless communications, the multipath environment
is modelled with stochastic Ricean fading processes. The derived
sensitivity limits are based on the stochastic models for multipath
and noise, being transformed by RF-downconversion, despreading, coherent
integration, envelope detection, noncoherent integration, and Neyman-Pearson
detection. These results are also provided as plots of probability
of detection versus carrier power to noise power spectral density,
parameterized for various noncoherent integration times and Ricean
factors.