TITLE:
GPS Signal Short-Term Propagation Characteristics Modeling in Urban Areas for Precise Navigation Applications
AUTHORS:
G. Sateesh Kumar, G. Sasi Bhushana Rao, M. N. V. S. S. Kumar
KEYWORDS:
GPS; Navigation; Multipath; Rayleigh and Rician
JOURNAL NAME:
Positioning,
Vol.4 No.2,
May
22,
2013
ABSTRACT: GPS navigation signal includes vital information
such as orbital parameters, clock error coefficients etc. This received signal
which is extremely weak is affected by several errors during its propagation
and is of the order of 10-16 W. The noise floor of this signal is
400 times higher than the transmitted signal. The situation becomes much worse
particularly when the GPS receiver is located at urban areas where the
multipath effect is predominant in the code and carrier phase measurements. GPS
usage is not limited to the aircraft en-route navigation and missile guidance
where the user receives the satellite signals from the open sky. At the present
time, it has become an essential utility in the car navigation, mobile phones, surveying and aircraft
landing application. The signal propagation characteristics particularly the
short-term variations
severely affect the quality, availability and continuity of the system. In this
paper, short-term propagation characteristics of GPS signal are modeled and analyzed. Short-term
variations are mainly due to multipath reflections and Doppler shift which degrades
the quality of received signal particularly in urban environments. The
variation of signal quality with respect to user velocity is observed using
Rayleigh and Rician fading models.