GPS Multipath Cancellation and Warning System

Accurate estimate of the multipath channel parameters allow the associated errors to be cancelled which greatly improves GPS system navigation performance. A multi-parameter maximum likelihood estimation technique has been shown through simulations to be very effective in antimultipath processing. This approach is based on implementing a multipath estimating delay locked loop (MEDLL). The key to this approach is the formation of a bamk of correlations at narrow spacings over the multipath delay interval. This allows estimation of all multimpath channel parameters over the region of interest. NAVSYS has an advanced GPS receiver (AGR) that utilizes such a bamk or correlators which have programmable tap spacings. The AGR provides an ideal test bed to implement the MEDLL or similar algorithm with multipath correlator bank. There are always certain scenarios in which multipath cannot be isolated. NAVSYS has developed a receiver autonomous integrity monitoring (RAIM) subsystem to warn the user of degraded performance in such situations. This RAIM subsystem will be included as part of the proposed system.