Multipath Effects in GPS Receivers with Correlation Operations

A standard global positioning system (GPS) receiver employs correlation operations in accomplishing its time and frequency tracking functions. This paper examines how the presence of a single multipath ray affects the correlation operations in the GPS receiver and thereby results in bias in the resulting timing estimate developed by the receiver. Surprisingly, in some cases there may be more than one value of bias that is manifest in the timing estimate, so the initial timing estimate introduced into the receiver can yield very different steady-state estimates of timing depending on the parameters that characterize the multipath ray.