Multipath Effects on GPS Code Phase Measurements

Abstract
An analysis of multipath errors in GPS code phase measurements is presented, assuming the code phase is measured with the widely used noncoherent delay lock loop. Both specular and diffuse reflections are considered. A rough estimate for the fading bandwidth is given for mobile and stationary users, showing that averaging is far more effective for mobile than for stationary users. In general, however, a certain mean range error is present for both stationary and mobile users, depending on the power-delay profile of the received signal. Measurements near buildings confirm the asymmetry of multipath errors, which causes the nonzero mean, and show that range errors can take values of more than 100 m.

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