Receivers in global navigation satellite systems (GNSS), such as the Global Positioning System (GPS), use range measurements that are based on line-of-sight signals from satellites. The receiver measures the time-of-arrival of one or more broadcast signals. This time-of-arrival measurement includes a time measurement based upon a coarse acquisition coded portion of a signal, called pseudo-range, and a phase measurement based on an L-band carrier signal, including L1 at 1.57542 GHz, L2 at 1.22760 GHz and L5 at 1.17645 GHz. Ideally, these measurements are based only on the direct line-of-sight signals. The actual signals received by the receiver, however, are a composite of the direct line-of-sight signals and one or more secondary reflected signals. These secondary signals, known as multi-path signals, are reflected by any number of structures, including buildings, equipment and the ground.
The path-length of the multi-path signal is longer than that of the direct-path signal resulting in the multi-path signal arriving at the signal receiver at a time instant later than a time of arrival of the direct path signal. As a result, a composite signal is received at the signal receiver which comprises the direct path signal and the delayed multi-path version of the direct path signal. The time delay in arrival of the multi-path signal with respect to the direct path signal results in an undesired detectable phase distortion in the composite signal.