Spreading code phase measurement technique for snapshot GNSS receiver

Driven by the expanding demand of location based services (LBS), the integration of satellite navigation receiver into mobile devices has received much attention in the last years. Snapshot positioning technique has turned out to be a very suitable candidate in LBS applications for its predominance of low cost and low power dissipation. However, the limited snapshot length is a major hurdle that limits the availability and accuracy of receivers. A code phase measurement technique is developed and used for snapshot receivers. By utilizing the features of the modernized global navigation satellite system (GNSS) signals and the characteristic of snapshot positioning, it uses a novel dual update-rate tracking loop with a non-causal smoothing estimator to obtain a relatively accurate estimation from a second or less snapshot data. Experiments with simulated data show that the proposed method has better estimation accuracy than the conventional code tracking loop in confined data length snapshot receivers.