Cross-correlation system for time recovery in network-assisted GPS positioning

摘要

A method and apparatus for measuring time related to satellite navigation data messages used with a satellite-based global positioning systems (GPS). A first record of at least a portion of a satellite data message is received at an entity, which is typically a base station of a wireless communication system. The first record is compared with a second record of the same satellite data message (navigation message) received by a GPS receiver. From the comparison, a time is determined indicating when the satellite date message was transmitted (broadcast). The comparison is made in a way that accounts for the only approximate removal of all modulation of the satellite data message by the acquisition and tracking stages of the GPS receiver.