Method and apparatus for determining time for GPS receivers

DETAILED DESCRIPTION The present invention discloses a method and apparatus for acquiring timing signals for use in a Global Positioning System (GPS) receiver.
In an embodiment of the present invention, the GPS receiver is contained in an integrated receiver which also includes a cell-based communication receiver.
In a method of the present invention, the communication receiver receives a commercial communication signal which contains a time indicator representing a time synchronized event, and the GPS receiver receives satellite position information from one or more global positioning system satellites.
The GPS receiver associates the time indicator with timing data at the receiver.
If the time indicator is a timing frame or pulse within the communication signal, the receiver determines its local time relative to such a frame or pulse using, in one embodiment, a time interval counter.
If the time indicator is system time transmitted along with the communication data, the receiver determines its local time from the transmitted system time.
The satellite position information and timing information are then used to determine the position of the GPS receiver.
Other features of the present invention will be apparent from the accompanying drawings and from the detailed description which follows.