Method and apparatus for locating mobile receivers using a wide area reference network for propagating ephemeris

Abstract

A method and apparatus for distribution and delivery of global positioning system (GPS) satellite telemetry data using a communication link between a central site and a mobile GPS receiver. The central site is coupled to a network of reference satellite receivers that send telemetry data from all satellites to the central site. The mobile GPS receiver uses the delivered telemetry data to aid its acquisition of the GPS satellite signal. The availability of the satellite telemetry data enhances the mobile receiver's signal reception sensitivity.

What is claimed is:  
     
         1 . A method for assisting a satellite positioning system mobile device comprising: 
 receiving satellite ephemeris data from all satellites in a global positioning system constellation of satellites;    communicating satellite ephemeris data to a central processing site;    selecting ephemeris data for a subset of all the satellites; and    providing the selected ephemeris data to said mobile device.    
     
     
         2 . The method of  claim 1  wherein said selecting step further comprises selecting ephemeris data for at least one satellite that is in view of the mobile device.  
     
     
         3 . The method of  claim 2  wherein said selecting step further comprises selecting ephemeris data for at least one satellite that will be within view of the mobile device.  
     
     
         4 . The method of  claim 3  wherein said at least one satellite will be within view of said mobile device within about four hours.  
     
     
         5 . The method of  claim 2  further comprising acquiring at least one satellite signal using said selected ephemeris data.  
     
     
         6 . The method of  claim 5  further comprising: 
 a. computing a frequency window having a plurality of frequency bins from said selected ephemeris data, a mobile receiver approximate position, and an approximate time;  
 b. searching for a signal correlation in a frequency bin within said frequency window;  
 c. determining whether there are signal correlations within said frequency bin; and  
 d. repeating steps (b) and (c) using different frequency bins until a signal correlation is detected.  
 
     
     
         7 . The method of  claim 5  further comprising computing position of the mobile receiver using said selected ephemeris data.  
     
     
         8 . The method of  claim 7  wherein said computing step is performed in the mobile device.  
     
     
         9 . The method of  claim 7  wherein said computing step is performed at a location remote from said mobile device.  
     
     
         10 . The method of  claim 3  further comprising acquiring said at least one satellite, in the future, using said selected ephemeris data.  
     
     
         11 . The method of  claim 10  further comprising: 
 a. computing a frequency window having a plurality of frequency bins from said selected ephemeris data, a mobile receiver approximate position, and an approximate time;  
 b. searching for a signal correlation in a frequency bin within said frequency window;  
 c. determining whether there are signal correlations within said frequency bin; and  
 d. repeating steps (b) and (c) using different frequency bins until a signal correlation is detected.  
 
     
     
         12 . The method of  claim 10  further comprising computing position of the mobile device using said selected ephemeris data.  
     
     
         13 . The method of  claim 12  wherein said computing step is performed in the mobile device.  
     
     
         14 . The method of  claim 12  wherein said computing step is performed at a location remote from said mobile device.  
     
     
         15 . The method of  claim 5  further comprising using information derived from said at least one satellite signal to assist in acquisition of other satellite signals.  
     
     
         16 . The method of  claim 15  further comprising: 
 a. computing a frequency window having a plurality of frequency bins and a code delay window having a plurality of code bins from said selected ephemeris data, and a receiver time and receiver frequency offsets;  
 b. searching for a signal correlation in a frequency bin within said frequency window and a code bin within said code delay window;  
 c. determining whether there are signal correlations within said frequency bin and said code bin;  
 d. repeating steps (b) and (c) using different frequency bins and code bins until a signal correlation is detected;  
 e. using said signal correlation to improve the receiver time offset and the frequency offset;  
 f. recomputing frequency delay windows and code delay windows for other satellite signals; and  
 g. acquiring at least one other satellite signal.  
 
     
     
         17 . The method of  claim 1  wherein said ephemeris data is used to derive at least one pseudo-range model.  
     
     
         18 . The method of  claim 17  wherein said selecting step further comprises selecting ephemeris data for at least one satellite that is in view of the mobile device.  
     
     
         19 . The method of  claim 18  wherein said selecting step further comprises selecting ephemeris data for at least one satellite that will be within view of the mobile device.  
     
     
         20 . The method of  claim 19  wherein said at least one satellite will be within view of said mobile device within, about four hours.  
     
     
         21 . The method of  claim 18  further comprising acquiring at least one satellite signal using said selected ephemeris data.  
     
     
         22 . The method of  claim 21  further comprising: 
 a. computing a frequency window having a plurality of frequency bins from said selected ephemeris data, a mobile receiver approximate position, and an approximate time;  
 b. searching for a signal correlation in a frequency bin within said frequency window;  
 c. determining whether there are signal correlations within said frequency bin; and  
 d. repeating steps (b) and (c) using different frequency bins until a signal correlation is detected.  
 
     
     
         23 . The method of  claim 19  further comprising acquiring a satellite signal from said at least one satellite, in the future, using said selected ephemeris data.  
     
     
         24 . The method of  claim 23  further comprising: 
 a. computing a frequency window having a plurality of frequency bins from said selected ephemeris data, a mobile receiver approximate position, and an approximate time;  
 b. searching for a signal correlation in a frequency bin within said frequency window;  
 c. determining whether there are signal correlations within said frequency bin; and  
 d. repeating steps (b) and (c) using different frequency bins until a signal correlation is detected.  
 
     
     
         25 . The method of  claim 21  wherein information derived from said at least one satellite signal is used to assist in acquisition of other satellite signals.  
     
     
         26 . The method of  claim 25  further comprising: 
 a. computing a frequency window having a plurality of frequency bins and a code delay window having a plurality of code bins from said selected ephemeris data, and a receiver time and receiver frequency offsets;  
 b. searching for a signal correlation in a frequency bin within said frequency window and a code bin within said code delay window;  
 c. determining whether there are signal correlations within said frequency bin and said code bin;  
 d. repeating steps (b) and (c) using different frequency bins and code bins until a signal correlation is detected;  
 e. using said signal correlation to improve the receiver time offset and the frequency offset;  
 f. recomputing frequency delay windows and code delay windows for other satellite signals; and  
 g. acquiring at least one other satellite signal.  
 
     
     
         27 . The method of  claim 17  wherein said at least one pseudo-range model comprises a pseudorange, and a pseudorange rate, and a pseudorange acceleration.  
     
     
         28 . The method of  claim 1  where said subset of all the satellites is based on an estimated position of said mobile device.  
     
     
         29 . The method of  claim 28  where said estimated position is the last known position of said mobile device.  
     
     
         30 . The method of  claim 28  where said estimated position is a position within a region served by a communications network used by the mobile device.  
     
     
         31 . The method of  claim 30  wherein said position within the region is at the center of said region.  
     
     
         32 . The method of  claim 28  where said estimated position is derived from a location of a radio tower used by the mobile device.  
     
     
         33 . Apparatus for assisting a satellite positioning system mobile receiver comprising: 
 a network of satellite signal receivers receiving satellite ephemeris from all satellites in a global positioning system constellation of satellites and communicating satellite ephemeris data to a central processing site; and    said central processing site selecting ephemeris data from a subset of all the satellites and providing the selected ephemeris data to a mobile receiver.    
     
     
         34 . The apparatus of  claim 33  wherein said selected ephemeris data comprises ephemeris data for at least one satellite that is in view of the mobile receiver.  
     
     
         35 . The apparatus of  claim 33  wherein said selected ephemeris data comprises ephemeris data for at least one satellite that will be within view of the mobile receiver.  
     
     
         36 . The apparatus of  claim 35  wherein said at least one satellite will be within view of said mobile device within about four hours.  
     
     
         37 . The apparatus of  claim 34  wherein said mobile device comprises means for acquiring at least one satellite signal using said selected ephemeris data.  
     
     
         38 . The apparatus of  claim 37  wherein said mobile device further comprises: 
 a. means for computing a frequency window having a plurality of frequency bins from said selected ephemeris data, a mobile receiver approximate position, and an approximate time;  
 b. means for searching for a signal correlation in a frequency bin within the frequency window;  
 c. means for determining whether there are signal correlations within said frequency bin; and  
 d. means for repeating operation of means (b) and (c) using different frequency bins until a signal correlation is detected.  
 
     
     
         39 . The apparatus of  claim 37  wherein said central processing site comprises means for computing a position of the mobile device using said selected ephemeris data.  
     
     
         40 . The apparatus of  claim 37  wherein said mobile device comprises means for computing a position of said mobile device.  
     
     
         41 . The apparatus of  claim 37  wherein a location remote from said mobile device comprises means for computing a position of said mobile device.  
     
     
         42 . The apparatus of  claim 35  said at least one satellite signal is acquired, in the future, using said selected ephemeris data.  
     
     
         43 . The apparatus of  claim 42  wherein said mobile device further comprises: 
 a. means for computing a frequency window having a plurality of frequency bins from said selected ephemeris data, a mobile receiver approximate position, and an approximate time;  
 b. means for searching for a signal correlation in a frequency bin within the frequency window;  
 c. means for determining whether there are signal correlations within said frequency bin; and  
 d. means for repeating operation of means (b) and (c) using different frequency bins until a signal correlation is detected.  
 
     
     
         44 . The apparatus of  claim 42  wherein said central processing site comprises means for computing a position of the mobile device using said selected ephemeris data.  
     
     
         45 . The apparatus of  claim 42  wherein said mobile device comprises means for computing a position of said mobile receiver.  
     
     
         46 . The apparatus of  claim 42  wherein a location remote from said mobile device comprises means for computing a position of said mobile device.  
     
     
         47 . The apparatus of  claim 37  wherein said central processing site comprises means for utilizing information derived from said at least one satellite signal to assist in acquisition of other satellite signals.  
     
     
         48 . The apparatus of  claim 47  wherein said mobile device comprises: 
 a. means for computing a frequency window having a plurality of frequency bins and a code delay window having a plurality of code bins from said selected ephemeris data, and a receiver time and receiver frequency offsets;  
 b. means for searching for a signal correlation in a frequency bin within said frequency window and a code bin within said code delay window;  
 c. means for determining whether there are signal correlations within said frequency bin and said code bin;  
 d. means for repeating operation of means (b) and (c) using different frequency bins and code bins until a signal correlation is detected;  
 e. means for using said signal correlation to improve the receiver time offset and the frequency offset;  
 f. means for recomputing frequency delay windows and code delay windows for other satellite signals; and  
 g. means for acquiring at least one other satellite signal.  
 
     
     
         49 . The apparatus of  claim 33  wherein said central processing site comprises a means for utilizing said ephemeris data to derive at least one pseudo-range model.  
     
     
         50 . The apparatus of  claim 49  wherein said central processing site is further configured to select ephemeris data for at least one satellite that is in view of the mobile device.  
     
     
         51 . The apparatus of  claim 49  wherein said central processing site comprises a means for selecting ephemeris data for at least one satellite that will be within view of the mobile device.  
     
     
         52 . The apparatus of  claim 51  wherein said at least one satellite will be within view of said mobile device within about four hours.  
     
     
         53 . The apparatus of  claim 50  wherein said mobile device further comprises a means for acquiring at least one satellite signal using said selected ephemeris data.  
     
     
         54 . The apparatus of  claim 53  wherein said mobile device further comprises: 
 a. means for computing a frequency window having a plurality of frequency bins from said selected ephemeris data, a mobile receiver approximate position, and an approximate time;  
 b. means for searching for a signal correlation in a frequency bin within the frequency window;  
 c. means for determining whether there are signal correlations within said frequency bin; and  
 d. means for repeating operation of means (b) and (c) using different frequency bins until a signal correlation is detected.  
 
     
     
         55 . The apparatus of  claim 51  said at least one satellite signal is acquired, in the future, using said selected ephemeris data.  
     
     
         56 . The apparatus of  claim 55  wherein said mobile device further comprises: 
 a. means for computing a frequency window from said selected ephemeris data, and means for computing a frequency window having a plurality of frequency bins from said selected ephemeris data, a mobile receiver approximate position, and an approximate time;  
 b. means for searching for a signal correlation in a frequency bin within the frequency window;  
 c. means for determining whether there are signal correlations within said frequency bin; and  
 d. means for repeating operation of means (b) and (c) using different frequency bins until a signal correlation is detected.  
 
     
     
         57 . The apparatus of  claim 53  wherein said mobile device comprises a means for utilizing information derived from said at least one satellite signal to assist in acquisition of other satellite signals.  
     
     
         58 . The apparatus of  claim 57  wherein said mobile device comprises: 
 a. means for computing a frequency window and a code delay window from said selected ephemeris data, and an approximate location of said mobile receiver, and an approximate receiver time and frequency offsets;  
 b. means for searching for a signal correlation in a frequency/code bin within said frequency window and code delay window;  
 c. means for determining whether there are signal correlations within said frequency/code bin;  
 d. means for repeating operation of means (b) and (c) using different frequency/code bins until a signal correlation is detected;  
 e. means for using said signal correlation to improve said receiver time offset and said frequency offset;  
 f. means for recomputing frequency delay windows and code delay windows for remaining satellites; and  
 g. means for acquiring at least one other satellite.  
 
     
     
         59 . The apparatus of  claim 49  wherein said pseudo-range models comprise a pseudorange, and a pseudorange rate, and a pseudorange acceleration.  
     
     
         60 . The apparatus of  claim 33  where said subset of all the satellites is based on the estimated position of said mobile device.  
     
     
         61 . The apparatus of  claim 60  where said estimated position is the last known position of said mobile device.  
     
     
         62 . The apparatus of  claim 60  where said estimated position is a position within a region served by a communications network used by the mobile device.  
     
     
         63 . The apparatus of  claim 62  wherein said position within said region is at the center of said region.  
     
     
         64 . The apparatus of  claim 60  where said estimated position is derived from a location of a radio tower used by the mobile device.