SYSTEMS AND METHODS OF ASSISTED GPS
Embodiments of an improved assisted global positioning system (GPS) method and system are described. Wireless access points send assistance data to GPS receivers that are integrated into cellular chipsets and other chipsets. The access points may also act as fixed location references for differential GPS (DGPS) mobile stations. Errors caused by multipath travel of the GPS signals are reduced by using fixed location reference receivers.
1 - 54 . (canceled)
55 . A method of determining a position of a mobile device using global positioning system (GPS) signals, the method comprising:
receiving, at the mobile device, GPS information from a plurality of GPS satellites, the mobile device experiencing multipath interference from signals received from at least one satellite of said plurality of GPS satellites;
selecting a particular access point from a plurality of short range access points comprising WLAN, Bluetooth, UWB, RFID, and ZigBee access points, the particular access point near the mobile device and experiencing a same multipath interference as the mobile device;
receiving GPS differential data from the particular short range access point, the GPS differential data from the particular access point comprising a difference between a known distance to said at least one satellite and a distance to said at least one satellite calculated based on GPS information received at the particular access point from said at least one satellite;
computing a distance from the mobile device to each of said plurality of satellites based on the GPS information received from said plurality of GPS satellites, the computed distance to said at least one satellite affected by said multipath interference;
compensating the effect of the multipath interference in the computed distance from the mobile device to said at least one satellite using said GPS differential data received from the particular access point experiencing the same multipath interference as the mobile station; and
computing the position of the mobile device based on said distance from the mobile device to each of said plurality of satellites.
56 . The method of claim 55 further comprising:
transmitting said GPS differential data to an assistance server, wherein said assistance server performs computing said position; and
receiving said position at said mobile device from the assistance server.
57 . The method of claim 55 , wherein the mobile station receives a plurality of time of arrival information from said plurality of access points, the method further comprising:
computing the position of the mobile device using triangulation of said plurality of time of arrival information; and
combining the position computed based on the distance from the mobile station to each of the plurality of satellites with the position computed based on the triangulation of the plurality of time of arrival information to further compensate for the effect of the multipath interference.
58 . The method of claim 55 , wherein the mobile station receives a plurality of phase information from said plurality of access points, the method further comprising:
computing the position of the mobile device using triangulation of said plurality of phase information; and
combining the position computed based on the distance from the mobile station to each of the plurality of satellites with the position computed based on the triangulation of the plurality of time of arrival information to further compensate for the effect of the multipath interference.
59 . The method of claim 55 , wherein the multipath interference is caused by reflections of signals transmitted by satellites on objects near the mobile device and the plurality of access points.
60 . The method of claim 55 , wherein the GPS differential data is further for reducing errors due to variations in a speed of radio waves travelling through the earth's atmosphere.
61 . The method of claim 55 , wherein the GPS differential data is further for reducing errors due to satellite clock inaccuracies.
62 . The method of claim 55 further comprising:
receiving a plurality of assistance data from at least one of said plurality of access points; and
computing a combined assistance data from said plurality of assistance data,
wherein computing said position further comprises using said combined assistance data.
63 . The method of claim 62 , wherein computing said position comprises:
computing said position by executing a weighted least squares process on said GPS information and said combined assistance data.
64 . The method of claim 62 , wherein computing said position comprises:
computing said position by executing an extended Kalman filter process on said GPS information and said combined assistance data.
65 . The method of claim 62 , wherein computing said position comprises:
computing said position based on said GPS information and said combined assistance data using a first set of weights in an indoor location and a second set of weights in an outdoor location.
66 . The method of claim 62 , wherein computing said position comprises:
computing said position based on said GPS information having a first weight and said combined assistance data having a second weight.
67 . The method of claim 62 , wherein said GPS information includes a final position, velocity and time solution, wherein computing said position comprises:
computing said position based on said final position, velocity and time solution having a first weight and said combined assistance data having a second weight.
68 . The method of claim 62 , wherein said GPS information includes raw GPS measurements, wherein computing said position comprises:
computing said position based on said raw GPS measurements having a first weight and said combined assistance data having a second weight.
69 . The method of claim 62 , wherein said GPS information includes in-phase and quadrature symbols, wherein computing said position comprises:
computing said position based on said in-phase and quadrature symbols having a first weight and said combined assistance data having a second weight.
70 . The method of claim 62 , wherein said combined assistance data includes a final position, velocity and time solution, wherein computing said position comprises:
computing said position based on said final position, velocity and time solution having a first weight and said GPS information having a second weight.
71 . The method of claim 62 , wherein said combined assistance data includes raw navigation measurements, wherein computing said position comprises:
computing said position based on said raw navigation measurements having a first weight and said GPS information having a second weight.
72 . The method of claim 62 , wherein said combined assistance data includes in-phase and quadrature symbols, wherein computing said position comprises:
computing said position based on said in-phase and quadrature symbols having a first weight and said GPS information having a second weight.
73 . The method of claim 55 , wherein said selecting the particular access point, said receiving the GPS differential data from the particular short range access point, said computing the distance from the mobile device to each of said plurality of satellites, said compensating the effect of the multipath interference, and said computing the position of the mobile device are performed at the mobile station.
74 . An apparatus for performing position determination using global positioning system (GPS) signals and compensating for effects of multipath signal interference, the apparatus comprising:
a GPS receiver for receiving GPS information from a plurality of GPS satellites;
a wireless communication module, communicatively coupled to said GPS receiver, the wireless communication module for receiving a plurality of GPS differential data from a plurality of short range access points comprising WLAN, Bluetooth, UWB, RFID, and ZigBee access points, the GPS differential data received from each access point comprising a difference between a known distance to said at least one satellite and a distance to said at least one satellite calculated based on GPS information received at the access point from said at least one satellite; and
a navigation processor, communicatively coupled to said GPS receiver and said wireless communication module, the navigation processor for:
selecting a particular access point from the plurality of access points, the selected particular access point near said apparatus and experiencing a same multipath signal interference as said apparatus;
computing a distance from the apparatus to each of said plurality of GPS satellites based on the GPS information received from said plurality of GPS satellites, the computed distance to at least one satellite in said plurality of satellites affected by said multipath signal interference;
compensating the effect of the multipath signal interference in the computed distance from the apparatus to said at least one satellite using said GPS differential data received from the particular access point experiencing the same multipath interference as the mobile station; and
computing a position of the apparatus based on said distance from the apparatus to each of said plurality of satellites.