Method and system for selecting optimal satellites for A-GPS location of handsets in wireless networks
A system and method for determining a set of satellites for which assistance data may be provided to a wireless device. A boundary for an approximate area in which the wireless device is located may be determined and one or more sets of satellites may be determined as a function of the boundary. An optimum set of satellites from the one or more sets of satellites may then be determined using a satellite selection function on the one or more sets of satellites at predetermined points substantially on the boundary.
1. A method for determining a set of satellites for which assistance data may be provided to a wireless device, comprising the steps of:
(a) determining a boundary for an approximate area in which the wireless device is located;
(b) determining one or more sets of satellites as a function of said boundary; and
(c) determining an optimum set of satellites by a communications network element from said one or more sets of satellites as a function of the visibility of each of said one or more sets of satellites at predetermined points substantially on said boundary.
2. The method of claim 1 wherein the step of determining one or more sets of satellites further comprises:
(i) determining a first number of satellites that can be provided to the wireless device;
(ii) determining a second number of satellites visible from the approximate area;
(iii) determining a third number of satellites to be removed from said one or more sets of satellites; and
(iv) determining said one or more sets of satellites as a function of said first, second and third numbers.
3. The method of claim 2 wherein the step of determining an optimum set of satellites further comprises determining an optimum set of satellites by maximizing the number of satellites in view from each of said one or more predetermined points.
4. The method of claim 2 wherein the step of determining an optimum set of satellites further comprises:
(i) determining an optimum set of satellites from said one or more sets of satellites as a function of the relationship:
f
satsViewBased
=
∑
i
=
1
noPoints
(
noSatsInView
i
≥
4
?
noSatsInView
i
:
0
)
where noSatsInView i represents a fourth number of satellites visible for each point (i) selected substantially on the boundary of the approximate area.
5. The method of claim 1 wherein said boundary defines an area selected from the group consisting of: a city, municipality, county, state, country, continent, a serving area of a base station serving said wireless device, and an approximate area of a communications network.
6. The method of claim 1 wherein the satellites are part of a Global Navigation Satellite System (“GNSS”).
7. The method of claim 6 wherein the GNSS is selected from the group consisting of: a Global Positioning System (“GPS”), Galileo system, GLONASS system, Quasi-Zenith Satellite System (“QZSS”), Beidou satellite system, Compass satellite system, and combinations thereof.
8. The method of claim 1 wherein the device is selected from the group consisting of: cellular device, text messaging device, computer, portable computer, vehicle locating device, vehicle security device, communication device, and wireless transceiver.
9. The method of claim 1 further comprising the steps of:
(d) transmitting assistance data to said device, said assistance data including information from said optimum set of satellites; and
(e) determining the location of the wireless device from said information.
10. The method of claim 1 wherein the communications network element is selected from the group consisting of an Mobile Location Center, a location information server, and a location information system.
11. A method for determining the location of a wireless device, comprising the steps of:
(a) determining a boundary for an approximate area in which the wireless device is located;
(b) determining one or more sets of satellites as a function of said boundary;
(c) determining an optimum set of satellites from said one or more sets of satellites as a function of the visibility of each of said one or more sets of satellites at predetermined points substantially on said boundary;
(d) transmitting assistance data to said device, said assistance data including information from said optimum set of satellites; and
(e) determining the location of the wireless device from said information.
12. The method of claim 11 wherein determining one or more sets of satellites further comprises:
(i) determining a first number of satellites that can be provided to the wireless device;
(ii) determining a second number of satellites visible from the approximate area;
(iii) determining a third number of satellites to be removed from said one or more sets of satellites; and
(iv) determining said one or more sets of satellites as a function of said first, second and third numbers.
13. The method of claim 12 wherein the step of determining an optimum set of satellites further comprises determining an optimum set of satellites by maximizing the number of satellites in view from each of said one or more predetermined points.
14. The method of claim 12 wherein the step of determining an optimum set of satellites further comprises:
(i) determining an optimum set of satellites from said one or more sets of satellites as a function of the relationship:
f
satsViewBased
=
∑
i
=
1
noPoints
(
noSatsInView
i
≥
4
?
noSatsInView
i
:
0
)
where noSatsInView i represents a fourth number of satellites visible for each point (i) selected substantially on the boundary of the approximate area.